SE TX/SW LA Winter WX - 2011-2012

[vbhoutex]

Jeff's evening update.

Sorry for the delay, I wanted to look over the 18Z guidance and forecast soundings to help nail down P-type and totals...not sure it changed the thinking much.

Winter Storm Watch in effect for all of coastal Texas and have been expanded into central TX and SW LA.

Historic snow and ice event within 24 hours of onset.

Record snowfall totals may be challenged by this event.

Discussion:
Little has changed with the overall pattern which conitnues to exhibit a classic TX winter storm profile. Deep upper trough digging into northern MX at this time will develop a NW Gulf of Mexico surface low which throws copious moisture NW into the frigid arctic air mass in place. While aloft the sub-tropical jet stream will bring moisture in from the Pacific. While the low levels are dry, the snow falling through the air column will gradully moisten the surface layer starting early Thursday. Widespread snow/sleet will develop by Thursday evening with heavy snow likely overnight.

Timing:
Models have trended a little faster today with the onset timing. In fact a few models suggest we could begin to see flurries along the coast before noon on Thursday, but this would be very light as the surface layer saturates. Wet bulb effects and ongoing cold air advection will likely keep temperatures below freezing. Light snow and sleet should develop along the coast and begin to spread inland around the noon-100pm time period. Light snow will expand northward over the rest of SE TX by 300-400pm with accumulations starting about an hour after the snow begins...possibly sooner if the temperatures are in the upper 20's at the onset. Thursday night weak warm layer tries to advance toward the coast and may push inland resulting in sleet and freezing rain and ice accumulations...I continue to be wary of this P-type change given how cold the air column is and the fact that the models may be overdoing the 1-2 degree above freezing warm nose (around or above the 850mb level) above a very cold surface. Will cut back on the ice accumulations around Galveston Bay and favor more sleet/snow instead...I may end up being wrong on this, but I just think this air mass is colder than the models show it to be.

Accumulations:

I am going with a 10:1 ratio but it could be closer to 12:1 given the very cold/dry air mass in place. This means an inch of liquid would produce 10-12 inches of snow. These are very high ratios for coastal TX, typical ratios are usually closer to 7:1 and in Dec 09 were around 5:1. Other aspect with accumulation is that the ground will be very cold, so what falls will not melt adding to the amounts.

I am very confident that snow will fall, I am not as confident on accumulations as much depends on what P-type is falling and for how long at a given location. Freezing rain will mean more ice, while freezing rain and sleet will also cut down on snow accumulations. With all that said here is my best try at accumulations right now:

Southeast of a line from McAllen to Alice offshore to Bay City to Kemah to High Island:
Light snow early changing to freezing rain/sleet Thursday afternoon/evening. Accumulations of ice of 1/10th to 1/4th of an inch. Mix changing to sleet/snow early Friday...snow accumulations of 1-2 inches.

Southeast of a line from San Antonio to Hempstead to Conroe to Livingston:
Snow/sleet will start the event with all snow likely after 600pm Thursday. Accumulations of 1-3 inches is likely with isolated totals of 4-5" possible. This area will be the favored location for meso scale snow bands and these bands may produce very heavy snow in this corridor including Wharton, Fort Bend, Harris, Montgomery, San Jacinto, Waller, Austin, and Colorado counties.

North of the line from San Antonio to Hempstead to Conroe to Livingston:
Snow for the entire event will accumulations of 1-3 inches likely with isolated amounts up to 4". While snow is favored the entire event, the moisture will be greater closer toward the coast which may cut back on totals this far north.

Meso Banding:
NAM and GFS both show convective precipitation with this event which was seen in Dec 2004 resulting in the banding of very heavy snow. Strong isentropic ascent combined with frontgenic forcing in the favorable baroclinic zone greatly enhances the threat for this meso banding along and about 50 miles N of the US 59 corridor. This is the area that could really get hammered with some impressive totals and the NAM has been hinting at this over NE Harris, N Liberty, San Jacinto, Polk, and E Montgomery counties the last few runs, I like that idea and will also include Waller, Fort Bend, Wharton and Austin to mesh where this zone may setup. It is impossible to forecast where these bands will form and how long they will remain over a certain location...so it is impossible to know where some of the higher totals will be. Under these bands snowfall rates of 1-2 inches will be possible per hour with visibilities falling to less than 1/4th of a mile.

