December: Warm Days & Cool-Foggy Nights To End 2011

[srainhoutx]

Heavy rain and perhaps a rumble or two of the thunder can be expected Monday night/Tuesday morning via the GFS as the front passes. That model also a possible blizzard across the Texas Panhandle and N Oklahoma into southern KS...

[srainhoutx]

A quiet couple of days are ahead before things get interesting on Monday. A potent Winter Storm will cross Southern New Mexico and track between Lubbock and Amarillo bringing heavy snows and possible blizzard conditions across the Panhandles of TX/OK in SW Kansas. In the warm sector, a negative tilted trough/strong cold front sets the stage for severe weather chances developing from Central Texas on E. The morning Day 3 update from the SPC mentions the possibility of a Slight Risk for mainly damaging winds being introduced in future convective outlooks. Chilly weather will follow the storm for Tuesday into Wednesday. Clouds begin to increase late Wednesday as over running conditions begin as a Coastal Trough sets up along the Texas Coastal waters. Rains may be likely on Thursday. Much colder air sweeps into the area and yet another upper low develops in the Desert SW during the Christmas Holiday period.

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0153 AM CST SAT DEC 17 2011

VALID 191200Z - 201200Z

...SYNOPSIS...

CUTOFF UPPER LOW NOW SITUATED OVER NRN BAJA THAT IS PART OF A WRN
U.S. REX BLOCK WILL BEGIN TO EJECT EWD SUNDAY AND CONTINUE THROUGH
THE SRN PLAINS MONDAY. ATTENDANT SFC LOW WILL LIKELY MOVE ACROSS NRN
TX OR OK WITH TRAILING PACIFIC FRONT ADVANCING THROUGH THE REMAINDER
OF TX.

...CNTRL THROUGH ERN TX AND WRN LA...

STRONG 50-60 KT SLY LLJ ASSOCIATED WITH THE EJECTING UPPER LOW WILL
TRANSPORT PARTIALLY MODIFIED GULF AIR INTO THE SRN PLAINS MONDAY
WITH SFC DEWPOINTS FROM THE LOW-MID 60S ACROSS SRN-SERN TX TO MID
50S OVER N-NCNTRL TX. WRN EXTENSION OF SERN U.S. SFC RIDGE IS
FORECAST TO BE IN PLACE EARLY MONDAY OVER CNTRL/ERN TX. INCREASING
SLY FLOW AND ISENTROPIC ASCENT ABOVE THIS COOL...STABLE LAYER WILL
LIKELY RESULT IN WIDESPREAD LOW CLOUDS EARLY IN PERIOD...LIMITING
DESTABILIZATION POTENTIAL SOMEWHAT. NEVERTHELESS...LOW LEVEL THETA-E
ADVECTION AND POTENTIAL FOR SOME OF THE LOW CLOUDS MIXING OUT FROM
THE SOUTH DURING THE AFTERNOON MAY SUPPORT AN AXIS OF MARGINAL
INSTABILITY WITH MLCAPE GENERALLY AOB 500 J/KG.

A BAND OF STORMS WILL LIKELY BE IN PROGRESS WITHIN ZONE OF DEEPER
ASCENT ALONG WARM CONVEYOR BELT ACROSS WRN TX MONDAY MORNING. SOME
OF THE STORMS MAY INTENSIFY AND BECOME SURFACE BASED AS THEY BEGIN
TO INTERACT WITH THE MOISTENING AND DESTABILIZING BOUNDARY LAYER
FARTHER EAST. GIVEN DEGREE OF FORCING...PRIMARY CONVECTIVE MODE IS
EXPECTED TO BE LINEAR. HOWEVER...ACTIVITY WILL REMAIN EMBEDDED
WITHIN STRONG LOW-LEVEL AND DEEP SHEAR ACCOMPANYING THE SHORTWAVE
TROUGH AS IT PROGRESSES EWD...SUPPORTING POTENTIAL FOR EMBEDDED
ORGANIZED STRUCTURES. PRIMARY THREAT IS EXPECTED TO BE ISOLATED
DAMAGING WIND...BUT A COUPLE OF TORNADOES CANNOT BE RULED OUT.
THREAT WILL SHIFT INTO THE LOWER MS VALLEY OVERNIGHT. DUE TO
POTENTIAL LIMITING FACTORS WITHIN THERMODYNAMIC ENVIRONMENT...5%
PROBABILITIES WILL BE INTRODUCED AT THIS TIME...BUT A PORTION OF
THIS AREA MAY NEED TO BE UPGRADED TO A SLIGHT RISK IN LATER
OUTLOOKS.

