FXUS64 KMAF 291144
AFDMAF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX
544 AM CST SUN NOV 29 2009

.DISCUSSION...
SEE AVIATION DISCUSSION BELOW.

&&

.AVIATION...
A STRONG COLD FRONT WILL MOVE THROUGH THE TERMINALS TODAY RESULTING
IN A WIND SHIFT TO THE NORTH WITH WIND SPEEDS OF 10 TO 20 MPH WITH
GUSTS TO 25 MPH. VFR CONDITIONS WILL PREVAIL THROUGH THIS EVENING
WITH TEMPO VFR CEILINGS POSSIBLE AT SEVERAL OF THE TERMINALS THIS
MORNING. INSERTED A PROB30 GROUP AFTER 21Z TODAY AT THE TERMINALS
FOR VFR CONDITIONS IN POSSIBLE LIGHT RAIN SHOWERS.

12

&&

.PREV DISCUSSION... /ISSUED 404 AM CST SUN NOV 29 2009/ 

DISCUSSION...
EVERYTHING IS BEGINNING TO TAKE SHAPE WITH THE UPPER LEVEL LOW
DIGGING INTO THE BAJA OF MEXICO AS EXPECTED. MODEL CONSENSUS IS
COMING AROUND WITH THE GENERAL EVOLUTION OF THE UPPER LEVEL
PATTERN WITH THE LOW MOVING INTO NORTHERN MEXICO THEN HEADING EAST
INTO THE BIG BEND OF TEXAS BEFORE EXITING OFF TO THE EAST
NORTHEAST. THE BIGGEST DISCREPANCY BETWEEN THE MODELS IS A
POTENTIAL WARM LAYER ALOFT INDICATED BY THE NAM WHICH IS NOT NEAR
AS STRONG ON THE GFS. THIS WARM LAYER WILL BE KEY IN DETERMINING
PRECIP TYPE AS WELL AS SNOWFALL AMOUNTS.

I FEEL THE NAM IS HANDLING THE ELEVATED WARM LAYER BETTER THAN THE
GFS. THE UPPER LEVEL LOW IS IN THE PROCESS OF BECOMING CUT OFF
FROM ITS NORTHERN SUPPORT AND WILL BE INFLUENCED MORE BY THE
EAST/WEST SOUTHERN STREAM JET MOVING IN OFF THE PACIFIC. I HAVE
LITTLE DOUBT THAT THIS SOUTHERN STREAM JET HAS WARM AIR THAT THE
UPPER LOW WILL TAP INTO WHICH WILL BE ADVECTED OVER OUR CWA GIVEN
THE SLOW MOVEMENT OF SAID LOW. THIS WARM LAYER WILL MOST LIKELY
KEEP THE P-TYPE RAIN OR IP ACROSS MOST AREAS THROUGH MONDAY NIGHT
WITH THE EXCEPTION OF THE MOST WESTERN AREAS WHICH ARE HIGHER
AND CLOSER TO THE LOW. THUS WILL GO WITH A WINTER STORM WATCH FOR
MAINLY AREAS ABOVE 5KFT MON/MON NIGHT AND WILL HOLD OFF ON ISSUING
ANYTHING FOR AREAS FURTHER EAST AT THIS TIME.

THE ELEVATED WARM LAYER WILL EVENTUALLY COOL AS THE UPPER LOW
APPROACHES WHICH SHOULD CAUSE THE P-TYPE TO CHANGE FROM MIXED TO
ALL SNOW ON TUESDAY BEGINNING IN THE TRANS PECOS REGION VERY EARLY
IN THE DAY THEN PROGRESSING EASTWARD. AT THIS POINT I BEGIN TO
PREFER THE GFS OVER THE NAM MAINLY IN REGARDS TO PRECIP AMOUNTS.
THE GFS KEEPS THE CYCLONIC CIRCULATION TIGHTER AS IT MOVES ACROSS
THE AREA WHICH DRAWS MORE MOISTURE INTO THE SYSTEM PROVIDING
HIGHER QPF AMOUNTS. THE NAM WEAKENS THE LOW TOO MUCH THE RESULT OF
WHICH IS TO QUICKLY BRING IN WESTERLY FLOW WHICH WOULD PUSH THE
PRECIPITATION OFF TO OUR EAST. THERE APPEARS TO ONLY BE A BRIEF
PERIOD OF TIME TUESDAY MORNING WHEN THE P-TYPE AND THE P-AMOUNTS
MATCH UP TO GIVE THE PERMIAN BASIN A DECENT SHOT AT ACCUMULATING
SNOWFALL AMOUNTS. I HAVE PUT IN UP TO TWO INCHES IN THE GRIDS FOR
NOW BUT THERE IS STILL TOO MUCH UNCERTAINTY...AND IT IS STILL A
BIT FAR OUT...TO BE ISSUING ANY WINTER WEATHER PRODUCTS FOR THIS
TIME FRAME AND WILL LEAVE TO LATER SHIFTS TO MONITOR AND UPDATE AS
NEEDED. 

LIGHT SNOW MAY LINGER INTO TUESDAY NIGHT AND EARLY WEDNESDAY BUT
PRECIP WILL SHUT OFF LEAVING A COLD AIR MASS ACROSS TEXAS FOR MUCH
OF THE EXTENDED PERIOD. THE ECMWF IS QUITE COLD IN FACT LATE IN
THE WEEK AS THE SURFACE HIGH PRESSURE SYSTEM IS SLOW TO MOVE EAST.
DECIDED TO HEDGE BETWEEN THE ECMWF AND GFS AND UNDERCUT MEX
GUIDANCE IN THE EXTENDED THOUGH NOT QUITE AS MUCH AS THE ECMWF
WOULD HAVE YOU BELIEVE. 

HENNIG

&&

.MAF WATCHES/WARNINGS/ADVISORIES...
NM...WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE MONDAY NIGHT 
     FOR THE FOLLOWING ZONES... EDDY COUNTY PLAINS...GUADALUPE 
     MOUNTAINS OF EDDY COUNTY.

TX...HIGH WIND WATCH FROM THIS EVENING THROUGH MONDAY MORNING FOR THE 
     FOLLOWING ZONES... GUADALUPE MOUNTAINS.

     WINTER STORM WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT 
     FOR THE FOLLOWING ZONES... GUADALUPE MOUNTAINS...VAN HORN 
     AND HIGHWAY 54 CORRIDOR.

&&

$$