December-Wet/Stormy New Years Eve Ahead

[tireman4]

This is the latest from the NWS HGX. They are still being vigilant...


POTENT UPPER TROF WILL APPROACH FROM THE WEST TONIGHT. AS THIS
OCCURS THE SFC BOUNDARY WILL BEGIN MOVING BACK NWD AS A WARM
FRONT AND BECOME A FOCUS FOR POSSIBLE STRONG/SEVERE STORMS. 00Z
MODEL RUNS DON`T CHANGE MUCH IN THE WAY OF TIMING & DETAILS
ALREADY BEING ADVERTISED. ANTICIPATE INCREASED SHRA/TSRA COVERAGE
TOWARD MIDNIGHT AS LARGE SCALE LIFT IS ENHANCED. CHANCES OF SEVERE
WX INCREASE OVERNIGHT...GENERALLY ALONG AND NORTH OF I-10 AND IN
THE VICINITY OF THE NWD MOVING WARM FRONT. POTENTIAL STILL EXISTS
FOR ISOLATED TORNADOS ESP IF ANY DISCREET CELLS MANAGE TO DEVELOP.
WIND/HAIL WILL BE SECONDARY THREATS. PRECIP SHOULD END FROM WNW-
TO-ESE DURING THE 10AM-1PM TIMEFRAME AS PREFRONTAL TROF PUSHES
THRU. FRONT ITSELF WILL THEN MOVE THROUGH DURING THE AFTN HOURS
WITH BREEZY/WINDY CONDITIONS AND FALLING TEMPS GOING INTO EVNG.
NUMERICAL GUIDANCE STILL SUGGESTING FREEZING TEMPS NW OF HWY 59
TUE NIGHT. HOWEVER...WINDS & WET GROUND MAY END UP BEING LIMITING
FACTORS FOR SOME SPOTS.


http://forecast.weather.gov/product.php ... glossary=1

[srainhoutx]

The 12Z GFS is suggesting some strong to severe storms may develop N and E of Houston.

[srainhoutx]

The HPC Medium Range Discussion this morning takes us right into the New Years Eve time frame...well worth the read...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1050 AM EST MON DEC 24 2012

VALID 12Z THU DEC 27 2012 - 12Z MON DEC 31 2012

...POSSIBLE COASTAL SYSTEM TO IMPACT THE NERN CONUS ON DEC 29/30...

