Texas/MX Obs And Discussion Thread.

[Scott747]

Yeah, it seems '83 and '89 get mentioned every year, and then the threat decreases. I guess one of these days it will happen and who knows... maybe this is it. The models do look insanely cold.

Correct. We go through the motions every year/season. Much like the tropical season everyone looks for the next event and compare to one of the biggies of years past. This potential event does have everyone talking and could be the real deal. Why I was being a smart a** and telling someone to PM when there is a 1055 H in the Rockies. I can do without the extreme cold and if it's gonna snow there better be some solid accumulations to make it worthy. Snow is one thing. Ice/sleet is one that we all would rather not see.

Quick snippet from Jeff -

Long Range: TROUBLE and a lot of it is brewing in the arctic regions! Fairly zonal upper air pattern looks to undergo major amplification and high latitude blocking by this weekend with Greenland upper air vortex retrograding toward SC Canada. At the surface this gives rise to a mamoth 1070mb arctic high pressure dome over NW Canada by early next week. Record US surface pressure is 1064mb in Montana during the Dec 1983 historic arctic outbreak...so we could be looking at something historic here. I have never seen such high pressures on extended model runs especially the ECMWF...so there is reason to be somewhat skeptical. Nonetheless, even if the models are off a little bit there appears little to stop a major outbreak of very cold air southward into the US by early next week as the upper air pattern and delivery look favorable to bring whatever is in NW Canada southward down the plains. Expect a shallow, but very cold air mass to enter TX sometime around Monday of next week and reach the coast by Tuesday..timing will likely change some. Models also show fairly significant amounts of moisture in the frozen/freezing air column suggesting P-type issues may abound across the entire region at some point next week. Arctic air masses are notorious for being shallow and supporting significant freezing rain/icing events instead of snow/sleet. Stay tuned!

[wxmx]

Correct. We go through the motions every year/season. Much like the tropical season everyone looks for the next event and compare to one of the biggies of years past. This potential event does have everyone talking and could be the real deal. Why I was being a smart a** and telling someone to PM when there is a 1055 H in the Rockies. I can do without the extreme cold and if it's gonna snow there better be some solid accumulations to make it worthy. Snow is one thing. Ice/sleet is one that we all would rather not see.

Quick snippet from Jeff -

Long Range: TROUBLE and a lot of it is brewing in the arctic regions! Fairly zonal upper air pattern looks to undergo major amplification and high latitude blocking by this weekend with Greenland upper air vortex retrograding toward SC Canada. At the surface this gives rise to a mamoth 1070mb arctic high pressure dome over NW Canada by early next week. Record US surface pressure is 1064mb in Montana during the Dec 1983 historic arctic outbreak...so we could be looking at something historic here. I have never seen such high pressures on extended model runs especially the ECMWF...so there is reason to be somewhat skeptical. Nonetheless, even if the models are off a little bit there appears little to stop a major outbreak of very cold air southward into the US by early next week as the upper air pattern and delivery look favorable to bring whatever is in NW Canada southward down the plains. Expect a shallow, but very cold air mass to enter TX sometime around Monday of next week and reach the coast by Tuesday..timing will likely change some. Models also show fairly significant amounts of moisture in the frozen/freezing air column suggesting P-type issues may abound across the entire region at some point next week. Arctic air masses are notorious for being shallow and supporting significant freezing rain/icing events instead of snow/sleet. Stay tuned!

I understand the concerns, and the main one for most of the south, is that we might get a shallow artic dump. But the pattern doesn't look very Dec '83 in the way that my area was in the lower teens with near 588dm 500mb heights! The last runs of the GFS are not as extreme, and doesn't really connect the W coast ridge with the EPO ridge...that will probably mean a shallow artic air mass...but they show a weak S/W traversing MX, with some amplification...and more than enough moisture in NE MX and S/SE TX.... The Euro is a lot more amplified, with the W Coast ridge and the EPO ridge connecting (I don't know how the 700-850mb layer looks like for cold and moisture). A long shot but possible scenario would be having a mix of scenarios, with the ridges connecting and a low latitude S/W traversing our area, loosing the PV vortex a bit, so that heights are low enough for the whole column to be subfreezing...an even better scenario (though, highly improbable), the 1 in a 1000 years one, for the S/W phasing with the polar jet energy...that would indeed be something. Or, thinking about it...a nice slow moving cutoff low would be just perfect...but I'm probably just rambling.

My thinking right now is that the whole state (TX) will have mins below freezing... but about precipitation and the state of the freezing column are still big unknowns at this point.

[Srain]

I'd keep an eye on the weekend. Regardless of what falls, it does look damp across the Lone Star State into MX.

[Flexo]

I just want this to actually happen this time

models <--- haters gonna hate

[Srain]

[Srain]

Oh boy...

[wall_cloud]

I'm not concerned about wintry precip in my neck of the woods. I just don't think the moisture will be present (although its quite easy to get flurries in arctic airmasses). Nothing to write home about. However, the temperature departures will be tremendous. I would venture to say that much of central/northern TX will struggle to hit the freezing mark Monday afternoon through at least Wednesday with only meager modification of the airmass by Thursday. Once this pattern changes it looks to stay around a while. The 06z/18z runs are generally taken with a grain of salt but another substantial wave is now progged to dive south across the western CONUS by midweek. This would reinforce the cold air by the end of the week so subfreezing temps could be possible even as we move into the weekend. If one was to worry about winter precip, this would be the timeframe that I would look at more closely. Its a slow moving trof with strong dynamics. Moisture will not be all that impressive but when temps are that low you don't need that much. Check out the 4 AM FTW AFD from today. It is very well written and has a lot of good information in it.

[Ed Lizard]

Would not be good for my citrus...

I wonder, looking at the Euro prog, if the coldest air might be below the 850 mb level...

..

[Srain]

Dallas/Ft Worth as wall_cloud mentioned...

MAIN WEATHER STORY IS THE COLDER WEATHER EXPECTED INTO THE REGION

NEXT WEEK. THERE REMAINS EXCELLENT AGREEMENT AMONG THE MODELS THAT

A PATTERN CHANGE WILL OCCUR AS BLOCKING UPPER HIGHS/LOWS DEVELOP

AND PERSIST ACROSS THE NORTHERN LATITUDES. A COLD AIR MASS WILL

BEGIN TO DEVELOP AND ORGANIZE ACROSS WESTERN CANADA THIS WEEKEND

WITH SURFACE TEMPS THERE BEGINNING TO FALL BELOW 0 AS A LARGE

SPRAWLING SURFACE HIGH GATHERS INTENSITY. THIS CANADIAN AIR MASS

IS POISED TO MOVE SOUTH AND ARRIVE INTO NORTH TEXAS BEGINNING

MONDAY. SINCE THE UPPER PATTERN STAYS BLOCKED...THE GATES TO THE

NORTH WILL REMAIN OPEN AND COLD AIR WILL CONTINUE TO POUR SOUTH

INTO THE CENTRAL US FOR SEVERAL DAYS. THUS IT IS WITH HIGH

CERTAINTY THAT WE CAN SAY AN EXTENDED PERIOD OF COLDER THAN

NORMAL WEATHER WILL OCCUR IN NORTH TEXAS NEXT WEEK.

