December Weather Discussion. Will We See Rain?

[srainhoutx]

The 12Z GEM (Canadian) is running and is coming in much colder and has a more robust Upper Air feature lagging to our W, for what it is worth.

[wxman57]

All of the models are indicating that the cold air will blast all the way down to the southern Gulf on Tuesday/Wednesday. That would would eliminate the chance of a frontal wave or west Gulf low developing near the TX coast, the main way we would typically get frozen precip here. What I see the 12Z Euro and Canadian doing (and to a much weaker extent the GFS) is moving another short wave eastward right into the ridge over Texas on Wednesday. We should have very dry air across Texas at the time, so the disturbance may not do much but spread some mid to high clouds across the state as it passes. If any precip was to fall from the mid level clouds, then it would have a hard time reaching the ground.

[wxman57]

168hr Euro is in. It does show that weak disturbance (brown area over SE TX on upper-left panel) moving right over us around sunrise Wednesday. However, look at the upper-right panel. High pressure right overhead and the 540 thickness line (dashed red line) WELL to the NE of Texas. That indicates a thin layer of cold air over Texas and very little moisture to work with.

[srainhoutx]

Also depicted to the longer range Euro is a +PNA Ridge popping up into AK. Also of note is the Euro eliminates the vortex near the Great Lakes and breaks down the blocking pattern (-NOA).

[TexasBreeze]

I don't see much of a threat either in the models. The disturbance is weak and in dry air and the models haven't really shown much except euro a couple days ago and even that's gone now. The coldest air goes east too.

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
229 PM EST WED DEC 01 2010

VALID 12Z SAT DEC 04 2010 - 12Z WED DEC 08 2010

FINAL PROGS RETAINED THE SAME BLEND AS THE UPDATED PRELIMS.
UPDATED PRELIM PROGS STARTED OFF WITH EARLY PRELIM CONTINUITY DAY
3-4 THEN TAPERED TO A MIX OF 30% CONTINUITY AND 70% ECMWF ENSEMBLE
MEAN BY DAY 7. THE 00Z/01 ECMWF MEAN WAS CHOSEN BECAUSE OF OUR
PREFERENCE FOR ITS SLOWER SCENARIO IN BRINGING THE CLOSED LOW INTO
THE SWRN CONUS DAYS 5-6.

A VERY STRONG NEGATIVE NAO FEATURES HUGE MEAN POSITIVE HEIGHT
ANOMALIES IN THE SRN DAVIS STRAIT AND A WEAKER POSITIVE ANOMALY
EXTENDING WWD OVER MUCH OF CANADA. MEAN TROFS WILL BE LOCATED OFF
EACH COAST WITH A MEAN RIDGE IN THE HIGH PLAINS. MODELS AGREE ON
THE LARGE SCALE FEATURES. A DEEP CYCLONE IS EXPECTED TO CONTINUE
HAUNTING THE NORTHEAST AND ATLANTIC CANADA THROUGH THE PERIOD.
THIS WILL REINFORCE WINDY COLDER AIR ACROSS MUCH OF THE EASTERN
AND CENTRAL PORTION OF THE LOWER 48....WITH WIDESPREAD LAKE EFFECT
SN AT LEAST THRU DAY 6. OFFSHORE THE PACIFIC NORTHWEST AND WESTERN
CANADA...A LARGE DEEP CYCLONE AND VARIOUS RELATED SHORTWAVES
ROTATING AROUND IT WILL BRING PACIFIC FRONTS INTO THE PACIFIC
NORTHWEST EARLY TO MID NEXT WEEK. THE GUIDANCE IS IN GOOD
AGREEMENT ON THESE IDEAS.

