Texas winter wx thread (2009-2010)

[Ntxw]

I have recalled in the past even though it doesn't show on the radar,usually when you see large areas of yellow on the radar, sleet can sometimes fall if the precipitation is coming down at a hard enough rate even if temps at the surface aren't cold enough (from personal experience even at temperatures in the upper 30s to lower 40s)

[snow and ice]

12z Ensembles unload the arctic air down into the lower 48 early next week.
http://www.meteo.psu.edu/~gadomski/ENSH ... /f192.html

[jeff]

I am not fully sold on the Friday event just yet...not sure where the S/W is getting all it moisture fromt given a fairly dry NW flow aloft and also the air north of us is not bitterly cold, so I am not sure evap. cooling will be able to cool to freezing. Could see snow falling and melting on contact until heavier bands develop and cool the surface layer. Still do not see the moisture or any WAA in any layer...could be the S/W squeezing it out...but the QPF being shown is fairly high for that.

[srainhoutx]

I am not fully sold on the Friday event just yet...not sure where the S/W is getting all it moisture fromt given a fairly dry NW flow aloft and also the air north of us is not bitterly cold, so I am not sure evap. cooling will be able to cool to freezing. Could see snow falling and melting on contact until heavier bands develop and cool the surface layer. Still do not see the moisture or any WAA in any layer...could be the S/W squeezing it out...but the QPF being shown is fairly high for that.

Thanks for the update Jeff. Tough call for the forecasters anytime in SE TX.

[jeff]

Looking at the GFS forecast soundings showing a warm layer to about 6,000 feet Friday morning with storng CAA in the 800mb to surface layer cooling the column. Moisture greatly saturates the 700-500mb during the day with the 00Z Sat sounding moist in that layer and CAA bringing the entire column at or below freezing. It never looks that moist below the 800mb level, so much of the moisture may be based in the mid levels. Additionally, it may start as rain and then mix/change to snow as the 6,000 above freezing layer shrinks during the day. All done by Friday evening...although I would not be surprised if things slowed down a little.

[srainhoutx]

HPC seems to have little confidence right now in guidance. Again another issue from forecasting point of view...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
209 PM EST TUE DEC 01 2009

VALID 12Z FRI DEC 04 2009 - 12Z TUE DEC 08 2009


PRELIMINARY UPDATE...

JUST BEYOND THE MEDIUM RANGE PERIOD...THERE IS AS STRONG A SIGNAL
AS NUMERICAL GUIDANCE IS WONT TO GIVE FOR A MASSIVE BUILD-UP OF
ARCTIC AIR OVER NORTHWEST CANADA. THE 00Z/01 GEFS MEAN...EC
ENSEMBLE MEAN...AND GEM ENSEMBLE MEAN ALL DEPICT THIS HERALD OF
MID WINTER...AND ARE IN CLOSE AGREEMENT ON THE PATTERN THAT LEADS
THERE FOR DAYS 3 THROUGH 7. THE DETERMINISTIC ECMWF HAS ABANDONED
THE IDEA OF A CLOSED LOW OFF THE NORTHWEST COAST...AND NOW
INCORPORATES THAT AIRMASS INTO THE MAIN BAND OF WESTERLIES OVER
THE CONTINENT. WITH SUCH GOOD AGREEMENT BETWEEN IT AND ITS
MEAN...AS WELL AS THE MEANS FROM THE OTHER MODELING
CENTERS...ELECTED TO USE THE ECMWF...BLENDED WITH ITS MEAN...FOR
THE UPDATED PRELIMINARY FRONTS AND PRESSURES. THE PATTERN IS DRY
AND SEASONABLY COLD OVER MUCH OF THE NATION...WITH THE POLAR JET
SUPPRESSED FAR TO THE SOUTH OF ITS NOVEMBER MEAN POSITION.
WHETHER A SHORTWAVE CAN ACHIEVE SUFFICIENT AMPLITUDE ALONG THE
POLAR FRONT TO HAUL GULF MOISTURE NORTHWARD AND WRING OUT
RAIN...ICE...AND SNOW OVER PARTS OF THE SOUTH AND EAST IS STILL
UNCLEAR. WILL WATCH FOR SUCH DEVELOPMENT IN THE COMING RUNS.


FINAL...