AS FAR AS HOW COLD...AND WHETHER THIS EVENT WILL BE ONE OF THOSE

MEMORABLE DECADE EVENTS...IS ANOTHER QUESTION. AT LEAST THROUGH

FRIDAY JAN 14TH...ODDS ARE THAT THIS COLD SPELL WILL NOT BE

ANYWHERE NEAR RECORD TERRITORY AND LOOKS COMPARABLE TO THE ONE

LAST YEAR IN EARLY JANUARY. LAST NIGHT I WROTE ABOUT THE BENEFITS

OF ANALYSIS OF THE SOURCE REGION OF THESE COLD AIR MASSES...

PARTICULARLY AT THE 500MB-700MB LEVEL. I DUG UP THE UPPER AIR DATA

FROM A DOZEN OF OUR BIGGEST COLD SNAPS SINCE 1970. THESE HISTORIC

ARCTIC OUTBREAKS UNANIMOUSLY CONTAINED 500-700MB TEMPS 5 TO 10 DEG

C COLDER THAN WHAT ANY MODEL IS FORECASTING OVER CANADA THIS

WEEKEND. IN ADDITION 850MB TEMPS ACROSS THE NORTHERN US ARE

FORECAST TO BE ABOUT 5 DEG C WARMER EARLY NEXT WEEK THAN WHAT OUR

SIGNIFICANT OUTBREAKS HAD. THUS WE CAN MAKE FORECAST TEMPERATURE

EXTRAPOLATIONS BASED OFF A MODEL/S UPPER AIR FORECASTS 5 DAYS OUT

RATHER THAN RELYING ON A MODEL/S SURFACE TEMP FORECAST 10 DAYS OUT

WHICH IS OBVIOUSLY PRONE TO MORE ERRORS.

SO FOR THE SPECIFICS...MONDAY/S HIGHS SHOULD LIKELY BE IN THE 40S

AS FROPA OCCURS THAT MORNING. LOWS MONDAY NIGHT SHOULD BE IN THE

20S AREA WIDE WITH BREEZY NORTH WINDS CONTINUING. HIGHS TUESDAY

THROUGH FRIDAY LOOK TO STAY IN THE 30S AREA WIDE DESPITE GENERALLY

SUNNY SKIES. WINDS SHOULD SUBSIDE MORE BY MID LATE WEEK WITH LOWS

LIKELY IN THE TEENS TO LOW 20S EACH NIGHT.

BEYOND JAN 14TH...IT IS TOUGH TO SAY EXACTLY WHAT WILL HAPPEN.

YESTERDAY/S MODEL RUNS WERE MORE BULLISH THAT NEXT WEEK/S COLD

SPELL WAS JUST THE START OF SOMETHING MORE SERIOUS. THE LATEST

GFS/ECMWF/GEM OPERATIONAL RUNS AND ENSEMBLE MEANS AT 240 HOURS ARE

DEPICTING AN UPPER LEVEL PATTERN NOT EXACTLY FAVORABLE FOR A

HISTORIC OUTBREAK. THEY HAVE ALL TRENDED THE BLOCKING HIGH OVER

ALASKA EITHER TOO FAR NORTH OR TOO FAR WEST INTO SIBERIA. THIS

MEANS THE POSITIVELY TILTED UPPER TROUGH AXIS OVER THE SW US /A

CRUCIAL COMPONENT TO GET AN ARCTIC OUTBREAK HERE...AND A KEY TO

MEETING THE REQUIREMENTS OF THE SO-CALLED MCFARLAND PATTERN

SIGNATURE/ BECOMES IN QUESTION...SINCE A POSITIVE TILT TROUGH OR

KINK OFTEN NATURALLY DEVELOPS SOUTHEAST OF AN UPPER HIGH. WITHOUT

THIS TROUGH THE REAL ARCTIC AIR JUST HAS A TOUGH TIME MAKING IT

THIS FAR SOUTH. HOWEVER...ABOUT 1/3 OF THE ENSEMBLE MEMBERS KEEP

THIS SW TROUGH IN TACT...AND THEY SHOW A VERY COLD/INTENSE POLAR

LOW DEVELOPING OVER CANADA AND THE US IN 10 DAYS. LOTS OF

UNCERTAINTY AND MODELS WILL CONTINUE TO CHANGE DAILY. BUT THE

REASON WHY WE ARE WATCHING THIS SO CLOSELY IS BECAUSE A 30 PERCENT

CHANCE OF OCCURRENCE IS PRETTY HIGH FOR AN EVENT WHICH WOULD HAVE

ENORMOUS AND WIDESPREAD ECONOMIC IMPLICATIONS FOR OUR REGION...AS

WE LEARNED IN THE DEEP FREEZES OF 83 AND 89.

TR.92

Dodge City as well...

DAYS 3-7...

THE EXTENDED PERIOD IS THURSDAY THROUGH NEXT TUESDAY. MADE SOME

MINOR CHANGES FOR THURSDAY AND FRIDAY WITH TEMPERATURES. I WARMED

TEMPERATURES UP A BIT BY BLENDING THE PREVIOUS FORECAST WITH THE 00Z

ECMWF. DRY UPPER LEVEL NORTHWEST FLOW WITH 500 HPA SHORTWAVE RIDGING

IN RESPONSE TO AN APPROACHING UPPER LEVEL TROF ACROSS THE DESERT

SOUTHWEST WILL ALLOW TEMPERATURES TO CLIMB ABOVE NORMAL TOWARDS THE

END OF THE BUSINESS WEEK. BY SATURDAY, THIS LOW WILL BE CLOSE

ENOUGH TO BRING IN POPS TO THE SOUTHEAST CWFA. A WARM AIR ADVECTION

PATTERN AHEAD OF THIS UPPER LEVEL TROUGH SHOULD ALLOW FOR RAIN AS

850 HPA TEMPERATURES WARM UP TO AROUND 7 DEG ACROSS SOUTHERN KANSAS

AND INTO OKLAHOMA BY SATURDAY AFTERNOON. THE UPPER TROF WILL

TRAVERSE EAST ACROSS TEXAS WHILE ANOTHER UPPER LEVEL TROF HEADS

ACROSS THE ROCKIES WITH A SURFACE REFLECTION IN THE FORM OF AN

ARCTIC COLD FRONT. HAVE LARGELY FOLLOWED ECMWF TIMING FOR BOTH OF THESE

FEATURES. THE ATMOSPHERIC COLUMN SHOULD BE COULD ENOUGH FOR SNOW BY

SUNDAY MORNING AS THE ARCTIC COLD FRONT TRAVERSES ACROSS KANSAS BY

SUNDAY NIGHT. AGAIN, BLENDED THE PREVIOUS FORECAST TO THE 00Z ECMWF.