THE MEDIUM RANGE PERIOD WILL ESSENTIALLY COVER THE REMAINDER OF
2012 WITH A VERY ACTIVE PATTERN IN STORE. THE MID-LEVEL FLOW IS
FCST TO CONSIST OF A HIGH AMPLITUDE PATTERN AS TROF ENERGY LOADS
UP IN THE SWRN CONUS BEFORE EJECTING EWRD TOWARD THE SRN
PLAINS/LWR MS VALLEY. SUCH A PATTERN APPEARS TO BE LOCKED IN PLACE
AS THE SYSTEM OVER THE COASTAL MID-ATLC EARLY D3/THU SHOULD FOLLOW
THIS PARTICULAR TRACK DURING THE SHORT RANGE. AS THIS DISTURBANCE
LIFTS UP TOWARD NOVA SCOTIA...BROAD SWRLY FLOW ALOFT WILL BE
FEATURED ACRS THE ERN U.S. AS A TROF BEGINS DIGGING OVER THE FOUR
CORNERS REGION. THRU D4...THE MODEL GUIDANCE IS IN RELATIVELY GOOD
AGREEMENT BUT SPREAD EVOLVES THEREAFTER. MUCH OF THE UNCERTAINTY
EXISTS IN HOW AMPLIFIED THIS SWRN TROF BECOMES AS IT CROSSES INTO
THE PLAINS/MS VALLEY. EARLY D5/SAT...THE 00Z UKMET IS MOST
AGGRESSIVE/PROGRESSIVE WITH THE SHRTWV REACHING THE LWR TN VALLEY
WHILE THE GFS SUITE OF SOLNS CONTINUES TO BE MORE SUPPRESSED.
LOOKING UPSTREAM...THE PAST FEW RUNS OF THE GFS CONTINUES TO
INSIST ON ENERGY SPLITTING OFF FROM THE NRN STREAM INTO THE PAC NW
WHICH IS NOT SUPPORTED BY ANY OF THE GLOBAL ENS MEANS. THIS GFS
IDEA LEADS TO A LOWER AMPLITUDE UPSTREAM RIDGE RESULTING A
FLATTER/QUICKER SOLN IN THE NERN U.S. ON THE OTHER HAND...THE 00Z
ECMWF SHOWS MUCH MORE AMPLIFICATION LEADING TO A STRONGER COASTAL
SYSTEM ALONG THE MID-ATLC/NEW ENGLAND COAST BY SAT NIGHT/SUN
MORNING. WHILE THE ENS MEANS ARE NOT QUITE AS DEVELOPED AS THE
DETERMINISTIC ECMWF...A LARGE AMT OF THE 540-DM SPAGHETTI PLOT 00Z
ECMWF ENS MEMBERS DEPICT LARGE AMPLIFICATION IN THE EAST. THE GEFS
MEMBERS ARE DEFINITELY IN STARK CONTRAST BEING MORE PROGRESSIVE
WITH LESS AMPLITUDE. LOOKING BACK TOWARD THE WRN U.S...AN
ANOMALOUS UPPER LOW IS FCST TO PEEL OFF THE BELT OF WESTERLIES AND
SINK SWRD TO NEAR 30N WELL OFFSHORE OF BAJA CA BY 31/1200Z. AT
THAT PT...IT APPEARS THIS SYSTEM SHOULD KEEP A LARGE ENOUGH
DISTANCE AWAY FROM THE POLAR JET TO REMAIN CUT-OFF FOR THE
FORESEEABLE FUTURE. ALL GUIDANCE AGREES ON SUCH AN EVOLUTION
ALTHOUGH THE RECENT GFS SOLNS HAVE BEEN FARTHER S RELATIVE TO THE
ENS MEANS. THE 00Z ECMWF AGREES ON THE POSN BUT IS MUCH MORE
INTENSE ALOFT.

THE PRIMARY IMPACTS DURING THIS PERIOD WILL BEGIN WITH THE
LINGERING HEAVY PCPN WITH THE COASTAL STORM AFFECTING NEW ENGLAND
ON D3...THU. LATER ON...THE THREAT SHIFTS TO THE CNTRL/ERN GULF
COAST WHERE HEAVY RAINFALL WILL BE POSSIBLE ON FRI INTO SAT. AS
THIS SAME SYSTEM LIFTS TOWARD THE NERN CONUS...A COASTAL STORM IS
FCST TO DEVELOP ALONG THE ERN SEABOARD WITH IMPACTS VARYING
DEPENDING ON THE MODEL. A SOLN CLOSER TO THE COAST COULD BRING A
SIGNIFICANT PCPN EVENT OVER THE NERN STATES ON SAT/SUN. GIVEN THE
COLD AIR MASS SETTLING INTO PLACE...MUCH OF THE PCPN WOULD BE SNOW
OR SOME SORT OF MIXTURE OF PCPN TYPES. GIVEN HOW FAR THIS SYSTEM
IS INTO THE MEDIUM RANGE...IT IS DIFFICULT TO SPECULATE ON ANY
DETAILS AT THIS TIME.

