Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 5

[1900hurricane]

If FWD is willing to mention a possible event that is beyond the current forecast period, it's time to start paying attention.

[1900hurricane]

Also from FWD:

 

 

Could be we looking at another shot of arctic air across North Texas? Many of the long-range forecast models are hinting at this, so this graphic depicts the possibilities. Two upper level low pressure systems may be responsible for sending arctic air our way in the 8-14 day portion of the forecast. The first, labeled L1, is currently over Alaska. This upper low is expected to move away from Alaska and send cold air our way December 20th or 21st. It will send some of the cold Alaska and northern Canada air south into the plains. How cold we'll get and how long it will last will depend at least partially on how far south it moves. If it takes a southerly track, we can expect at least a few days of temperatures well below normal late next week. The secondary upper low, labeled L2, is what may bring a reinforcing shot of arctic air into the United States. If this secondary upper low moves south, over the western United States, it will likely send some very cold Siberian air into the central U.S., but this would not happen until just before Christmas, if it happens at all. While models indicate we'll get colder late next week, there is not very good agreement on the track and strength of the cold air associated with L2. If L2 takes the southern track depicted with the white 2. in the image, it will send a reinforcing shot of very cold air south on December 22nd or 23. If it just circles around the Arctic Circle, as depicted by the white 1. in the image, it will have very little to no impact on temperatures across North Texas. We'll be watching these systems closely over the next several days. Keep in mind a LOT can change between now and then, 8-14 day forecasts typically change dramatically before models come to a consensus solutions.

[Quixotic1]

I like FWD AFD. They take a lot of time to educate. I learned something new the other night about super cooled droplets needing particles to become solid, thanks to them.

[bubba hotep]

Also from FWD:

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FWD doing Work! I've never seen them focus on a long range event like this. Typically they may mention it and then say something like, "but it is beyond this forecast package" or what not. I am really liking the snow pack that is in place, this could be one for the record books.

[DFWWeather]

FWD doing Work! I've never seen them focus on a long range event like this. Typically they may mention it and then say something like, "but it is beyond this forecast package" or what not. I am really liking the snow pack that is in place, this could be one for the record books.

 

They are mentioning it ahead of time for a couple reasons. One being it is Christmas week and a major travel period. The second being that this setup has the potential of delivering dangerous (by our standards anyway) cold to much of Texas. The upper air pattern is quite similar to December 1983/1989. Cold air outbreaks like this near the winter solstice tend to be some of the worst. In addition, one of the most expansive snowpacks in years exists between us and the cold giving very little room for airmass modification, especially on a favorable setup for a fast delivery. For what its worth, I don't think this event will have any significant wintry precipitation associated with it. It will be remembered for the cold. It will be dry with a very suppressed storm track, even for our area. It also has the markings of a protracted event with a possible second and even third cold air surge lasting well into Christmas week. It is the second cold air surge, on or after the 23rd, that has everyone concerned as it has the potential to unleash a direct discharge of a Siberian airmass. Models forecasting ridges in Alaska 580+ heights in the upper levels (which all three are showing ECMWF, Canadian, GFS) have been associated with some of our coldest air outbreaks.

[wxmx]

Yes, the potential is there for a series of severe cold air discharges. Like 1989, there was continuous cold from the latest days of Nov and all December...unlike it, the axis of cold is further West, going thru the heart of the CONUS this time. 1989 and 1983 had the most severe and expansive cold in the last 50 years for our neck of the woods, and even though it has been pretty cold, we have not at those years level....yet. Nothing a 1060mb+ high in Montana can't fix.

