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000
FXUS64 KFWD 112338 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
538 PM CST WED DEC 11 2013

.AVIATION...

CONCERNS...POTENTIAL FOR IFR/LIFR CIGS/VIS AND FREEZING FOG.


THE 00Z TAF SET IS BUILT UPON THE THOUGHT OF SOME MVFR
VISIBILITIES DEVELOPING LATE TONIGHT THROUGH THURSDAY
MORNING. OTHERWISE VFR THE NEXT 24-30 HOURS.

HOWEVER...DUE TO THE ICE PACK BETWEEN THE METROPLEX AND RED
RIVER...LIGHTER NORTH WINDS OVERNIGHT WOULD BE ABLE TO CHILL AS
MUCH AS NORMAL RADIATIONAL COOLING INTO SPACE. ALSO...THIS PROCESS
COULD HELP KEEP DEWPOINTS IN THE MID 20S AND THUS A VERY SMALL
TEMP/DEWPOINT SPREAD BEFORE AND AFTER DAYBREAK. IF THIS
HAPPENS...1-3SM BR WOULD BE LIKELY. IF SKIES CLEAR LATE
TONIGHT...THEN CONDITIONS COULD DETERIORATE TO LIFR/IFR VIS/CIGS
( 1/4SM FG OR FZFG AND OVC001 OR VV001 ).

SURFACE WINDS WILL REMAIN NORTHERLY OVERNIGHT WITH SPEEDS COMING
DOWN TO LESS THAN 5 KT. WINDS WILL GO LIGHT SOUTHEAST THURSDAY
AFTERNOON THEN SOUTHERLY 5-10 KNOTS ON THURSDAY EVENING.

AS FOR KACT...VISIBILITIES OF 5SM BR 10-16Z. OTHERWISE...VFR WITH
SIMILAR WINDS AS ACROSS THE METROPLEX.  75

&&

.PREV DISCUSSION... /ISSUED 309 PM CST WED DEC 11 2013/
A FRONT IS CURRENTLY MAKING ITS WAY THROUGH THE REGION...AND WHILE
SIGNIFICANTLY COOLER TEMPERATURES ARE NOT PRESENT BEHIND THIS
FRONT IT WILL REINFORCE THE COOL TEMPERATURES FOR ANOTHER DAY.
DESPITE SOME HIGH CLOUD COVER THROUGHOUT THE DAY TODAY...
TEMPERATURES THIS AFTERNOON HAVE WARMED NICELY INTO THE UPPER 30S
TO LOWER 50S ACROSS THE REGION. HOWEVER...OVERNIGHT LOWS WILL
AGAIN BE BELOW FREEZING IN THE 20S AND LOWER 30...SO WE WILL
REPEAT THE CYCLE OF ANY ICE MELT OR WATER REFREEZING FOR ONE MORE
NIGHT. IN ADDITION...IT APPEARS SOME FREEZING FOG IS POSSIBLE
AROUND THE REGION AFTER MIDNIGHT THROUGH THE MID MORNING HOURS ON
THURSDAY. AT THIS POINT...IT IS UNCERTAIN HOW LOW VISIBILITIES
WILL FALL AND MOS GUIDANCE OFFERS VERY LITTLE HELP WITH THIS
QUESTION. HAVE DECIDED NOT TO ISSUE A FREEZING FOG ADVISORY AT
THIS TIME AND SEE HOW TRENDS DEVELOP LATER TONIGHT. IT IS POSSIBLE
THAT ANY LOCATIONS THAT FALL BELOW ONE MILE COULD SEE A THIN
LAYER OF ICE DEPOSIT ON ROADWAYS.

WE HAVE BEEN UNDER THE INFLUENCE OF ZONAL FLOW ALOFT FOR A FEW
DAYS BUT THE UPPER LEVEL PATTERN STARTS TO CHANGE TOMORROW. AS THE
UPPER LEVEL LOW THAT IS CURRENTLY WEST OF BAJA MOVES ONSHORE
TOMORROW...IT WILL INDUCE UPPER LEVEL RIDGING OVER THE STATE. THE
SURFACE HIGH BEHIND TODAY/S FRONT WILL SLIDE EAST TOMORROW AND
SOUTH WINDS WILL RETURN THURSDAY NIGHT. THE LOW NEAR BAJA WILL
OPEN INTO A SHORTWAVE THAT PASSES OVER THE REGION ON FRIDAY.
FORECAST SOUNDINGS SHOW THE MOISTURE RETURN WILL BE FAST ENOUGH AND
DEEP ENOUGH FOR RAIN FRIDAY AND FRIDAY NIGHT. THE BEST RAIN
CHANCES WILL BE OVER THE EASTERN HALF OF THE REGION DURING THE DAY
ON FRIDAY. LAPSE RATES CONTINUE TO BE TOO WEAK FOR A MENTION OF
THUNDER BUT DO THINK SHOWER-TYPE ACTIVITY IS POSSIBLE ON FRIDAY.
THE SHORTWAVE WILL QUICKLY PASS NORTHEAST OF THE REGION FRIDAY
NIGHT AND ANOTHER FRONT WILL ARRIVE ON THE HEELS OF THIS DEPARTING
SHORTWAVE. TEMPERATURES ON FRIDAY WILL BE INFLUENCED BY THE RAIN
AND CLOUD COVER WITH WARMER TEMPERATURES ACROSS OUR WESTERN COUNTIES.

