Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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000
FXUS64 KFWD 160958
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
358 AM CST TUE DEC 16 2014

.DISCUSSION...

00Z UPPER AIR ANALYSIS SHOWED A LARGE UPPER LOW OVER MISSOURI AND
IOWA...WITH UPPER LEVEL RIDGING OVER THE CONUS ROCKIES AND BROAD
TROUGHING OVER THE WEST CONUS COAST. WITHIN THIS BROAD WEST COAST
TROUGH...WATER VAPOR SATELLITE IMAGERY SHOWED SHORTWAVE TROUGHS
JUST OFF THE COAST OF BAJA CALIFORNIA...RIGHT OVER THE COAST OF
CENTRAL CALIFORNIA...AND ANOTHER DIGGING SOUTH OVER THE OPEN
WATERS OF THE PACIFIC ABOUT 600 MILES WEST OF OREGON. THESE
FEATURES WILL HELP BRING RAIN BACK INTO THE FORECAST ACROSS NORTH
AND CENTRAL TEXAS WEDNESDAY AND FRIDAY.

TODAY...THE CONSENSUS OF GUIDANCE IS THAT THE STRONG SHORTWAVE
TROUGH WEST OF OREGON RIGHT NOW WILL CONTINUE SOUTH TOWARDS
SOUTHERN CALIFORNIA OVER THE NEXT 24 HOURS...HELPING TO KICK THE
WEAKER SHORTWAVE TROUGH CURRENTLY JUST WEST OF BAJA CALIFORNIA
EAST OVER THE REGION FOR WEDNESDAY. WHILE THIS IS HAPPENING OUT
WEST...THE UPPER LEVEL RIDGE THAT IS IN BETWEEN THESE TROUGHS AND
THE SOUTHERN PLAINS WILL MOVE EAST OVER THE REGION FOR TODAY. THIS
UPPER RIDGE WILL SPREAD LARGE SCALE FORCING FOR SUBSIDENCE OVER
THE AREA FOR THE NEXT 18 HOURS OR SO...ENSURING A DRY FORECAST FOR
THE CWA THROUGH THIS EVENING. SKIES WILL START OUT CLEAR...BUT WE
SHOULD START TO SEE SOME UPPER LEVEL CIRRUS BUILD OVER THE REGION
AROUND SUNSET AS THE SUBTROPICAL UPPER JET BUILDS EAST OVER THE
REGION OUT AHEAD OF THE BAJA SHORTWAVE TROUGH. DESPITE MOSTLY
SUNNY SKIES TODAY...WE ARE EXPECTED TO REMAIN QUITE A BIT COOLER
THAN YESTERDAY WITH HIGHS TOPPING OUT IN THE LOWER TO MID 50S FOR
MOST LOCATIONS. HIGHS ARE EXPECTED TO REMAIN 10 TO 15 DEGREES
COOLER THAN YESTERDAY BECAUSE CLEAR SKIES AND DRY AIR WILL ALLOW
FOR A COOLER START TO THE DAY...AND BECAUSE NORTHERLY WINDS WILL
KEEP COLD AIR ADVECTION OVER THE AREA ALL DAY TODAY.

TONIGHT INTO WEDNESDAY...THE BAJA SHORTWAVE TROUGH IS EXPECTED TO
MOVE EAST OVER THE SOUTHWEST CONUS AND OVER THE SOUTHERN PLAINS
TONIGHT THROUGH WEDNESDAY. THE SUBTROPICAL JET BUILDING EAST OVER
THE AREA OUT AHEAD OF THE TROUGH WILL HELP TO INCREASE MID TO UPPER
LEVEL MOISTURE OVER THE REGION...HOWEVER THE BULK OF THE TROPICAL
MOISTURE WILL BE BLOCKED BY THE HIGH TERRAIN OF NORTHERN MEXICO.
REGARDLESS...00Z RAOB ANALYSIS INDICATED THAT 850 MB DEW POINTS OF
8 TO 12 DEG C WERE IN PLACE ALONG THE GULF COAST FROM CORPUS
CHRISTI TO NEW ORLEANS. AS THIS TROUGH SPREADS LARGE SCALE FORCING
FOR ASCENT OVER THE REGION IN THE FORM OF DEEP WARM AIR
ADVECTION...THE VEERING WIND PROFILE WITH HEIGHT WILL TAP INTO
THIS RESERVOIR OF MOISTURE AND SEND IT NORTH OVER NORTH AND
CENTRAL TEXAS ON WEDNESDAY. AS A RESULT...THINK THAT RAIN CHANCES
WILL INCREASE AFTER SUNRISE ON WEDNESDAY...WITH RAIN AND MOISTURE
BUILDING IN FROM THE SOUTHWEST TO NORTHEAST THROUGHOUT THE DAY.
HAVE THE HIGHEST POPS IN PLACE SOUTH OF INTERSTATE 20 AND WEST OF
INTERSTATE 35 WEDNESDAY MORNING...SPREADING EAST TO INCLUDE THE
ENTIRE CWA WEDNESDAY AFTERNOON AND EVENING.