Preparations:

Looks like much of the area will fall below freezing tonight and not get back above freezing until maybe midday Saturday. This extended period of sub-freezing temperatures may freeze pipes as happened last night at some locations. Make sure pipes are protected and check your water pressure regularly to ensure pipes are not frozen.

Travel conditions on area roadways is going to go downhill very quickly Thursday afternoon/evening. Not sure if we wil get the evening rush hour complete before roads begin to accumulate ice/snow. Best estimate now is onset of precipitation over the heavy metro areas in the 300-500pm time period with accumulations starting 30 minutes to an hour after snow begins to fall...this really does not get us through the rush hour and feel by 600pm snow will start to accumulate on bridges/overpasses and some surface streets. After 700pm expect travel to be extremely dangerous and by Friday morning nearly impossible as all roadways will be ice covered and snow packed. Road crews are going to be overwhelmed with the event and will not be able to spread snad fast enough to keep most roadways open. Travel after 600pm Thursday is being strongly discouraged through all day on Friday and likely through noon on Saturday.

School Closings:

Early Release on Thursday:
Wharton ISD: noon
Lamar CISD: around noon

Additional ISD's will likely release early on Thursday especially southwest and many schools will likely be closed on Friday.

[vbhoutex]

BTW, for those of you who didn't have the joy of experiencing rolling blackouts today I just want to let you know they SUCK!! Makes me even madder when I find out via the news no less that they are making sure that nothing connected with the super bowl goes down, which basically most of DFW!

[ksstormhunter]

Just updated some 02Z runs for the Houston, New Orleans area. Houston show a good shot of sleet and snow, light accumulation so far, will run again in 4 hours to see any changes.


http://smartwxmodel.net

[SaskatchewanScreamer]

LOL vbhoutex I thought you'd be soooo excited by receiving my gift of an arctic air mass but all I've seen is you complain re cold, cold and wet, etc and all the joys it brings (and then there is your big upcoming game in the mix). ;D Yer tough Scots blood has been a wee bit spoiled living down there in lotus land.

[Jagno]

Just updated some 02Z runs for the Houston, New Orleans area. Houston show a good shot of sleet and snow, light accumulation so far, will run again in 4 hours to see any changes.


http://smartwxmodel.net

There must be a problem on this site. Everytime I click on one of the cities I get an error 404 message. I'm in Lake Charles, Louisiana but was clicking on Port Arthur, Tx and Baton Rouge, LA to check theirs. Bing in the middle I figured I'd have a good idea of what to expect.

[BigB0882]

Yes, I also can't click on the links. I get error messages.

[Jagno]

Okay, I'm getting a bit P.O'd. Every forecast, including my local, talks about what's going to take place east, south, north and west of my area but not a single mention of what's going to happen south of I-10, south of Lake Charles, north of Cameron in SW Louisiana. The only thing I'm fairly certain of is that it's going to be cold.

[ksstormhunter]

Sorry guys posted the files to the wrong folder, they are in and you can open Baton Rouge, New Orleans and Port Arthur.

[BigB0882]

Sorry guys posted the files to the wrong folder, they are in and you can open Baton Rouge, New Orleans and Port Arthur.

Thanks! What does VCSH stand for? BR is rain?

[PTrackerLA]

Is this thunder sleet forecasted for Lake Charles?

36 02/04 12Z 30 29 345 8 0.05 0.02 550 569 0.5 -14.5 1025 100 -TSPL 000OVC253 0.0 5.1


Also, 00z NAM shows over 1/2" of freezing rain for Lafayette, then it changes to rain but the temp is still 32.

http://68.226.77.253/text/NAMSFC/NAM_klft.txt

[southerngale]

hmmm. Not sure, PT.


My latest NWS forecast:

Thursday: A chance of rain and snow, mainly after noon. Mostly cloudy, with a high near 35. North wind around 10 mph. Chance of precipitation is 40%. Little or no snow accumulation expected.

Thursday Night: Snow likely before midnight, then snow and sleet. Low around 26. North wind around 10 mph. Chance of precipitation is 80%. New snow and sleet accumulation of 1 to 2 inches possible.

Friday: A chance of snow and sleet before noon, then a chance of rain. Cloudy, then gradually becoming mostly sunny, with a high near 39. North wind around 10 mph. Chance of precipitation is 50%.


