Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 281529 AAA
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1029 AM CDT TUE APR 28 2015

.UPDATE...TO RAISE TEMPERATURES SLIGHTLY AND LOWER POPS THIS
AFTERNOON.

&&

.DISCUSSION...
A WEAK BOUNDARY EXTENDS FROM OFF THE SOUTH CAROLINA COAST WEST
THROUGH CENTRAL ALABAMA. THIS BOUNDARY EXTENDS FURTHER WEST INTO
LOUISIANA...WHERE AN UPPER LOW IS IN PLACE OVER SOUTHWESTERN
MS/EASTERN LOUISIANA. AN AREA OF MAINLY VIRGA AND SOME ISOLATED LIGHT
RAIN SHOWERS CONTINUE TO PUSH NORTHEAST ON THE EASTERN EDGE OF THIS
AREA OF LOW PRESSURE ALOFT OVER CENTRAL NW MS. MODELS PROG THE UPPER
LOW AND THE FORCING WITH IT TO INCH EASTWARD THROUGH THE AFTERNOON
HOURS. THIS WILL BRING AN AREA OF ISOLATED TO SCATTERED SHOWERS INTO
NW ALABAMA AND LOCATIONS MAINLY WEST OF I-65 AFTER 1 PM.

CURRENT TEMPERATURES ARE IN THE UPPER 50S TO LOWER 60S IN MOST
LOCATIONS. THE EXCEPTION TO THIS IS HUNTSVILLE AREA...WHICH IS
ALREADY 65 DEGREES AT 10 AM. MOSTLY CLOUDY CONDITIONS HAVE ALREADY
SPREAD OVER LOCATIONS MAINLY WEST OF I-65. SOME OF THIS WILL ERODE
THROUGH THE MORNING HOURS...BUT PREDOMINATELY MOSTLY CLOUDY
CONDITIONS ARE EXPECTED ALONG AND WEST OF I-65 THIS MORNING. THESE
MOSTLY CLOUDY CONDITIONS WILL OVERSPREAD THE AREA THIS AFTERNOON.

VERY DRY AIR IS IN PLACE AT THE SURFACE THIS MORNING WITH SURFACE
DEWPOINTS INT THE LOWER 40S TO 50 DEGREES. WITH TEMPERATURES
INCREASING TO THE UPPER 60S TO AROUND 70 DEGREES THIS AFTERNOON...ANY
RAIN ALOFT WILL EVAPORATE THROUGH THE MORNING HOURS. HOWEVER...SURFACE
CONDITIONS WILL BECOME MORE SATURATED THIS AFTERNOON. COMBINED WITH
THE FORCING FROM THE APPROACHING UPPER LEVEL LOW...ISOLATED TO
SCATTERED SHOWERS COULD MAKE IT AS FAR EAST AS THE I-65 CORRIDOR THIS
AFTERNOON. OVERALL DREW BACK POP IN SOUTHERN MIDDLE TN AND
NORTHEASTERN AL THIS AFTERNOON.

KTW

&&

.AVIATION...
/ISSUED 713 AM CDT TUE APR 28 2015/
FOR 12Z TAFS...CONDS WILL REMAIN VFR THRU AT LEAST FIRST HALF OF
VALID TAF PERIOD...WITH SCT CI OVERSPREADING REGION THIS MORNING
FOLLOWED BY SCT LAYERS OF SC/AC BY MID-AFTN. A FEW LGT SHRA WILL
DEVELOP BY LATE AFTN TO THE NORTH OF A SFC LOW OVER THE CENTRAL GULF
COAST. THIS ACTIVITY WOULD MOST LIKELY IMPACT MSL. A BRIEF PERIOD OF
-SHRA WILL OCCUR AT EACH TERMINAL OVERNIGHT...BEGINNING FIRST AT MSL
ARND 29/00Z AND ENDING LAST AT HSV ARND 12Z. STRATUS CIGS WILL LIKELY
LOWER TO ARND 3500 FT AS PRECIP BEGINS...WITH VSBY DROPPING TO ARND
6SM. CONDS MAY END UP BEING SLIGHTLY LOWER...BUT CONFIDENCE TOO LOW
TO PUT MVFR CIGS IN TAF ATTM. ENE FLOW 5-10 KTS WILL BACK WITH TIME
IN RESPONSE TO DEVELOPMENT OF WEAK SFC TROF EXTENDING NORTH FROM
GULF COAST LOW.