WITH RELATIVELY COOL AIR IN PLACE OVER THE CWA FROM PERSISTENT
COLD AIR ADVECTION LAST NIGHT THROUGH THIS AFTERNOON...THE STRONG
WARM AIR ADVECTION INDUCED BY THE UPPER TROUGH IS EXPECTED TO
RESULT IN STRONG LIFT OVER THE ENTIRE AREA. WENT AHEAD WITH BROAD
BRUSHED 60 POPS AS CONFIDENCE IN ALL AREAS RECEIVING MEASURABLE
RAINFALL IS FAIRLY HIGH DUE TO THIS STRONG LIFT. POPS WILL LIKELY
NEED TO BE INCREASED AS LONG AS MOISTURE REMAINS READILY AVAILABLE
ALONG THE GULF COAST TO BE INGESTED INTO THIS SYSTEM.

FORECAST SOUNDINGS INDICATE THAT THE DEPTH OF COOL AIR OVER THE
REGION EXTENDS TO ABOUT THE 800 MB LEVEL...SO THIS IS WHERE A
FAIRLY STOUT INVERSION WILL BE IN PLACE FOR THE DURATION OF THIS
RAIN EVENT. FORECAST SOUNDINGS INDICATE THAT AIR LIFTED ABOVE THIS
INVERSION WILL HAVE SOME POSITIVE BUOYANCY AS COOLER AIR ALOFT
ADVECTS OVER THE REGION WEDNESDAY AFTERNOON AND EVENING. AT THIS
TIME...ONLY 100 TO 250 J/KG OF CAPE IS EXPECTED...OR JUST ENOUGH
TO SUPPORT SOME OCCASIONAL LIGHTNING STRIKES EMBEDDED IN THE
WIDESPREAD RAIN SHOWER ACTIVITY THAT IS EXPECTED TO DEVELOP OVER
THE CWA. RAINFALL TOTALS ARE EXPECTED TO RANGE FROM ONE TENTH OF
AN INCH TO ONE HALF OF AN INCH ACROSS THE REGION BY WEDNESDAY
EVENING WHEN RAINFALL WILL BEGIN TO END FROM WEST TO EAST AS THE
UPPER TROUGH MOVES AWAY FROM NORTH TEXAS.

THURSDAY...THE STRONGER UPPER TROUGH WEST OF OREGON EARLY THIS
MORNING IS EXPECTED TO MOVE EAST OVER THE SOUTHWESTERN CONUS ON
THURSDAY...AND THEN OVER THE CWA ON FRIDAY. IN BETWEEN THE
DEPARTING TROUGH AND THIS APPROACHING TROUGH...WEAK UPPER LEVEL
RIDGING IS EXPECTED TO SET UP OVER THE REGION. AS A
RESULT...DESPITE THE FACT THAT MOST DETERMINISTIC MODELS CONTINUE
TO SPIT OUT LIGHT QPF ACROSS THE CWA DURING THE DAY ON
THURSDAY...WE WILL PROBABLY BE DRY FOR THE MOST PART. LEFT IN SOME
BROAD BRUSHED 20 POPS WITH A MENTION OF LIGHT RAIN ON THURSDAY AS
MODELS DO INDICATE THAT SOME LOW-LEVEL MOISTURE AND WEAK LIFT MAY
PERSIST OVER THE CWA ON THURSDAY. THIS MAY RESULT IN SOME
SPRINKLES OR DRIZZLE ACROSS THE AREA.

THURSDAY NIGHT AND FRIDAY...MODELS ARE STILL STRUGGLING TO RESOLVE
DETAILS REGARDING THE EXACT TRACK AND EVOLUTION OF THIS STRONG
UPPER TROUGH OVER THE REGION THURSDAY NIGHT INTO FRIDAY. AS A
RESULT...DID NOT MAKE ANY SIGNIFICANT CHANGES TO THE PREVIOUS
FORECAST AS SMALL CHANGES IN THE TRACK OF THIS UPPER LEVEL SYSTEM
CAN HAVE BIG IMPACTS ON THE TIMING AND PLACEMENT OF RAINFALL
DURING THIS TIME FRAME.