THE 00Z ECMWF IS A LITTLE WEAKER THAN COMPARED TO THE 12Z ECMWF AS

FAR AS SURFACE PRESSURE RISES ARE CONCERNED BUT THE SAME SYNOPTIC

PATTERN CONTINUES. SO AS IT STANDS RIGHT NOW, THE INTRODUCTION TO

THE ARCTIC AIR WILL HAPPEN SOMETIME BETWEEN SUNDAY NIGHT AND MONDAY

MORNING. TEMPERATURES MONDAY WILL BE MUCH COOLER...GENERALLY IN THE

LOW TO MID 20S FOLLOWED BY SINGLE DIGIT LOWS TUESDAY MORNING. THE

COLD WEATHER WILL COME IN MULTIPLE SURGES OF ARCTIC AIR WITH THE

COLDEST TEMPERATURES EXPECTED BY THE MIDDLE OF NEXT WEEK AS A

1045-1050 HPA SURFACE HIGH SLIDES OVER THE GREAT PLAINS. WITH THE

VERY STRONG 500 HPA HIGH DOMINATING OVER ALASKA AND A CONTINUED LONG

FETCH OF NORTH TO SOUTH ARCTIC AIR, I DO NOT SEE TEMPERATURES

MODERATING THAT MUCH AND THINK THAT THE ARCTIC AIR WILL REMAIN

ENTRENCHED OVER THE PLAINS ALL NEXT WEEK WITH TEMPERATURES FOR THE

DODGE CITY CWFA REMAINING IN THE SINGLE DIGITS FOR LOWS (WITH A GOOD

CHANCE OF NEGATIVE TEMPERATURES TO THE NORTH) AND TEENS FOR HIGHS

WELL INTO THE END OF NEXT WEEK. -SUGDEN

[Ed Lizard]

Not an expert at looking at these, but it would seem if the Euro ensembles are in the ballpark, the worst of the cold will miss us to the East for part two of the cold snap.

Cold, but major not a major economic impact type cold in Texas. I hope.

[am19psu]

Not an expert at looking at these, but it would seem if the Euro ensembles are in the ballpark, the worst of the cold will miss us to the East for part two of the cold snap.

Cold, but major not a major economic impact type cold in Texas. I hope.

FWIW, the ensemble members are a lot more skewed to the north than the south. About half of the members are driving the 0C line well south of the Rio Grande.

[wall_cloud]

FWIW, the ensemble members are a lot more skewed to the north than the south. About half of the members are driving the 0C line well south of the Rio Grande.

I would imagine that is the case in almost every arctic intrusion.

[Srain]

E-mail from Jeff...

Radar already showing numerous showers along and south of I-10 from San Antonio to western Harris County. Showers and maybe a clap of thunder are forming north of a returning warm front currently located along the upper TX coast from offshore of Matagorda Bay to roughly 20 miles south of Galveston. Warm moist Gulf air mass is being lifted over the retreating shallow cold dome resulting in lifting and the formation of showers. Fog has also developed across the region as is typical north of a warm front.

Noisy SW flow aloft will provide a few small scale disturbances today and tonight to help interact with the warm front and a developing surface trough over the NW Gulf to keep decent rain chances in place. Strong mid level capping inversion should keep thunderstorms on the low side except maybe near the coast. Overall foggy, rainy, and cool conditions through tonight. Warm front may push slightly inland this evening allowing mid 60 degree dewpoints to spread across mid 50 degree water temperatures. This would support an episode of dense sea fog starting late this afternoon through about mid morning on Wednesday along the beaches and the coastal bays. Weak cold front will cross the area Wednesday afternoon pushing fog offshore and drying the area under increasing offshore flow.

Thursday and Friday will be dry and “mild” or near normal for early January standards with lows in the 40’s and highs in the 60’s under mostly sunny skies.

Next storm system heads toward the region this weekend as a strong cut-off low pressure system off southern CA coast gradually becomes dislodged and forced eastward. After being in decent agreement yesterday, forecast models have once again developed some timing differences on when this system will impact the state. Models are typically too fast in ejecting cut-off lows eastward and will side with the slower solution focusing the highest rain chances on Sunday morning or possibly during the day Sunday versus the faster GFS showing the system Saturday evening. Track of the short wave has also bounced around some overnight and now is expect to be slightly further north. Still expect a good shot at widespread rainfall Saturday evening-Sunday midday with strong upper level dynamics coming in to play with a moist Gulf air mass. A little too early to look at severe parameters, but we could be talking about some severe weather especially along and S of I-10 with a 120kt jet streak overhead by early Sunday morning. Widespread rains of 1-2 inches looks likely with this system with a few isolated totals upwards of 3 inches which will be welcomed in the drought areas.

Potential Arctic Outbreak:

Very cold air mass will be building over NW Canada late this week with potential delivery into the US late this weekend.

Upper level pattern will undergo significant amplification with a building ridge over Alaska and NW Canada and high latitude blocking downstream over eastern and central Canada. Extremely cold air mass now over northern Siberia (-60F to -80F) will begin to slide across the north pole and southward into NW Canada where building surface pressures will begin to brew a massive arctic high pressure cell. Models continue to advertise at least a 1060mb+ arctic high over NW Canada by late this weekend with a favorable upper level delivery pattern southward. Will taper the severity of this potential outbreak at least for the initial shot early next week. Bitter cold should enter the US via Montana Saturday and surge rapidly southward down the plains as the cold and dense air mass dams up against the Rockies. Shallow arctic air masses tend to move southward faster than models predict and this will need to be watched for a faster arrival than currently expected. Arctic boundary should reach TX Monday and clear the coast Tuesday with very cold air spreading across the entire state. Expect lows well into the 20’s by Wednesday morning and highs only in the 30’s and 40’s for the middle of next week. Appears that moisture may make an attempt at spreading into the cold air mass toward the end of next week or the following weekend. GFS shows a secondary strong surge arriving around the 16th of the month with several days at or below freezing. In fact the GFS guidance for DFW shows temperatures below freezing from the 12th to the 20th during the entire period. At this point this does not appear to be a historic outbreak (such as Dec 1983 or Dec 1989), but possibly as severe as last January. The real bad outbreaks in the past have come in waves with each surge building on the previous surge and keeping sub-freezing temperatures locked in place for days and days. The models are showing this “surge” type pattern in the extended ranges…the questions remain as to how much cold air comes southward and does it all dump at once for a quick hit or do we get front after front keeping the cold air locked in place for several days. <BR clear=all>

[Srain]

Not too shabby...

[Srain]

Any guesses how many times McFarland is mentioned in the afternoon Disco's???...

[Srain]

I guess it's going to get cold...

[Scott747]

Impact weather snippet via the SciGuy -

There is now an increasing risk for a hard freeze along the immediate Gulf coast from south Texas through Mobile Bay as the Arctic Air-mass builds over the region. Even though it's a little too early to predict overnight lows this far out, there is some potential that temperatures could fall as low as the low to mid 20s over the immediate coast from South Texas to the Florida Panhandle sometime during the time period from January 12th through 17th.

Just inland from the coast from South Texas to South Georgia temperatures as low as the teens and low 20s will be possible, with the best chance occurring again from the 12th to the 17th. Lows in the single digits and teens are looking increasingly more likely from north Texas and Oklahoma, eastward across northern Mississippi and Alabama to the western Carolinas.

Another huge concern over the Deep South are daytime highs may average only in the 20s and 30s from Texas to the Carolinas and Florida Panhandle during this same time period.

[Srain]

Absolutely pouring in SE TX with frequent lightning. While we watch for the Arctic Air mass, we do have better rain chances this weekend as well with the CA cutoff low moving across The Lone Star State.

[BikiniBottom]

I sure hope there's some precip around when the colder air arrives. Measurable snow 2 winters in a row... I've gotten quite spoiled.

