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Texas/MX Obs And Discussion Thread.


Srain

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Oh boy...:pepsi:

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX

336 PM CST WED JAN 5 2011

.DISCUSSION...

COLD FRONT WELL OFFSHORE AND DRY AIR INFILTRATING FROM THE

NORTHWEST. HIGH PRESSURE WILL SETTLE THROUGH THE HILL COUNTRY AND

THEN TRACK OFFSHORE ACROSS THE COASTAL BEND THURSDAY NIGHT/FRIDAY

MORNING. SLOW TO MODIFY AIR WILL SLIDE BACK INTO THE MATAGORDA BAY

REGION SATURDAY AHEAD OF THE NEXT STORM SYSTEM. MODELS DIFFER ON

THE TRACK OF THE SURFACE LOW AND STRENGTH OF THE LL WIND FIELDS

SIGNIFICANTLY BY SATURDAY EVENING. AM CURRENTLY FAVORING A TRACK OF

THE SURFACE LOW THROUGH THE UPPER TEXAS COASTAL WATERS BUT AS IT

DEEPENS IT WILL DRAG BACK ABUNDANT MOISTURE SATURDAY AFTERNOON AND

NIGHT. THE LOW OFF THE CA COAST LOW THIS AFTERNOON HAS STOPPED

RETROGRADING BUT WILL BE A WHILE BEFORE IT GETS MOVING EAST AND

THEN SLOWLY SLOWLY. EVENTUALLY THE TROUGH AXIS MOVES THROUGH THE

BIG BEND SATURDAY NIGHT. THE OVERRUNNING LIGHT RAIN SHOULD

INCREASE IN COVERAGE LATE SATURDAY AND THEN SUNDAY MORNING AS THE

TROUGH ROTATES EAST THE INSTABILITY ACROSS THE UPPER TEXAS COASTAL

WATERS AND SOUTHERN CWA SHOULD SUPPORT WIDESPREAD RAIN WITH SCATTERED

TO NUMEROUS TSRA/POSSIBLY AN A STRONG ONE OR TWO NEAR THE COAST. IT

WILL BE A COLD RAIN WITH DEWPOINTS IN THE LOWER 40S TO AROUND 50 AND

TEMPERATURES SATURDAY NIGHT/SUNDAY IN THE 40S TO LOW 50S. A

CONCERN IS THE MUCH COOLER TEMPERATURES THAT THE ECMWF IS

DEVELOPING OVER THE NORTHERN ZONES AS THE LOW DEVELOPS OVER THE

COASTAL WATERS. GFS MODEL SOUNDINGS GETTING CLOSE TO A RAIN SNOW

MIX AND THE ECMWF IS LOOKING LIKE A SNOW AND RAIN MIX FOR THE

NORTHERN AREAS (CLL-UTS- LIVINGSTON) NORTHWARD ON SUNDAY. HAVE

OPTED TO ADD RAIN/SNOW MIX FOR THESE NORTHERN AREAS BUT SURFACE

TEMPERATURES WILL PRECLUDE ANY STICKING TO ROADWAYS BUT TREES AND

GRASSY AREAS MIGHT SEE A LITTLE ACCUMULATION. PRECIP TAPERS OFF

DURING THE AFTERNOON SUNDAY BUT CLOUDS WILL LINGER IN WRAP AROUND.

MONDAY EVENING THE MUCH TOUTED ARCTIC COLD FRONT WILL BE DROPPING

INTO NORTH TEXAS AND BY 12Z TUESDAY WILL BE THROUGH SOUTHEAST

TEXAS. THE PATTERN DOESN`T SUPPORT THE BITTER COLD AIR THAT WAS

PROGGED TO COME SOUTH A FEW DAYS AGO. IT WILL STILL BE COLD BUT

NOT AS COLD...LOWS 29-33 WILL BE COMMON TUESDAY MORNING AND THEN

WARMING INTO THE 40S...DIPPING BACK DOWN INTO THE MID 20S NORTH

AND MID TO UPPER 30S COAST. UNFORTUNATELY THE MODELS ARE

INDICATING ANOTHER ARCTIC AIRMASS LINING UP ACROSS CANADA AND

NORTHERN HIGH PLAINS AS EARLY AS THE FOLLOWING SATURDAY (15TH). 45

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Early results...

Borderline cat five hype over the last few days.

Trending towards a high end two or a low end three.

