Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 280738
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
238 AM CDT FRI AUG 28 2015

.DISCUSSION...

AN UNSEASONABLY COOL AND DRY AIR MASS WILL ABATE LATER TONIGHT AS
THE SOUTHERN FLANK OF AN EXITING TROUGH OFF THE EAST COAST BECOMES
CUTOFF FROM THE PREVAILING WESTERLIES. CURRENTLY THIS UPPER LOW IS
LOCATED OVER THE NORTH CENTRAL GULF COAST. OVER THE COURSE OF TODAY
AND TONIGHT, IT WILL GRADUALLY BEGIN TO AFFECT THE PREVAILING LOW TO
MID LEVEL FLOW ACTING TO SLOWLY SATURATE THE MID LEVELS. THOUGH
SATURATION WILL NOT OCCUR RAPIDLY ENOUGH TO RESULT IN STORM
DEVELOPMENT, LOW LEVEL CLOUD COVER ADVECTING FROM THE EAST SHOULD
DEVELOP THIS AFTERNOON. AN ADDITIONAL IMPACT WILL BE THE WIND
DIRECTION SHIFT TO EASTERLY TO SOUTHEASTERLY FOR LOW-MID LEVELS.
THIS CHANGE IN WIND DIRECTION WILL ACT TO INCREASE MOISTURE
ADVECTION FROM BOTH THE GULF OF MEXICO AND ATLANTIC. SO THAT BY
SATURDAY, SATURATION IS ANTICIPATED THROUGH MUCH OF THE VERTICAL
COLUMN, WHICH COMBINED WITH THE APPROACHING CUTOFF LOW WILL INCREASE
CHANCES FOR PRECIPITATION. A LOOK AT FORECAST SOUNDINGS AND PLAN
VIEW REPRESENTATION OF INSTABILITY SHOW STEEP LOW TO MID LEVEL LAPSE
RATES WITH LOW TO MODERATE CONDITIONAL INSTABILITY ON SATURDAY AND
AGAIN ON SUNDAY. AS A RESULT, THUNDERSTORM DEVELOPMENT IS FORECAST,
BUT WITHOUT APPRECIABLE WIND SHEAR, ANY THUNDERSTORMS THAT DO OCCUR
TO BE PULSE-LIKE IN NATURE. DUE TO THE MODEL RUN CONSISTENCY, WILL
RAISE POPS, ESPECIALLY FOR THE AFTERNOONS ON BOTH SATURDAY AND
SUNDAY. ON THE TEMPERATURE FRONT, WITH THE TN VALLEY BACK IN A
MARITIME TROPICAL ENVIRONMENT ON BOTH DAYS, EXPECTING DAYTIME HIGH
TEMPERATURES TO RISE CLOSE TO 90 WITH A HIGHER PROBABILITY FOR
BREAKS IN THE CLOUDS OVER THE WESTERN HALF OF THE CWA TO CONTRIBUTE
TO THESE HIGHS.

THEN, BY SUNDAY, THE CUTOFF LOW APPEARS TO BEGIN SHIFTING NORTHEAST
TOWARDS THE EASTERN APPALACHIANS (MERGING WITH AN APPROACHING
SHORTWAVE TROUGH) RESULTING IN A DECREASE IN SHOWER/STORM ACTIVITY.
BECAUSE OF ITS PROGGED EXIT, HAVE TAPERED POPS TO MAINLY NE AL/S
MIDDLE TN ON MONDAY. A SHEARED TROUGH THEN FORMS ON THE SOUTHERN
FLANK OF THE APPROACHING SHORTWAVE TROUGH OVER MI/IL/IN. THIS
PORTION OF THE SHORTWAVE TROUGH MAY ACT AS A FOCUS FOR THUNDERSTORM
ACTIVITY BY WEDNESDAY, BUT DUE TO THE UNCERTAINTY WITH THIS AND THE
TRACK OF TC ERIKA, IF IT SURVIVES, WILL KEEP LOW POPS MAINLY FOR
WEDNESDAY. THERE IS PRETTY LOW CONFIDENCE IN THE FORECAST DUE TO THE
INTERACTIONS WITH THIS SHEARED TROUGH AND POSSIBLE DIRECT/INDIRECT
IMPACTS FROM TC ERIKA. FURTHERMORE, WILL KEEP TEMPERATURES NEAR OR
JUST BELOW AVERAGE (30 YEAR) FOR THIS TIME OF YEAR ON MONDAY AND
TUESDAY (DAYTIME HIGHS NEAR 90S AND OVERNIGHT LOWS IN UPPER 60S).
HOWEVER, WITH THE INCREASE IN SFC DEWPOINTS (I.E. RETURN OF SUMMER
LIKE HUMIDITY), EXPECT IT TO FEEL WARMER WITH HEAT INDEX VALUES
RETURNING TO THE LOW TO MID 90S BY MID WEEK.

SL.77

&&

.AVIATION...
/ISSUED 1146 PM CDT THU AUG 27 2015/
FOR 06Z TAFS...WITH HIGH PRESSURE TO THE NE CONTINUING TO IMPACT THE
WX ACROSS THE REGION...VFR CONDS ARE XPCTED THROUGH THE TAF PERIOD.
ONLY EXCEPTION MAY BE SOME BRIEF -BR NEAR THE KMSL TERMINAL DURING
THE EARLY MORNING HRS...ALTHOUGH THE PROB IS NOT HIGH ENOUGH TO
INCLUDE IN THE FORECAST ATTM. SCT MID CLOUDS SHOULD ALSO ONCE AGAIN
DEVELOP DURING THE LATE MORNING/EARLY AFTERNOON HRS IN RESPONSE TO
DAYTIME HEATING.

09

&&

.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE    88  68  85  68 /   0   0  30  30
SHOALS        89  68  86  68 /   0   0  20  20
VINEMONT      87  68  83  68 /   0   0  30  30
FAYETTEVILLE  88  67  83  67 /   0   0  30  30
ALBERTVILLE   88  68  82  68 /  10  10  40  30
FORT PAYNE    88  67  82  67 /  10  10  40  40

&&

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

$$

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



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