[Srain]

I sure hope there's some precip around when the colder air arrives. Measurable snow 2 winters in a row... I've gotten quite spoiled.

Stop that bragging. You put my flizzards and snirga storms to shame.

[wall_cloud]

Stop that bragging. You put my flizzards and snirga storms to shame.

doesn't look likely in my neck of the woods but what's new. For you snow junkies, if I get any I'll bottle it up and mail it ALL to you. I really don't like the white stuff.

[Srain]

doesn't look likely in my neck of the woods but what's new. For you snow junkies, if I get any I'll bottle it up and mail it ALL to you. I really don't like the white stuff.

Severe season will be here soon enough, I suspect. I'm just worried about ICE...

[BikiniBottom]

I'll be waiting, wall_cloud.

[BikiniBottom]

Wow... getting one wild thunderstorm right now. Tons of thunder & lightning and very heavy rain... with a lot of that house shaking thunder.

[TXWXCHX]

Absolutely pouring in SE TX with frequent lightning. While we watch for the Arctic Air mass, we do have better rain chances this weekend as well with the CA cutoff low moving across The Lone Star State.

It's been misting rain here as well... very pleasant to have some moisture on the ground, even if just a trace. Here's hoping there's more on the way! Re: the approaching Arctic Air Mass: our local emergency services coordinator sent out a missive today detailing concerns regarding fire equipment and freezing temps. In addition to obvious issues such as water lines/pumps freezing in anomalously cold weather, diesel engines may have "cold start" problems at low temps (dependent on humidity) and municipality/state biodiesel fleets that are not prepared could experience significant issues...

http://www.lcbamarke...eather_meet.htm

http://www.marquemotors.com/?p=175

http://www.biodiesel.org/cold/

[Srain]

Here is a wrap up of the morning discussion highlights across the region. A great read and some fine forecasting analysis as well...

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX

426 AM CST WED JAN 5 2011

.DISCUSSION...

AN ACTIVE SUBTROPICAL UPPER JET WAS CONTINUING OVER SE TX THIS

MORNING. THE UPPER CUT OFF LOW WEST OF SOUTHERN CA IS EXPECTED

TO PUSH EASTWARD LATER THIS WEEK AND SHEAR OFF AS AN UPPER TROUGH

AS IT MOVES ACROSS TEXAS. THIS SYSTEM WILL BE FOLLOWED BY A COLDER

AIR MASS EARLY NEXT WEEK. LIKED HOW THE NAM HANDLED THE FIRST

COUPLE OF DAYS AND THEN PREFERRED THE SLIGHTLY SLOWER ECMWF FOR

THE WEEKEND SYSTEM AND FOR THE COLD AIR OUTBREAK FOR EARLY NEXT

WEEK.

THE MAIN ITEM OF CONCERN FOR TODAY WILL BE THE FOG AND DRIZZLE

OCCURRING FROM THE DEPARTING SYSTEM. MAY NEED TO ISSUE A DENSE FOG

ADVISORY LATER THIS MORNING. FOR NOW THE FOG HAS BEEN PATCHY DENSE

IN ISOLATED SPOTS. AS NORTHERLY WINDS DEVELOP LATER...THE FOG AND

DRIZZLE IS EXPECTED TO END IN THE MID TO LATE MORNING PERIOD.

THURSDAY AND FRIDAY ARE EXPECTED TO BE NICE FAIR WEATHER DAYS. ON

FRIDAY SOUTHWESTERLY WINDS AT THE SURFACE SHOULD HELP WARM THE

DAYTIME HIGH TEMPERATURES TO NEAR 70.

OVER THE WEEKEND...THE STRONG UPPER TROUGH IS SETTING UP A PATTERN

FOR WIDESPREAD RAIN AND THUNDERSTORMS OVER SE TX. STILL NOT

CONFIDENT ON THE TIMING GIVEN THE DIFFERENT MODEL SOLUTIONS BUT

FOR NOW THINK THAT THE BEST RAIN CHANCES WILL BE LATE SATURDAY

AFTERNOON THROUGH SATURDAY NIGHT. THERE WILL POSSIBLY BE A SEVERE

WEATHER THREAT WITH A NEGATIVE TILTED UPPER TROUGH...STRONG

DIFFLUENCE COUPLED WITH A FAVORABLE REGION OF THE UPPER JET...AND

FAVORABLE LOW-LEVEL FLOW.

FOLLOWING THIS STORM SYSTEM...THE ECMWF MOVES AN ARCTIC AIR MASS

INTO THE PLAINS TUESDAY. SE TX LOOKS TO BE ON THE EDGE OF THE COLD

AIR WITH THE ECMWF COLDER THAN THE GFS. HOWEVER...THE MODEL HAS

BACKED OFF A BIT AND MODIFIED THE SYSTEM WARMER. FOR NOW WILL GO

WITH A BLEND OF THE ECMWF OUTPUT...THE MEX...AND THE ENSEMBLE

MEAN FOR TEMPERATURES MONDAY AND TUESDAY.

Dallas/Ft Worth:

.EXTENDED/COLD WX NEXT WEEK...

CONFIDENCE REMAINS HIGH THAT MUCH OF THE CONTINENTAL US WILL SEE

TEMPERATURES WELL BELOW NORMAL FOR MUCH OF NEXT WEEK AND THERE

HAS BEEN MUCH DISCUSSION AS TO WHETHER OR NOT IT WILL GET AS COLD AS

SOME OF THE MORE SEVERE ARCTIC INTRUSIONS OF YEARS PAST. LATEST

GLOBAL MODEL GUIDANCE CONTINUES TO SHOW EXPECTED OSCILLATIONS WITHIN

THE OVERALL UPPER AIR PATTERN BUT THE GENERAL CONSENSUS IS THAT

RIDGING OVER ALASKA WILL BUILD SUFFICIENTLY STRONG AND BECOME

PARTIALLY BLOCKED AS TO ALLOW A MASSIVE CHUNK OF COLD AIR TO HEAD

SOUTH INTO THE CONTINENTAL US. THE FIRST SHOT OF THIS COLD AIR WILL

MOVE RAPIDLY INTO NORTH TEXAS EARLY MONDAY WITH STRONG NORTHERLY

WINDS AND SHARPLY COLDER TEMPERATURES. AS WE HEAD THROUGH NEXT WEEK

HOWEVER...THERE ARE SOME CONCERNS AS TO WHETHER THE OVERALL PATTERN

WILL REMAIN FAVORABLE FOR CONTINUED SURGES OF COLD AIR.

EXTENSIVE ANALYSIS OF ARCHIVED UPPER AIR DATA FROM PREVIOUS RECORD

BREAKING COLD EVENTS INCLUDING THE SEVERE COLD SNAPS OF 1983 AND

1989 YIELD A COUPLE OF INTERESTING DETAILS. THE MOST SIGNIFICANT

ARE THE TEMPERATURES AT THE SOURCE OF BITTERLY COLD AIR.