[wxman57]

Looks like some snow in the northern TX and OK panhandles on Monday. No significant cold here through Christmas. A bit better model agreement for next weekend. Lows in the 40s, highs in the 50s for Christmas.

[redneckweather]

If I were to go chase some snow, what would be the nearest possible place to head to? I'm talking about at least 4 to 6 inches.

[srainhoutx]

If I were to go chase some snow, what would be the nearest possible place to head to? I'm talking about at least 4 to 6 inches.

Amarillo. Blizzard conditions with up to 12 inches of snow in the trowal and even thundersnow. The system may well bomb out/stall and totals may need to be increased. HPC morning Winter Storm Charts and Graphs...expect further 'fine tuning'. This has the potential to be a big Winter event for those areas...

[srainhoutx]

The 12Z WRF/NAM suggests a track of the Upper/Surface Low over Lubbock. While this is a bit far out in time for that model, it will be worth monitoring the Globals today into tomorrow to see if a slower, further S track plays out. Severe weather chances in the warm sector, although not that impressive, suggest a squall line with some possible surface based thunderstorms. This will be a very dynamic storm, so expect further changes over the next couple of days.

[txflagwaver]

I thought today was gonna be cloudy and rainy??

[srainhoutx]

The 12Z GFS suggests an early Tuesday morning arrival of the storms/front. The bigger threat of anything of the severe nature would tend to be E of the I-35 corridor...

[srainhoutx]

Looking ahead to Thursday, the 12Z GFS suggests an upper air disturbance/short wave moving in from the W underneath the base of the Western trough as well as a Coastal trough/low developing near the Middle Texas Coast...

[srainhoutx]

The 12Z Euro also suggests a very impressive Winter Storm taking shape across the S Plains. Guidance is agreeing that a linear line of storms will sweep E across TX during the Monday night/early Tuesday morning time frame.

[srainhoutx]

The 12Z Euro has joined the GFS/Canadian solution suggesting a coastal trough/low forming mid week. That model is also suggesting a bit strong upper air disturbance sweeping from W to E bringing down some chilly air for the Christmas Weekend...

[srainhoutx]

As I posted in wxman57's Christmas thread, some chilly air is showing up in the Euro today for next Sunday (Christmas Day) into Monday...

[JackCruz]

Looking good.

[redneckweather]

Man, that is a heck of a drive to go see snow but it looks like it's gonna be a butt whooper for sure. Still kicking it over.

[srainhoutx]

Winter Storm Warnings are now in effect for SW New Mexico with Winter Storm Watches extending NE into NE Kansas. Blizzard Watches have been hoisted from E N MX, the NW TX/OK Panhandles and SW/S Central Kansas for up to 12-14 inches of snow.

In the warm sector, The SPC has as Slight Risk of severe weather for parts of Eastern TX including areas just S of Dallas/FT Worth and including the Houston/Galveston region, mainly N of I-10. This storm looks eerily similar to the December 29, 2006 storm that brought numerous tornadoes across N TX and the Dallas/ Fort Worth area, but is not as strong at the 5H level and not as far S as that event. Severe Weather events, while not uncommon in December, have a history of catching folks off guard so it is prudent to at least mention the severe side of the very dynamic Winter Storm with the busy Holiday period approaching.

The squall line should get going Monday afternoon across Central Texas and march E during the overnight hours into early Tuesday morning before clearing the area. Damaging winds with some hail are the most likely threat, but an isolated tornado or two cannot be ruled out.

Cloudy skies and breezy conditions can be expected Tuesday into Wednesday. The fly in the ointment appears on Thursday. The guidance is all over the place concerning a possible coastal trough and over running rains along southern areas, or no precip chances at all. The same can be said for the Christmas Holiday Weekend. Guidance suggests light rains/drizzle with over running rains on Christmas Eve into Christmas Day. Temps will remain cool with increasing thick clouds.

There is much uncertainty with the week ahead, so expect changes in the very active un La Nina pattern with upper lows dropping S into the S CA/Baja Regions all week creating model mayhem and some forecasting challenges.