[DFWWeather]

Yikes folks...there is nothing warm about this pattern and it continues today on the 12z runs of the ECMWF, GFS, and CMC:

 

[bubba hotep]

It looks like the models are trending more towards a glancing blow with the cold and not dumping the core of the coldest air down the spine of the Rockies.  However, the individual members of the ensembles are still all over the place.  We will probably see a different solution out of the operationals tomorrow lol

[wxmx]

It looks like the models are trending more towards a glancing blow with the cold and not dumping the core of the coldest air down the spine of the Rockies.  However, the individual members of the ensembles are still all over the place.  We will probably see a different solution out of the operationals tomorrow lol

Models are still having difficulties, which is reasonable at this time lead. 18z GFS had a more SW-NE orientated ridge near the GoA, while the latest 0z has a more N-S ridge. At this moment the 0z is still running, but I'm sure it will be colder farther south.

[Srain]

Yes, the potential is there for a series of severe cold air discharges. Like 1989, there was continuous cold from the latest days of Nov and all December...unlike it, the axis of cold is further West, going thru the heart of the CONUS this time. 1989 and 1983 had the most severe and expansive cold in the last 50 years for our neck of the woods, and even though it has been pretty cold, we have not at those years level....yet. Nothing a 1060mb+ high in Montana can't fix.

Models are still having difficulties, which is reasonable at this time lead. 18z GFS had a more SW-NE orientated ridge near the GoA, while the latest 0z has a more N-S ridge. At this moment the 0z is still running, but I'm sure it will be colder farther south.

Heh...

[Srain]

Morning Update from Meteorologist Jeff L (Harris County Flood Control District):

 

Old arctic high pressure cell that has been around for over a week now is finally beginning to erode and move eastward this morning.

 

A storm system over the SW US will eject into TX today and with increasing low level moisture off the western Gulf of Mexico expect to see light rain develop and increase fairly quickly after noon from west to east across the region. Surface warm front over the northern Gulf waters will move northward and may reach the coastal counties from Victoria to High Island this evening allowing 60 degree dewpoints to push over the “chilled” nearshore waters in the upper 40’s. This will potential create a dense sea fog bank right along the coast. Most areas will hold in the 50’s yet again today, but a few coastal locations could push above 60 if the warm front passes onshore. Rain chances should end fairly quickly late tonight as moisture is swept eastward by the storm system and the next cold front pushes across the region. Rainfall amounts will average generally less than .25 of an inch south of I-10 and .25 to.50 of an inch north of I-10.  

 

Front will move offshore on Saturday with cold air advection returning. Moisture looks to become trapped in the lower levels and this may result in clouds linger much of the day on Saturday and possibly into Sunday morning as many times it is hard to scour out that frontal inversion saturation level. Temperatures will fall back into the 50’s both Saturday and Sunday with lows by Monday morning under clear skies, calm winds, and low dewpoints falling to near freezing.

 

A longer term warm up begins by Tuesday of next week as established southerly winds return to the region with lows climbing into the 50’s by late next week and highs possibly pushing the mid to upper 70’s. Will likely see a sea fog threat return at some point after Tuesday as dewpoints begin to rise above nearshore water temperatures once again…something we will be dealing with for weeks to come with such cold nearshore temperatures.

 

Dec 21-26:

Upper air pattern will undergo significant amplification along the US west coast with upper level high pressure building northward deep into Alaska and possibly northern Siberia. Global forecast models show heights rising into the 2-3 standard deviations above normal in this region by the middle of next week. Additionally, the water temperatures in the northern Pacific Ocean are some of the warmest in recent decades (nearing some historical values) and this warm pool in the region south of the Gulf of Alaska tends to favor not only building high pressure in this region, but larger and stronger high pressures cells. Upper level high pressure development in this region helps to foster a strong downstream trough over Canada and the US and its intensity/depth is dependent on the intensity of the ridging over Alaska…so the stronger the Alaskan ridge the deeper the downstream US trough.

 

All of the major global forecast models show a pattern of varying degrees of building high pressure along the US west coast deep into Alaska and potentially northern Russia by the middle to end of next week. This pattern also allows the formation of intense surface high pressure cells over NW Canada promoting the development of a pool of bitter cold air as this area is currently experiencing near zero sunshine. This cold air pool has yet to fully develop and that is why forecast models are having such a hard time determining how cold it is going to get the week of Christmas.