GENERALLY... ARCTIC INTRUSIONS INTO NORTH TEXAS BEGIN WITH EXTREMELY

COLD AIR PARCELS WITHIN THE 800 TO 500MB LAYER LOCATED OVER

NORTHWEST/ NORTH-CENTRAL CANADA. THESE PARCELS WILL GRADUALLY

SUBSIDE AND WARM AS THEY HEAD SOUTH BUT ARE USUALLY STILL VERY COLD

BY THE TIME THEY REACH THE SURFACE. IN AT LEAST A HALF-DOZEN MAJOR

COLD SNAPS INCLUDING 1983/1989/1996...THE 500MB TEMPS ACROSS

NORTHWEST CANADA WERE TYPICALLY IN THE -45 TO -50C RANGE...AND 700MB

TEMPS WERE TYPICALLY IN THE -30 TO -35C RANGE. THE RECORD COLD OF

1983 HAD A SAMPLED 500MB TEMP OF -50C IN NORTHERN MONTANA. AS OF

NOW...NEITHER THE GFS NOR THE ECMWF HAS TEMPERATURES THAT COLD

ACROSS CANADA. PROGGED 850MB TEMPS ACROSS NORTH TEXAS ARE IN THE

-10 TO -15C RANGE WHICH DEFINITELY SUPPORTS COLD TEMPERATURES AT THE

SURFACE...HOWEVER IN THE EXTREME EVENTS...H85 TEMPS WERE IN THE -17

TO -20C RANGE WITH A FRIGID -24C AT OKC IN 1983. GIVEN THE FORECAST

TEMPERATURES THROUGH NEXT WEEK...CONFIDENCE IS INCREASING THAT THIS

WILL NOT BE HISTORICALLY COLD ACROSS NORTH TEXAS. OF COURSE THIS

ASSUMES A PERFECT PROG OF THE MODEL TEMPERATURES. THE OTHER CONCERN

IS THE POSITION OF THE UPPER RIDGE OVER ALASKA. THE LATEST RUNS

CONTINUE TO BUILD AN ANOMALOUSLY STRONG RIDGE OVER AK THEN HAVE HAD

SOME TROUBLE AS TO WHETHER IS WILL MOVE NORTH OR WEST INTO SIBERIA.

THIS RIDGE POSITION HAS IMPLICATIONS ON THE UPPER PATTERN OVER THE

WESTERN US. TYPICALLY WE LIKE TO SEE A STRONG TROF POSITIONED OVER

THE WEST/SW US WHICH DOES NOT MOVE TO KEEP THE COLD AIR FLOWING

SOUTHWARD. THESE MODEL DISCREPANCIES ARE EXPECTED IN THE 10-15 DAY

PERIOD AND WILL CONTINUE TO BE MONITORED.

AS OF NOW WE WILL CONTINUE TO SHOW THE STRONG FRONT ON MONDAY/END OF

THE CURRENT FORECAST PERIOD/ AND WILL INTRODUCE HIGH TEMPERATURES IN

THE UPPER 20S/LOWER 30S FOR TUESDAY THROUGH THE END OF NEXT WEEK.

OVERNIGHT LOWS WILL GENERALLY BE IN THE LOWER TEENS AND LOWER 20S.

IT SHOULD BE STRESSED THAT CONSIDERABLE DISCREPANCIES WITHIN THE

FINER DETAILS EXIST THIS FAR OUT AMONG NOT ONLY THE OPERATIONAL

GUIDANCE BUT AMONG THE INDIVIDUAL ENSEMBLE MEMBERS. SEVERAL

ENSEMBLE MEMBERS TO INDICATE A FAVORABLE RIDGE/TROF POSITION THROUGH

NEXT WEEK AND KEEP THE COLD AIR COMING SO IT WILL BE NECESSARY TO

FINE TUNE TEMPERATURE FORECASTS THROUGH NEXT WEEK. WHAT MAKES THIS

SYSTEM SIGNIFICANT IS THE POTENTIAL FOR THERE TO BE AN EXTENDED

PERIOD OF VERY COLD TEMPERATURES ACROSS THE REGION. IT IS THE

DURATION OF SUB-FREEZING AIR THAT CAN HAVE SERIOUS IMPACTS TO THE

REGION VERSUS JUST THE TEMPERATURES THEMSELVES.

CONCERNING PRECIPITATION POTENTIAL...LATEST 12Z ECMWF DOES SHOW AN

AREA OF QPF ALONG THE FRONT ON MONDAY LIKELY IN AN AREA OF STRONG

FRONTOGENETIC FORCING SQUEEZING OUT ANY AVAILABLE MOISTURE. TEMPS

ARE SUFFICIENTLY COLD FOR SNOW...BUT IT IS THE ONLY MODEL DOING SO

WITH SUCH VIGOR ATTM. BEING 7 DAYS OUT...WILL LEAVE THE 10 POPS IN

AND SEE IF THIS TREND CONTINUES. INTO NEXT WEEK...WITH TEMPS SO

COLD ANY MOISTURE COULD CREATE WINTRY PRECIPITATION BUT AS OF NOW IT

APPEARS THAT THINGS WILL BE VERY DRY. THESE DETAILS WILL BE WORKED

OUT OVER THE NEXT SEVERAL DAYS.

San Angelo:

.LONG TERM...

THE PRIMARY FOCUS IN THE LONG TERM PORTION OF THE FORECAST IS THE

TIMING AND INTENSITY OF THE COLD AIR THAT IS FORECAST TO IMPACT MUCH

OF THE CONUS EARLY NEXT WEEK. HOWEVER...THERE ARE A FEW INTERESTING

DAYS BETWEEN NOW AND THEN. TRANSIENT WAVES IN THE ACTIVE NORTHWEST

FLOW ALOFT WILL BRING WEAK SURFACE BOUNDARIES INTO WEST CENTRAL TX

THURSDAY AND FRIDAY YET WX CONDITIONS WILL REMAIN PLEASANT BOTH

DAYS. THURSDAY WILL BE THE COOLER OF THE TWO WITH HIGHS RANGING FROM

THE UPPER 50S ALONG THE I-20 CORRIDOR TO THE LOW/MID 60S TO THE

SOUTH. ON FRIDAY...MOST AREAS SHOULD CLIMB INTO THE MID 60S WITH A

FEW 70S POSSIBLE ALONG AND SOUTH OF THE CONCHO RIVER.

MID/HIGH CLOUDS WILL BE ON THE INCREASE BY THE END OF THE WORK WEEK

AS THE QUASI STATIONARY UPPER LOW SPINNING OF THE CA COAST

APPROACHES. THIS FEATURE WILL BE ACCOMPANIED BY STRONG LARGE SCALE

FORCING AS IT MOVES ACROSS TX. SOUTH WINDS FRIDAY NIGHT AND SATURDAY

WILL ADVECT LOW LEVEL MOISTURE INTO THE CWA SETTING THE STAGE FOR

DECENT RAIN CHANCES. THE STRONG QG FORCING APPEARS TO BE CENTERED

AROUND 00Z SUNDAY WITH THE STRONGEST LOW LEVEL CONVERGENCE ACROSS

THE EASTERN HALF OF THE AREA. THUS...POPS ARE HIGHEST HERE WITH

50/60 POPS ACROSS THE HEARTLAND. ABUNDANT CLOUD COVER AND COOL

EASTERLY WINDS WILL KEEP HIGHS RATHER COOL ON SATURDAY. MAX TEMPS

WERE LOWERED TO THE MID/UPPER 50S ACROSS MUCH OF THE CWA. PRECIP

CHANCES CONTINUE AREAWIDE THROUGH SATURDAY NIGHT AS THE LOW MOVES

ACROSS THE REGION. ON SUNDAY...POPS WERE INCLUDED NORTHEAST OF A

LINE FROM JAYTON...TO ABILENE...TO BROWNWOOD. THIS WOULD BE MORE A

STRATIFORM LIGHT RAIN ASSOCIATED WITH THE WRAP AROUND REGION OF THE

DEPARTING LOW. TEMPS ON SUNDAY HAVE ALSO BEEN LOWERED AS SURFACE

EAST TO NORTHEAST WINDS SHOULD KEEP CLOUDS IN PLACE IN CONJUNCTION

WITH LOW LEVEL COLD ADVECTION. NOW TO THE TOUGH PART OF THE

FORECAST...

