FXUS64 KFWD 011129 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
529 AM CST TUE DEC 1 2009

.AVIATION...
/12Z TAFS/

VFR TO BEGIN THE TAF PERIOD...BUT CLOUD DECKS WILL GRADUALLY LOWER
THROUGH THE DAY. EXPECT RAIN SHOWERS MOVING INTO WACO BY 18Z AND
THE METROPLEX BY 21-22Z. MVFR CONDITIONS WILL PREVAIL FROM 21Z
THROUGH THE END OF THIS TAF CYCLE.

EAST TO NORTHEAST WINDS WILL AVERAGE NEAR 7 KTS TODAY...SHIFTING
TO THE NORTH/NORTHWEST BY 01Z. NORTHWEST WINDS WILL INCREASE TO 15
KTS BY 16Z WEDNESDAY.
 

&&

.PREV DISCUSSION... /ISSUED 429 AM CST TUE DEC 1 2009/
UPPER LEVEL LOW IS BEGINNING TO ENTER WEST TEXAS AND ISENTROPIC
LIFT AHEAD OF THE SYSTEM IS RESULTING IN THICKENING CLOUD COVER
AND ALSO AREAS OF RAIN TO OUR SOUTH AND WEST. STRENGTHENING MID
LEVEL FLOW ATOP THE FRONTAL ZONE WILL INTENSIFY ISENTROPIC LIFT
AND MOISTURE ADVECTION...WITH RAIN BECOMING WIDESPREAD OVER NORTH
TEXAS DURING THE AFTERNOON. UPPER LOW IS FORECAST TO TRACK ALONG
A SAN ANGELO TO SHREVEPORT LINE TONIGHT AND INTO WEDNESDAY. THIS
MEANS DRY SLOT WILL WORK IN FROM THE SOUTHWEST...WITH THE STEADY
RAIN ENDING IN THE SOUTHERN HALF OF THE CWA THIS EVENING. RAIN
WILL CONTINUE THROUGH THE OVERNIGHT GENERALLY NORTH OF I-20 WHERE
WRAP AROUND PRECIP CONTINUES IN ASSOCIATION WITH THE TROWAL. RAIN
AMOUNTS OF AROUND AN INCH OVER THE WHOLE AREA ARE EXPECTED.

PRECIP TYPE TONIGHT AND WEDNESDAY MORNING WILL BE MAINLY RAIN...AS
THE LOW LEVELS ARE JUST TOO WARM FOR A SIGNIFICANT WINTER EVENT.
MODELS CONTINUE TO DISPLAY GOOD RUN TO RUN CONSISTENCY WITH THE
UPPER LOW...AND IF ANYTHING ARE A TAD WARMER WITH THERMAL
PROFILES. THE MID-UPPER LEVELS ARE COLD ENOUGH FOR SNOW...BUT
FREEZING LEVELS OF 2000-4000 FEET WILL MAKE IT TOUGH FOR SNOW TO
SURVIVE THE TRIP TO THE SURFACE. COOLING OF THE NEAR SURFACE LAYER
CAN OCCUR AS LATENT HEAT IS ABSORBED FROM MELTING SNOW...BUT THIS
OFTEN REQUIRES A LOT OF MELTING SNOW. WILL CONTINUE THE FORECAST
OF RAIN/SNOW MIX WEST OF A LINE FROM GOLDTHWAITE TO WEATHERFORD TO
SHERMAN...WHERE THE HEAVIEST CLOUD-LEVEL SNOW IS EXPECTED TO
OCCUR. NO ACCUMULATION IS FORECAST...ALTHOUGH IT IS POSSIBLE IF
PRECIP IS HEAVY ENOUGH...A LOCALIZED CHANGE OVER TO SNOW AND SOME
BRIEF ACCUMULATIONS ON ELEVATED SURFACES MAY OCCUR.

AMPLIFICATION OF THE UPPER LEVEL PATTERN ACROSS WESTERN CANADA AND
THE DEVELOPMENT OF A LARGE/BROAD/DEEP TROUGH OVER THE US BY
THURSDAY WILL SEND A PIECE OF ARCTIC AIR SOUTHWARD INTO THE
REGION. THIS COLD AIRMASS IS NOT ANYTHING TOO UNUSUAL FOR THE TIME
OF THE YEAR...BUT IT WILL CERTAINLY KNOCK TEMPS DOWN WELL BELOW
NORMAL. WHILE THE MOS HAS COOLED SEVERAL DEGREES DURING THE LAST
DAY...BELIEVE IT IS STILL NOT COLD ENOUGH. WILL FORECAST A FREEZE
OVER MUCH OF NORTH TEXAS WED/THU/FRI NIGHTS...AND HIGHS GENERALLY
STUCK IN THE 40S.

UNFORTUNATELY THE FORECAST GETS MORE COMPLICATED THAN JUST TEMPS.
ALL OF THE MODELS ARE SHOWING A PV ANOMALY OVER MANITOBA DROPPING
SOUTHWARD INTO THE PLAINS AROUND THE WESTERN SIDE OF THE LONG WAVE
TROUGH. AS IT ROUNDS THE BASE OF THE TROUGH ON THURSDAY NIGHT...IT
WILL INDUCE A RESPONSE IN THE ISENTROPIC SURFACES OVER OUR
REGION...WITH UPGLIDE ORGANIZING. THERMAL PROFILES ARE CERTAINLY
COLD ENOUGH FOR SNOW BY THIS TIME...BUT MOISTURE BECOMES MORE
QUESTIONABLE. GFS IS MOST AGGRESSIVE WITH MOISTURE AND THUS HAS
ACCUMULATING SNOWFALL...BUT THE CANADIAN IS DRY. NAM/ECMWF/SREF
OFFER A REASONABLE COMPROMISE...AND THUS HAVE RELUCTANTLY ADDED
SNOW TO THE FORECAST LATE THURSDAY NIGHT AND FRIDAY. CONFIDENCE IS
LOW SINCE THE MODELS DID NOT SHOW THIS YESTERDAY...SO WILL KEEP
POPS LOW AND GENERALLY CONFINED TO LOCATIONS SOUTH OF I-20. THIS
REGION APPEARS TO HAVE THE BEST CHANCES OF ANY ACCUMULATING
SNOW BECAUSE OF BETTER MOISTURE...ALTHOUGH FLURRIES WILL BE
POSSIBLE OVER THE ENTIRE AREA. AGAIN...I WANT TO STRESS THAT
THIS FORECAST IS OF VERY LOW CONFIDENCE...AND SNOWFALL IS NOT A
CERTAINTY AT THIS POINT BUT ONLY A POSSIBILITY. 

FOR THE WEEKEND AND INTO NEXT WEEK...FORECAST LOOKS DRY WITH TEMPS
GRADUALLY MODERATING TO NEAR NORMAL.
 
TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  52  39  50  34  46 /  80 100  40   5   5 
WACO, TX              49  39  53  32  49 / 100 100  20   5   5 
PARIS, TX             54  39  47  32  48 /  30 100  80   5   5 
DENTON, TX            52  36  50  31  46 /  80 100  50   5   5 
MCKINNEY, TX          53  37  49  32  48 /  60 100  60   5   5 
DALLAS, TX            52  39  50  35  47 /  70 100  40   5   5 
TERRELL, TX           52  40  50  32  48 /  60 100  50   5   5 
CORSICANA, TX         51  40  52  33  48 /  80 100  40   5   5 
TEMPLE, TX            49  39  53  32  49 / 100  90  20   5   5 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$