KFDM going with 60% frozen stuff on Thursday and 80% on Friday (freezing rain, sleet, or snow, depending on where you are and maybe all three)
They also have much lower highs for Thursday and Friday, only reaching 34 or 33. I guess that would be in Beaumont, so maybe not above freezing for some areas, like today.

[BigB0882]

Yes, TSPL is thundersleet.

[ksstormhunter]

VCSH is showers in the vicinity and BR is Mist, basically fog that is greater than 5/8 of a mile but less than 7 miles.

[ksstormhunter]

Just ran new data for Lafayette, LA. Right now looking at a good chance for .56 inches of Freezing Rain from 3-Feb at 23Z to 4-Feb at 16Z. Could get nasty down in that region. Output is at http://smartwxmodel.net

[CajunMama]

Thank you ksstormhunter. That was very nice of you to include lafayette. It is appreciated.

[southerngale]

The Winter Weather Advisory for Beaumont and other parts of the Golden Triangle has been replaced with a Winter Storm Watch and it looks like they will be issuing a Winter Storm Warning sometime soon.



AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
1146 PM CST WED FEB 2 2011

.DISCUSSION...
UPDATED FIRST PERIOD TEMPERATURES TO ACCOUNT FOR LATEST
TRENDS...WHICH RESULTED IN A SMALL INCREASE IN FORECAST LOWS.
READINGS ARE STILL EXPECTED TO FALL INTO HARD FREEZE CRITERIA...SO
NO ADJUSTMENT WAS NECESSARY TO THE HAZARD.

A COUPLE OF CONCERNING DEVELOPMENTS HAVE EMERGED IN LATEST MODEL
DATA FOR TOMORROW...LOWER TEMPERATURES AND HIGHER QPF AMOUNTS.
GIVEN THE INCREASING PROBABILITY THAT WARNING CRITERIA WILL BE MET
FROM THE GOLDEN TRIANGLE INTO LAKE CHARLES...HAVE REPLACED THE
ADVISORY IN THESE AREAS WITH A WINTER STORM WATCH. PRECIPITATION
TYPE ACROSS THE REGION CONTINUES TO BE PROBLEMATIC...WITH MORE
FREEZING RAIN AND SLEET SHOWING UP IN DETERMINATION METHODS THAN
SNOW. WILL LET THE MIDSHIFT FURTHER EVALUATE THIS AS ADDITIONAL
DATA BECOMES AVAILABLE.



.PREV DISCUSSION... /ISSUED 1104 PM CST WED FEB 2 2011/

AVIATION UPDATE...REGARDING 06Z TAF ISSUANCE. ALTOCUMULUS AT
AROUND 9K FT HAS OVERSPREAD THE AREA. CLOUDINESS INCOMING AHEAD
OF OUR NEXT POTENTIAL WEATHER MAKER NOW OVER NEW MEXICO AS A MID
LEVEL LOW.

SYSTEM TO MAKE AN EASTWARD ADVANCE THURSDAY BRINGING DETERIORATING
WEATHER CONDITIONS TO THE AREA WITH AN UNUSUAL POTENTIAL FOR WINTER
TYPE PRECIPITATION. PRECIP TO INITIALLY SPREAD INTO THE ACADIANA
AREA THURSDAY MORNING INCLUDING ARA AND LFT. FORECAST SOUNDINGS
SUGGEST LOW LEVELS WILL BE SUFFICIENTLY COOL BELOW AN ELEVATED
WARM LAYER FOR A SLEET/FREEZING RAIN MIX. AS THE DAY
PROGRESSES WITH WARMING SURFACE TEMPERATURES ABOVE FREEZING...WILL
CARRY A RAIN/SLEET MIX BEFORE RETURNING BACK TO SLEET/FREEZING
RAIN GOING THROUGH THE EVENING HOURS. BELIEVE PRECIP WILL HOLD OFF
UNTIL AFTERNOON FOR LCH AND BPT. WILL START OUT WITH A CHANCE OF
LIGHT RAIN/SLEET...SWITCHING TO FREEZING RAIN/SLEET AFTER SUNSET.
FURTHER NORTH AT AEX WITH COOLER TEMPERATURES IN PLACE...EXPECTING
PRECIP AS A FREEZING RAIN/SNOW MIX.