THE MEDIUM RANGE MODELS HAVE BACKED OFF SLIGHTLY ON THE SPEED OF THE

INEVITABLE ARCTIC INTRUSION AND CONTINUE TO WAFFLE BACK AND FORTH ON

ITS INTENSITY. THE 05/00Z GFS NOW DELAYS THE COLD FRONT UNTIL MONDAY

NIGHT WHILE THE ECMWF IS ABOUT 12 HOURS FASTER...BRINGING THE FRONT

THROUGH MUCH OF THE AREA BY 18Z MONDAY. THE DGEX IS FASTER STILL BUT

IN MY OPINION REMAINS TOO SLOW. MY CONCERN IS THE UPPER LOW THAT IS

PROGGED TO TRAVERSE THE REGION OVER THE WEEKEND WILL ALLOW THE COLD

AIR TO RUSH SOUTH FASTER THAN EXPECTED. THE TRUE ARCTIC AIR MAY BE

SLIGHTLY DELAYED BUT COOLER TEMPS ARE ANTICIPATED EARLIER RATHER

THAN LATER. SURFACE PRESSURE FALLS AHEAD OF THE AFOREMENTIONED

UPPER JUXTAPOSED WITH THE BAROCLINICITY ALONG THE TX COAST ARE

EXPECTED TO PRODUCE A COASTAL TROF THIS WEEKEND WITH NORTHEAST

WINDS DEVELOPING ACROSS MUCH OF THE STATE. THE COLD AIR IS PROGGED

TO BE AS FAR SOUTH AS THE ARKLATEX REGION BY SUNDAY AFTERNOON. MY

THINKING IS AS THE NORTHEAST WINDS OVERSPREAD THE AREA...THE

EFFECTIVE COLD FRONT WILL BACKDOOR INTO THE AREA SUNDAY NIGHT WITH

EVEN COLDER AIR ARRIVING DURING THE DAY ON MONDAY. I ADDED A

SLIGHT CHANCE OF SNOW NORTH OF I-20 FOR MONDAY AS LARGE SCALE LIFT

SPREADS ACROSS THE SOUTHERN PLAINS BUT AT THIS TIME I DO NOT THINK

IT WILL AMOUNT TO MUCH. TEMPS ON MONDAY ARE EXPECTED TO TOP OUT IN

THE 30S ACROSS THE BIG COUNTRY WITH HIGHS NEAR 50 IN THE SOUTH. AS

MENTIONED YESTERDAY...THESE HIGHS TEMPS COULD BE RATHER GENEROUS

IF THE FRONT DOES INDEED ARRIVE EARLY. HIGHS TUESDAY IN THE WAKE

OF THIS FRONT MAY STRUGGLE TO REACH FREEZING ACROSS PORTIONS OF

THE AREA WITH THE SOUTHERN ZONES EXPECTED TO SEE MID/UPPER 30S

FOR HIGHS.

THE BLOCKING HIGH IS PROGGED TO REMAIN ENTRENCHED OVER AK THROUGH

MUCH OF NEXT WEEK. THIS MEANS THE PATTERN SHOULD CHANCE LITTLE WITH

MUCH COLDER THAN NORMAL CONDITIONS EXPECTED THROUGH MUCH OF THE

WEEK. THE GFS DEVELOPS A LEE CYCLONE BY MIDWEEK THAT SCOURS OUT THE

COLD DOME OVER WEST CENTRAL TX BY WEDNESDAY NIGHT AND THURSDAY BUT

THE WAVE ASSOCIATED WITH THIS CYCLONE LOOKS RATHER WEEK. IT WOULD

TAKE A QUITE STRONG SHORTWAVE TO ERODE THIS AIRMASS THAT QUICKLY.

Norman, OK:

SOME WINTRY

PRECIP WILL BE POSSIBLE SATURDAY NIGHT AS THE COLD AIR MOVES SETTLES

INTO THE REGION. MODELS THEN SHOW ANOTHER SHORTWAVE/DISTURBANCE

APPROACHING FROM THE NORTH MOVING ACROSS THE PLAINS LATE SUNDAY INTO

EARLY NEXT WEEK. THIS WILL BRING ANOTHER ROUND OF COLD ARCTIC AIR

INTO THE REGION. PRECIP CHANCES WILL CONT SUNDAY INTO EARLY NEXT

WEEK BUT THE BEST CHANCE FOR PRECIPITATION WITH THIS SECOND SYSTEM

WILL BE SUNDAY NIGHT INTO MONDAY NIGHT WITH MOST OF THE PRECIP

LIKELY FALLING IN THE FORM OF SNOW. THE COLD CONDITIONS WILL PERSIST

THROUGH AT LEAST WEDNESDAY. ANOTHER CHANGE IS THAT THE MODELS ARE

NOW SHOWING THAT THE SFC HIGH AND COLD AIR MAY BEGIN TO SHIFT EAST

CAUSING A SLIGHT WARM UP LATE NEXT WEEK. HOWEVER... BEFORE THAT

HAPPENS TEMPERATURES IN SOME LOCATIONS MAY NOT CLIMB ABOVE FREEZING

FOR SEVERAL DAYS NEXT WEEK.

Dodge City:

DAYS 3-7...

THE EXTENDED FORECAST IS A BIT MORE CHALLENGING AS THE MODELS, WHICH

HAVE BEEN REASONABLY CONSISTENT IN THE LAST FEW DAYS ARE NOW IN MORE

DISAGREEMENT. THE 00Z GFS SEEMS LIKE AN OUTLIER COMPARED TO THE 00Z

GEM AND 00Z ECWMF AS IT SLOWS THE ARCTIC FRONT PASSAGE CONSIDERABLY.

THIS RESULTS IN 5 TO 10 DEGREE TEMPERATURE CHANGE IN THE FORECAST.

