Texas winter weather thread - Cold snap next week

[jeff]

For central TX readers:

Sleet advisory issued for areas north and west of Austin (Travis County).

I have not looked at the 18Z model runs and will try and do that before 800pm.

Feel rain mixed with IP is possible over Austin metro and even southward with some complete change to IP and SN north and west of metro areas.

Surface temps are a bear this evneing as they may hover just above freezing from Austin southward resulting in melting on contact...or they may slip below freezing by a degree resulting in ice acc. on bridges and overpasses. NWS may need to shift sleet adv or issue a WWA for Austin metro early Thursday based on trends.

We are moving into the radar/temp trend period where the models have done a decent job a week ago of forecast an arctic air outbreak...trying to pinpoint to the city block who will see rain vs sleet vs snow in such an even is difficult even an hour ahead of time. Cold air depth, surface temp, and moisture will all be determining factors through the day on Thursday.

Let me look at the 18Z runs and I will try and get something out this evening for the corridor from Austin to KCLL and KUTS as N TX is simply in the Warning area and areas southward are a little more questionable per above mentioned factors.

[jasons2k]

Gainesville is reporting light snow but I'd look at this ob with caution - they have reported snow before when it wasn't really snowing. Spinks west of FTW does the same thing a lot.

[Kelarie]

Thanks Jeff for the central Texas update!

[Portastorm]

Yeah Jeff, thanks a bunch! Really appreciate your work and sharing your forecasts with us!

Meanwhile, the polar front continues to defy the models. NWS San Angelo had this to say at 6 p.m.:

THE TEMPERATURES BEHIND THE FRONT ARE FALLING VERY
QUICKLY AND THIS IS HARD TO PIN DOWN IN THE GRIDS...BUT GAVE IT
ANOTHER SHOT BASED ON THE LATEST DATA. COLD FRONT IS CURRENTLY
FROM ABOUT STERLING CITY TO SOUTH OF BALLINGER TO JUST NORTH OF
BROWNWOOD. CONVECTION CONTINUES TO DEVELOP RIGHT ALONG THE FRONT
AND SHOULD CONTINUE TO DO SO FOR THE NEXT SEVERAL HOURS. SO WITH
TEMPERATURES FALLING A LITTLE FASTER THAN EXPECTED...FREEZING
PRECIPITATION COULD START A FEW HOURS FASTER THAN EARLIER THOUGHT.
SO HAVE INCREASED THE SLEET AND SNOW ACCUMULATIONS. CROSS SECTIONS
SHOWING A GOOD DEAL OF UPRIGHT CONVECTIVE POTENTIAL AS WELL AS
SLANT WISE. THROUGH 15Z TOMORROW. MY ONLY CONCERN IS THE DRY SLOT
THAT IS CURRENTLY PUSHING INTO THE FORECAST AREA MAY HINDER THE
PRECIPITATION. WILL HAVE TO WAIT FOR THE MAIN UPPER LOW TO MOVE
ACROSS LATE TONIGHT FOR PRECIPITATION DEVELOPMENT. PROFILES MUCH
COLDER AND THUS MORE POTENTIAL FOR SNOW. WILL RETAIN THE MENTION
OF THUNDER WITH ALL THE INSTABILITY PRESENT.

WITH THAT SAID...WILL LEAVE HEADLINES AS IS FOR NOW AND UPDATE
LATER IF NEEDED. MAY HAVE TO EXTEND THE WARNING BACK WEST A LITTLE
IN THE BIG COUNTRY AND THE ADVISORY TO THE SOUTH A LITTLE MORE
ACROSS THE HEARTLAND. WILL CONTINUE TO ANALYZE MORE DATA BEFORE
MAKING THAT DETERMINATION THOUGH.

[jasons2k]

as some have said in the past, the biggest surprises usually come when they're not expected. Now I am not calling for a major storm or anything, but I think that there is a very good chance I will be seeing something by tomorrow afternoon/evening. I have that feeling in my gut about this for some reason. I guess we shall see though, anything is possible. I could either be dead wrong or 100% correct, but ATM I am still just "monitoring" the situation.

The 0Z models should be helpful.

Up until about a year ago I had the same gut feelings - it was called wanting it so badly I just KNEW the NWS would be wrong.....well that and them usually busting on the warm/dry end of things with marginal/questionable events. You are right - the big events seem to come when it's least expected.

