Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 250349 AAA
AFDSHV

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SHREVEPORT LA
949 PM CST WED DEC 24 2014

.DISCUSSION...
CLOUDS ARE QUICKLY MOVING EAST AND OUT OF SRN AR/N CNTRL LA. TEMPS
SHOULD BEGIN TO QUICKLY DROP IN THOSE AREAS AS SKIES CLEAR AND
WIND SPEEDS DIMINISH. UPDATED SKY GRIDS TO REFLECT LATEST TRENDS
IN SAT IMAGERY. OTHERWISE...BIGGEST QUESTION MARK TONIGHT IS
TEMPS. SEVERAL LOCATIONS ARE ALREADY WITHIN 5 DEGREES OF FCST
LOWS. MOST OF THE MODELS ARE WAY TOO WARM AND OF LITTLE HELP. THE
00Z MET GIVES KSHV A LOW OF 38 TONIGHT DESPITE THE CURRENT TEMP
BEING 36 DEGREES F. COOLING TONIGHT WILL BE ENTIRELY DRIVEN BY
RADIATIONAL COOLING...WHICH IS TYPICALLY THE MOST DIFFICULT
SITUATION TO FCST SINCE MICROSCALE EFFECTS ON A LOCAL LEVEL CAN
HAVE A BIG INFLUENCE. IF WIND SPEEDS INCREASE SLIGHTLY...THE
INCREASED MIXING WILL KEEP TEMPS FROM PLUMMETING TOO FAR. ON THE
FLIP SIDE...LIGHT AND VARIABLE WINDS COULD ALLOW TEMPS TO FALL
BELOW FCST VALUES.

LONG STORY SHORT...WILL KEEP THE MIN TEMP FCST INTACT BUT ANY
ADDITIONAL COOLING BEYOND WHAT IS FCST WILL LIKELY RESULT IN
TEMPS AT OR BELOW FREEZING. /09/

&&

.PREV DISCUSSION... /ISSUED 625 PM CST WED DEC 24 2014/

AVIATION...
VFR CONDITIONS WILL PERSIST ACROSS THE REGION THIS TAF
PERIOD...EXCEPT AT MLU...WHERE LOW CEILINGS AND -RA WILL GIVE WAY
TO PERIODS OF MVFR CONDITIONS BEFORE 03Z. CEILINGS WILL CONTINUE
TO DISSIPATE AS CLOUDS MOVE OUT OF THE AREA FROM WEST TO EAST.
WINDS WILL GRADUALLY SHIFT FROM THE WEST TO THE SOUTH BY DAYBREAK
AREA WIDE AND WIND SPEEDS WILL GRADUALLY INCREASE TO 10-15 KNOTS DURING
THE LATER PORTION OF THE TAF PERIOD.

PREV DISCUSSION... /ISSUED 213 PM CST WED DEC 24 2014/

DISCUSSION...

UPPER TROUGH AXIS HAS SHIFTED EAST OF THE REGION THIS AFTN BUT WE
ARE STILL SEEING SOME SPRINKLES ACROSS PORTIONS OF NW LA INTO
EXTREME S AR. FEEL LIKE THIS PRECIPITATION WILL BE ENDING QUICKLY
THIS EVENING SO WILL NOT MENTION IT IN THE FCST OVERNIGHT. WHAT WE
SHOULD SEE IS THE CLOUD COVER EXIT THE REGION FROM WEST TO EAST
OVERNIGHT WHICH WILL SET UP FOR A COLD NIGHT TONIGHT. ALL AREAS
SHOULD SEE LOWER 30S TONIGHT WITH MID TO UPPER 20S POSSIBLE ACROSS
THE PROTECTED AREAS OF SW AR INTO SE OK. IF SHV SEES 32 DEGREES
EARLY IN THE MORNING...IT WILL BE OUR FIRST FREEZE SINCE NOV
19TH...A SIGNIFICANT PERIOD OF TIME TO BE ABOVE FREEZING FOR OUR
REGION.