HPC FAVORED A NEARLY EQUAL BLEND OF THE 06Z GFS AND 00Z
ECMWF/UKMET ON DAYS 3/4 GIVEN THE GENERAL AGREEMENT IN THE
GUIDANCE. THEREAFTER...THE 00Z UKMET WAS REMOVED GIVEN IT BECAME
TOO PROGRESSIVE WITH THE LEAD SHRTWV IN THE TN VALLEY. FOR THE
FINAL TWO DAYS OF THE PERIOD/YEAR...GLOBAL ENS MEANS WERE USED
MORE HEAVILY WITH EQUAL CONTRIBUTIONS OF THE 06Z GEFS/00Z ECMWF
ENS MEAN GIVEN THE UNCERTAINTY. HOWEVER...A SMALL AMT OF 00Z ECMWF
WAS ADDED DURING THIS PERIOD TO INTRODUCE ADDITIONAL ISOBARS GIVEN
THE THREAT OF A STRONG SYSTEM BEING IN PLAY.


RUBIN-OSTER

[srainhoutx]

SPC Update:

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1029 AM CST MON DEC 24 2012

VALID 241630Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVERNIGHT FOR PORTIONS
CENTRAL-E TX AND WRN LA...

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN WAS ANALYZED THIS MORNING OVER
CONUS...FEATURING TWO SHORTWAVE TROUGHS OF PRIMARY PERTINENCE TO
THIS FCST INITIALLY OVER...
1. MID-SOUTH REGION TO MS/AL COAST. THIS FEATURE WILL MOVE EWD AND
DEAMPLIFY SLIGHTLY BEFORE MOVING OFFSHORE SC AROUND 03Z.
2. INLAND PAC NW SSEWD ACROSS NV. PERTURBATION IS FCST TO
STRENGTHEN THROUGH PERIOD AND MOVE SEWD ACROSS CENTRAL/SRN
ROCKIES...REACHING CENTRAL/SRN HIGH PLAINS BY 12Z. EMBEDDED/500-MB
CLOSED LOW SHOULD FORM BY 12Z OVER TX PANHANDLE/SOUTH-PLAINS
REGION...WHILE MID-UPPER HEIGHT GRADIENT INTENSIFIES MARKEDLY TO ITS
SW-SE. BY 12Z...EXPECT 500-MB JET MAX 90-100 KT OVER SERN NM/TX
PERMIAN BASIN REGION...WITH FLOW STRENGTHENING TO 60-70 KT RANGE
OVER SFC WARM SECTOR IN SE TX.

AT SFC...WEAK LOW NOW OVER NRN KY IS FCST TO PROCEED NEWD UP OH
VALLEY THROUGH REMAINDER DAYLIGHT HOURS AND WEAKEN...WITH OCCLUSION
TRIPLE-POINT LOW POSSIBLY FORMING INVOF SERN NY COASTAL WATERS
AROUND 06Z. ACCOMPANYING SFC COLD FRONT WAS ANALYZED AT 15Z FROM
LOW SSWWD ACROSS NRN AL...SWRN MS...SWRN LA...AND S-CENTRAL TX. TX
PORTION OF BOUNDARY IS DECELERATING...AND IS FCST TO MOVE NWD ACROSS
PORTIONS CENTRAL/SE TX OVERNIGHT AS WARM FRONT. MEANWHILE...LEE
CYCLONE IS FCST TO DEEPEN CONSIDERABLY TODAY ACROSS NERN NM AND SERN
CO REGION...WITH APCH OF AMPLIFYING TROUGH ALOFT. DURING LAST 6
HOURS OF PERIOD...SFC CYCLONE WILL TRANSITION TO FRONTAL-WAVE
FEATURE AND MOVE/REPOSITION SEWD ALONG ZONE OF
FRONTOGENESIS...REACHING POSITION OVER CENTRAL TX BY 12Z.