 

The pattern will certainly favor an arctic air outbreak into the US by the weekend of the 21^st, but how cold and how long remain viable questions this morning. With model guidance now so widely available on the internet one must be cautious to avoid believing each model run and the “extreme” numbers that at times can be shown and have been shown over the past 3-4 days. The area to watch over the coming days will be northern Russia into NW Canada and eastern Alaska in the Sunday-Tuesday time period to see how cold the air mass in the source region becomes and if surface pressures build to the forecasted values being shown (1050-1060mb). Surface air temperatures in this region are already running in the -25F to -40F range this morning. This will be much of the focus for the next several days leading into Christmas week.  

 

[DFWWeather]

Models seemed to have backed down considerably with the Arctic front Christmas weekend. Doesn't even look like an Arctic front anymore, just a Canadian/polar front. The really harsh cold gets swept into trough out over the Atlantic.

[Quixotic1]

There's still hope. chances are the models are still behind on the extent of the cold, though any 1983 parallels are probably hyperbole now.

[Srain]

FINALY...we have clear skies and chilly temperatures this morning across the Region. Temps have dipped below freezing here in NW Harris County this morning , but the sunshine will be welcomed after a long duration of dreary cold days except for last Wednesday when managed to get a brief break albeit chilly. Sub freezing temps are expected again tomorrow morning N and E of Metro Houston and then the moderation begins. Foggy conditions are likely mid week before Major changes develop.

The medium range is looking rather wet and stormy as we head towards later in the week. The operational and ensemble guidance are in somewhat agreement that a very deep trough will drop S into the Baja Region and a robust upper low will develop and slowly begin to move E across Northern Mexico towards Texas. The fly in the ointment aappears to be the potential of a Coastal Low developing along the Lower/Middle Texas Coast on Friday which would tend to favor heavy rainfall and elevated storms, some possibly strong in the warm sector while the Canadian air mass settles S across the Central/Southern Plains. Across the cold sector a variety on Winter Weather may be possible with freezing rain/sleet and snow further N. If the upper low/trough remains closed or stronger, a significant Winter Storm may develop late Friday into Sunday. Once the frontal boundary slips S, over running moisture may be possible next weekend as the trough may linger to our W with SW winds aloft or a warm nose and colder temperatures at the surface. If things develop as the appear as of this morning, this would be the 3rd such event of this kind since just before Thanksgiving so the movie "Ground Hog Day" come to mind. This remains a very complicated and complex forecast and pattern, so expect changes...some possibly very big as even NWS Houston/Galveston stated this morning.

[CranberryWX]

27 degrees with heavy frost this morning in my back yard...coldest morning of the season so far. Yesterday was cold and blustery reminding me of late Fall days back home in the northeast.

[Quixotic1]

And then, depression set in.

[Ed Lizard]

Looking pretty boring,  a touch cool, but noting terrible.

 

Obviously hoping for a milder end to Winter and generally onshore winds so in April and May flow off the Southern Gulf and Caribbean doesn't have too much cool shelf water to cross, with the frequent result in SETX of even a very breakable cap never breaking because of the low overcast all day.

 

That can ruin FUNderstorm season in SETX, looking bad at the moment...

 

[bubba hotep]

And then, depression set in.

00z GFS is a step back in the right direction. Maybe the model warming trend is over and we can start trending cooler. I'm kind of an optimist at this point...

[1900hurricane]

Model forecast confidence: Troll.

 

[Ed Lizard]

Even in the most boring of weather patterns, I continue to pan for that small fleck of gold.

 

 

[Ed Lizard]

^^ GFS and Euro still suggest some capping issues with a bit of a Westerly component at 850 mb, but that is the only negative factor I can see for SETX Saturday FUNderstorms, wind energy and instability there,

 

Manly low coming into SW, with sub 540 dm heights below it on both GFS and Euro.  Doubt it actually snows on the Baja, but wouldn't that be awesome?  Just a hint of a negative tilt, the capping issues wouldn't be so bad, and we have five days, almost, to get that fixed.

