Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 040827
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
327 AM CDT FRI SEP 4 2015

.DISCUSSION...

ANOTHER QUIET NIGHT ACROSS THE TENNESEE VALLEY...AS HIGH PRESSURE
MAINTAINS ITS HOLD OVER THE REGION. LATEST WATER VAPOR IMAGERY SHOWS
MUCH OF THE CENTRAL AND EASTERN CONUS UNDER A FAIRLY BROAD
RIDGE...WITH A STRONG UPPER TROUGH MOVING ASHORE THE WEST
COAST...WHILE A WEAK SHORTWAVE WAS TRAVERSING SLOWLY ACROSS THE
GREAT LAKES REGION. CLEAR SKIES ACROSS THE FORECAST
AREA...COMBINED WITH LITTLE TO NO WIND AND VERY LOW DEWPOINT
DEPRESSIONS HAS SET THE STAGE FOR WIDESPREAD LIGHT FOG. THE TRICKY
PART IS TRYING TO DETERMINE HOW REDUCED THE VISIBILITIES WILL BECOME
AS WE PROGRESS THROUGH THE REMAINDER OF THE OVERNIGHT HOURS. SEVERAL
OBSERVATIONS SITES HAVE BOUNCED BETWEEN 1 AND 5 MILES...WITH A FEW
ISOLATED LOCATIONS FALLING BELOW 1 MILE. BASED ON THIS
UNCERTAINTY...DO NOT FEEL CONFIDENT ENOUGH AT THIS POINT TO ISSUE AN
ADVISORY...HOWEVER IT MAY BE NEEDED LATER IN THE MORNING. AS IS
TYPICAL...ANY FOG THAT DOES DEVELOP WILL QUICKLY DISSIPATE AFTER
14Z...AS SURFACE HEATING BEGINS AND BOUNDARY LAYER MIXING OCCURS.
THIS WILL LEAVE A MOSTLY DRY DAY FOR THE AREA...WITH TEMPERATURES
WARMING TO SEASONAL NORMS. AN ISOLATED SHOWER OR THUNDERSTORM IS
POSSIBLE DURING THE AFTERNOON...AS WEAKNESSES MOVE AROUND THE EASTERN
PERIPHERY OF THE RIDGE. HOWEVER...DEEP LAYER MOISTURE AND VERY WEAK
LIFT WILL KEEP ANY WIDESPREAD ACTIVITY FROM DEVELOPING.

SURFACE HIGH PRESSURE WILL BUILD DOWN THE EASTERN SIDE OF THE
APPALACHIAN MOUNTAIN RANGE ON SATURDAY...AS THE UPPER LEVEL HIGH
STRENGTHENS OVER THE NORTHEAST. AN INVERTED TROUGH WILL DEVELOP AND
PUSH INTO THE SOUTHEAST ATLANTIC COAST...WITH A WEAK FRONT DEVELOPING
AT THE SURFACE. THIS WEAK FRONT/BOUNDARY WILL SLIDE WESTWARD INTO THE
AREA SATURDAY AFTERNOON...PULLING MOISTURE INTO THE AREA FROM THE
ATLANTIC. ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP ALONG THIS
FEATURE...MAINLY ACROSS THE EASTERN HALF OF THE FORECAST AREA.
DIURNAL HEATING WILL AID IN THE LIFT...MEANING THAT COVERAGE WILL
DECREASE OVERNIGHT SATURDAY AND INTO SUNDAY. THE UPPER LEVEL INVERTED
TROUGH WILL STRENGTHEN SLIGHTLY ON SUNDAY AND CLOSE OVER THE
SOUTHEAST. THEREFORE...LIFT WILL BE SOMEWHAT HIGHER...THOUGH STILL
NOT OVERLY STRONG...AND MOISTURE WILL CONTINUE TO INCREASE. THE
COVERAGE OF THUNDERSTORMS WILL BE GREATER ON SUNDAY...BUT THE BETTER
CHANCES WILL STILL BE OVER THE EASTERN PORTION OF THE AREA.

THE WEAK UPPER LEVEL CLOSED LOW WILL CONTINUE TO PROPAGATE TO THE
SOUTHWEST AND SETTLE OVER THE NORTHERN GULF BY THE EARLY PART OF
NEXT WEEK. RAIN CHANCES WILL BE ON THE LOW SIDE...GIVEN THE HIGH
LIKELIHOOD THAT THE FORECAST AREA WILL BE CUT OFF FROM THE DEEP LAYER
MOISTURE. MODEL GUIDANCE IS SLIGHTLY DIFFERING ON THE STRENGTH AND
TIMING OF THE UPPER LOW...HOWEVER A BLEND OF THE MODELS WILL STILL
LEND TO ONLY ISOLATED TO WIDELY SCATTERED THUNDERSTORMS THROUGH
MIDWEEK. MEANWHILE...AN UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW
WILL DEVELOP OVER THE UPPER PLAINS...WITH A SURFACE COLD FRONT
TRAILING SOUTHWARD. STILL FAR IN THE EXTENDED...HOWEVER THE COLD
FRONT IS EXPECTED TO REACH THE FORECAST AREA BETWEEN THE THURSDAY AND
FRIDAY TIME FRAME...IF IT IS ABLE TO HOLD TOGETHER.

73

&&

.AVIATION...
/ISSUED 1211 AM CDT FRI SEP 4 2015/
FOR 06Z TAFS...
MVFR CONDITIONS FROM FOG/MIST SHOULD DEVELOP DURING THE COURSE OF
THE NIGHT...GIVEN HUMID CONDITIONS WITH LIGHT WINDS AND GENERALLY
CLEAR SKIES. VIS REDUCTIONS TO IFR...POSSIBLE LOWER HAVE BEEN KEPT AS
A TEMPO FOR PREDAWN TO AFTER DAYBREAK. ANY FOG/MIST PRESENT SHOULD
DISSIPATE BY 04/1400Z...WITH VFR WEATHER RETURNING AND CONTINUING
FOR THE REMAINDER OF THE TAF. THAT BEING SAID...STRONG DAYTIME
HEATING COULD LEAD TO CU/TCU FORMATION IN THE LATE MORNING...WITH
ISOLATED CONVECTION POSSIBLE...MAINLY EAST OF I65 IN THE AFTERNOON.

RSB

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    93  71  93  72 /  10  10  10  10
SHOALS        92  70  92  70 /  10  10  10  10
VINEMONT      90  68  91  68 /  10  10  10  10
FAYETTEVILLE  90  69  91  69 /  20  10  20  20
ALBERTVILLE   89  69  89  69 /  20  10  30  20
FORT PAYNE    90  67  89  68 /  20  10  30  20

&&

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

$$

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


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