...TX/LA AREA OVERNIGHT...
CONVECTIVE POTENTIAL WILL INCREASE OVERNIGHT...FIRST N OF SFC FRONT
LATE EVENING THROUGH PRE-DAWN HOURS WITH MOST INTENSE CELLS POSING
HAIL THREAT. ACTIVITY MAY DEVELOP PROGRESSIVELY CLOSER TO FRONT
THROUGH END OF PERIOD...EVENTUALLY BECOMING SFC-BASED WITH
SUPERCELLS AND BOW/LEWP FEATURES POSSIBLE. AS SUCH...THREAT EXISTS
DURING LAST FEW HOURS OF PERIOD FOR SVR HAIL/GUSTS. TORNADO RISK
EXISTS FROM ANY SFC-BASED AND RELATIVELY DISCRETE CELLS IN WHAT
SHOULD BE VERY FAVORABLE SHEAR ENVIRONMENT...BUT COVERAGE OF
SFC-BASED TSTMS IS TOO UNCERTAIN ATTM FOR MORE THAN 5% UNCONDITIONAL
TORNADO RISK.

DEEP SHEAR AND LOW-LEVEL HODOGRAPHS EACH ARE EXPECTED TO STRENGTHEN
OVER RETURNING WARM SECTOR TONIGHT...AS 60S F SFC DEW POINTS
CONTRIBUTE TO 1000-1500 J/KG MLCAPE BY 12Z ALONG AND S OF FRONT OVER
SE TX. LARGEST LOW-LEVEL HODOGRAPHS WILL BE ALONG FRONT...WHERE
BACKED SFC WINDS WILL CONTRIBUTE TO EFFECTIVE SRH 300-500 J/KG. SRH
ALSO WILL BE FAVORABLE FARTHER S OVER COASTAL AREAS IN WARM
SECTOR...HOWEVER FCST SOUNDINGS SUGGEST PRONOUNCED EML-BASE
INVERSION BETWEEN 850-700 MB THAT MAY RESTRICT TSTM COVERAGE AWAY
FROM BOUNDARIES.

...CENTRAL-ERN GULF COASTAL PLAIN...NEXT 4-6 HOURS...
BULK OF CONVECTION IS EXPECTED TO OUTRUN LOW-LEVEL DESTABILIZATION
OVER THIS REGION THROUGH REMAINDER DAYLIGHT HOURS. HOWEVER...AT
LEAST ISOLATED TSTMS STILL MAY DEVELOP OVER THIS AREA THROUGH AROUND
21Z...SOME OF WHICH MAY BECOME SFC-BASED. DAMAGING WIND AND TORNADO
RISKS ARE NONZERO BUT VERY CONDITIONAL. DESTABILIZATION WILL BE
SLOWED BY ONGOING CLOUDS/PRECIP...WHICH WILL RESTRICT PACE OF
DIURNAL WARMING. LOW-LEVEL THETAE ADVECTION SHOULD RESULT IN
POTENTIAL INFLOW PARCELS EFFECTIVELY BECOMING SFC-BASED ACROSS THIS
REGION THROUGH MID-AFTN...WHILE DEEP-LAYER ASCENT WEAKENS. THESE
OFFSETTING INFLUENCES WILL AFFECT TSTM COVERAGE...BUT ANY
SUSTAINED/SFC-BASED CONVECTION HAS POTENTIAL TO BECOME
SUPERCELLULAR. AS SUCH...WILL MAINTAIN MRGL UNCONDITIONAL SVR
PROBABILITIES FOR THIS OUTLOOK.

..EDWARDS/COHEN.. 12/24/2012

[jasons2k]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1022 AM CST MON DEC 24 2012

.UPDATE...
MORNING FORECAST UPDATE.