CONSIDERED THIS IS A MODEL PERTURBATION AND DID NOT MAKE THIS

DRASTIC CHANGE. AS A RESULT, LEFT TEMPERATURES AS IS. I DID MAKE A

FEW CHANGES TO POPS TO GET US MORE IN COORDINATION WITH SURROUNDING

WFOS AND THE NEW GUIDANCE SUGGESTS THAT THE SOUTHERN SHORTWAVE

TROUGH WILL HAVE LESS OF AN IMPACT TO KANSAS AND WILL REMAIN SOUTH

INTO OKLAHOMA AND TEXAS ON SATURDAY. WHAT WILL GIVE US A FAIRLY GOOD

CHANCE AT PRECIPITATION IS THE SHORTWAVE TROUGH DIVING ACROSS THE

ROCKIES SUNDAY. HAVE LOW BALLED QPF AND SNOW AMOUNTS IN THE GRIDS

SINCE THIS IS FAR OFF IN THE EXTENDED, HOWEVER, THIS COULD BE A SNOW

ADVISORY AMOUNT EVENT AS BOTH THE GFS AND ECMWF INDICATE DECENT SNOW

AMOUNTS. WE WILL BE IN THE LEFT EXIT REGION OF A 250 HPA JET SO

THERE WILL BE PLENTY OF DYNAMICS AND LIFT TO GENERATE SIGNIFICANT

PRECIPITATION AMOUNTS. THIS IS SOMETHING THAT WILL HAVE TO BE

WATCHED. BREEZY NORTHERLY WINDS WILL ALSO PRODUCE NEGATIVE WIND

CHILLS IN THE EXTENDED, AND PROBABLY WILL NEED A WIND CHILL ADVISORY AT

SOME POINT AS WELL.

Lubbock:

.LONG TERM...

LITTLE CHANGES WERE MADE TO THE LONG TERM FORECAST AS ARCTIC AIR

BLAST CONFIDENCE IS INCREASING FOR NEXT WEEK. A WEAK SHORT WAVE WILL

TRANSVERSE THE AREA TOMORROW AFTERNOON AND EVENING.

HOWEVER...MOISTURE IS VERY LIMITED AND THERE IS LITTLE TO NO LIFT

BEING GENERATED FROM THIS DISTURBANCE. THERE WILL BE A BRIEF PERIOD

OF SHORT WAVE RIDGING ON FRIDAY BEFORE THE NEXT DISTURBANCE BEGINS

TO AFFECT THE AREA. A CLOSED LOW THAT HAS BEEN PARKED OFF THE

CALIFORNIA COAST WILL MOVE ON SHORE FRIDAY AND MOVE ACROSS THE

DESERT SOUTHWEST. ALL MODELS GENERALLY DEPICT THIS SYSTEM OPENING UP

BEFORE IT MOVES OVER THE AREA THOUGH THERE IS STILL SOME DEGREE OF

UNCERTAINTY OF HOW STRONG THE WAVE WILL BE ONCE IT REACHES WEST

TEXAS. MODELS RANGE FROM THE NAM BEING THE LEAST OPTIMISTIC FOR QPF

WHILE THE LATEST ECM RUN DEPICTS A STRONGER AND SHARPER WAVE.

PRECIPITATION TYPE IS EXPECTED TO BE MOSTLY IN LIQUID FORM ON

SATURDAY. HOWEVER...IF PRECIPITATION WERE TO PERSIST LONG ENOUGH

INTO THE EVENING THERE COULD BE A CHANGE OVER TO SNOW OR A WINTRY

MIX WITH COLDER AIR FILTERING INTO THE REGION. ANOTHER SYSTEM IS

EXPECTED TO DIVE DOWN FROM THE PACIFIC NORTHWEST WITH LIFT

SKIRTING OUR NORTHERN AREAS. STILL BELIEVE A SLIGHT CHANCE IS

WARRANTED FROM THIS SYSTEM ON MONDAY.

SURFACE RIDGING IS NOW PROGGED TO BEGIN BUILDING INTO THE AREA ON

SATURDAY WITH GENERALLY EASTERLY UPSLOPE FLOW PERSISTING ALL OF

NEXT WEEK. THE STRONGER COLD AIR PUSH WILL BE FROM A FRONTAL

PASSAGE ON SUNDAY EVENING. A 1040MB SURFACE HIGH WILL SPREAD

ACROSS THE CENTRAL PLAINS INTO AT LEAST THE MIDDLE OF NEXT WEEK

ALLOWING FOR A PERIOD OF SIGNIFICANT COLDER TEMPERATURES.

ADDITIONALLY...LOW LEVEL MOISTURE WILL BE ABUNDANT IN THE UPSLOPE

FLOW KEEPING CONDITIONS CLOUDY FOR SEVERAL DAYS.

Shreveport:

THE EXTENDED PACKAGE HAS DONE A SIGNIFICANT COOL DONE AS WE MOVE

INTO THE WEEKEND AND EARLY NEXT WEEK. MODELS ARE STILL BOLD ON

RAIN FORECAST THIS WEEKEND...WITH THE HEAVIEST RAIN FALLING

SATURDAY NIGHT. I DID NOT PLACE THIS IN THE FORECAST...BUT I

WOULD NOT BE SURPRISED IF WE SEE SOME SLEET MIXED IN WITH THE RAIN

SATURDAY NIGHT...ESPECIALLY IN THE I30 CORRIDOR AND NORTHWARD

WHERE WE WILL SEE TEMPS FALL INTO THE MID 30S OVERNIGHT.

AS WE MOVE INTO THE NEXT WORK WEEK TEMPS WILL BE VERY COLD...AS A

STRONG ARCTIC RIDGE SURGES INTO THE HEART OF THE COUNTRY. AND

DEPENDING ON MOISTURE WE COULD SEE SOME SNOW IN THE TUESDAY/WEDNESDAY

TIME FRAME. GUIDANCE POP NUMBERS ARE STILL LOW ATTM...SO HELD OFF

ON MENTIONING IN THE FORECAST PACKAGE UNTIL I SEE MORE CONFIDENT

NUMBERS

Midland/Odessa:

MONDAY...ANOTHER SHORTWAVE WILL DIVE INTO THE CENTRAL

PLAINS...DROPPING A MODIFIED ARCTIC FRONT INTO THE REGION MONDAY

NIGHT...FOR WELL-BELOW NORMAL TEMPS INTO THE EXTENDED. LONG RANGE

MODELS ADVERTISE GOOD ISENTROPIC UPGLIDE AS THE FRONT MOVES

THRU...KEEPING THE AREA SOCKED IN THRU WEDNESDAY. GUIDANCE LOOKS

TOO WARM FOR THIS SCENARIO...SO WE/LL STAY WELL BELOW MACHINE

NUMBERS FROM MONDAY ONWARD.

Austin/San Antonio:

AN ARCTIC OUTBREAK IS EXPECTED EARLY NEXT WEEK FOR SOUTH CENTRAL TEXAS.

A DENSE ARCTIC AIRMASS WILL MOVE SOUTHWARD AND ENTER TEXAS ON MONDAY.

THIS AIRMASS WILL OVERSPREAD SOUTH CENTRAL TEXAS MONDAY NIGHT AND WILL

REMAIN ENTRENCHED ACROSS OUR REGION THROUGH WEDNESDAY OF NEXT WEEK.

THIS WILL BE A DRY SYSTEM. THE GFS MOS GUIDANCE FOR MONDAY NIGHT

THROUGH TUESDAY NIGHT IS AROUND 10 DEGREES TOO WARM. THE GFS

TRADITIONALLY HAS A HARD TIME WILL SHALLOW ARCTIC OUTBREAKS ACROSS

TEXAS DUE TO THE MODELS POOR RESOLUTION IN THE LOWER LEVELS.