I do think you are right in some respects with this system; I think it will end-up being more intense for areas north of here than has been forecasted. I think DFW is going to get a good storm out of this with totals higher than forecasted. I think the sleet/ice line will come further south than originally expected.

But I don't think we'll see anything here - by that I mean south of a Livingston to Brenham line...maybe MAYBE up to Hempstead/Conroe but IMO that's a BIG stretch.

[jasons2k]

Love has dropped to 54F and the front is now at Downtown Dallas...

And if you believe the obs, Bridgeport is reporting a Thunderstorm with snow.

[Extremeweatherguy]

as some have said in the past, the biggest surprises usually come when they're not expected. Now I am not calling for a major storm or anything, but I think that there is a very good chance I will be seeing something by tomorrow afternoon/evening. I have that feeling in my gut about this for some reason. I guess we shall see though, anything is possible. I could either be dead wrong or 100% correct, but ATM I am still just "monitoring" the situation.

The 0Z models should be helpful.

Up until about a year ago I had the same gut feelings - it was called wanting it so badly I just KNEW the NWS would be wrong.....well that and them usually busting on the warm/dry end of things with marginal/questionable events. You are right - the big events seem to come when it's least expected.

I do think you are right in some respects with this system; I think it will end-up being more intense for areas north of here than has been forecasted. I think DFW is going to get a good storm out of this with totals higher than forecasted. I think the sleet/ice line will come further south than originally expected.

But I don't think we'll see anything here - by that I mean south of a Livingston to Brenham line...maybe MAYBE up to Hempstead/Conroe but IMO that's a BIG stretch.

you very well may be right too. Tomorrow will be an interesting day to see what actually plays out. It would be fun though if we could get a sleet pellet/snow flake down here before it is all over with, but I agree it will be a big stretch. We should know more tomorrow.

If not winter precip. though, there does seem to be a chance of hail with any storms we get tonight. So ice, in some form, does look possible down here from this system.

[gatorcane]

wow what a temperature contrast. 73F in Dallas and 29F just a few hours north up the road!

Check out the current US temps:
http://www.weather.com/maps/maptype/cur ... enter_maps

[jasons2k]

True

[Extremeweatherguy]

check out this report from Bridgeport, TX:

Bridgeport Municipal Airport
Last Update on Nov 29, 7:08 pm CST

Thunderstorm Snow

36°F
(2°C)
Humidity: 100 %
Wind Speed: N 9 G 25 MPH
Barometer: 29.91"
Dewpoint: 36°F (2°C)
Wind Chill: 29°F (-2°C)
Visibility: 0.75 mi.

Thudersnow is pretty rare for the south. This is impressive.

[Extremeweatherguy]

[Portastorm]

This just in ...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
734 PM CST WED NOV 29 2006

.UPDATE...
MADE QUICK UPDATE TO MAKE A FEW ADJUSTMENTS TO CURRENT WEATHER. ALSO
CHANGED THE SLEET ADVISORY TO A WINTER WEATHER ADVISORY WHICH IS
MORE APPROPRIATE GIVEN THE STRONG WINDS AND WIND CHILLS IN
ADDITION TO THE SLEET THURSDAY MORNING.

*******************
Guess I'm a little more optimistic about this event.

The trend over the last 6 hrs from the NWS is certainly for a worse situation tomorrow morning.

[double D]

This just in ...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
734 PM CST WED NOV 29 2006

.UPDATE...
MADE QUICK UPDATE TO MAKE A FEW ADJUSTMENTS TO CURRENT WEATHER. ALSO
CHANGED THE SLEET ADVISORY TO A WINTER WEATHER ADVISORY WHICH IS
MORE APPROPRIATE GIVEN THE STRONG WINDS AND WIND CHILLS IN
ADDITION TO THE SLEET THURSDAY MORNING.

*******************
Guess I'm a little more optimistic about this event.

The trend over the last 6 hrs from the NWS is certainly for a worse situation tomorrow morning.

Watch us wake up in the morning and it's snowing outside. Okay, mabye I'm -removed- a little bit, but you never know.

[gboudx]

Front if through Rockwall. I can personally verify that. Nice and chilly outside.

[Extremeweatherguy]

Dallas (executive airport) has gone from 73F to 49F in one hour! That is another 24F one hour drop to add to the list. Also, in Fort Worth, it is now 38F! That is a 37F temperature drop in just 3 hours!