STUCK WITH THE BLEND USED FOR THE UPDATE PACKAGE FOR THE FINAL
ISSUANCE. THERE IS NO SYNOPTIC TREND ACROSS THE BOARD THIS
CYCLE...SO TWEAKING ONE SYSTEM OR ANOTHER DID NOT SEEM LIKE AN ACT
OF CONFIDENCE. THE SPLIT FLOW OVER THE WEST IS BOUND TO BE
REPRESENTED DIFFERENTLY IN THE DAYS TO COME...WITH THE CHOSEN
BLEND THAT INCORPORATED SO MUCH OF THE MOST RECENT EC ENSEMBLE
MEAN AS SAFE A BET AS ANY. THE REAL FLY IN THE OINTMENT IS HOW
DEVELOPED THE WAVE OVER THE WESTERN ATLANTIC BECOMES
SATURDAY...WITH THE POTENTIAL FOR THE SEASONS FIRST WIDESPREAD
SNOWFALL OVER THE LOWER ELEVATIONS OF THE MID ATLANTIC AND
NORTHEAST AT LEAST AN OUTSIDE CHANCE.


CISCO

[wxgirl69]

Looking at the GFS forecast soundings showing a warm layer to about 6,000 feet Friday morning with storng CAA in the 800mb to surface layer cooling the column. Moisture greatly saturates the 700-500mb during the day with the 00Z Sat sounding moist in that layer and CAA bringing the entire column at or below freezing. It never looks that moist below the 800mb level, so much of the moisture may be based in the mid levels. Additionally, it may start as rain and then mix/change to snow as the 6,000 above freezing layer shrinks during the day. All done by Friday evening...although I would not be surprised if things slowed down a little.

how cold does it need to be for snow..

[jeff]

Looking at the GFS forecast soundings showing a warm layer to about 6,000 feet Friday morning with storng CAA in the 800mb to surface layer cooling the column. Moisture greatly saturates the 700-500mb during the day with the 00Z Sat sounding moist in that layer and CAA bringing the entire column at or below freezing. It never looks that moist below the 800mb level, so much of the moisture may be based in the mid levels. Additionally, it may start as rain and then mix/change to snow as the 6,000 above freezing layer shrinks during the day. All done by Friday evening...although I would not be surprised if things slowed down a little.

how cold does it need to be for snow..

This is a loaded question. It greatly depends on the air above the ground and the depth of warm air and the near surface temperatures. Below freezing from the surface up results in snow. Warm layers can have sleet mixed in. Warm aloft and freezing at the surface supports freezing rain. 00Z Sat KIAH sounding is pretty close to a snow sounding.

[HockeyTx82]

Jeff,

What do you think of a rain/snow mix for us up here in Denton (North of Dallas area) tonight and tomorrow morning? Our local NWS keeps going back and forth on it with the forecast.

Thanks in advance.

[Tireman4]

Thank you Jeff for all you do.

[joshskeety]

I am not fully sold on the Friday event just yet...not sure where the S/W is getting all it moisture fromt given a fairly dry NW flow aloft and also the air north of us is not bitterly cold, so I am not sure evap. cooling will be able to cool to freezing. Could see snow falling and melting on contact until heavier bands develop and cool the surface layer. Still do not see the moisture or any WAA in any layer...could be the S/W squeezing it out...but the QPF being shown is fairly high for that.

Its energy that laid back and didn't phase with the Low pressure that is out to sea in the Atlantic.. In other words.. Had it phased it would of acted kind of like a clipper system, however, it is left out to be picked up by the southern Jet which is turned on at max right now..

My worry is not if the moisture will be there the models at this point are in pretty good agreement, but as we saw with this ULL all three major models had trouble putting TOO MUCH cold air..

Right now I put my crosshairs on a track from Amarillo, Lubbuck, Big Spring, San Angelo, Fredericksburg, Kileen rather than Houston.. Although, for the sake of many good Houston people here, I do hope Im wrong and they get the storm they want.. I just think there won't be enough cold air...

[msstateguy83]

it appears we could be down in the mid 30s by early-mid evening and closer to 32
by say around 9 to 10 pm or so in nw tx. rightnow its 40 in graham & munday... we have dropped to 42 here in w.falls in the last few mins.

[vbhoutex]

I am not fully sold on the Friday event just yet...not sure where the S/W is getting all it moisture fromt given a fairly dry NW flow aloft and also the air north of us is not bitterly cold, so I am not sure evap. cooling will be able to cool to freezing. Could see snow falling and melting on contact until heavier bands develop and cool the surface layer. Still do not see the moisture or any WAA in any layer...could be the S/W squeezing it out...but the QPF being shown is fairly high for that.