 

Glass quarter full.  5 years, 3 months, 4 days since 50 knot gusts IMBY...

 

 

EDIT TO ADD

 

1900 Hurricane's post below makes me a happy camper.  Still a bit worried about capping, but LI's -7 to -9ºC and 40 knot plus 850 mb winds, well, happy camper time.

[Srain]

Another chilly morning across our Region, but dew points have risen, so no heavy frost issues today (we did have frost on roof tops in NW Harris County with a low temp of 33 F). The surface high pressure ridge over Louisiana will slide E today and a return flow off the Gulf will begin with SE winds and warming temps and increasing moisture as well as fog. Today should be the end of the sorely needed sunshine before clouds increase and sea fog develops and temperatures continue to moderate to above normal.

 

The general synoptic pattern of a split zonal flow where the cold air is bottled up along the Northern US and a Ridge off the Pacific West Coast and a SE Ridge over the Bahamas should allow for further warming and streamer showers and drizzle to develop by Friday. Changes lurk ahead as a potent short wave dives S into the Baja/Southern California late Thursday and cuts off while a modified Polar front drops S into Texas on Friday.

 

Uncertainty arises as to how far S the front sags before stalling across Central Texas as well as when the SW upper low begins its journey E towards Texas. The GFS appears to be too fast moving the U/L to the E while the Euro and Canadian are slower. Since the slower ejection solution of similar patterns we have seen so far this fall season seems likely, more credence will be given to the non American guidance at this time.

 

Saturday should be the warmest day we see this week and also the most unsettled. Showers and storms, some possibly severe may warrant an increase in Severe Weather Watch mode and will need to be monitored later this week. It does appear that there is a chance for a bit of negative tilt to the trough which suggests all modes of severe weather may be possible. A surface low could develop over Central Texas on Saturday as the upper low approaches from NE Mexico. We will also need to monitor for the potential of heavy rainfall as moisture increases to near 3 standard deviation above normal for this time of year. Saturday evening could be very stormy, so be aware if you have Holiday party plans.

 

Sunday looks to turn much colder as the front finally pushes offshore. Another stronger front may pass on Monday as a wound up Winter Storm moves NE across the Mid Mississippi Valley towards the Upper Mid West early next week. With a general pattern of a Ridge to our West offshore of the Coast of California  and another to our East offshore in the Atlantic, cooler and dry weather should arrive for Christmas.

 

EXTENDED FORECAST DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

118 AM EST TUE DEC 17 2013

 

VALID 12Z FRI DEC 20 2013 - 12Z TUE DEC 24 2013

 

...OVERVIEW...

GEFS...NAEFS AND EC ENSEMBLES RECOGNIZE SPLIT-FLOW PATTERN ALONG

THE WEST COAST OF NORTH AMERICA AND CONFLUENT PATTERN DOWNSTREAM

OVER THE CANADIAN MARITIMES AND NORTH ATLANTIC THIS MEDIUM RANGE

PERIOD.

 

NORTHERN STREAM IS EXPECTED TO BECOME ENTRAINED WITH A SERIES OF

MIGRATORY PACIFIC SYSTEMS AND WILL LIKELY CONTAIN THE WINTER-TYPE

PRECIPITATION--MAINLY FOR THE NORTHERN ROCKIES-PLAINS...GREAT

LAKES AND NORTHEAST THIS FORECAST PERIOD. FROM A SYNOPTIC-SCALE

PERSPECTIVE...THE PACIFIC STORM TRACK SHOULD BE A SERIES OF SUBTLE

BUT DISTINGUISHABLE MID-LEVEL CIRCULATIONS TRACKING FROM THE

SOUTHERN CANADIAN ROCKIES OF ALBERTA...EASTWARD THROUGH THE UPPER

MIDWEST AND ST LAWRENCE VALLEY THIS FORECAST PERIOD.