Also, Granbury, TX has dropped from about 72F to 39F in just over 2 hours time...that is a 33F drop (they also dropped from 72F to 48F in just 40 minutes earlier today! That is a 24F drop in 40 minutes!)

[jeff]

Arctic boundary extends from SE NM to east side of Dallas with numerous elevated thunderstorms N of the boundary...some producing sleet.

Per observation from Rockwall, TX temp fell from 76 to 54 in 4 minutes with frontal passage and is now at 51 degrees.

After review of 18Z model data NAM and GFS along with 00Z TH RUC run it would appear winter precip. is possible for areas of central TX along and NW of a line from just south of Austin to N of Giddings to College Station to NW of Huntsville on Thursday.

Main difference in the models in onset of dry slot to rotate through the south side of the upper level low. Cold air is a little more robust and is clearly noted in current observations along and N of arctic boundary. Strong convective elements north of frontal boundary is producing high enough rainfall rates to cool the air column and result in snow and sleet NW and W of the metroplex of Dallas. Feel this will become more common as the night goes on with N of the arctic boundary.

Threat for sleet, snow mix will be possible Austin metro and northward and westward maybe as far south as Del Rio Thursday AM before dry slot sweeps eastward. GFS is slower with the drying indicating a longer threat. Like the RUC handling of the moisture, but feel the freezing temps. in this model are slightly too far west and would adjust about 40-50 miles eastward to include the I-35 corridor. All models show mean RH falling below 70% by 00Z Friday suggesting precip. will end rapidly during the afternoon from WSW to ENE.

Further east...models are not very aggresive in driving the freezing line into SE TX. GFS 2m 0C line remains N of SE TX thorugh 00Z Friday suggesting any threat would be liquid as 850mb 0C also remains W of the area. Feel the models may be under forecasting the potential for cooling due to precipitation processes N and W of the region...although agreement in all solutions is that freezing/frozen precip. should just touch the NW zones of SE TX (Burleson, Madison, Houston counties) as the good vorticity swings just NW of this area and the track of the upper low core is NE from SE NM toward C OK.

Elsewhere:

May need to update N TX accumulation totals if present convetive snow/sleet showers become more widespread and accumulations onset sooner than expected.

[Extremeweatherguy]

0Z NAM now coming in and it looks even slightly cooler than the 18Z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _024.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_024l.gif

seems like they are getting cooler and cooler with each run (especially 850mb temps.) Looks like the 0C 850mb line now reaches areas of NW Houston by early evening tomorrow if this is correct.

Jeff, would these cooler 850mb temps. possibly lead to a chance of winter precip. above 32F?

[jeff]

0Z NAM now coming in and it looks even slightly cooler than the 18Z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _024.shtml

seems like they are getting cooler and cooler with each run (especially 850mb temps.) Looks like the 0C 850mb line now reaches areas of NW Houston by early evening tomorrow if this is correct.

Jeff, would these cooler 850mb temps. possibly lead to a chance of winter precip. above 32F?

That run of the NAM is colder, however look at the 700mb moisture and precip at that time...it is pretty dry by the time the temperature is cold enough for anything.

Precip processes in the atmosphere could lead to frozen precip. with the surface temp above freezing, although the profiles really do not support this in SE TX...more likely in C TX.

[Extremeweatherguy]

0Z NAM now coming in and it looks even slightly cooler than the 18Z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _024.shtml

seems like they are getting cooler and cooler with each run (especially 850mb temps.) Looks like the 0C 850mb line now reaches areas of NW Houston by early evening tomorrow if this is correct.

Jeff, would these cooler 850mb temps. possibly lead to a chance of winter precip. above 32F?

That run of the NAM is colder, however look at the 700mb moisture and precip at that time...it is pretty dry by the time the temperature is cold enough for anything.

Precip processes in the atmosphere could lead to frozen precip. with the surface temp above freezing, although the profiles really do not support this in SE TX...more likely in C TX.

thanks jeff!

BTW: Do you see any chance at all that places in northern Harris county could see any kind of winter precip. out of this (even if only mixed with rain)? Or do you think it is pretty much a no deal situation for us?

[Portastorm]

NWS just issued a Tornado Watch for the Austin area!

I don't think I can remember a time when we had a Winter Weather Advisory and Tornado Watch in effect for the same areas.

An amazing storm system for sure ...