HPC:

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
343 AM EST SUN DEC 18 2011

VALID 12Z SUN DEC 18 2011 - 12Z TUE DEC 20 2011

...HEAVY SNOW AND POSSIBLE BLIZZARD CONDITIONS WILL BE POSSIBLE
FROM AREAS OF NEW MEXICO INTO THE SOUTHERN/CENTRAL HIGH PLAINS...

...AN UNSTABLE AIR MASS ACROSS SOUTHEASTERN TEXAS SHOULD SUPPORT A
THREAT FOR SEVERE WEATHER ON MONDAY...


AFTER A BRIEF QUIET PERIOD IN THE WEATHER ACROSS THE
NATION...THINGS SHOULD BECOME MUCH MORE ACTIVE FROM SUNDAY NIGHT
ONWARD INTO EARLY NEXT WEEK. FUELING THIS CHANGE IS AN ANOMALOUS
UPPER CYCLONE WHICH HAS SEEMINGLY BEEN SWIRLING IN THE VICINITY OF
NORTHERN BAJA CALIFORNIA THE PAST FEW DAYS. ANOTHER SYSTEM
DROPPING SOUTHWARD FROM THE PACIFIC NORTHWEST WILL FINALLY GIVE
THIS STAGNANT UPPER LOW A PUSH TO THE EAST WITH THE ENERGY
REACHING EXTREME WEST TEXAS BY MONDAY MORNING. BEFORE THIS
OCCURS...SCATTERED INSTABILITY RAIN SHOWERS WILL BE POSSIBLE
ACROSS SOUTHERN CALIFORNIA AND PORTIONS OF ARIZONA WITH
PRECIPITATION TOTALS ON THE LIGHTER END GIVEN LIMITED LOW-LEVEL
MOISTURE. ONCE THIS DISTURBANCE TRACKS TOWARD THE EAST LATE
SUNDAY/EARLY MONDAY...IT WILL BEGIN INTERCEPTING AN INCREASE IN
GULF MOISTURE WHICH IS EXPECTED TO EXPAND THE SWATH OF
PRECIPITATION. IN ADDITION...AS A FRONTAL BOUNDARY TO THE NORTH
SURGES TOWARD THE SOUTHERN PLAINS...PLENTY OF COLD AIR WILL INVADE
THE REGION. ULTIMATELY THIS WILL QUICKLY LEAD TO A CHANGEOVER TO
SNOW WITH SIGNIFICANT ACCUMULATIONS FORECAST FROM CENTRAL NEW
MEXICO NORTHEASTWARD THROUGH THE TEXAS/OKLAHOMA PANHANDLES AND
INTO SOUTHWESTERN KANSAS. THE CURRENT HPC WINTER WEATHER GRAPHICS
EXPECT THIS REGION TO SEE A WIDESPREAD 6 TO 12 INCHES OF SNOWFALL
ACCUMULATIONS WITH POCKETS OF LOCALLY HEAVIER AMOUNTS. IN
ADDITION...A TIGHTENING IN THE PRESSURE GRADIENT WILL LEAD TO AN
ENHANCEMENT IN THE WINDS MAKING BLIZZARD-LIKE CONDITIONS MORE
POSSIBLE. FOR THE LATEST INFORMATION ON THIS WINTER STORM...PLEASE
VISIT THE NATIONAL WEATHER SERVICE HOMEPAGE AT WWW.WEATHER.GOV.

THE OTHER ASPECT OF THIS SYSTEM WILL BE THE THREAT FOR SEVERE
WEATHER ACROSS PORTIONS OF SOUTHEAST TEXAS. STRONG UPPER DYNAMICS
COMBINED WITH AMPLE GULF MOISTURE AND A POTENT FRONTAL BOUNDARY
WILL LEAD TO AN ACTIVE AREA OF THUNDERSTORMS ON MONDAY. BY THE
OVERNIGHT HOURS...THE THREAT SHOULD DIMINISH AS THE SYSTEM WILL
HAVE ADVANCED INTO THE LOWER MISSISSIPPI VALLEY WITH THE WINDS
SHIFTING TO THE WEST-NORTHWEST.

GIVEN A LACK OF LOW-LEVEL MOISTURE ADVANCING INTO THE NORTHERN
SECTOR OF THE COUNTRY...MUCH OF THIS PORTION OF THE U.S. WILL BE
RELATIVELY QUIET. A PROGRESSIVE FLOW WITHIN AN ACTIVE JET STREAM
WILL CONTINUE TO DRAW A SERIES OF PACIFIC DISTURBANCES THROUGH THE
NORTHERN TIER STATES. SUCH A FLOW REGIME SHOULD KEEP TEMPERATURES
NEAR NORMAL AS THE COLDEST AIR REMAINS UP IN CANADA.

