FXUS64 KMAF 301148
AFDMAF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX
548 AM CST MON NOV 30 2009

.DISCUSSION...
SEE AVIATION DISCUSSION BELOW.

&&

.AVIATION...
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE DAYLIGHT TODAY AT
THE TERMINALS. AFTER 00Z TUESDAY A MIXTURE OF LIGHT RAIN...LIGHT
SLEET...AND OR LIGHT SNOW WILL TEMPO MVFR CEILINGS AND
VISIBILITIES AT MOST OF THE TERMINALS THROUGH THE NIGHT.

12

&&

.PREV DISCUSSION... /ISSUED 419 AM CST MON NOV 30 2009/ 

DISCUSSION...
EVERYTHING APPEARS TO BE ON TRACK THIS MORNING WITH THE UPPER
LEVEL LOW HOLDING OVER THE BAJA OF MEXICO SENDING RAIN INTO THE
BIG BEND AND LOWER TRANS PECOS...WITH THE DIFFLUENT AREA SITTING
OVER OUR WESTERN COUNTIES PRODUCING SOME SNOW AND MIXED PRECIP IN
THE GUADALUPE MOUNTAINS. THE ELEVATED WARM LAYER SEEN ON THE MAF
00Z SOUNDING FROM 85O-700MB WILL REMAIN UNTIL THE UPPER LEVEL LOW
GETS CLOSER TO TEXAS. THIS WARM LAYER MAY OCCASIONALLY BE ERODED
DUE TO EVAPORATIVE COOLING DURING HEAVIER PRECIP EVENTS ALLOW
PRECIP TO CHANGE FROM MIXED TO SNOW AS HAS BEEN SEEN ON THE GDP
OBSERVATION EARLIER THIS MORNING. IT IS THIS FACTOR THAT WILL MAKE
FORECASTING SNOW AND ICE AMOUNTS VERY DIFFICULT. STILL IT ONLY
TAKES A HALF INCH OF ICE ACCUMULATION FROM SLEET TO VERIFY A
WARNING AND THERE IS TOO MUCH POTENTIAL FOR SIGNIFICANT ICE AND
SNOW ACCUMULATION TO HOLD OFF WITH A WARNING ANY LONGER IN THE
REMAINING HIGH ELEVATION AREAS OF THE CWA. THE AREAS MOST LIKELY
TO SEE THE GREATEST SNOWFALL AMOUNTS WILL BE THE GUADALUPE
MOUNTAINS AND ANY OTHER LOCATIONS ABOVE 5KFT. TWO AREAS THAT WILL
NEED TO BE CLOSELY LOOKED AT FOR POTENTIAL INCLUSION IN THE
WARNING ARE BREWSTER COUNTY...MAINLY THE NORTHERN PART...AND
NORTHERN LEA COUNTY WHICH IS 1KFT HIGHER THAN SOUTHERN LEA COUNTY.
THE REMAINING AREAS OF THE CWA WILL HAVE TO BATTLE THE WARM LAYER
AS WELL AS UNCERTAIN QPF AMOUNTS AS THE LOW MOVES ACROSS THE BIG
BEND REGION ON TUESDAY. NORTH OF I-20 SEEMS TO HAVE THE BEST
POTENTIAL FOR SNOW ACCUMULATION BUT RIGHT NOW INDICATIONS ARE
AMOUNTS WILL HOLD TO LESS THAN 4 INCHES WHICH IS THE CRITERIA FOR
A WATCH. THEREFORE WILL HOLD OFF ISSUING ANY OTHER PRODUCTS BEYOND
THE WARNING FOR THE TIME BEING.

THE COLD AIR THAT INITIALLY ACCOMPANIED THE FRONT WILL MODIFY AS
IT HAS GOTTEN COMPLETELY CUTOFF FROM ITS SOURCE REGION. THAT MEANS
ANY COLD AIR AFFECTING THE P-TYPE WILL HAVE TO BE ACCOMPANIED WITH
THE UPPER LEVEL LOW WHICH MEANS THE BEST CHANCE FOR HEAVY SNOW
WILL BE A RELATIVELY BRIEF TIME WINDOW AS THE LOW TRANSITS THE
AREA. FOR THE PERMIAN BASIN THAT WINDOW MAY BE AS LITTLE AS A FEW
HOURS BUT PRECIP RATES COULD BE FAIRLY HEFTY SO DECENT SNOWFALL
TOTALS WILL NOT BE OUT OF THE QUESTION. THERE COULD ALSO BE SOME
WRAP AROUND MOISTURE TUESDAY NIGHT BUT P-TYPE ONCE AGAIN COMES
INTO QUESTION AS THE COLD AIR WILL BE MOVING EAST AND WARMER AIR
WILL BE MOVING IN WHICH WILL LIMIT ANY ADDITIONAL ACCUMULATIONS.

THE UPPER LOW WILL INTERACT WITH A DEEPENING TROUGH OVER THE NORTH
CENTRAL U.S. SENDING A SECONDARY SURGE OF COLD AIR SOUTHWARD
WEDNESDAY. THIS WILL KEEP TEMPERATURES FROM INCREASING MUCH IF AT
ALL DURING THE WEEK. THE GFS AND ECMWF DIFFER BY LATE WEEK WITH
THE GFS TRYING BRING ABOUT A ZONAL PATTERN WHICH WOULD FINALLY
BEGIN A WARMING TREND WHILE THE ECMWF MAINTAINS THE WEST COAST
RIDGE LEAVING US COOL. DID NOT SPEND A GREAT DEAL OF TIME ON THIS
PORTION OF THE FORECAST BUT ONCE AGAIN DECIDED TO SPLIT THE
DIFFERENCE BETWEEN THE TWO MODELS. THE 06Z GFS IS JUST NOW COMING
IN AND TRENDING CLOSER TO THE ECMWF SO COLDER MAY IN FACT BE THE
BETTER WAY TO GO. 

HENNIG

&&

.MAF WATCHES/WARNINGS/ADVISORIES...
NM...WINTER STORM WARNING UNTIL 5 AM MST TUESDAY FOR THE FOLLOWING 
     ZONES... GUADALUPE MOUNTAINS OF EDDY COUNTY.

     WINTER STORM WARNING FROM 11 AM THIS MORNING TO 11 AM MST 
     TUESDAY FOR THE FOLLOWING ZONES... EDDY COUNTY PLAINS.

TX...HIGH WIND WARNING UNTIL 8 AM MST THIS MORNING FOR THE FOLLOWING 
     ZONES... GUADALUPE MOUNTAINS.

     WINTER STORM WARNING UNTIL 5 AM MST TUESDAY FOR THE FOLLOWING 
     ZONES... GUADALUPE MOUNTAINS.

     WINTER STORM WARNING FROM NOON TODAY TO NOON CST TUESDAY FOR THE 
     FOLLOWING ZONES... DAVIS/APACHE MOUNTAINS AREA...MARFA 
     PLATEAU...VAN HORN AND HIGHWAY 54 CORRIDOR.

&&

$$

12/10