Its energy that laid back and didn't phase with the Low pressure that is out to sea in the Atlantic.. In other words.. Had it phased it would of acted kind of like a clipper system, however, it is left out to be picked up by the southern Jet which is turned on at max right now..

My worry is not if the moisture will be there the models at this point are in pretty good agreement, but as we saw with this ULL all three major models had trouble putting TOO MUCH cold air..

Right now I put my crosshairs on a track from Amarillo, Lubbuck, Big Spring, San Angelo, Fredericksburg, Kileen rather than Houston.. Although, for the sake of many good Houston people here, I do hope Im wrong and they get the storm they want.. I just think there won't be enough cold air...

Why do you think the track will be further North than the models are currently showing?

[Portastorm]

My worry is not if the moisture will be there the models at this point are in pretty good agreement, but as we saw with this ULL all three major models had trouble putting TOO MUCH cold air..

Which models are you talking about? The 12z Euro is much drier than its 0z run and the Canadian is almost bone dry. Furthermore, the 12z GFS run has less moisture for south Texas than its 0z run.

I think the question of whether or not there is sufficient moisture for the short wave to work with is a very valid one. Even NCEP is questioning it as evidenced from their discussion. I would place that question along with the issue of cold-enough temps on the table still.

[jeff]

Jeff,

What do you think of a rain/snow mix for us up here in Denton (North of Dallas area) tonight and tomorrow morning? Our local NWS keeps going back and forth on it with the forecast.

Thanks in advance.

I have not looked much into N TX since this past weekend. Main question is the dynamical cooling under the upper low. It seems possible especially Wed for something frozen on the backside of the low as deeper CAA enters the picture. Current soundings show WAA east of I-35 with a fairly large above freezing layer. 12Z FWD sounding showed above freezing up to 700mb...not going to get anything but rain with that profile. Out west the El Paso and Midland soundings were colder, but not a great snow profile under the colder portion of the upper low. Maybe some rain/sleet/snow mix mainly NW of the metro areas. I will punt off to any forecaster up that way that has looked better at the data. I have been highly focused on our ongoing offshore event (33kt gust in the NW Gulf) and the Friday event in the making on the models.

[msstateguy83]

i would put its still a 50/50 chance its not totally out of the question
overnight & into the morning drive tomorrow across the metroplex if it does though just flakes,
nothing big by any means, ground temps way to warm still for it to stick so nothing to worry about
or cause any type of travel problems in the dallas area.

edit: by dallas 'area' iam talking west of a denton to ft worth line i will admit i have not had a whole
lot of time today to look over the new data i just dont see temps getting low enough e of ft worth
to put any winter precip out tonight or in the am, but western sections say even ft worth up to denton
over towards decatur, weatherford might get a light winter mix.

[goCoogs]

Where can I find ground temps?
Thanks.

[joshskeety]

Why do you think the track will be further North than the models are currently showing?

Great question!!!

Most winter storms are going to follow the track of transition between cold air and warm(er) air.. Im not exactly saying that the moiture will be any further north, Im just stating with that moisture will it be cold enough on the gulf coast for frozen precip..

I see that the models have it that way, and I do hope for it to happen, but the NAM up to 60h out was showing this ULL as being much colder than it actually was.. Even I didn't believe it up until this morning.. My gut feeling is the trend will be further north..

I hope I am wrong though.. I know you guys want it...

[southerngale]

So just as I start getting sucked into this possibility, the models are backing away from the precip?

[joshskeety]

My worry is not if the moisture will be there the models at this point are in pretty good agreement, but as we saw with this ULL all three major models had trouble putting TOO MUCH cold air..

Which models are you talking about? The 12z Euro is much drier than its 0z run and the Canadian is almost bone dry. Furthermore, the 12z GFS run has less moisture for south Texas than its 0z run.

I think the question of whether or not there is sufficient moisture for the short wave to work with is a very valid one. Even NCEP is questioning it as evidenced from their discussion. I would place that question along with the issue of cold-enough temps on the table still.

The Euro has the storm, not as dynamic FOR SE Texas maybe, but remember, I am focusing on west Central Texas.. The GFS did drop up some, however has the Houston storm in place.. My question for you guys is NOT the moisture.. I question the cold air and it being cold enough on every layer including the 850mb to snow considering that you guys are already on the dividing line. And both the 12z ETA and GFS basically punch the 850 line to you guys at the last moment..

And say the Euro is more correct and there is limited moisture over SE Texas, it would take a heck of a lot of evap cooling.. I know you guys want this storm and I hope it verifies, but I think Austin has a much better chance to see snow than Houston at this point...