Corpus Christi:

LATEST MEDIUM RANGE MODELS SHOW MORE IN THE WAY OF

COOLING BEHIND THE FRONT THAT MOVES THROUGH BEHIND THIS SYSTEM AND

DROPPED EXPECTED MAX TEMPS QUITE A BIT FOR SUNDAY AS HIGH PRESSURE

NOSES INTO THE REGION. MODELS ALSO SHOW THAT HIGH PRESSURE WILL

BE BUILDING INTO THE AREA AS A PIECE OF THE ARCTIC AIRMASS COULD

BE INTO THE REGION BY MONDAY. SHOWED A TREND FOR SLIGHT COOLING

FROM SUNDAY. THEN THE ARCTIC AIRMASS ARRIVES MONDAY NIGHT ALONG

WITH POST FRONTAL CLOUDINESS. COULD SEE SOME THINNING OF THE

CLOUDS OVER THE COASTAL AREAS TUESDAY BUT IT WILL STILL BE COLD

FOR THE AREA WITH READINGS NOT EXPECTED TO MAKE IT OUT OF THE 40S.

Brownsville:

.LONG TERM...6 PM THURSDAY THROUGH TUESDAY...A WEST COAST MID

LEVEL CLOSED LOW WILL OPEN UP AND WILL MOVE ACROSS TX ON SAT AND

SAT NIGHT INCREASING POPS A BIT. MOST OF THE DEEPER MOISTURE WILL

REMAIN POOLED TO THE NORTH OF DEEP SOUTH TX AND WILL ACCORDINGLY

MAINTAIN ONLY SOME 20 TO 30 % POPS FOR SAT AND SAT NIGHT WITH THE

PASSAGE OF THE TROUGH AXIS. AFTER THIS TROUGH EXITS THE REGION

BROAD MID LEVEL TROFFING WILL PREVAIL OVER THE NORTH CENTRAL AND

NORTHEASTERN PORTIONS OF THE LOWER 48 STATES. THIS WILL USHER

THROUGH A FAIRLY COLD CANADIAN AIRMASS LATE IN THE FORECAST

PERIOD RESULTING IN A PRETTY DRASTIC DROP IN TEMPS NEXT TUES.

MODEL TO MODEL AGREEMENT BETWEEN THE GFS AND THE ECMWF IN THE 3 TO

7 DAY RANGE LOOKS REASAONABLE AT THE 500 MB LEVEL. RUN TO RUN

CONSISTENCY WITH THE GFS MEX MOS LOOKS GOOD AND WILL GO CLOSE TO

THE LATEST MEX RUN THROUGH MON AND WILL GO BELOW MEX GUIDANCE ON

TUES AFTER THE FRONT.

[Srain]

E-mail from Jeff. We may need to start focusing on a severe weather event this weekend and not get too far ahead of ourselves regarding the colder air...

Dense fog blankets much of the area this morning behind the departing short wave from last night. Visibilities are running anywhere from 2 miles to 1/8th of a mile at most locations. Warm front is located along a line from Lake Charles to BUSH IAH to Victoria. Dense fog is widespread north of this boundary and then along the coast where sea fog is forming over the nearshore waters and bays. Surface wave over SE TX should progress eastward this morning allowing NW winds to develop and helping to clear out the drizzle and fog by late morning. A few showers are also noted on radar this morning over the coastal counties and these should be moving offshore and east of the area by mid morning.

Dry and seasonable weather for Thursday and Friday with lows in the 30’s and highs in the upper 60’s to near 70 by Friday.

Next big change arrives this weekend as the current cut-off low off of southern CA gets picked up by a trough moving into the Pacific NW and is then drug eastward across TX. Still dealing with model timing differences with this system, but looks like Saturday night into Sunday morning the area will be under the gun for widespread rainfall and possibly severe weather. Strong upper forcing from the upper level trough will develop surface low pressure late Saturday near Big Bend which will move ENE across TX Saturday night. A strong 35-40kt low level jet develops over the coastal bend Saturday afternoon transporting deep moisture northward into the region. Warm front will back northward toward the coast and likely move inland over SE TX allowing an unstable Gulf air mass to arrive just prior to the strong dynamics aloft. Numerous showers/thunderstorms are expected from Saturday afternoon/evening into Sunday morning. There is a threat for severe weather along and south of the warm front…so its position will be important come Saturday evening. With a strong low level jet below a 120kt mid level jet streak…there will be lots of wind energy that could be transported to the surface in downdrafts so severe winds look most likely, but would not rule out a few tornadoes if enough instability is available. Favorable backed wind profiles in the lower levels may help enhance this risk near/along the warm frontal boundary.

Next Week:

Models have backed off on the strong arctic air event for next week in their 00Z and 06Z runs, but will not fully bite on this downplaying of the event. Models typically have a very hard time resolving these outbreaks due to their shallow nature east of the Rocky mountains and it is more surprising how much agreement they have had over the past 2-3 days on this event. With that said, all models do continue to show a favorable delivery pattern for arctic air to enter the US Saturday and reach the southern plains by Sunday. 1048mb high is progged just north of the Montana border early next week with 1040mb pressures building into WC TX by Tuesday. Note that these pressures are about 10mb lower than what we were looking at 2 days ago suggesting the intensity of the arctic high may not be as strong. Passing weekend southern plains/TX storm system should help grab the shallow arctic air mass over the central plains and sling it rapidly southward on Sunday. Will toss out the model guidance for Monday in favor of the arctic air mass pushing southward under its own density and arriving to the TX coast by Monday afternoon/evening. Typically once these air masses get moving there is little to stop them. Will need to undercut the GFS guidance from Tuesday onward by at least 10 degrees on the afternoon highs as the model is just not grasping this air mass today as in previous runs. Will go with highs in the 40’s on Tuesday under strong cold air advection and then highs in the 30’s on Wednesday as the arctic dome becomes fully entrenched. Not sure how much clearing will take place behind the front as there does look to be a period of post frontal low stratus and this will help temper the overnight lows…so low 30’s on Tuesday morning to upper 20’s on Wednesday morning. Should clouds clear out…overnight lows will be about 5-8 degrees colder.

GFS attempts to completely erode the arctic dome by Thursday and Friday of next week as it spins up low pressure in the lee of the Rockies inducing southerly flow over TX. Once in place arctic cold domes are hard to dislodge, and suspect the model is moving the cold air too quickly eastward. GFS then crashes a secondary surge down the plains next weekend arriving around the 16/17 of the month.

As mentioned before we are not looking at anything historic or record breaking from this pending event, but a prolonged period of well below normal cold with potential for hard freezes over multiple days still looks likely. It remains questionable on how intense this outbreak may be and how long it will last. Stay tuned.

[bubba hotep]

Little bit of freezing Fog/Mist around here this morning. Was surprised when I turned on the wipers this morning and they stuck and then skipped across an iced over windshield.

[wxmx]

As the NWS's discussions posted by Steve state, it looks like we are looking at nothing historical, but a week or so of really low temps. A bit of a let down for me, since this far south I need historical to get interesting weather. Block is strong, but looks like it's too far N and W...probably would need it closer to the AK/Can border, not over the Bering strait.

On the bright side, there's potential for some stratospheric warming and the MJO forecasts have changed a bit:

[Srain]

Shall we hug the Canadian, Jorge? 1065mb in AK and fropa beyond Veracruz...