.DISCUSSION...
WEAK COLD FRONT HAS PUSHED INTO THE HOUSTON AREA AND SHOULD
BECOME STATIONARY BEFORE REACHING THE COAST THIS AFTERNOON. MAY
SEE A FEW SHOWERS/THUNDERSTORMS ALONG THE FRONT THIS AFTERNOON BUT
ISO ACTIVITY IF ANY. FORECAST STILL LOOKS ON TRACK FOR BOUNDARY TO
PUSH NORTH TONIGHT AHEAD OF STRONG UPPER LEVEL TROUGH EXPECTED TO
PUSH INTO TX CHRISTMAS MORNING. ONLY CHANGES TO THE FORECAST WERE
TO UPDATE TEMPS BASED ON FRONTAL POSITION AND UPDATE POPS/WX FOR
TODAY. EARLY ANALYSIS STILL SHOWING THE POSSIBIILTY OF SEVERE
WEATHER TOMORROW MORNING. AFTERNOON FORECAST UPDATE WILL ADDRESS
THIS IN MORE DETAIL.

[Ptarmigan]

The weather is nice right now, but don't let that fool you. It could be a stromy Christmas morning. I think we could see storms as early as tonight to Christmas morning.

[srainhoutx]

Update from NWS Dallas/Ft Worth:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
1131 AM CST MON DEC 24 2012

.UPDATE...
HAVE LOWERED MAX TEMPS FOR TODAY 2-3 DEGREES DUE TO CONTINUED COLD
AIR ADVECTION BEHIND THE COLD FRONT THAT ARRIVED LAST EVENING.

AFTER A QUICK LOOK AT SEVERAL OF THE MORNING MODELS...WE ARE NOT
PLANNING TO MODIFY THE CHRISTMAS DAY FORECAST AT THIS TIME. WE
STILL FEEL THAT A CONSENSUS OF THE GFS/ECMWF/CMC IS THE BETTER
SOLUTION FOR THE UPPER LOW TRACK AND SNOW ACCUMULATION AMOUNTS.

THE SEVERE THUNDERSTORM POTENTIAL EARLY CHRISTMAS MORNING NOW HAS
OUR ATTENTION AS THE LOCATION OF THE SURFACE FRONT WILL BE
IMPORTANT IN WHETHER STORMS CAN BECOME SURFACE BASED. ALSO...ANY
STRONG STORMS MOVING OVER THE FRONT WILL HAVE INCREASED HELICITY
TO WORK WITH WHICH COULD RESULT IN A BRIEF TORNADO.

[srainhoutx]

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CST MON DEC 24 2012

VALID 251200Z - 261200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF LA...CENTRAL/SRN
MS...AND WRN AL...

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX ACROSS THE GULF
COAST/LOWER MS VALLEY AND SRN APPALACHIANS...

...SIGNIFICANT SEVERE WEATHER EVENT EXPECTED FOR CHRISTMAS DAY OVER
PARTS OF THE GULF COAST STATES...

...SYNOPSIS...
AN ENERGETIC FLOW PATTERN IS EVIDENT IN SATELLITE IMAGERY FROM THE
EASTERN PACIFIC ACROSS THE CONUS AS A SERIES OF VIGOROUS UPPER
TROUGHS PROGRESS EWD. THE PRIMARY SYSTEM ASSOCIATED WITH A MAJOR
SEVERE WEATHER THREAT TOMORROW IS CURRENTLY OVER THE GREAT BASIN.
WITH LATEST UPPER AIR DATA INDICATING THE STRONGEST MID/UPPER LEVEL
WINDS DIGGING INTO THE SWRN PORTION OF THE TROUGH...MODEL CONSENSUS
INDICATES THE SYSTEM WILL AMPLIFY/DEVELOP INTO A PROGRESSIVE CLOSED
LOW MOVING ACROSS THE SRN PLAINS DURING THE DAY REACHING THE MIDDLE
MS VALLEY BY 26/12Z. AT THE SURFACE...A BROAD LOW PRESSURE REGION
OVER CENTRAL/ERN TX EARLY IN THE PERIOD IS FORECAST TO CONSOLIDATE
INTO A DEEPENING LOW MOVING ACROSS NRN LA DURING THE AFTERNOON AND
CONTINUING INTO MIDDLE TN BY THE END OF THE PERIOD. AN EAST-WEST
ORIENTED WARM FRONT FROM SERN TX ACROSS THE SRN PARTS OF MS/AL AND
GA WILL SLOWLY LIFT NWD AS THE LOW MOVES NEWD...WHILE A COLD FRONT
EXTENDING SWWD FROM THE LOW IS EXPECTED TO ACCELERATE EWD
/ESPECIALLY DURING THE NIGHT/ ACROSS THE LOWER MS VALLEY REACHING AL
BY 26/12Z.