:D

And like your analogy, 18z GFS drag us back. The key is if the vortex between the NAO and EPO ridges prevents the fusion of the heights...if it does, a more zonal with pacific jet undercut will ensue...less cold air drainage and less dense airmass...on the other hand, if the NAO ridge can retrograde back enough and help the W coast ridging and it connects with the EPO ridge... :snowman:

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The 12Z NAM is painting a mighty wet Saturday/Sunday across the Lone Star State. That model also suggests possible wintry weather in parts of N TX as the Upper Low and surface low in the Gulf begin to shift E.

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Morning e-mail from Jeff just arrived...

Much to talk about this morning in the middle and extended portions of the period.

Cut-off upper low off the southern CA coast has pulled up stationary and will begin to move eastward later today. Massive plume of mid and high level moisture south of this system currently extending from the central Pacific to NC MX will swing eastward into NE MX and TX over the next 24-36 hours. Approaching upper level system will induce surface pressure falls over SW TX late Saturday afternoon with surface low pressure forming in the region from the Big Bend to Laredo. Strong warm air advection will ensue into this system with a warm front moving toward the coast and possibly inland Saturday evening. Large scale lift with the upper level storm will begin to affect the area by Saturday evening resulting in the formation of showers across the entire region and thunderstorms over the Rio Grande plains.

Big show appears to be in store Saturday night-Sunday as surface low deepens over SC TX and pushes over the upper TX coastal counties from Matagorda Bay to Galveston Bay Sunday. Appears the warm front will move just inland of the coast…possibly to US 59 ahead of the surface low. Forecasted low level winds south of this boundary are strongly backed to the E or ESE with rapid veering of the winds to the SW in the mid levels supporting strong low level wind shear favorable for updraft rotation and supercell storm structures. Current limiting factor for a significant severe weather/tornado outbreak appears to be the amount of instability with progged indices of around 1000J/kg south of the warm front. With all that said, still expect isolated severe weather along and south of the warm front early Sunday morning with potential for damaging winds and an isolated tornado.

North of the warm front a cold rain as low level NE winds wrap in cold air over NE TX and N LA into the system. Expect temperatures south of the warm front to rise into the 60’s while north of the boundary temperatures will remain in the 40’s all day Sunday with widespread rain. As the surface low deepens and moves east of the area strong offshore flow will develop drawing the cold air mass southward. Slower upper trough ejection will bring a chance of showers across the area behind the main surface low keeping rain chances into Sunday afternoon. Low level cold air advection will drive temperatures into the low to mid 30’s over our northern counties by Sunday evening, but at this time it appears the moisture will be east of the region before the onset of any freezing at the surface.

Widespread rainfall of 1-2 inches appears likely with this system, although I am becoming a little concerned about the warm front placement as these features tend to focus and train excessive rainfall. Additionally, the placement of this boundary by early Sunday morning could be close to US 59 where excessive rainfall fell on the 29th of Dec resulting in heavy rainfall over wet/soggy grounds. A few locations near the warm front could see 3-4 inches of rainfall.

Early Next Week:

Much talked about arctic front still on tap to bring very cold air to the region starting late Monday. Suspect clouds will linger much of Monday behind the departing Sunday system keeping highs in the 40’s on Monday even prior to the arctic invasion. Large 1055mb arctic high will begin to surge down the plains Sunday reaching the TX coast late Monday. May need a faster timing with this boundary as such cold dense air masses tend to move very quickly southward. Very strong cold air advection will ensue post boundary by Monday night with NW winds of 20-30mph and possibly higher along the coast. Temperatures will rapidly fall from the 40’s into the 30’s and possibly upper 20’s by Tuesday morning. Models are bouncing around with the idea of keeping clouds in the area at times Tuesday and Wednesday and this will have big effects on overnight lows and afternoon highs in the post frontal air mass. Will continue the trend yesterday of undercutting the GFS guidance numbers by several degrees from Tuesday onward. Will go with lows in the upper 20’s for Tuesday morning (even with strong winds and clouds) and highs only in the low to mid 40’s. For Wednesday will go with lows again in the upper 20’s (could see lower 20’s if skies clear) and highs in the upper 30’s to near 40. Thursday will go with lows in the upper 20’s and highs in the low 40’s. GFS tries to generate some light precipitation by Thursday of next week in the cold air mass, but not confident that this will occur.

Possibly some warming Friday and Saturday of next week before another surge of very cold arctic air arrives late next weekend. Next week to week and a half will feature well below normal temperatures across the entire state. In fact highs may run 15-20 degrees below normal.