ONSET OF PRECIPITATION AT ALL SITES WILL BE ACCOMPANIED BY LOWERING
CEILINGS INTO MVFR. WINDS WILL REMAIN NEAR STEADY AT AROUND 10
KNOTS FROM THE NORTH THROUGH THIS TAF PACKAGE.

MARCOTTE

[BigB0882]

I have seen a few mentions of models showing lower temps. Is this true for all areas? That would be really big news for places that were previously progged to be sitting at about 33-34 in a cold rain.

[TexasSam]

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
442 AM CST THU FEB 3 2011

...WINTER STORM WARNING FOR ALL OF SOUTHEAST TEXAS FROM NOON CST
THURSDAY TO NOON CST FRIDAY...

.AN UPPER LEVEL STORM SYSTEM APPROACHING FROM THE WEST WILL
COMBINE WITH INCREASING MOISTURE AND COLD TEMPERATURES IN THE
LOWER ATMOSPHERE TO GENERATE A MIX OF SNOW...SLEET...AND FREEZING
RAIN ACROSS SOUTHEAST TEXAS THURSDAY AFTERNOON THROUGH FRIDAY
MORNING.

TXZ163-164-176>179-195>200-210>214-226-227-235>238-031845-
/O.UPG.KHGX.WS.A.0001.110203T1800Z-110204T1800Z/
/O.NEW.KHGX.WS.W.0001.110203T1800Z-110204T1800Z/
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-
GALVESTON-GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-MADISON-MATAGORDA-
MONTGOMERY-POLK-SAN JACINTO-TRINITY-WALKER-WALLER-WASHINGTON-
WHARTON-
INCLUDING THE CITIES OF...ALVIN...ANAHUAC...ANGLETON...BAY CITY...
BELLVILLE...BRENHAM...BROOKSHIRE...BRYAN...CALDWELL...CLEVELAND...
COLDSPRING...COLLEGE STATION...COLUMBUS...CONROE...CORRIGAN...
CROCKETT...DAYTON...EAGLE LAKE...EDNA...EL CAMPO...FREEPORT...
FRIENDSWOOD...GALVESTON...GROVETON...HEMPSTEAD...HOUSTON...
HUMBLE...HUNTSVILLE...KATY...LAKE JACKSON...LAKE SOMERVILLE...
LEAGUE CITY...LIBERTY...LIVINGSTON...MADISONVILLE...
MISSOURI CITY...MONT BELVIEU...NAVASOTA...ONALASKA...PALACIOS...
PASADENA...PEARLAND...PIERCE...PRAIRIE VIEW...RICHMOND...
ROSENBERG...SEALY...SHEPHERD...SUGAR LAND...TEXAS CITY...
THE WOODLANDS...TOMBALL...TRINITY...WEIMAR...WHARTON...WILLIS...
WINNIE
442 AM CST THU FEB 3 2011

...WINTER STORM WARNING IN EFFECT FROM NOON TODAY TO NOON CST
FRIDAY...

THE NATIONAL WEATHER SERVICE IN HOUSTON/GALVESTON HAS ISSUED A
WINTER STORM WARNING FOR SNOW...SLEET AND FREEZING RAIN...WHICH
IS IN EFFECT FROM NOON TODAY TO NOON CST FRIDAY. THE WINTER STORM
WATCH IS NO LONGER IN EFFECT.

AN UPPER LEVEL STORM SYSTEM APPROACHING FROM THE WEST WILL
COMBINE WITH INCREASING MOISTURE AND COLD TEMPERATURES IN THE
LOWER ATMOSPHERE TO GENERATE A MIX OF SNOW...SLEET...AND FREEZING
RAIN ACROSS SOUTHEAST TEXAS THIS AFTERNOON THROUGH FRIDAY
MORNING. THE PRECIPITATION IS EXPECTED TO BEGIN DURING THE EARLY
AFTERNOON NEAR THE COAST...AND SPREAD AREA WIDE BY EVENING. THE
WINTRY MIX WILL CONTINUE THURSDAY NIGHT THEN TAPER OFF LATE
MORNING FRIDAY.

