Area Forecast Discussion
Issued by NWS Huntsville, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KHUN 301157
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
657 AM CDT THU JUL 30 2015

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 533 AM CDT THU JUL 30 2015/
TRANQUIL CONDITIONS CURRENTLY EXIST ACROSS THE LOCAL FORECAST AREA...
WITH 09Z SURFACE OBS SUGGESTING THAT A WEAK PREFRONTAL SURFACE
TROUGH CONTINUES TO PUSH SOUTHWARD INTO NORTHERN ALABAMA. ALTHOUGH
EVENING CONVECTION DISSIPATED RATHER QUICKLY AROUND MIDNIGHT...
ABUNDANT BOUNDARY LAYER MOISTURE FROM RAINFALL YESTERDAY HAS LED TO
THE DEVELOPMENT OF AREAS OF FOG AND TRENDS WILL CONTINUE TO BE
MONITORED FOR POTENTIAL ISSUANCE OF AN SPS. ON THE SYNOPTIC
SCALE...GLOBAL MODELS REMAIN IN AGREEMENT IN FORECASTING A MID- LEVEL
SUBTROPICAL RIDGE -- CURRENTLY CENTERED ACROSS THE ARKLATEX -- TO
RETROGRADE OVER THE RED RIVER VALLEY OF N TX/S OK TODAY AS A PAIR OF
VORTICES DIG EAST-SOUTHEASTWARD ACROSS THE UPPER MISSISSIPPI
VALLEY/GREAT LAKES. THE EASTERN EXTENT OF THE RIDGE AXIS IS PROGGED
TO REMAIN IN PLACE OVER THE CENTRAL TENNESSEE VALLEY...WITH STRONG
ANTICYCLONIC CURVATURE/SUBSIDENCE ALOFT AND NORTHERLY PREFRONTAL FLOW
AT THE SURFACE PROVIDING AN UNFAVORABLE ENVIRONMENT FOR THE
DEVELOPMENT OF DEEP CONVECTIVE UPDRAFTS AS THE TRUE COLD FRONT
ARRIVES EARLY THIS AFTERNOON. THE MOST SUBSTANTIAL THREAT FOR
SHOWERS/THUNDERSTORMS WILL LIKELY BE ACROSS THE FAR SOUTHEASTERN
COUNTIES LATE THIS MORNING -- IMMEDIATELY IN ADVANCE OF THE FRONT. A
SUBSTANTIAL DROP IN MOISTURE IS EXPECTED AS NORTHERLY FLOW INCREASES
IN THE WAKE OF THE FRONT...WITH DEWPOINTS FALLING INTO THE LOWER/MID
60S BY LATE AFTERNOON.

FOR THE REMAINDER OF THE SHORT TERM PERIOD...THE SUBTROPICAL HIGH IS
FORECAST TO GRADUALLY WEAKEN AND BECOME CENTERED ACROSS THE FOUR
CORNERS REGION. THIS WILL EFFECTIVELY PLACE THE REGION BENEATH A
STRONGER NORTHWEST FLOW ALOFT...WHICH WILL BE ENHANCED FURTHER BY THE
DEVELOPMENT OF A DEEP UPPER LOW OVER HUDSON BAY. AT THE SURFACE...A
BROAD REGION OF PACIFIC HIGH PRESSURE WILL SPREAD SLOWLY EASTWARD
ACROSS THE CENTRAL PLAINS -- BECOMING CENTERED OVER THE MID-
MISSISSIPPI VALLEY BY LATE SATURDAY AFTERNOON. NORTH-NORTHEASTERLY
LOW-LEVEL FLOW -- WHICH COULD BE QUITE GUSTY AT TIMES ON FRIDAY
AFTERNOON -- WILL CONTINUE TO ADVECT DRY AIR INTO THE REGION WITH
DEWPOINTS EXPECTED TO REMAIN IN THE MID 50S TO AROUND 60 THROUGH THE
WEEKEND. THAT SAID...FORECAST SOUNDINGS SUGGEST THE DEVELOPMENT OF A
DEEP MIXED BOUNDARY LAYER DURING THE AFTERNOON HOURS WHICH MAY ALLOW
DEWPOINTS TO FALL INTO THE LOWER 50S -- ESPECIALLY ACROSS NORTHEAST
ALABAMA. OVERALL...VERY PLEASANT CONDITIONS ARE EXPECTED WITH
RAINFALL THREAT CONFINED WELL TO THE SOUTH/EAST OF THE REGION. HIGHS
WILL BE IN THE UPPER 80S/LOWER 90S WITH LOWS IN THE LOWER/MID
60S...ALTHOUGH A FEW REPORTS OF UPPER 50S WOULD NOT BE OUT OF THE
QUESTION IN SOUTHERN TENNESSEE/NORTHEAST ALABAMA ON FRIDAY NIGHT.
PATCHY FOG WILL BE POSSIBLE EACH NIGHT...BUT MAINLY IN SHELTERED
VALLEYS AND NEAR LARGER BODIES OF WATER.

IN THE EXTENDED PERIOD...SIMILAR CONDITIONS ARE EXPECTED TO PERSIST
FOR THE SECOND HALF OF THE WEEKEND...ALTHOUGH LOW-LEVEL FLOW WILL
BECOME LIGHT/VARIABLE AS SURFACE RIDGE MIGRATES INTO THE CENTRAL
APPALACHIANS. MEDIUM RANGE GUIDANCE FROM THE ECMWF/GFS IS IN
AGREEMENT THAT MID-LEVEL HEIGHTS WILL BEGIN TO RISE MORE
SUBSTANTIALLY FROM MONDAY-WEDNESDAY...AS THE CANADIAN UPPER LOW
LIFTS OUT TO THE NORTHEAST AND THE SUBTROPICAL RIDGE EXPANDS EASTWARD
ACROSS THE SOUTHERN CONUS. ALTHOUGH FLOW ALOFT WILL REMAIN ZONALLY
ORIENTED ACROSS THE REGION...THERE IS SOME EVIDENCE OF STRONGER
SYNOPTIC SCALE FORCING FROM A WAVE LIFTING ACROSS THE MID-MISSISSIPPI
VALLEY ON WEDNESDAY. THIS -- COUPLED WITH STRENGTHENING SOUTHWEST
FLOW AND MOISTURE ADVECTION -- WILL WARRANT A SLIGHT CHANCE POP FOR
THE LATTER PERIODS OF THE FORECAST.

70/DD

&&

.AVIATION...
FOR 12Z TAFS...
A COLD FRONT IS ADVANCING S/SE THROUGH NORTHWESTERN TENNESSEE AS OF
1145Z THIS MORNING. A DECK OF LOW/MID LEVEL CLOUDS BETWEEN 1500-3000
FT HAS FORMED OUT AHEAD OF THIS FRONT AND IS CURRENTLY SPREADING
SOUTH INTO THE AREA. MVFR CIGS WILL BE POSSIBLE THROUGH 15-16Z AS THE
FRONT ENTERS THROUGH THE REGION. DRIER AIR BEHIND THE FRONT WILL
ALLOW FOR MAINLY HIGH CLOUDS FOR THE REMAINDER OF THE TAF PERIOD.
NORTHERLY WINDS WILL PICK UP BEHIND THE FRONT WITH GUSTS UPWARDS OF
20 KTS POSSIBLE.

ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE TODAY FOR
PORTIONS OF NORTHEAST ALABAMA. NOT EXPECTING ANYTHING FORMING NEAR
EITHER TERMINAL AS THE DRIER AIR SHOULD ARRIVE BEFORE STORMS DEVELOP.

STUMPF

&&

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

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.