 

SOUTHERN STREAM ENERGY AND MOISTURE REMAINS THE VOLATILE 'WILD

CARD'...WITH WEST-SOUTHWESTERLY FLOW DRIVING DOWNSTREAM FROM THE

DESERT SOUTHWEST AND MID-RIO GRANDE VALLEY EASTWARD INTO THE

OZARKS AND OHIO VALLEYS. THE VOLATILITY WILL BE TWO-FOLD...A BROAD

MID-LEVEL CYCLONE OFF THE CENTRAL CALIFORNIA COAST MIGRATES INLAND

EARLY IN THE PERIOD...FOLLOWED BY A DIGGING EASTERN PACIFIC

SHORTWAVE...THAT BRIEFLY CLOSES OFF INVOF THE LOWER COLORADO RIVER

BASIN--THEN EJECTS EASTWARD ACROSS THE SOUTHERN ROCKIES AND

PLAINS. BOTH HAVE THE POTENTIAL TO DELIVER DECENT PULSES OF

PRECIPITATION TO THE SOUTHWEST...SOUTHERN ROCKIES AND DOWNSTREAM

THROUGH THE SOUTHERN TIER OF STATES THIS FORECAST PERIOD. 

 

BOTH JET STREAMS MERGE DOWNSTREAM OVER THE NORTHEAST AND CANADIAN

MARITIMES...GENERATING A BROAD CYCLONIC FLOW SOUTHEAST OF

GREENLAND. AS PREVIOUSLY MENTIONED...THE MERGING STREAMS SERVE AS

THE WESTERN/NORTHWEST FLANKS OF STRONG RIDGING IN THE

BAHAMAS...FLORIDA AND THE EASTERN GULF OF MEXICO.

 

...MODEL PREFERENCES AND UNCERTAINTY ASSESSMENT...

FOLLOWING THE PREVIOUS WPC GRAPHICS THROUGH DAY 7 WAS AN EASY

TASK...WITH A COMBINATION OF THE 16/12Z EC ENSEMBLES MEAN AND

NAEFS MEANS MAINTAINING DECENT CONTINUITY WITH THE FRONTAL

PROGRESSION OF THE ARCTIC FRONT DAY 4-5...BUT THE MEANS GENERALLY

LOSE ANY/ALL SUBTLE NORTHERN STREAM FEATURES EXITING SOUTHERN

ALBERTA. GIVEN THE STRONGLY-SHEARED ENVIRONMENT ALOFT OVER CENTRAL

CANADA AND THE DRY ARCTIC AIRMASS IN PLACE...THE MEANS FOCUS OF

THE CENTERS OF HIGH PRESSURE RATHER THAN ANY MID-LEVEL CYCLONIC

FLOW MIGRATING DOWNSTREAM FROM WEST TO EAST.  BOTH MEANS MAINTAIN

MORE OF A DOMINANT SOUTHERN STREAM FLOW FROM THE OZARKS

NORTHEASTWARD INTO THE OHIO VALLEY AND NORTHEAST-CANADIAN

MARITIMES BY THE END OF THIS PERIOD.

 

SOME ASPECTS OF THE GFS/ECMWF/CANADIAN AND UKMET WERE VALID AND

COULD ADD DETAIL TO THE PROJECTED FLOW PATTERN ACROSS THE CONUS

THIS PERIOD.

 

THE 16/12Z DETERMINISTIC UKMET...15/18Z GFS AND 15/12Z ECMWF HAD

THE GENERAL IDEA ALL ALONG...WITH A SECOND ALBERTA CLIPPER-TYPE

SYSTEM TRACKING THROUGH THE UPPER MIDWEST SATURDAY NIGHT AND

SUNDAY...AND ALL RECENT PIECES OF GUIDANCE CONTINUE TO REAFFIRM

THE FRONTAL POSITION AT THE START OF DAY 3 (20/12Z) BETWEEN LAKE

HURON AND THE SOUTHERN OZARKS. THIS HAS BEEN A TRACK-ABLE FEATURE

FOR 5 DAYS NOW...AND IS GOING TO BE RATHER CLOSE TO THE MODEL

PROGS FROM 12Z DECEMBER 13TH.