PRECIPITATION TYPE: VERY LIGHT SNOW AND SLEET IS EXPECTED AT THE
ONSET OF THE EVENT THURSDAY ACROSS ALL OF SOUTHEAST TEXAS.
THURSDAY NIGHT AND FRIDAY MORNING...A MIX OF SLEET AND SNOW IS
EXPECTED TO THE WEST OF A LINE FROM MATAGORDA TO DOWNTOWN HOUSTON
TO NORTHERN LIBERTY COUNTY...WITH ALL SNOW ACROSS THE NORTHWEST
HALF OF THE AREA. EAST OF THIS LINE...FREEZING RAIN IS EXPECTED
TO MIX IN WITH THE SLEET AND SNOW MAINLY BEFORE MIDNIGHT. OVER
SOUTHERN BRAZORIA... SOUTHERN GALVESTON...CHAMBERS...AND SOUTHERN
LIBERTY COUNTIES MOSTLY ICE IS EXPECTED. AFTER MIDNIGHT THESE
AREAS MAY HAVE A SLEET AND SNOW MIX. FREEZING RAIN MIXED WITH
SLEET AND SNOW MAY STILL BE POSSIBLE FOR MOST OF CHAMBERS COUNTY
AND SOUTHERN MOST GALVESTON COUNTY INCLUDING GALVESTON ISLAND.
PRECIPITATION MAY CONTINUE TO CHANGE OVER TO ALL SNOW AFTER 6AM
FRIDAY EXCEPT FOR THE IMMEDIATE COAST WHERE SLEET MAY MIX WITH
THE SNOW. PRECIPITATION SHOULD COME TO AN END NEAR OR SHORTLY
AFTER NOON FRIDAY.

AMOUNTS: IN THE SNOW AND SLEET AREA...ACCUMULATIONS OF 1 TO
3 INCHES ARE EXPECTED WITH ISOLATED TOTALS AROUND 4 INCHES. THE
BEST CHANCE OF 4 INCH ACCUMULATIONS WILL BE ACROSS THE PINEY
WOODS AND LAKES AREA OF EAST TEXAS. IN THE FREEZING RAIN THREAT
AREA...ICE ACCUMULATIONS OF 1/10 TO 1/4 INCH ARE EXPECTED.

IMPACTS: DUE TO EVAPORATIVE COOLING IN THE VERY DRY AIRMASS...
TEMPERATURES WILL RUN 5 TO 7 DEGREES COLDER WITH THIS EVENT THAN
DURING THE LAST FEW WINTER WEATHER EVENTS TO IMPACT THIS AREA.
THESE COLDER TEMPERATURES WILL RESULT IN A MUCH HIGHER LIKELIHOOD
OF ROADS BECOMING ICED OVER...EVEN WITH LIGHT PRECIPITATION
AMOUNTS. THIS WILL ESPECIALLY BE THE CASE WITH ELEVATED SURFACES
LIKE BRIDGES AND OVERPASSES. ROAD CONDITIONS ARE EXPECTED TO
DETERIORATE BEGINNING AROUND SUNSET THURSDAY. IN ADDITION...POWER
OUTAGES WILL BE POSSIBLE ESPECIALLY IN THE FREEZING RAIN THREAT
AREA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

ROADS...BRIDGES...AND OVERPASSES IN THE WATCH AREA MAY BECOME
SLICK AND HAZARDOUS. ACCUMULATION OF SNOW OR ICE ON ROADWAYS...
BRIDGES AND OVERPASSES MAY MAKE TRAVEL TREACHEROUS. EXERCISE
CAUTION IF TRAVEL IS NECESSARY. IN ADDITION...POWER OUTAGES WILL
BE POSSIBLE.

[vbhoutex]

LOL vbhoutex I thought you'd be soooo excited by receiving my gift of an arctic air mass but all I've seen is you complain re cold, cold and wet, etc and all the joys it brings (and then there is your big upcoming game in the mix). ;D Yer tough Scots blood has been a wee bit spoiled living down there in lotus land.

Yes, I fear you are correct concerning the blood. Lotus land has spoiled me. We are already seeing some light snow and sleet down in the coastal areas much earlier than expected. The atmosphere may wet up more quickly than expected and it is possible that the onset may be even earlier than expected if that happens.

[Jagno]

Talk to me my Tx border friends. Looking at radar I'm seeing rain showers developing and moving into the Beaumont area. Now my forecast didn't show anything until this afternoon. Correct me if I'm wrong but we are below freezing and from past experience it doesn't take 4 hours for showers to move from Beaumont to Lake Charles. I have an MRI and physical therapy scheduled for this morning and now I'm worried about getting out on the roads if there will be ice on them. What is going on in your land?