[srainhoutx]

There still remains some uncertainty regarding storm track and timing of just how quickly the 5H low will trek E across Northern Mexico. The U/L has been stationary, but indications via WV imagery suggest that the storm system is beginning to move inland across the northern Baja region. Satellite data suggest lightening is occurring with this U/L depicting the strength of the feature. The 06Z GFS/NAM was a bit faster while the Euro remained about 6-8 hours slower regarding the movement into the TX Panhandle. It will be interesting to watch how things evolve today as the northern stream short wave trough progresses inland and the attending 'cold front' dives S into the Plains later this afternoon setting the stage for rapid development across the Southern Rockies/Southern Plains tomorrow...


NCEP Operational Status Message

Sun Dec 18 13:27:09 2011 GMT

NOUS42 KWNO 181325
ADMNFD

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD
1321Z SUN DEC 18 2011
THE 12Z NAM HAS STARTED AND IS ON-TIME...THE FOLLOWING UPR AIR
REPORTS WERE AVBL FOR INGEST...13 ALASKAN...31 CANADIAN...72
CONUS...9 MEXICAN AND 7 CARIBBEAN.
12Z NAM RAOB RECAP...
NAS/78073 - PURGED TEMP/RH 754-747 MB...WET BULB EFFECT...
PURGED WINDS 1001-784 MB...SPURIOUS
ROR/91408 - UNAVBL
OTZ/70133 - 10145...UNFAVORABLE WX CONDITIONS
PCZ/78807 - MISSING TTAA/TTBB
CRITICAL WEATHER DAY STATUS...THERE IS A POSSIBILITY OF CRITICAL
WEATHER DAY...CWD...DUE TO THE WINTER STORM IMPACTING THE
SOUTHWEST AND SOUTH CENTRAL U.S. WITHIN THE NEXT THREE DAYS

[Ptarmigan]

Climate Prediction Center weekly update at 12/12/11

A little bit less cold in the Pacific compared to last week,but La Nina still holds firm.

Last Week's update

Niño 4=-0.6ºC
Niño 3.4= -1.1ºC
Niño 3= -1.2ºC
Niño 1+2= -1.3ºC

Average = -1.05ºC or -1.1ºC

This Week's update

Niño 4= -0.7ºC
Niño 3.4= -1.0ºC
Niño 3= -1.1ºC
Niño 1+2= -1.0ºC

Average = -0.95ºC or -1ºC

http://www.cpc.ncep.noaa.gov/products/a ... ts-web.pdf

The trend overall is going down. We are in a moderate La Nina. I don't expect another strong La Nina like last winter.

ENSO Model


Most predict Neutral by Summer 2012.

Southern Oscillation


The higher the SOI is, the stronger La Nina is.

[srainhoutx]

SPC Day 2 Update suggests a bit of increased opportunity for severe weather chances and even a mention of an isolated possible tornado or two...

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST SUN DEC 18 2011

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS CENTRAL/SOUTHEAST TX TO
FAR WESTERN LA...

...SYNOPSIS...
WHILE THE PRIMARY WESTERLIES PERSIST OVER CANADA/CONUS NORTHERN
TIER...THE CLOSED/SLOW-MOVING UPPER LOW CURRENTLY CENTERED OVER
NORTHERN BAJA/FAR NORTHWEST MEXICO WILL BEGIN TO MODESTLY ACCELERATE
EAST-NORTHEASTWARD AS IT REACHES THE SOUTHERN PLAINS BY MONDAY
AFTERNOON/NIGHT.

...CENTRAL/EAST TX TO WESTERN LA...
AS THE AFOREMENTIONED UPPER LOW EMERGES FROM NORTHWEST MEXICO/DESERT
SOUTHWEST...A PERSISTENTLY STRONG 50-60 KT SOUTHERLY LOW LEVEL JET
WILL AID IN THE NORTHWARD TRANSPORT OF A PARTIALLY MODIFIED GULF
AIRMASS INTO THE SOUTHERN PLAINS ON MONDAY. EAST OF A GRADUALLY
DEEPENING SOUTHERN HIGH PLAINS SURFACE LOW AND A
DRYLINE/EASTWARD-MOVING PACIFIC FRONT...THIS WILL GENERALLY RESULT
IN SURFACE DEWPOINTS IN THE LOWER TO MIDDLE 60S ACROSS
CENTRAL/SOUTHEAST TX BY AFTERNOON...WITH MIDDLE TO UPPER 50S F
DEWPOINTS INTO NORTH-CENTRAL TX/FAR SOUTHERN OK.

