Texas winter wx thread (2009-2010)

[Ntxw]

Constantly reiterated, believe when you see it

[srainhoutx]

18Z NAM is looking good out to 60 hours...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... f_060l.gif

[msstateguy83]

i think by far the biggest event will be thu night - sat am atleast
and temps will be lowered in later forecast for that time peroid to i
would say between 32-40 for daytime highs with lows around 25
for a large portion of ok into nrn, nwrn tx.. still of course to hard
to pinpoint snow accums at this point but i have more hope for that
upcoming event then i do this one.

[southerngale]

Constantly reiterated, believe when you see it

Ain't that the truth! There will be many more disappointments than snow events, no doubt. But most of us still hope and dream.

[joshskeety]

Looking at the 18z NAM it is dryer.. However, snow ratio's for West Central Texas are easily 12-15:1 with that cold air.. Could be 2-4" there..

[joshskeety]

18z give Houston about a 1-3 inch swath of snow there as well 84h out.

[southerngale]

Got a link handy? I'm wondering what it shows just east of Houston, in the Beaumont area. It's often similar, but not always.

Not that I believe any of this nonsense...

[srainhoutx]

Yep. The 18Z NAM would drop snow in SE TX. Long way out yet, but the trends are moving in the right direction.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

[joshskeety]

Got a link handy? I'm wondering what it shows just east of Houston, in the Beaumont area. It's often similar, but not always.

Not that I believe any of this nonsense...

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084l.gif

[southerngale]

Thanks... I'll pick this run to verify. Where do I checkout?

[wxman57]

Here are some model soundings for IAH (Bush Airport, Houston). I'm comparing the 12Z GFS with the 18Z NAM. First the GFS forecast for 21Z (3pm) Friday

Note that the green (dew point) and red (temp) lines are touching (or nearly so) from the surface up to 500mb, meaning that the air is saturated. Plenty of moisture there. And note that the air is well below freezing from just above the surface Friday afternoon during the peak of the precip event, according to the GFS:



Now look at the GFS projection for 3Z Saturday (9pm CST Friday). Quite a difference! The GFS ends the precip by 00Z Sat (6pm Friday) and dries us out very fast Friday evening.



The 18Z NAM is slower with the impulse coming across, making the time of peak precip Friday evening. It's also warmer in the lower levels and with a bit less moisture. The NAM typically shows less moisture in these kind of events. Usually it's in error. As with the GFS, I indicated the freezing level with the red line across the text part of the forecast.



Now look at the NAM forecast for 03Z Saturday (9pm Friday). Still warmer than the GFS, but that sounding is quite saturated up to 500mb. Good amount of moisture while the GFS, at the same time, says clearing. So it's a question of timing of the precip. The later it occurs, the greater the chances of accumulation.



For now, I'm getting more confident that southeast Texas will see some snow. I'm just not confident in amounts.

[srainhoutx]

HGX thoughts for now...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
317 PM CST TUE DEC 1 2009

.DISCUSSION...
A STRONG CLOSED UPPER LEVEL LOW CONTINUES TO PUSH ACROSS THE BIG
BEND AND INTO W TX THIS AFTERNOON. SFC ANALYSIS DEPICTS A COASTAL
LOW PRESSURE OFF THE TX GULF COAST. THE COASTAL LOW WILL HELP
MAINTAIN EASTERLY WINDS WHICH WILL TURN MORE TO THE NORTH
OVERNIGHT. THIS SHOULD BRING AN END TO ANY COASTAL FLOODING
ISSUES. THE CLOSED LOW SHOULD PUSH ACROSS TX TONIGHT WITH ANOTHER
ROUND OF MODERATE RAIN ON ITS WAY. REGIONAL RADARS SHOW THIS RAIN
OVER MUCH OF W C TX AND C TX. ITS EASTERN EDGE IS JUST STARTING
TO REACH SE TX. RAIN WILL PASS THROUGH SE TX MAINLY BETWEEN 00Z
AND 06Z WED WITH RAIN TAPERING OFF AFTER 06Z. SOME LINGERING RAIN
WILL BE POSSIBLE INTO WED MORNING BUT DRIER CONDITIONS ARE
EXPECTED WED AFTERNOON.