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The HPC says don't get too comfortable with that warmup depicted late next week as it will likely be short lived...

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

740 AM EST FRI JAN 07 2011

VALID 12Z TUE JAN 11 2011 - 12Z FRI JAN 14 2011

BLOCKY NOAM PATTERN TO CONTINUE BUT ANOMALY HEIGHT REARRANGEMENT

OCCURRING AS THE STRONG POSITIVE HT ANOMALY OVER NRN CENTRAL

CANADA WEAKENS THIS PERIOD AND RIDGING BUILDS IN THE NORTHEAST

PACIFIC THRU THE BERING SEA RESULTING IN A VERY STRONG MID LEVEL

HIGH. HEIGHTS BUILD ENOUGH HERE TO ALLOW UNDERCUTTING PACIFIC

ZONAL FLOW TO RETURN EARLY NEXT WEEK AND PERSIST THROUGH THE

FORECAST PERIOD BRINGING MILDER CONDITIONS INTO THE WEST AND

PLAINS BY LATE NEXT WEEK. THESE MILDER CONDITIONS LOOK SHORT LIVED

AS THE CURRENT AND PERSISTENT NEGATIVE AO LOOKS TO TANK TO VALUES

SEEN IN MID DEC IN THE 10-14 DAY PERIOD. SEE CPC DISCUSSIONS.

SHORTWAVE ENERGY MOVING EASTWARD ACTROSS TX SUN WILL INDUCE WRN

GLFMEX CYCLOGENESIS WITH A REFORMING LOW OFF THE SOUTHEASTERN

SEABOARD WHICH WILL MOVE NORTHEAST OFF THE NEW ENG COAST AND

SEAWARD MID TO LATE PERIOD. NEXT BROAD CLOSED LOW OVER B.C. WILL

DROP SOUTHWARD AND ROTATE THRU THE PLAINS KEEPING WESTERLIES

SUPRESSED ACROSS THE SRN TIER OF STATES WITH THIS DIFFUSE MID

LEVEL LOW BETTER ORGANIZED BY CMC AND BOTH GFS AND ECMWF ENS MEANS

EXITING OVER NEW ENG WATERS LATE WEEK.

MODELS HAVE SETTLED DOWN CONSIDERABLY HANDLING THE GLFMEX EAST

COAST LOW AND CONTINUE TO SHOW HIGH PRESSURE DOMINATION OF THE

ENTIRE NATION EARLY PERIOD THEN A STRONG THERMAL CLASH ALONG THE

ROCKIES AND PACIFIC ZONAL FLOW DEVELOPS WHILE COLD HIGH PRESSURE

DOMINATES THE PLAINS AND EAST MID TO LATE WEEK.

WITH A COLD AIRMASS IN PLACE OVER THE EAST AND LOW PRESSURE

REFORMING FROM THE NORTHEAST GLFMEX TO THE GA/SC COAST MDT TO

LOCALLY HEAVY RAINS POSSIBLE ALONG THE GULF COAST WHILE INLAND

ACROSS CENTRAL AND NRN PORTIONS OF AL INTO GA AND MUCH SC THERE IS

A VERY POSSIBLE SIGNIFICANT WINTER WEATHER THREAT MAINLY ICING

MONDAY WITH THIS SPREADING INTO NC MONDAY NIGHT. SNOW MORE LIKELY

NWD THRU THE SRN AND CENTRAL APPLCHNS AND NORTHEASTWARD WITH THE

HEAVIEST PCPN ACROSS PORTIONS OF ERN VA AND THE DELMARVA. DETAILS

TO BE SOLVED IN THE SHORT RANGE. SEE LOCAL NWS FORECAST OFFICE

OUTLOOKS AND FUTURE ADVISORIES AND WARNINGS.

RAINS SPREADING INTO THE WEST COAST AS THE PACIFIC WESTERLIES

RETURN MID WEEK WITH MDT TO HVY AMOUNTS ALONG THE COASTAL RANGES

AS FAR SOUTH AS CENTRAL CA AND INLAND TO THE SIERRA. SIGNIFICANT

HIGHER ELEV SNOWS AGAIN IN THE ID/WY/UT ROCKIES BY FRIDAY.

NEXT ARCTIC SURGE MAY BEGIN TO NOSE DOWN OUT OF OF ALBERTA AND

SASKATCHEWAN INTO MT AND THE DAKOTAS FRI AND SAT.