WITH SHOWERS/TSTMS LIKELY TO BE ONGOING EARLY MONDAY ACROSS WEST TX
INTO PARTS OF NORTH/CENTRAL TX AND OK...WIDESPREAD LOW CLOUDS MAY
LIMIT APPRECIABLE DESTABILIZATION INTO EARLY AFTERNOON.
NONETHELESS...CONTINUED THETA-E ADVECTION AND DIURNAL HEATING/MIXING
SHOULD YIELD A WEAKLY CAPPED BOUNDARY LAYER WITH A CORRIDOR OF
MLCAPE OF 500-800 J/KG ACROSS CENTRAL/SOUTHEAST TX BY MID/LATE
AFTERNOON TO THE EAST OF THE DRYLINE/PACIFIC FRONT. ALONG WITH
ARRIVAL OF MORE APPRECIABLE FORCING FOR ASCENT...THIS SHOULD RESULT
IN AN AFTERNOON/EVENING INCREASE OF SURFACE BASED TSTMS.

GIVEN THE DEGREE OF FORCING...EXPECTED EASTWARD PROGRESSION OF THE
PACIFIC FRONT ACROSS TX...AND CURRENTLY FORECAST VEER-BACK-VEER LOW
TO MID-LEVEL WIND PROFILES...THE PRIMARY CONVECTIVE MODE IS EXPECTED
TO BE LINEAR ESPECIALLY ACROSS CENTRAL INTO NORTH TX.
NONETHELESS...ASIDE FROM DAMAGING WINDS...AT LEAST SOME TORNADO
THREAT WILL EXIST GIVEN THE DEGREE OF LOW LEVEL SHEAR/SRH. SUCH A
TORNADO THREAT COULD BE THE CASE WITH INITIAL WARM SECTOR STORMS
EAST OF THE PACIFIC FRONT...ANY QLCS-EMBEDDED CIRCULATIONS THAT
EVOLVE...AND/OR WITH QLCS-SOUTH PERIPHERAL STORMS THAT SHOULD BE OF
A MORE DISCRETE NATURE /FORCING FOR ASCENT WILL BE A BIT MORE
SUBTLE/ WITHIN A HIGHER MOISTURE CONTENT AIRMASS ACROSS SOUTHEAST
TX. AT LEAST AN ISOLATED/MARGINAL DAMAGING WIND/TORNADO THREAT
SHOULD CONTINUE THROUGH MONDAY NIGHT AND INTO EARLY TUESDAY ACROSS
SOUTHEAST/EAST TX INTO WESTERN/SOUTHWEST LA.

...NORTHWEST TX/SOUTHWEST OK...
EVEN WITH A COOL/MARGINALLY MOIST BOUNDARY LAYER...LOW-TOPPED TSTMS
CAPABLE OF HAIL TO AROUND SEVERE LEVELS AND/OR PERHAPS A TORNADO
COULD DEVELOP EARLY/MID AFTERNOON MONDAY IN CLOSE PROXIMITY TO THE
NEARLY STACKED SOUTHERN HIGH PLAINS CYCLONE. SHOULD
MODEST/SUFFICIENT HEATING OCCUR...THIS COULD INITIALLY BE THE CASE
ACROSS NORTHWEST TX INCLUDING THE TX SOUTH PLAINS/SOUTHERN TX
PANHANDLE VICINITIES. GIVEN THE LIMITED NATURE OF THE
MOISTURE/BUOYANCY AND EXPECTED COLD FRONTAL PROGRESSIONS...ANY
STRONG/SEVERE TSTM THREAT SHOULD REMAIN MARGINAL AND OF A RELATIVELY
LIMITED DURATION.

[wxman57]

Latest GFS has the post-Christmas cool-down at the end of the high-res period. Still forecasting cold/rainy for Christmas Day (low 50s). Could be a light freeze by Tuesday the 27th.

[srainhoutx]

I don't want to get too far ahead of the severe weather we may see tomorrow, but the Christmas Day and the Monday after timeframe are beginning to raise an eyebrow...