12Z 500MB ANALYSIS ALONG WITH WATER VAPOR IMAGERY SHOW THE NEXT
SHORTWAVE TO AFFECT SE TX IN THE PAC NW. THIS WAVE PASSES THROUGH
THE ROCKIES RATHER SLOWLY OVER THE NEXT COUPLE OF DAYS UNTIL A
110KT JET STREAK AT 300MB PUSHES INTO THE SHORTWAVE THU NIGHT.
THIS SHORTWAVE THEN SWINGS ACROSS TX INTO SE TX BY 00Z SAT. THE
NAM/GFS SOLUTIONS ARE IN FAIRLY DECENT AGREEMENT ALTHOUGH THE
MAIN PROBLEM OVER THE NEXT COUPLE OF DAYS WILL BE THE TIMING OF
THIS FEATURE AND WHETHER IT SPEEDS UP OR SLOWS DOWN. AS THE
SHORTWAVE MOVES ACROSS THE AREA...STRONG COLD ADVECTION OCCURS
ALLOWING FOR FALLING TEMPERATURES DURING THE DAY. TEMPS AT 850MB
DROP BELOW FREEZING DURING THIS TIME. LOOKING AT MOISTURE FIELDS
AND FORCING...IT LOOKS LIKE PRECIPITATION WILL LIKELY START AS
RAIN DURING THE MORNING AND CHANGE OVER TO SNOW DURING THE DAY ON
FRIDAY AS TEMPERATURES DROP. THIS IS ALL DUE TO THE SHORTWAVE
TROUGH MOVING OVER THE REGION WITH STRONG QG LIFT. FRONTOGENESIS
INCREASES DURING THE DAY MAINLY IN THE MID LEVELS. THE NAM IS
STRONGER THAN THE GFS WITH THE FORCING AND SUPPORTS BANDED
PRECIPITATION OVER THE REGION. STILL BOTH MODELS SHOW A
TRANSITION OF RAIN TO SNOW IN THE MODEL SOUNDING DATA AS FAR
SOUTH AS KHOU. GENERALLY THINK AREAS NORTH OF I-10 WILL SEE A
COMPLETE TRANSITION WITH AREAS SOUTH OF I-10 SEEING A MIX OF
RAIN/SNOW. AGAIN A LOT OF THE FORECAST DETAILS HINGE ON THE
TIMING OF THE SHORTWAVE TROUGH AS WELL AS HOW MUCH MOIST COLD AIR
WILL BE AVAILABLE IN THE LOWER LEVELS. POPS WERE INCREASED TO 40
PERCENT AREA WIDE BUT COULD SEE HIGHER CHANCES SHOULD THE MODELS
BEGIN TO KEY ON A SPECIFIC AREA FOR RAIN/SNOW. SNOW ACCUMULATIONS
ARE DIFFICULT TO DETERMINE AT THIS TIME BUT SHOULD THE MODELS
CONTINUE WITH THESE TRENDS...THERE MAY BE THE THREAT OF ENOUGH
SNOW ACCUMULATION TO WARRANT A WINTER WEATHER WATCH/WARNING. A
SPECIAL WEATHER STATEMENT (SPS) WILL BE ISSUED TO HANDLE MORE
DETAILS AND PROVIDE UPDATES AS FORECASTERS MONITOR THIS
DEVELOPING WINTER WEATHER SCENARIO.
THE SYSTEM SHOULD BE FAST MOVING SO ANY RAIN/SNOW SHOULD BE OUT
OF SE TX FRI NIGHT. ANOTHER WEAK SHORTWAVE IN THE STRONG ZONAL
FLOW ON SUNDAY WILL PROVIDE ENOUGH LIFT FOR A ROUND OF SHOWERS.
POPS WERE INCREASED TO 30 PERCENT FOR SUNDAY WITH DRIER
CONDITIONS ON MONDAY. GIVEN A RATHER PROGRESSIVE PATTERN WITH
SHORT WAVE TROUGHS AND JET STREAKS PROPAGATING THROUGH THE
FLOW...WILL MAINTAIN 20 POPS FOR ALL OF EARLY NEXT WEEK. THIS
WILL MAINLY BE DUE TO SHOWERS DEVELOPING WITH ANY WARM
ADVECTION/ISENTROPIC LIFT SITUATIONS THAT DEVELOP. TEMPERATURES
DO MODERATE EARLY NEXT WEEK BUT WILL STILL RUN BELOW NORMAL FOR
THE WEEKEND.

39/OVERPECK

[Portastorm]

OK, I guess it is my turn to gripe about my local NWS forecaster. The afternoon forecast out of New Braunfels says only rain for Austin on Thursday night and Friday. The GFS and NAM runs show 1-2 inches of accumulating snow and the skew-T's I saw earlier showed an atmospheric profile which supported frozen precip.

I'll be interested to see if they change their tune tomorrow morning.