WHAT ALL MODELS SEEM TO AGREE UPON:

LOW-LEVEL MOISTURE IS EXPECTED TO REMAIN IN PLACE NEAR THE TX GULF
COAST ONCE AGAIN BEHIND WEDNESDAY`S UPPER TROUGH. AS A RESULT...
SUFFICIENT MOISTURE FOR RAINFALL ASSOCIATED WITH THIS UPPER TROUGH
SHOULD BE IN PLACE.

THE STRONGEST FORCING FOR ASCENT WILL OCCUR OVER CENTRAL TEXAS AS
OPPOSED TO NORTH TEXAS. WHILE THE ENTIRE CWA MAY END UP RECEIVING
MEASURABLE RAINFALL DURING THIS EVENT...RAINFALL AMOUNTS WILL
LIKELY BE SIGNIFICANTLY HIGHER ACROSS CENTRAL TEXAS...OR WHEREVER
THE STRONGEST FORCING SETS UP.

THE GFS AND CANADIAN SEEM TO INDICATE THE BEST FORCING WILL SET UP
FARTHER SOUTH THAN THE ECMWF AND NAM SOLUTIONS AT THIS TIME. THE
AXIS OF HEAVIEST RAINFALL APPEARS TO BE AT LEAST SOMEWHAT
CORRELATED TO THE POSITION OF THE 850 MB FRONT DURING THIS
EVENT...SO WILL KEEP A CLOSE EYE ON THE POSITION OF THIS FEATURE
IN LATER FORECASTS. FOR NOW IT LOOKS MOST LIKELY THAT THIS FRONT
WILL EXTEND SOMEWHERE ALONG OR SOUTH OF A LINE FROM ATHENS TO
HILLSBORO. WHEREVER THIS H850 FRONT WINDS UP...MODELS ARE
CONSISTENTLY PAINTING AN AXIS OF 1-1.5 INCHES OF RAINFALL...WITH
RAINFALL TOTALS CLOSER TO ONE TENTH TO ONE HALF OF AN INCH TO THE
NORTH OF THIS FRONT. WENT AHEAD AND KEPT THE AXIS OF HEAVIEST
RAINFALL OVER THE FAR SOUTHEASTERN CWA FOR NOW...BUT THIS COULD
CHANGE IN LATER FORECASTS AS MODELS GET A BETTER HANDLE ON HOW FAR
NORTH/SOUTH THIS FRONT WILL SET UP FRIDAY MORNING.

SATURDAY THROUGH MONDAY...MODELS CONSISTENTLY SHOW STRONG DRY AIR
ADVECTION AND SUBSIDENCE SPREADING ACROSS THE REGION ON SATURDAY
BEHIND FRIDAY`S STRONG UPPER TROUGH. MODELS DO INDICATE THAT
ANOTHER UPPER TROUGH WILL MOVE OVER NORTH TEXAS SOMETIME BETWEEN
SUNDAY AND MONDAY AFTERNOON. AT THIS TIME IT DOES NOT LOOK LIKE WE
WILL HAVE ENOUGH MOISTURE IN PLACE FOR MUCH MORE THAN SOME VERY
LIGHT RAIN OR SPRINKLES AS THE TROUGH MOVES OVER THE REGION. JUST
WENT AHEAD WITH SOME BROAD BRUSHED 20 POPS ON MONDAY FOR NOW TO
ACCOUNT FOR THIS.

CAVANAUGH


&&

.AVIATION...
/ISSUED 1114 PM CST MON DEC 15 2014/
GENERALLY CLEAR SKIES WITH N/NW WINDS NEAR 10KT WILL PREVAIL
THROUGH SUNSET TUESDAY. WINDS WILL BECOME LIGHT NE TUESDAY EVENING
WITH CIGS NEAR 8000FT ARRIVING AROUND 9Z. RAIN SHOWERS WILL HOLD
OFF UNTIL LATE WEDNESDAY MORNING...WITH CIGS LOWERING TO MVFR OR
LOWER WEDNESDAY EVENING AS THE COLUMN SATURATES FROM TOP-DOWN.

TR.92


&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  52  40  47  43  56 /   0   0  60  50  20
WACO, TX              55  40  48  44  59 /   0   0  60  60  20
PARIS, TX             48  33  46  40  51 /   5   0  50  60  20
DENTON, TX            52  37  45  41  55 /   0   0  60  50  20
MCKINNEY, TX          51  36  46  41  54 /   0   0  60  60  20
DALLAS, TX            52  40  46  43  57 /   0   0  60  60  20
TERRELL, TX           51  36  48  42  55 /   0   0  60  60  20
CORSICANA, TX         53  39  50  45  58 /   0   0  60  60  20
TEMPLE, TX            56  41  49  46  61 /   0   0  60  60  20
MINERAL WELLS, TX     53  40  45  40  58 /   0   0  60  40  20

&&

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

&&

$$

 /





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