THE SMALLER SCALE FEATURES ARE TRICKIER. THERE ARE TWO SYS WHERE
THERE IS SIGNIFICANT DISAGREEMENT AMONG THE DETERMINISTIC MODELS.
THE FIRST SYS WITH WHICH THE MODELS SHOW CONSIDERABLE DISAGREEMENT
AND LARGE DAY-TO-DAY AND RUN-TO-RUN CONTINUITY CHANGES IS A
SHORTWAVE MOVING FROM THE MIDWEST THROUGH THE MID-ATLANTIC STATES
THIS WEEKEND. THE 12/01 ECMWF HAS BACKED OFF FROM ITS CLOSED
MID-LEVEL CYCLONE MOVING THROUGH VIRGINIA...BUT IS STILL ON THE
STRONG SIDE OF THE ENVELOPE OF SOLUTIONS. A STRIP OF LIGHT TO
MODERATE SN IS POSSIBLE TO THE LEFT OF THE SHORTWAVE VORT MAX
TRACK. A LIGHTLY WEAKER VERSION OF THE ECMWF IS PREFERRED OFF THE
CA COAST 12Z/05...THOUGH THE RAPID DEEPENING OF THE SYS OFFSHORE
FROM THAT POINT ON SHOWN BY OTHER 12Z MODELS IS NOT UNREASONABLE.
THE 12Z/01 UKMET AND NAM ARE ON THE STRONGER SIDE OF SOLUTIONS
WITH THIS DAY 3 SYS AS IT HEADS ESE FROM THE OH VLY ACROSS VA.

THE NEXT DISAGREEMENT REMAINS FROM THE SUBTROPICAL EASTERN PACIFIC
INTO THE SOUTHWEST AND SOUTHERN PLAINS WHERE THE 00Z/01
GFS...ECMWF...AND CANADIAN HAD COMPLETELY SWAPPED POSITIONS WITHIN
THE DETERMINISTIC SPREAD SINCE THIS TIME YESTERDAY. A SLOWLY
PROGRESSIVE RIDGE ACROSS SOUTHWEST CANADA FAVORS A RELATIVELY
PROGRESSIVE DEEP CYCLONE 20 DEGREES UNDER ITS BASE ACROSS THE
DESERT SOUTHWEST. THIS GIVES US A BROAD GENERAL AREA FAVORING THE
LOCATION OF SUCH A FEATURE. NEW ENSEMBLE SPAGHETTI PLOTS STILL
SHOW QUITE A BIT OF SPREAD AS EARLY AS DAY 4 CONCERNING THE
BEHAVIOR OF THIS SYS AS IT MOVES ONSHORE INTO THE SWRN CONUS.

12Z MODELS DETERMINISTIC MODELS CONFIRM OUR DESIRE TO STICK WITH
THE SLOWER ECMWF SOLUTION AS THE SYS COMES ASHORE INTO THE SW
EARLY NEXT WEEK. THE NEW UKMET AND CANADIAN SUPPORTED OUR UPDATED
PRELIM REASONING HERE THAT THE SLOWER SPREED OF THE 00Z/01 ECMWF
IS PREFERRED OVER THE FASTER GFS. THEY ARE SLIGHTLY MORE THAN 12
HOURS FASTER BRINGING THIS SYS ACROSS THE SW QUADRANT OF THE
CONUS. THE 12Z ECMWF WAS ROUGHLY 6 HOURS SLOWER THAN THE
CANADIAN/UKMET. THE SYS LOOKS TO HAVE ENOUGH PACIFIC MOISTURE TO
BRING MODERATE QPF TO THE MOUNTAINS OF CA ON ITS TREK
INLAND...WITH LIGHTER AMOUNTS OVER THE INTERIOR SOUTHWEST.

[wxman57]

Also depicted to the longer range Euro is a +PNA Ridge popping up into AK. Also of note is the Euro eliminates the vortex near the Great Lakes and breaks down the blocking pattern (-NOA).

Fine with me. Winter's over!

[srainhoutx]

Also depicted to the longer range Euro is a +PNA Ridge popping up into AK. Also of note is the Euro eliminates the vortex near the Great Lakes and breaks down the blocking pattern (-NOA).

Fine with me. Winter's over!

I thought you would like that. Break out the shorts and t-shirts and open the pool!

[TexasBreeze]

I can't remember the last time I've seen hail at my house. Its been awhile since there's been a wide severe weather outbreak around here!

[Portastorm]

Also depicted to the longer range Euro is a +PNA Ridge popping up into AK. Also of note is the Euro eliminates the vortex near the Great Lakes and breaks down the blocking pattern (-NOA).