[wxgirl69]

Here are some model soundings for IAH (Bush Airport, Houston). I'm comparing the 12Z GFS with the 18Z NAM. First the GFS forecast for 21Z (3pm) Friday

Note that the green (dew point) and red (temp) lines are touching (or nearly so) from the surface up to 500mb, meaning that the air is saturated. Plenty of moisture there. And note that the air is well below freezing from just above the surface Friday afternoon during the peak of the precip event, according to the GFS:



Now look at the GFS projection for 3Z Saturday (9pm CST Friday). Quite a difference! The GFS ends the precip by 00Z Sat (6pm Friday) and dries us out very fast Friday evening.



The 18Z NAM is slower with the impulse coming across, making the time of peak precip Friday evening. It's also warmer in the lower levels and with a bit less moisture. The NAM typically shows less moisture in these kind of events. Usually it's in error. As with the GFS, I indicated the freezing level with the red line across the text part of the forecast.



Now look at the NAM forecast for 03Z Saturday (9pm Friday). Still warmer than the GFS, but that sounding is quite saturated up to 500mb. Good amount of moisture while the GFS, at the same time, says clearing. So it's a question of timing of the precip. The later it occurs, the greater the chances of accumulation.



For now, I'm getting more confident that southeast Texas will see some snow. I'm just not confident in amounts.

Wow.. If you think we may get snow.. It's time for everyone to get excited!!!!

[joshskeety]

18z GFS Shows ABI/SJT with .30-.40 QPF with snow ratio's 12:1 That would be 3-5 inches of snow..

[srainhoutx]

18Z GFS thumps Houston as well. Signs of oa Coastal Low/Trough forming in S TX. Goodness.

[joshskeety]

lol...

...WINTRY WEATHER POSSIBLE THURSDAY NIGHT INTO FRIDAY...
UPPER TROUGH IN PACIFIC NW...WILL MOVE INTO THE REGION BEGINNING
THURSDAY EVENING AND ENDING AROUND NOON FRIDAY. THERE WAS VERY
GOOD DYNAMICS AND LIFT FROM 500 TO 800 MB WITH THIS SYSTEM.
ALSO...THERE WAS NO SHORTAGE OF COLD AIR FOR SNOW. PROFILES
SOUNDINGS FOR ABILENE... SAN ANGELO...JUNCTION ALL SHOW A SNOW
PROFILE WITH SOUNDINGS BELOW FREEZING AND SATURATING IN THE
LOW/MID LEVELS BY THURSDAY MIDNIGHT. GFS AND NAM QFP (RAINFALL)
COMES IN AROUND .10 TO .40 INCHES...OR 1 TO 4 INCHES OF SNOW AT A
1 TO 10 RATIO. WILL NOT GO THAT HIGH ON QPF AND SNOW
ACCUMULATIONS ON THIS FORECAST...KEEPING SNOW AMOUNTS IN WEATHER
GRIDS LESS THAN 1 INCH. HOWEVER WITH THE VERY STRONG JETS AND
DYNAMIC...THAT MAY CHANGE IN LATER RUNS...AS CONFIDENCE INCREASES
AS THE EVENT APPROACHES. NAM AND GFS ARE CLOSE IN
AGREEMENT...WITH THE ECMWF DELAYING THE SYSTEM AND PRECIPITATION
UNTIL AFTER 6 AM FRIDAY.


-------------

I wont say "conservative".. I PROMISE..

[double D]

I know that everyone is focused on the Friday and Saturday event, but the 18z GFS is showing a massive 1056 high coming down the western side of Canada next week. It looks like we might be getting our Christmas presents early if you like COLD!

[double D]

OK, I guess it is my turn to gripe about my local NWS forecaster. The afternoon forecast out of New Braunfels says only rain for Austin on Thursday night and Friday. The GFS and NAM runs show 1-2 inches of accumulating snow and the skew-T's I saw earlier showed an atmospheric profile which supported frozen precip.

I'll be interested to see if they change their tune tomorrow morning.

The forecaster this morning actually added snow for Thursday and Friday, so it sounds like the afternoon shift did not agree. Sometimes it seems that EWX are last to jump on board on these type of events.

[natlib]

18z GFS Shows ABI/SJT with .30-.40 QPF with snow ratio's 12:1 That would be 3-5 inches of snow..

I think the San Angelo meteorologists are "conservative" because of the donut hole San Angelo is in. Rain usually goes around us, and we have only had one appreciable snowfall here in the past 7 years. I think that's why they always take a "believe it when I see it" attitude. I was hoping they were wrong about today, but again, they were right on.

That being said, I hope they are wrong on Friday and we get dumped on.