Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 132307 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
507 PM CST SAT FEB 13 2016

.UPDATE...
FOR 00Z TAFS

&&

.DISCUSSION...
/ISSUED 413 PM CST SAT FEB 13 2016/
DESPITE ABUNDANT SUNSHINE TODAY...TEMPERATURES ONLY MANAGED TO CLIMB
INTO THE 30S IN MOST LOCATIONS. EXTREMELY DRY AIR IS IN PLACE AS WELL
COURTESY OF VERY STRONG COLD AIR ADVECTION PRODUCED BY AN 1036 MB
AREA OF HIGH PRESSURE JUST WEST OF THE OHIO VALLEY.

ALTHOUGH DEWPOINTS ARE EXTREMELY LOW /NEAR ZERO DEGREES/ WINDS
TONIGHT SHOULD KEEP LOW TEMPERATURES FROM REALLY BOTTOMING OUT...AS
GRADIENT WINDS REMAIN BETWEEN 5 AND 10 MPH. IF WE DECOUPLE AND LOSE
THAT WIND...LOWS WILL DROP MUCH LOWER THAN CURRENT FORECAST OF UPPER
TEENS AND LOWER 20S.

AS AN AREA OF LOW PRESSURE DEVELOPS ALONG A FRONTAL BOUNDARY OVER
CENTRAL TEXAS ON SUNDAY MORNING...MODEL PROG FRONTOGENESIS TO OCCUR
ALONG A WARM FRONT EXTENDING EAST FROM THAT LOW INTO NW TN. THE MAIN
PUSH OF CONCENTRATED MOISTURE CONVERGENCE IN THE BOUNDARY LAYER WILL
OCCUR OVER NORTHERN ARKANSAS INTO WESTERN TN THROUGH NOON.
HOWEVER...THERE MIGHT BE JUST ENOUGH MOISTURE IN PLACE IN THIS LAYER
TO PRODUCE SOME RAIN ALOFT OVER NW AL IN SOUTHERN MIDDLE TN AS EARLY
AS 9 OR 10 AM. DUE TO VERY DRY AIR IN PLACE AT THE SURFACE ANY
PRECIPITATION THAT REACHES THE GROUND WILL BE ISOLATED TO WIDELY
SCATTERED IN NATURE. GIVEN STRONG LIFT SEEN IN THE 290K LAYER WHERE
THIS MOISTURE IS CONCENTRATED...COULDN`T RULE OUT SOME REACHING THE
GROUND AS THE SURFACE TEMPERATURE WET-BULBS. IN WHAT FORM DURING THE
ONSET (~8 AM TO 11 AM) IS THE BIG QUESTION.

AT THIS POINT SINCE MODELS DO NOT SHOW TEMPERATURES IN THAT LAYER
REACHING -8 TO -10 DEGREES...BELIEVE SNOW DOES NOT LOOK LIKELY. IF
THE PRECIPITATION REACHES THE GROUND IT COULD BE A MIX OF RAIN AND
FREEZING RAIN DURING THE PERIOD...WITH NO ACCUMULATION OF FREEZING
RAIN EXPECTED.

THE GOOD NEWS IS THAT MODELS BY NOON DO SHOW A STRONG WARM NOSE
DEVELOPING. THIS SHOULD CHANGE ALL PRECIPITATION OVER TO RAIN AROUND
THAT TIME. MODELS CONTINUE TO STRENGTHEN THIS WARM NOSE INTO THE
EARLY EVENING HOURS ON SUNDAY. THIS WILL KEEP PRECIPITATION AS ALL
RAIN. MODELS COULD DROP DOWN TO NEAR 32 DEGREES AROUND DAYBREAK ON
MONDAY. AT THIS TIME...LOOKS LIKE A VERY COLD RAIN...BUT DUE TO THE
STRENGTH OF THE WARM NOSE BY THAT TIME...DO NOT EXPECT ANY FROZEN
PRECIPITATION...ALTHOUGH IT COULD BE JUST NORTH AND EAST OF OUR TN
COUNTIES

DURING THE DAY ON MONDAY...MODELS MOVE AN AREA OF LOW PRESSURE JUST
NORTH OF THE FORECAST AREA IN TENNESSEE. ALTHOUGH NO THUNDERSTORMS
ARE EXPECTED...VERY STRONG ISENTROPIC LIFT SHOULD PRODUCE A PERIOD OF
HEAVIER RAINFALL ON MONDAY. ONE TO TWO INCHES LOOK REASONABLE...WITH
SOME ISOLATED HIGHER AMOUNTS POSSIBLE.

AS FAIRLY ZONAL FLOW REMAINS IN PLACE BEHIND THE FRONT...A WEAK
SHORTWAVE WILL LIKELY PUSH THROUGH FLOW ALOFT AND GIVE US ANOTHER
CHANCE OF ISOLATED TO SCATTERED RAIN SHOWERS ON TUESDAY. THERE IS NOT
A LOT OF COLD AIR IS FORECAST BY MODELS BEHIND THIS.

UPPER LEVEL RIDGING AND MUCH WARMER WEATHER WILL BUILD INTO THE
SOUTHERN CONUS FROM TUESDAY THROUGH THE REMAINDER OF THE WEEK. BY
THE WEEKEND..COULD SEE HIGHS BACK INTO THE LOWER TO MID 60S.

KTW

&&

.AVIATION...
FOR 00Z TAFS...

VFR CONDITIONS SHOULD PREVAIL FOR THE NEXT 24 HOURS ACROSS N AL/S
MIDDLE TN. THE PRIMARY EFFECTS WILL BE NORTHERLY WINDS CHANGING
TO A SOUTHERLY DIRECTION AS A HIGH PRESSURE SYSTEM SHIFTS EAST
OVERNIGHT. WINDS SHOULD SHIFT TO SOUTHERLY BY 12Z-14Z AND BEGIN TO
GUST TO 15 KTS BY 17Z-18Z. RAIN IS EXPECTED TO DEVELOP AFTER 15Z BUT
MAY BE BRIEFLY ACCOMPANIED WITH FZRA. AM NOT CONFIDENT ENOUGH THAT
FZRA WILL OCCUR NEAR KHSV/KMSL TO INCLUDE IN TAFS, BUT HIGHER CHANCES
EXIST OVER S MIDDLE TN AND FAR NE AL.

SL.77

&&

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

$$

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


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