Yep, after this next frontal passage, looks like semi-zonal to zonal flow and good fire weather for West Texas and the Panhandle, unfortunately.

[srainhoutx]

HGX thoughts regarding Sunday through Wednesday...

THE 12Z NAM/GFS/ECMWF ARE MORE IN LINE WITH THE PASSAGE OF THE
NEXT FRONT. ALL THE MODELS BRING THE FRONT INTO SE TX BY 00Z SUN
AND THEN OFF THE COAST OVERNIGHT. THERE SHOULD BE A DECENT
TEMPERATURE DROP WITH ANOTHER POLAR AIRMASS COMING IN BEHIND THE
FRONT. GFS DOES SUGGEST SOME SHOWERS WITH THE FRONT ALONG THE
COAST BUT AS STATED EARLIER...HAVE DOUBTS AS TO THE QUALITY OF
MOISTURE TO SUPPORT THE SHOWERS. FOR NOW I WILL KEEP POPS OUT OF
THE FORECAST BUT COULD ALSO SEE SUPPORT FOR A 20 POP. RIGHT NOW I
HAVE ENOUGH UNCERTAINTY TO LEAVE IT OUT. TEMPERATURES FOR SUNDAY
WERE DECREASED QUITE A BIT WITH THE CHANGE IN AIRMASS AND BECAUSE
OF THE MODELS COMING MORE IN LINE WITH THE TIMING OF THIS FRONT.

GFS/ECMWF KEEP NORTHERLY WINDS IN PLACE BUT DIFFER IN THAT THE
ECMWF KEEPS CONTINUAL NORTHERLY FLOW WITH NW FLO ALOFT THROUGH
THE MIDDLE OF NEXT WEEK. THE GFS KEEPS THIS IDEA OF NW FLOW ALOFT
BUT BRINGS ANOTHER STRONGER SURGE OF POLAR AIR INTO THE AREA
EARLY TUE MORNING. GFS HAS MORE PRECIP DEVELOPING ALONG THE FRONT
AND OVER THE FRONT BUT 295K/300K ISENTROPIC ANALYSIS REALLY DOES
NOT SUPPORT A LOT OF LIFT FOR PRECIP. FORE NOW I LIKE THE GFS
SOLUTION FOR CONTINUITY PURPOSES AND THE FORECAST WILL KEEP 20
POPS FOR NOW WITH LIGHT RAIN POSSIBLE. CLOUD/RAIN SHOULD CLEAR
OUT BY THE AFTERNOON SO MAY HAVE TEMPS WARM INTO THE MID/UPPER
50S. HIGH PRESSURE WILL MOVE OVER THE ARE NEXT WED SO MIN TEMPS
MAY DROP BACK INTO THE 30S.

[TexasMetBlake]

This board is dead....man, stupid Euro model.

[srainhoutx]

This board is dead....man, stupid Euro model.

Ya never know. We could see a major flip via guidance yet again overnight. And those short waves have burned many a forecaster in the past.

[srainhoutx]

lol, the 18Z GFS develops a Coastal near the Middle TX Coast near hour 138 along the short wave that passes to our N and is pushed offshore S of LA. I strongly suspect we have not seen the last of model flip flops in this difficult pattern. Remember we are talking about an event that may or may not happen Monday night through Wednesday morning of next week.

[biggerbyte]

All models are bi-polar... Lol

Too many variables with this forecast, using the models, or not. I won't even touch it until Sunday.

[TexasMetBlake]

I agree with Wxman...the dry flow aloft is going to choke any moisture that can form. This is just a poor, poor setup for snow.

[TexasMetBlake]

18z GFS Ensembles:

[helloitsb]

18z GFS Ensembles:
http://raleighwx.americanwx.com/models/ ... p12144.gif

Sorry for my "amateur " ability to read models but that looks good for us right?

[srainhoutx]

Step back to hour 132. If the 'coldest' air is shunted to our E, those E/NE winds would make for some chilly CAA (cold air advection) into our part of the world.

[srainhoutx]

The Big/Wide viem from water vapor imagery this afternoon. I'm watching a feature near HI and also near 165E...