ANOTHER SHORTWAVE COMES DOWN THE WEST COAST ON FRIDAY AND SWINGS
ACROSS THE REGION ON SATURDAY. THIS WILL HELP DRIVE SOME CHILLY
AIR INTO THE REGION FOR THE WEEKEND BUT NOTHING IN COMPARISON TO
WHAT WE HAVE EXPERIENCED THE PAST FEW DAYS. THE MODELS ARE HINTING
AT THE DEVELOPMENT OF SOME LIGHT PRECIPITATION ON SATURDAY AS THIS
NEXT SHORTWAVE PASSES OVERHEAD. FORECAST MODEL SOUNDINGS SHOW SOME
DECENT LOW LEVEL MOISTURE BUT DRIER MID LEVELS BY THAT TIME. WILL
INCLUDE A 20 PERCENT POP ON SATURDAY FOR SOME LIGHT RAIN OR
POSSIBLY DRIZZLE. ANY PRECIPITATION WILL REMAIN AS LIQUID.

BEYOND THE WEEKEND...THE UPPER LEVEL PATTERN TRANSITIONS TO
NORTHWEST FLOW ALOFT AS A BROAD TROUGH SETS UP OVER THE COUNTRY.
THE FORECAST FOR EARLY NEXT WEEK IS QUIET WITH A WARM UP EXPECTED.
HOWEVER...SIGNIFICANT WEATHER CHANGES ARE STARTING TO SHOW ON THE
HORIZON BEYOND 7 DAYS /SEE BELOW/.    82/JLD

&&

.LONG RANGE FORECAST...

...FOR THE 8 TO 12 DAY FORECAST PERIOD...
...THURSDAY DEC 19 THROUGH MONDAY DEC 23...

THERE WILL BE A POTENTIAL FOR A SIGNIFICANT COLD OUTBREAK ACROSS
NORTH AND CENTRAL TEXAS THAT COULD START JUST BEYOND THE 7 DAY
FORECAST PERIOD. GIVEN THE EXTENDED RANGE...THERE IS STILL
CONSIDERABLE UNCERTAINTY ON POTENTIAL IMPACTS. A CLOSE INSPECTION OF
THE LATEST 42-MEMBER NORTH AMERICAN ENSEMBLE (NAEFS) SUGGESTS THAT
THE LOWER END OF POTENTIAL IMPACTS WILL BE A RELATIVELY SHORT /TWO
TO THREE DAY/ PERIOD OF MUCH-BELOW NORMAL TEMPERATURES WITH LITTLE
OR NO WINTRY PRECIPITATION ACROSS NORTH AND CENTRAL TEXAS. THE UPPER
END OF THE IMPACTS SUGGEST A 3-4 DAY PERIOD OF MUCH-BELOW NORMAL
TEMPERATURES WITH A CHANCE FOR WINTRY PRECIPITATION IN MANY AREAS OF
NORTH AND CENTRAL TX.

BASED ON THE LAST 3-4 RUNS OF THE NAEFS...CONFIDENCE IS GROWING THAT
A VERY COLD ARCTIC AIRMASS WILL BEGIN SPREADING INTO NORTH TEXAS ON
DEC 19 OR DEC 20. THE FORECAST 500 MB PATTERN AND FORECAST MID LEVEL
TEMPERATURES ACROSS SOUTHERN CANADA STRONGLY SUPPORT A SOUTHWARD
PLUNGING AIRMASS AT LEAST AS COLD AS THE AIRMASS THAT ARRIVED IN
TEXAS ON DEC 5-6. THIS MORNINGS /12Z/ DETERMINISTIC RUNS OF BOTH THE
GFS AND ECMWF SUGGEST THAT THE INITIAL COLD SURGE WILL ARRIVE LATE
THURSDAY DEC 19 OR FRIDAY DEC 20. IF THE FORECAST HOLDS TRUE...THEN
TEMPERATURES AVERAGING 20-25 DEGREES BELOW NORMAL CAN BE EXPECTED
OVER ALL OF NORTH AND CENTRAL TEXAS OVER THE WEEKEND DEC 21-22.

THE PRECIPITATION FORECAST AT THIS EXTENDED RANGE IS MUCH MORE
PROBLEMATIC AND A GREAT DEAL OF UNCERTAINTY EXISTS REGARDING WINTRY
PRECIPITATION AND ANY POTENTIAL IMPACTS. THE NAEFS...WHICH IS
ESSENTIALLY 42 INDIVIDUAL MODEL RUNS USING TWO SEPARATE PHYSICS
PACKAGES...SHOWS A HUGE RANGE OF POTENTIAL IMPACTS. THAT HUGE RANGE
IS TYPICAL WITH ANY STRONG SYSTEMS IN THE 8 TO 12 DAY FORECAST
PERIOD. BUT GIVEN THE INCREASING CHANCES THAT VERY COLD AIR WILL
BE IN PLACE FOR THE PERIOD DEC 20-23...ANY PRECIPITATION THAT
FALLS ACROSS NORTH OR CENTRAL TEXAS COULD HAVE SIGNIFICANT IMPACTS.

09/PATRICK

&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  26  45  38  50  38 /   0   0  20  60  20
WACO, TX              28  49  38  49  39 /   0   0  20  60  20
PARIS, TX             24  44  33  44  40 /   0   0  10  60  40
DENTON, TX            22  43  36  48  35 /   0   0  20  50  20
MCKINNEY, TX          24  44  36  47  38 /   0   0  20  60  20
DALLAS, TX            27  46  39  50  39 /   0   0  20  60  20
TERRELL, TX           26  46  36  47  39 /   0   0  20  60  30
CORSICANA, TX         28  49  37  46  41 /   0   0  20  70  30
TEMPLE, TX            29  50  37  49  38 /   0   0  20  60  20
MINERAL WELLS, TX     24  43  36  53  32 /   0   0  20  50  10

&&

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

&&

$$

75/