...GULF COAST REGION/LOWER MS VALLEY...
AREAS OF STRONG/SEVERE THUNDERSTORMS ARE EXPECTED TO BE ONGOING FROM
ERN TX INTO THE LOWER MS VALLEY AT THE START OF THE PERIOD AS
INTENSE LARGE SCALE ASCENT IN THE LEFT EXIT REGION OF THE UPPER
LEVEL JET COINCIDES WITH FOCUSED LOW LEVEL CONVERGENCE/WARM
ADVECTION ALONG/NORTH OF THE WARM FRONT. SOUTH OF THE WARM
FRONT...SURFACE DEW POINTS IN THE LOW/MID 60S F WILL BE RETURNING
NWD ACROSS A BROAD WARM SECTOR EXTENDING ACROSS MUCH OF THE GULF
COAST REGION. THIS WILL CONTRIBUTE TO AN UNSTABLE ENVIRONMENT WITH
MLCAPE RANGING FROM 1000-1250 J/KG NEAR THE COAST TO AOB 500 J/KG
NORTH OF THE WARM FRONT.

STRONG WINDS IN THE MID AND UPPER LEVELS /70-90 KT AT 500 MB AND
110+ KT AT 250 MB/ WILL RESULT IN DEEP LAYER SHEAR SUPPORTIVE OF
ROTATING UPDRAFTS...INCLUDING ELEVATED SUPERCELLS NORTH OF THE WARM
FRONT. AS THE DAY PROGRESSES...FORCED ASCENT ALONG THE ADVANCING
COLD FRONT IS EXPECTED TO RESULT IN QLCS DEVELOPMENT CONTAINING
EMBEDDED FAST-MOVING BOW ECHOES AND POSSIBLE
SUPERCELLS/MESO-VORTICES AS IT MOVES EWD ACROSS LA AND THE SRN HALF
OF SRN MS. THERE WILL ALSO BE CONTINUED POTENTIAL FOR A FEW
DISCRETE SUPERCELLS IN THE WARM SECTOR AND ALONG THE WARM FRONT
AHEAD OF THE QLCS. LOW LCL HEIGHTS AND CLOCKWISE TURNING LOW LEVEL
HODOGRAPHS /SRH VALUES OF 200-400 M2 PER S2/ INDICATE POTENTIAL FOR
TORNADIC SUPERCELLS. THE POSSIBILITY EXISTS FOR SEVERAL LONG-TRACK
STRONG TORNADOES ASSOCIATED WITH ANY LONG-LIVED FAST-MOVING
SUPERCELLS...ALONG WITH MORE WIDESPREAD DAMAGING WINDS ALONG THE
MOST INTENSE PARTS OF THE BOWING QLCS. DESPITE GRADUALLY DECREASING
INSTABILITY AS BOUNDARY LAYER COOLING OCCURS AFTER DARK...A SEVERE
THREAT IS EXPECTED TO SPREAD EWD/NEWD ACROSS PARTS OF AL...SRN TN
AND WRN GA DURING THE NIGHT AS THE SYSTEM CONTINUES TO STRENGTHEN.

..WEISS.. 12/24/2012

[Portastorm]

Not surprised to see portions of the Austin metro area and Houston back in the slight risk category. Models are trending further south with the progged shortwave tomorrow morning. Could be a rough start to the holiday for some of us.

Ed, that graphic was very interesting (and concerning). Thanks for posting!