WEAK UPPER RIDGING REPLACES THE TROUGH ON CHRISTMAS DAY AND WITH A
TIGHTENING PRESSURE GRADIENT AT THE SURFACE...SOUTH WINDS WILL
ALLOW TEMPERATURES TO WARM QUICKLY ON THURSDAY WITH A BEAUTIFUL
CHRISTMAS DAY EXPECTED. OUR NEXT WEATHER MAKER IN THE FORM OF A
CLOSED UPPER TROUGH WILL DIG INTO THE FOUR CORNERS REGION OF THE
COUNTRY LATE THURSDAY NIGHT WHICH WILL ALLOW FOR RETURNING CLOUD
COVER THURSDAY NIGHT AND RETURNING PRECIPITATION CHANCES FOR
FRIDAY...MAINLY ACROSS OUR WEST HALF. THE TROUGH SHOULD STAY
ANCHORED ACROSS THE SOUTHWEST CONUS THROUGH SATURDAY BUT
DISTURBANCES OUT AHEAD OF THE POSITIVELY TILTED TROUGH AXIS WILL
RESULT IN INCREASING RAIN CHANCES FRIDAY NIGHT AND UNFORTUNATELY
FOR SATURDAY WITH MANY OUTDOOR PLANS EXPECTED. THE RAIN WILL TRY
TO TAPER OFF OUR NORTHWEST HALF SAT AFTN BEHIND A COLD FRONT BUT
RAINFALL MAY NOT COME TO AN END ACROSS NW LA UNTIL THU EVENING IF
THEN. TROUGH FINALLY EJECTS OUT INTO THE PLAINS SAT NIGHT/SUN
WITH RAIN EXITING OUR SOUTHEAST PARISHES LATE SUN NIGHT/EARLY
MON MORNING.

BIG CHANGES COMING TO THE REGION FOR THE LAST WEEK OF 2014 IN THE
FORM OF MUCH COLDER AIR AND PERHAPS SOME WINTER PRECIPITATION.
DEEP UPPER TROUGH DIGS INTO THE INTER MOUNTAIN WEST ON MONDAY
BEFORE CLOSING OFF AND DIGGING INTO THE FOUR CORNERS REGION FOR
TUE. THIS WILL KEEP US UNDER STRONG SOUTHWESTERLY FLOW ALOFT WHICH
WILL RESULT IN CONTINUED RAIN CHANCES TUESDAY/TUESDAY NIGHT. THE
LEADING EDGE OF A MUCH COLDER...POLAR AIRMASS WILL BE MOVING INTO
OUR REGION LATE TUESDAY INTO TUE NIGHT AS WELL. THICKNESS AND MODEL
FCST SOUNDINGS SUGGEST A CHANGE OVER FROM RAIN TO SNOW TUE NIGHT
ACROSS OUR NORTHERN THIRD WITH A RAIN SNOW MIXTURE WEDNESDAY AGAIN
ACROSS OUR NORTHERN ZONES. MORE OF THE AREA COULD GET IN ON SOME
WINTER PRECIPITATION FOR NEW YEARS DAY...ESPECIALLY IF THE ECMWF
MODEL SOLUTION COMES TO FRUITION BUT NEEDLESS TO SAY...THIS
REMAINS A LONG WAY OUT INTO THE EXTENDED PORTION OF THE FORECAST.
OBVIOUSLY...THIS SYSTEM WILL CONTINUE TO BE MONITORED CLOSELY.
THERE IS ONE THING THE MEDIUM RANGE PROGS DO AGREE WITH HOWEVER...
AND THAT IS THAT A MUCH COLDER AIRMASS WILL BE ARRIVING INTO THE
FOUR STATE REGION NEXT WEEK.

PRELIMS TO FOLLOW...13.

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  33  60  44  63  56 /   0   0  10  20  60
MLU  31  58  40  64  55 /   0   0  10  20  60
DEQ  26  58  36  59  49 /   0   0  10  30  60
TXK  32  58  42  59  52 /   0   0  10  30  60
ELD  29  58  39  62  54 /   0   0  10  20  60
TYR  33  61  47  62  53 /   0   0  10  30  60
GGG  31  61  45  62  55 /   0   0  10  30  60
LFK  32  63  47  65  59 /   0   0  10  30  60

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
LA...NONE.
OK...NONE.
TX...NONE.
&&

$$

09




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