 

THE FACT THAT THE FLOW ALOFT OVER CENTRAL CANADA AND ARCTIC CANADA

HAS RESOLVED ITSELF...ADDS CONFIDENCE TO THE FORECAST...WITH THE

DAY 3 OPEN WAVE EXITING THE GREAT LAKES--SHEARING OUT QUICKLY OVER

EASTERN CANADA. IT IS FOLLOWED BY ANOTHER PACIFIC WAVE EXITING

SOUTHERN ALBERTA...BY DAY 4-5...AND TAKING A STORM TRACK THROUGH

SOUTH CENTRAL CANADA. A THIRD SYSTEM MOVES OUT OF THE SOUTHERN

CANADA ROCKIES DAYS 6-7.

 

THE SPACING BETWEEN NORTHERN STREAM SYSTEMS CONTINUES TO BE RATHER

ACCURATE AND PREDICTABLE. THIS DAY 4-5 WAVE TRACK THROUGH SOUTHERN

CANADA BRINGS THE ARCTIC AIRMASS INTO THE NORTHERN PLAINS AND

UPPER MIDWEST FOR FRIDAY AND SATURDAY. MORE IMPORTANTLY...IS OPENS

THE DOOR FOR MORE PACIFIC ENERGY TO ESTABLISH A NORTHWEST FLOW OFF

THE PACIFIC AND INTO/THROUGH THE PACIFIC NORTHWEST AND ROCKIES

THROUGH THE END OF THE MEDIUM RANGE PERIOD. THIS SERVES AS THE

RATHER STABLE NORTHERN STREAM SPLIT IN THE FLOW PATTERN ALONG THE

WEST COAST OF THE CONTINENT.

 

THE 16/12Z DETERMINISTIC GUIDANCE HAS COME INTO BETTER

AGREEMENT...THOUGH NOT PERFECT...WITH THE SOUTHERN STREAM AND

SURFACE WAVE DEVELOPMENT ALONG THE ARCTIC FRONT. THE LATEST IDEA

IS FOR AT LEAST TWO PULSES OF SHORTWAVE ENERGY AND PRECIPITATION

TO RIDE ALONG THE FRONT...WITH THE SOUTHERN PLAINS...OZARKS AND

OHIO VALLEY REGIONS TAPPING THE WESTERN GULF OF MEXICO.

HENCE...THE DEEPER LOW-LEVEL MOISTURE...AND HEAVY RAINFALL THREAT

BEGINS TO TAKE SHAPE ON SATURDAY OVER TEXAS/OKLAHOMA AND

LOUISIANA-ARKANSAS AND THE LOWER MS VALLEY...WESTERN OHIO VALLEY

SATURDAY NIGHT AND SUNDAY MORNING.

 

HERE...THE EC AND NAEFS MEANS BASICALLY STRETCH OUT THE SURFACE

TROUGH NORTH-NORTHEASTWARD FROM THE NORTHWEST GULF OF MEXICO INTO

THE MID-OHIO VALLEY...WITH THE INDIVIDUAL MEMBERS RUNNING AT

DIFFERENT PACES ALONG THE FRONT. THEREFORE...THE MEANS CONTINUE TO

SERVE AS THE BASELINE FOR THE SURFACE GRAPHICS. BUT THE 16/12Z

DETERMINISTIC GFS...CANADIAN AND/OR ECMWF WOULD SUGGEST A 996MB TO

1000MB SURFACE WAVE AND BROAD WARM FRONT DEVELOP IN THE SOUTHERN

STREAM...AND REMAINING SEPARATED FROM THE NORTHERN STREAM UNTIL

THEY CAN MERGE OVER THE ST LAWRENCE VALLEY AND NORTHERN NEW

ENGLAND ON SUNDAY NIGHT AND MONDAY.