[tireman4]

So what we are saying....watch, be vigilant, stay tuned here and the NWS (and as Katdaddy stresses, make sure you have fresh batteries in your weather radio) for updates on this situation.

[jeff]

The severe threat is for real on Tuesday...but SE TX will be on the SW edge of a much bigger and more damaging outbreak over LA nd MS. Still wind damage and a few tornadoes will be possible in our area especially near/along the warm front...College Station to Conroe to Liberty NNE from there will be the best threat. Warm sector looks capped to a degree, but would expect that to be broken with incoming strong lift from the west...but maybe more scattered in nature with big supercells to our NE.

Visible is now slearly showing teh front boundary to our south with some recent ehancement in the clouds near the boundary. Suspect some develop will get going by mid evening as the boundary lift northward and lift increases.

[SusieinLP]

So what are we looking at for those along and south of I 10? Since most of the action seems far north from this area are we looking at a rain gusty wind event?

[gocuse22]

Forecast for the Houston Area...6am Christmas Morning

http://graphical.weather.gov/images/hgx/Wx9_hgx.png

[Andrew]

GFS is hinting at a possible inversion between 800 and 850mb. Could limit some of the severity tomorrow

http://beta.wxcaster.com/cgi-bin/parse_ ... IONID=KHOU

[tireman4]

The AFD from the HGX-NWS

NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
334 PM CST MON DEC 24 2012

...INCREASING POTENTIAL FOR SEVERE WEATHER CHRISTMAS DAY...

.DISCUSSION...
STILL A CHALLENGING FORECAST FOR THE NEXT 24 TO 48 HOURS. FRONTAL
BOUNDARY THAT PUSHED INTO THE AREA HAS STALLED ALONG THE COAST
BASED ON SFC OBS AND SATELLITE. THIS HAS ALLOWED FOR A GOOD 10
DEGREE TEMPERATURE GRADIENT ACROSS SE TX WITH 60S FOR THE NORTHERN
HALF AND 70S FOR THE SOUTHERN HALF. IN FACT GALVESTON BROKE A
RECORD HIGH TEMP WITH 76. GALVESTON MAY EVEN REACH ANOTHER RECORD
FOR CHRISTMAS DAY.

SHORT RANGE MODEL GUIDANCE ARE ALL IN PRETTY GOOD AGREEMENT WITH
THE CHRISTMAS FORECAST. FRONTAL BOUNDARY SHOULD PUSH NORTH AS A
WARM FRONT REACHING KCLL TO KJAS LINE BY 12Z TUE PER GFS. THE
NAM/ECMWF PUSH THE FRONT A LITTLE FARTHER NORTH. MODELS ALL BRING
A STRONG JET INTO TEXAS OVERNIGHT WITH ONE INITIAL JET STREAK
MOVING OVER THE AREA AT 06Z TUE AHEAD OF THE MAIN JET. LARGE SCALE
ASCENT WILL INCREASE MORE AS THE NOSE OF THE JET PUSHES INTO C TX
AND E TX FROM 12-18Z TUE. GIVEN FAVORABLE JET DYNAMICS AND
DIFFLUENT FLOW ALOFT...EXPECT SFC LOW TO FORM ALONG WARM FRONT AND
MOVE ALONG IT. DEEP MOISTURE WILL NOT BE MUCH OF A QUESTION WITH
SFC DEWPOINTS IN THE 60S SOUTH OF THE BOUNDARY WITH PRECIP WATER
VALUES AROUND 1.4 INCHES. INSTABILITY WILL BE AN ISSUE FOR SEVERE
WEATHER BUT MODELS STILL SHOW AT LEAST 1000-1500 J/KG OF CAPE IN
THE WARM SECTOR WITH POSSIBLY 2000 J/KG ALONG THE COAST. ONE OF
THE OTHER ISSUES WILL BE CAPPING FROM ELEVATED MIXED LAYER. BOTH
NAM/GFS BUFR SOUNDINGS SHOW CAPPING IN THE 800-700MB LAYER FOR
KIAH AND POINTS SOUTHWARD. MODEL SOUNDINGS FROM KCXO/KUTS/KCLL
SHOW MUCH WEAKER CAP. DEEP LAYER SHEAR OF 50-60KTS AND LOW LEVEL
SHEAR AROUND 20-30KTS ARE EXPECTED TO BE STRONG ENOUGH FOR STORM
ROTATION. THE QUESTION WILL BE HOW MUCH THE CAP HOLDS AND HOW MUCH
THE CAP INHIBITS SURFACE BASED STORMS IN THE WARM SECTOR. STILL
ANY STORMS THAT CAN BE ROOTED IN THE BOUNDARY LAYER SHOULD ROTATE
AND TORNADOES WILL BE THE MAIN THREAT. THINK SPC DAY 1 AND 2
OUTLOOKS REALLY HIGHLIGHT THE THREAT. GENERALLY THIS WILL BE NORTH
OF I-10 MAINLY ALONG THE WARM FRONT AND FROM 3-4AM THROUGH NOON ON
CHRISTMAS DAY. THINK THE MAIN UNCERTAINTY WILL BE WHERE THE WARM
FRONT MOVES AND HOW STRONG CAPPING BECOMES.

