Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 191732 AAC
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1232 PM CDT SUN APR 19 2015

.UPDATE...
FOR 18Z TAFS

&&

.DISCUSSION...
/ISSUED 1015 AM CDT SUN APR 19 2015/

COMPLICATED WEATHER PATTERN IN PLACE THIS MORNING. A WARM FRONT THAT
BROUGHT SOME HEAVIER RAINFALL AND A FEW STRONGER STORMS IN DEKALB
COUNTY THIS MORNING CONTINUES TO MOVE OFF SLOWLY TO THE EAST AND
NORTHEAST. SOME MODERATE RAIN WILL CONTINUE THROUGH 10:30 IN EXTREME
EASTERN JACKSON AND DEKALB COUNTIES BEFORE ENDING. ANOTHER BOUNDARY
EXTENDING SOUTH FROM A MESOLOW IN WESTERN TN EXTENDS FROM NW MS INTO
ARKANSAS. A DRY SLOT CAN BE SEEN IN SATELLITE IMAGERY AND UPPER AIR
ANALYSIS BETWEEN THE WARM FRONT A SECOND BOUNDARY FURTHER WEST. THIS
SECOND BOUNDARY WILL DRIVE THE FORECAST FOR THE REMAINDER OF THE DAY
OVER NORTHERN ALABAMA AND SOUTHERN MIDDLE TN. MOSTLY CLOUDY
CONDITIONS ARE STILL IN PLACE ACROSS MUCH OF THE AREA...BUT ARE
BECOMING PARTLY CLOUDY IN NATURE WEST OF I-65 AS OF 10 AM. ADDITIONAL
DRY AIR WILL ADVECT INTO THE AREA THROUGH THE DAY ABOVE ~ 700 MB.
THIS AND WEAK ISENTROPIC DOWNGLIDE ASSOCIATED WITH SOME SUBSIDENCE
SHOULD ALLOW PARTLY CLOUDY CONDITIONS TO CONTINUE TO DEVELOP AND PUSH
FURTHER EAST AS THE DAY PROGRESSES. HOWEVER...MOISTURE BELOW
850...ESPECIALLY NEAR THE SURFACE WILL CONTINUE TO INCREASE AHEAD OF
THE APPROACHING BOUNDARY THIS AFTERNOON. TIMING OF THIS BOUNDARY WILL
BE KEY IN THE TIMING OF THUNDERSTORM DEVELOPMENT. SOME SHOWERS HAVE
ALREADY FORMED NEAR AND AHEAD OF THIS BOUNDARY IN NW MS. BASED ON
RADAR TRENDS THIS ACTIVITY WOULD APPROACH NW AL AROUND 1 OR 2 PM.

DUE TO EXPECTED LESSENING OF CLOUD COVER...INSOLATION SHOULD ALLOW
FOR DECENT CAPE VALUES AHEAD OF THIS BOUNDARY AS IT APPROACHES
NORTHERN ALABAMA AND SOUTHERN MIDDLE TN LATER THIS AFTERNOON.
COMBINED WITH DRY AIR ALOFT AND WET-BULB ZERO HEIGHTS DROPPING TO
AROUND 8000 FEET LATE THIS AFTERNOON...LARGE HAIL AND DAMAGING WINDS
ARE POSSIBLE WITH ANY SEVERE CONVECTION THAT DEVELOPS. HAIL...ESPECIALLY
IF CAPES AROUND 2000 J/KG COULD BE QUITE LARGE.

IN ADDITION...STRONGER STRAIGHT LINED WIND GUSTS TO AROUND 70 MPH
LOOK POSSIBLE AS WELL. LUCKILY MODELS AND UPSTREAM OBS CONTINUE TO
SHOW NO DIRECTIONAL SHEAR DEVELOPING...SO NOT EXPECTING A TORNADO
THREAT WITH THIS ACTIVITY THIS AFTERNOON. HOWEVER...A ISOLATED
TORNADO DUE TO OUTFLOW INTERACTIONS CANNOT BE DISMISSED. EXPECT
TIMING OF POSSIBLE SEVERE THUNDERSTORM DEVELOPMENT TO BE BETWEEN NOON
AND 2 PM IN NW AL AND 1 AND 3 PM FURTHER EAST.

ADJUSTED TEMPERATURES TO ACCOUNT FOR MORE PROLONGED MOSTLY CLOUDY
CONDITIONS IN NE AL AND RAISED DEWPOINTS A BIT HIGHER INTO THE MID
60S THIS AFTERNOON AS WELL.

KTW

&&

.AVIATION...
FOR 18Z TAFS...MVFR CONDITIONS DUE TO CEILINGS ARE EXPECTED THROUGH
THE BEGINNING PORTION OF THE FORECAST UNTIL AROUND 01Z AT BOTH HSV
AND MSL. AN AREA OF SHOWERS/EMBEDDED THUNDERSTORMS WILL MOVE THROUGH
THE AREA BETWEEN THE 19Z-20Z TIME FRAME AND HAVE ACCOUNTED FOR
EXPECTED 5SM SHRA WITH THE SHOWERS. THE NEXT ROUND OF SHOWERS ARE
EXPECTED BETWEEN THE 09Z-10Z TIME FRAME AT HSV AND MSL. HAVE FOR NOW
LEFT OUT THE PREDOMINANT MENTION OF TSRA DUE TO THE SCATTERED/WIDELY
SCATTERED STORMS POSSIBLE. EXPECT THAT THE SHRA SHOULD END BETWEEN
14Z-15Z AT BOTH HSV AND MSL. HAVE CONTINUED WITH MVFR CEILINGS
THROUGH THE END OF THE FORECAST PERIOD.

TT

&&

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

$$

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


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