ROSENSTEIN

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This might just be a decent event. Texas winter weather (and specifically SE Texas) is lacking. Just hard to get into it and it takes quite a bit before I consider it significant. Potential is there but as per the norm I don't know how many times in the past we have seen the 'potential' to have a large and deep Arctic airmass come our way.

Chatter is definitely out there....

Add another.

The GFS giveth and the GFS taketh away.

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Add another.

The GFS giveth and the GFS taketh away.

I wouldn't get too hung up on the operational GFS. It is performing poorly lately and is out of step with its own ensembles which still show a mighty good chance of significant cold well into deep south Texas before this pattern abates. Another Arctic surge is expected next weekend with a possible third the following week. Although, the latter may be directed more southeastward as per the December pattern. The GFSMOS numbers for next week in DFW are about 8 to 10 degrees too warm if the ensembles are correct in daily temperatures departures nearly 20 below normal, and next Thursday the GFSMOS temperatures are really too warm with the operational run eroding the Arctic air much too aggressively. Highs in the 40s probably will not occur at DFW until at least Friday (and low 40s at that), and I doubt we will see 50 degrees before the next Arctic surge.

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The GFS giveth and the GFS taketh away.

12z GFS even struggles to take 0C 850mb to near Austin...that's probably too warm since GFS and Euro ensembles are significantly colder...but even the coldest outlier isn't exciting at all...next!

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Hmmm, the clown maps over on Harris show a real sharp gradient on the backside of the snow fall area. It looks like my area could get 2 - 4 if taken literally with a 25 mile shift in either direction taking us from boom to bust! I don't have time to dig really deep into this right now but after a quick glance, I would not be surprised to see some flurries but anything more than a dusting would shock me.

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12z Canadian can't be more different for S TX and MX...it's even colder, for a longer time and with decent moisture for wintry precip., mostly thanks to an, out of nowhere, shortwave (Almost two days of flurries/light snow for me and several inches around Victoria, TX). Obviously not buying it, specially in light of the 1060mb (1063) high over Wyoming.

f150.gif

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Would you buy it if the Euro showed it as well, Jorge...:scooter:

Yeah, noticed that, but the Euro is faster and farther north with the piece of energy...it would still be a threat for your area. GFS shows a weaker version with little to no amplification...and shearing because of it's screaming speed. This piece of energy might be the key of how far south we can get the cold/moisture.

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Looks like DFW is gonna get nailed Sunday through Monday. 12z ECMWF is particularly agressive with sleet before change over to snow. If surface temps can cool quickly via evaporational cooling and cold air advection, this could produce some significant accumulations. This system reminds me of events that took place on February 24, 2003, November 25, 1993, and January 6,1988, all which produced significant sleet.

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Would you buy it if the Euro showed it as well, Jorge...:scooter:

:unsure: WOW. I'm trying to get a read on the wx for an T-Th, far West Texas to North Texas truck run... snowfall/winter weather will be a critical factor for my logistics, but models are struggling as far as consistency re: moisture... arghhhhh!!!

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Looks like DFW is gonna get nailed Sunday through Monday. 12z ECMWF is particularly agressive with sleet before change over to snow. If surface temps can cool quickly via evaporational cooling and cold air advection, this could produce some significant accumulations. This system reminds me of events that took place on February 24, 2003, November 25, 1993, and January 6,1988, all which produced significant sleet.

Do you have a link to the specific graphics you're referring to?

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Well the NWS said take your "flurries to a dusting" call and go sit back in the amateur section but this :weenie: is ready to buy! The NE burbs have been the place to be for rain the past few months so maybe that trend will continue with the winter weather.

image2.gif

I'm not sure, but I feel like your post was little harsh. First off, 3 inches is not a dusting at DFW, its a significant event. Second, you need to read their forecast discussion and special weather statement. Third, the ECMWF is forecasting a significant winter storm with more sleet than snow which would meet criteria for a Winter Storm Warning. If it falls as mostly snow, then 1 to 3 inches will be enough for a Snow Advisory. Given that 540dm line stays north of the area while 0 line at H85 is south of the are during most of this event on most models, this looks like a sleet event. Thus, the NWS has forecasted a 70% chance of sleet/snow on Sunday. If as much sleet gets involved with this storm as I think, this can potentially be as bad as the other dates I mentioned above, except 2003. Not convinced it will be that extreme yet.

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