70/DD

&&

.PREV DISCUSSION...
/ISSUED 347 AM CDT TUE APR 28 2015/
SATELLITE IMAGERY THIS MORNING SHOWS THE CLOSED UPPER LEVEL IS NOW
LOCATED NEAR OK/TX BORDER. SURFACE CYCLOGENSIS IS UNDER WAY IN THE
WESTERN GULF...WITH A WARM FRONT EXTENDING NE ACROSS THE GULF COAST
STATES AND INTO THE FL PANHANDLE AND AN MCS RIDING THE SOUTHERN EDGE
OF THE FRONT. SOME OF THE CIRRUS FROM THIS MCS WAS ACROSS THE AREA
EARLIER THIS EVENING BUT HAS NOW SHIFTED EAST AND THE CIRRUS
ASSOCIATED WITH THE CLOSED LOW TO OUR WEST MAY NOT SPREAD IN UNTIL
SUNRISE. TEMPS HAVE FALLEN PRETTY QUICKLY IN AREAS THAT HAVE CLEARED
OUT COMPLETELY. WITH LIGHT WINDS EXPECTED FOR THE REMAINDER OF THE
MORNING WE COULD SEE SOME PATCHY FOG DEVELOP IN LOW LYING AREAS. KEPT
THE MENTION OF FOG OUT OF THE GRIDS DUE TO THE ISOLATED NATURE.

00Z SOUNDINGS AROUND THE AREA SHOWED A DECENT AMOUNT OF DRY AIR IN
THE LOW/MID LEVELS OF THE ATMOSPHERE AND WITH NO REAL ADVECTION OF
MOISTURE INTO THE AREA UNTIL LATER TODAY HAVE REMOVED THE MENTION OF
PRECIP THROUGH 18Z. AFTER 18Z AS THE UPPER LEVEL LOW APPROACHES THE
AREA AND THE SURFACE LOW LIFTS INTO SOUTH CENTRAL AL WE COULD SEE
A FEW LIGHT SHOWERS SPREAD INTO THE AREA. HOWEVER...WITH WINDS OUT OF
THE NE THROUGH ABOUT 850MB WE WILL CONTINUE TO HAVE DRY AIR ADVECTING
INTO THE AREA NEAR THE SURFACE AND ANY PRECIP THAT DOES MOVE IN WILL
LIKELY FALL AS VIRGA.

THE LOWEST LAYERS OF THE ATMOSPHERE LIKELY WONT COMPLETELY SATURATE
UNTIL CLOSER TO 00Z TODAY. THE BEST CHANCES FOR LIGHT TO MODERATE
RAIN WILL BE OVERNIGHT TONIGHT AS THE UPPER LEVEL LOW MOVES OVER THE
AREA. RAIN WILL TAPER OFF WEDNESDAY MORNING AS THE LOW SHIFTS EAST OF
THE AREA. A FEW LINGERING SHOWERS WILL BE POSSIBLE THROUGH THE EARLY
AFTERNOON HOURS ACROSS NE ALABAMA AND SOUTHERN MIDDLE TENNESSEE.

THE FORECAST FOR PRECIP CHANCES ON THURSDAY CONTINUES TO REMAIN
UNCERTAIN. MODELS ARE IN AGREEMENT IN DROPPING AN UPPER LEVEL LOW
OUT OF THE GREAT LAKES REGION INTO THE APPALACHIANS. HOWEVER...THE
LATEST NAM/GFS HAVE SHIFTED THE TRACK SLIGHTLY FURTHER EAST THAN THE
ECMWF. THE TRACK WILL LIKELY DEPEND ON THE STRENGTH OF THE RIDGE
BUILDING INTO PLAINS STATES. IN EITHER CASE...FORECAST SOUNDINGS SHOW
STEEP LAPSE RATES THROUGH AROUND 700MB AND THE FORCING ASSOCIATED
WITH THE UPPER LEVEL LOW COULD KICK OFF SOME CONVECTIVE SHOWERS ON
THURSDAY AND WILL KEEP THE MENTION OF SHOWERS THROUGH THURSDAY
AFTERNOON/EVENING.

HEADING INTO NEXT WEEK WE TRANSITION INTO MORE OF A TYPICAL SUMMER
TIME PATTERN WITH THE JET STREAM WELL TO THE NORTH AND ZONAL FLOW
ACROSS A MAJORITY OF THE SOUTHERN US. THIS SHOULD TRANSLATE INTO A
WARMING TREND IN TEMPS THROUGH EARLY NEXT WEEK WITH A RETURN TO AT TO
SLIGHTLY ABOVE NORMAL TEMPS.

STUMPF

&&

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

$$

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


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