 

THIS SEEMS TO FIT THE GENERAL IDEA THAT A CONFLUENT FLOW AND AREA

FOR MERGING JET STREAMS WILL REMAIN INVOF THE NORTHEAST AND

ATLANTIC CANADA THIS MEDIUM RANGE PERIOD.

 

...SENSIBLE WEATHER HIGHLIGHTS...

BROAD-SCALE WARM UP AHEAD OF THE ARCTIC BOUNDARY WILL CONTAIN A

MODIFIED WESTERN GULF OF MEXICO AIRMASS.

 

HEAVY RAINFALL EVENT(S) ARE GATHERING MODEL MOMENTUM AND CONSENSUS

INVOF THE MERGING JET STREAMS WITH EMPHASIS ON THE SOUTHERN

STREAM'S ABILITY TO GATHER LOW-LEVEL INFLOW OFF THE GULF. THIS

BEGINS TO DEVELOP IN EARNEST ACROSS THE SOUTHERN PLAINS OF

TEXAS...EASTERN OKLAHOMA...THE OZARKS EARLY IN THE FORECAST

PERIOD. AND THIS WEEKEND INTO MONDAY...THE OHIO VALLEY AND

PORTIONS OF THE SOUTHEAST AND NEW ENGLAND WILL BE UNDER THE

INFLUENCE OF MOIST SOUTH TO SOUTHWEST FLOW ALOFT.

 

VOJTESAK

 

[1900hurricane]

@mikebettes TorCon 5...five days in advance! Unheard of! pic.twitter.com/7eFuqEn40b

 

[1900hurricane]

If I were the SPC (which I most certainly am not), I might have highlighted the following area for Day 5/Saturday.

 

[Srain]

^^

 

With all the volatility suggested with the deterministic and ensemble guidance as well as capping issues, I believe a conservative approach by the SPC is warranted at this time. They have mentioned the potential and if trends favor an upgrade in the next day or two, we will likely see an outlined area introduced.

[1900hurricane]

Yup, no complaints from me with the approach by the SPC, but just throwing in some of my thoughts as to who might be under the gun. Capping (as usual) looks to be issue number one with regards to severe weather, especially if we're clouded over and sea fog is prevalent.

[Srain]

It looks like the cap may be too strong for surface based storms to develop as the Euro and Canadian have slowed the cut off upper low a bit and SW flow aloft keeps the cap large and strong across Central and SE Texas via the GFS, but the Euro/Canadian suggest a bit more negative tilt and better dynamics for severe weather and are much 'wetter' and even suggest training showers/storms across Central Texas as a surface low develops. Further N in the cold sector, icy conditions with freezing rain look likely across portions of the Panhandle and Oklahoma and locations further NE. Warm sector heavy training rains may be possible across Arkansas/Tennessee and on E where severe storms have a better chance to develop extending into the SE Region. Another freeze may be possible early next week as well. Late Christmas Day looks changeable as yet another SW upper low approaches from our W and a secondary re enforcing shot of 'colder air' drops S into the Southern Plains on Christmas Eve. It may take another day or two to sort out any severe weather potential for Texas as the short wave that will develop into a robust upper low across Southern California/Baja late Thursday into Friday is further sampled by the RAOB network.

The longer range beyond Christmas Day looks very unsettled with several disturbance crossing our Region and perhaps much colder air drops S from Canada into the Inter Mountain West and Plains and a strong storm system ejects out of Mexico with a noisy sub tropical jet. We will see.

 

 

 

[1900hurricane]

Looks like SETX gets to play Russian Roulette with the cap. Will it or won't it?

[Srain]

The 12Z GFS suggests a Del Rio/Austin (Hill Country) Texarkana track of the surface low on Saturday and now has a more of a negative tilt ~vs~ an totally open wave at 500mb. Areas along that surface low track will be where the best dynamics and possible erosion of the cap should take place. It does appear there is a sufficient jet streak that may assist breaking the cap. As always, timing and the eventual track will determine where the severe potential will increase.

[1900hurricane]

Looking at the very end of the NAM for guidance isn't always the best course of action, but man, the 12Z run is slow...