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Area Forecast Discussion

849
FXUS64 KHUN 251139
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
539 AM CST SUN JAN 25 2015

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 256 AM CST SUN JAN 25 2015/
THE ALBERTA CLIPPER TYPE-SYSTEM THAT WAS ANALYZED TO BE MOVING
SOUTHEAST THROUGH THE UPPER PLAINS STATES AT 06Z...SHOULD BE CENTERED
OVER NORTHERN MISSOURI BY 12Z TODAY. AS THE UPPER LOW/COLD FRONT
APPROACHES THE LOWER OHIO VALLEY REGION TODAY...CLOUDS WILL BE ON THE
INCREASE. WARM ADVECTION WILL CONTINUE TODAY IN ADVANCE OF THE
SYSTEM...WITH TEMPS ACROSS THE FORECAST AREA PROGGED TO MAKE IT INTO
THE LOW TO MID 50S...EVEN WITH INCREASED CLOUDS AS THE DAY CONTINUES.
WILL ALSO FOLLOW THROUGH WITH THE CONTINUED HIGHER END CHANCE POP FOR
MOST OF THE FORECAST AREA...WITH THE EXCEPTION OF CULLMAN COUNTY FOR
TODAY.

AS THE COLD FRONT ASSOCIATED WITH THE WEAK SURFACE LOW AND 500
MILLIBAR LOW MOVES THROUGH THE FORECAST AREA BY AROUND 06Z
TONIGHT...COLD ADVECTION WILL QUICKLY MOVE ACROSS THE REGION.
BOUNDARY LAYER TEMPS AS PER FORECAST SOUNDINGS AND MODEL TIME
SECTIONS INDICATE THAT TEMPS WILL FALL AFTER 06Z INTO THE MID
30S...WITH 850 MILLIBAR TEMPS PROGRESSIVELY FALLING TO -2 TO -4
DEGREES CELSIUS BETWEEN THE 06Z AND 09Z TIME FRAME EARLY ON MONDAY
MORNING. HAVE DECIDED TO CONTINUE WITH THE CHANCE/SLIGHT CHANCE OF
LIGHT RAIN/LIGHT SNOW MIX BETWEEN THE 06Z AND 12Z TIME PERIOD FOR THE
ENTIRE FORECAST AREA. WILL KEEP IN A MENTION OF SCATTERED FLURRIES
FOR MONDAY MORNING MAINLY IN PORTIONS OF SOUTHERN MIDDLE TENNESSEE
AND NORTHEAST ALABAMA.

THE UPPER TROUGH SHOULD REMAIN ACROSS THE EASTERN PORTION OF THE U.S.
THROUGH 12Z WEDNESDAY. A LARGE AREA OF SURFACE HIGH PRESSURE IS
EXPECTED TO SLOWLY MOVE EAST TO THE MID ATLANTIC COAST DURING THIS
TIME FRAME. HAVE TRENDED TOWARD THE SLIGHTLY COOLER ECMWF MODEL TEMP
GUIDANCE FROM MONDAY THROUGH WEDNESDAY. THE SURFACE RIDGE AXIS IS
PROGGED BY THE MODELS TO MOVE TO THE MID ATLANTIC COAST BY 00Z
THURSDAY...WITH WARM ADVECTION EXPECTED TO OCCUR ACROSS THE TENNESSEE
VALLEY THROUGH THURSDAY. HAVE TRENDED MORE TOWARD THE WARMER GFS
TEMPS FOR THURSDAYS HIGH TEMPS. BETWEEN 12Z WEDNESDAY AND 12Z
THURSDAY...THE MODELS INDICATE THAT A WEAK AREA OF LOW PRESSURE
SHOULD REMAIN GENERALLY NORTH OF THE TENNESSEE VALLEY REGION. THIS
SHOULD KEEP WARM ADVECTION OCCURRING UNTIL THE TRAILING WEAK COLD
FRONT MOVES THROUGH THE FORECAST AREA ON OR BEFORE 00Z FRIDAY.

HIGH PRESSURE AT SURFACE AND ALOFT IS EXPECTED TO PROGRESSIVELY WORK
ITS WAY EAST TO THE MID ATLANTIC COAST BY 00Z SATURDAY. THE NEXT
STRONGER STORM SYSTEM WILL TAKE SHAPE DURING THIS TIME FRAME IN THE
SOUTHERN ROCKY MOUNTAIN STATES. A DECENT AMOUNT OF LOW LEVEL MOISTURE
IS PROGGED BY THE MODELS TO MOVE EAST-NORTHEAST THROUGH THE SOUTHERN
PLAINS TOWARD THE FORECAST AREA BY 12Z SATURDAY. THE GFS MODEL IS
MORE PRONOUNCED WITH THIS FEATURE...COMPARED TO THE DRIER AND SLOWER
SOLUTION OF THE ECMWF MODEL. THE ECMWF MODEL IS MORE PRONOUNCED IN
ITS DEPICTION OF LOW LEVEL MOISTURE/OVERRUNNING PRECIP ALONG A
BOUNDARY ACROSS THE REGION...COMPARED TO THE DRIER DEPICTION OF THE
SYSTEM BY THE GFS MODEL. WILL KEEP IN A LOW CHANCE POP FOR NOW DUE TO
UNCERTAINTY. WILL AGAIN KEEP TEMPS MORE IN LINE WITH THE SLIGHTLY
COOLER ECWMF MODEL THROUGH THE EXTENDED FORECAST.

TT

&&

.AVIATION...
FOR 12Z TAFS...
A LOW PRESSURE LOCATED IN THE MIDWEST AS OF 12Z WILL BEGIN TO PUSH
MID/HIGH LEVEL CLOUDS INTO THE MID SOUTH THIS MORNING. CLOUDS WILL
CONTINUE TO INCREASE THIS AFTERNOON WITH CIGS LOWERING TO AOA 8KFT BY
18Z. WINDS GUSTS UP TO 20KTS WILL BE POSSIBLE BETWEEN 18Z AND 00Z
AHEAD OF THE INCOMING COLD FRONT. LIGHT RAIN OUT AHEAD OF THE FRONT
SHOULD SPREAD INTO BOTH TERMINALS AROUND 00Z THIS AFTERNOON.

MVFR CONDITIONS ARE EXPECTED BEHIND THE FRONT. FORECAST SOUNDINGS
AND GUIDANCE BOTH SUGGEST THAT CEILINGS MAY LOWER TO AROUND 1000 FEET
AFTER 06Z TONIGHT. AS TEMPERATURES DROP TO NEAR FREEZING OVERNIGHT
THE LIGHT RAIN MAY TRANSITION OVER TO A RAIN/SNOW MIX BETWEEN 06Z AND
12Z. HOWEVER...CONFIDENCE REMAINS LOW AND HAVE LEFT THE MIX OUT OF
THE TAFS.

STUMPF

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.



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