DRY LINE AND THEN COLD FRONT WILL PUSH THROUGH LATER CHRISTMAS
AFTERNOON/EVENING. MUCH COLDER CONDITIONS FOR WED/THUR. COLDEST
MORNING APPEARS TO BE THUR MORNING AS FAR AS MORNING LOW TEMPS ARE
CONCERNED BUT WIND CHILLS WILL BE QUITE COLD WEDNESDAY MORNING
WITH WINDS CONTINUING. MAY NEED A WIND ADVISORY FOR BEHIND THE
FRONT.

GFS/ECMWF STILL AGREE WITH RETURN FLOW THUR/FRI WITH NEXT UPPER
LEVEL TROUGH. WILL KEEP HIGH CHANCE POPS IN THE FORECAST ALTHOUGH
LOOKS LIKE BULK OF PRECIP WILL BE ALONG TX/LA BORDER. COLD FRONT
SHOULD PUSH THROUGH LATE FRI SO WEEKEND LOOKS TO BE ON THE COLD
SIDE. SO WE MIGHT HAVE ANOTHER STRETCH OF BELOW NORMAL TEMPS FOR
THE WEEKEND.

http://forecast.weather.gov/product.php ... glossary=1

[Andrew]

Latest graphic from Houston/ Galveston Weather:

[wxman57]

Here's the 12Z Euro 24hr snow accumulations. Values are in millimeters liquid. 25mm = about 1" = about 10" snow. 5mm = about 2". It has the 1mm line over D-FW, which is under 1/2". Of course, these forecasts are far from precise.

18Z GFS indicates rain here between 6am and 2pm, followed by frontal passage and a sharply dropping temp from 65F at 3pm to 48F by 6pm.

[Ptarmigan]

GFS is hinting at a possible inversion between 800 and 850mb. Could limit some of the severity tomorrow

http://beta.wxcaster.com/cgi-bin/parse_ ... IONID=KHOU

Wonder where that would come from.

[Ptarmigan]

Here's the 12Z Euro 24hr snow accumulations. Values are in millimeters liquid. 25mm = about 1" = about 10" snow. 5mm = about 2". It has the 1mm line over D-FW, which is under 1/2". Of course, these forecasts are far from precise.

18Z GFS indicates rain here between 6am and 2pm, followed by frontal passage and a sharply dropping temp from 65F at 3pm to 48F by 6pm.

Looks like tonight should not be rough for Santa Claus.

[weatherrabbit]

A beautiful Christmas eve evening out! temp at 54 now and dropping..noticing that the wind is veering more south and east. dewpoints now at 38 should start to rise.