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 280340
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1040 PM CDT WED MAY 27 2015

.UPDATE...
EVENING UPDATE TO PUBLIC FORECAST.

&&

.DISCUSSION...
ONLY VERY MINOR CHANGES TO EARLY EVENING UPDATE TO GRIDS...MAINLY TO
ACCOUNT FOR POP TRENDS THIS EVENING. ALTHOUGH LATEST RADAR DATA
SUGGESTS THAT HIGHEST THREAT FOR STRONG/SEVERE CONVECTION HAS NOW
SHIFTED NORTHEASTWARD...A LARGE AREA OF TRAILING STRATIFORM
PRECIPITATION AND EMBEDDED LIGHTNING CONTINUES FOR MUCH OF THE AREA.
THUS...WILL MAINTAIN CATEGORICAL POPS THRU 06Z FOR ALL BUT FAR NW
ALABAMA...AND FOR ONLY NE ALABAMA/SRN TENNESSEE AFTER 06Z.

BEYOND MIDNIGHT...IT REMAINS UNCLEAR AS TO WHETHER OR NOT CONVECTION
WILL REDEVELOP DURING THE PREDAWN HOURS ON THURSDAY. AT THE
MINIMUM...CHANCE POPS WILL BE RETAINED THROUGHOUT THE NIGHT AS A VERY
MOIST/UNSTABLE AIRMASS WILL RESIDE ACROSS THE REGION...AND MID- LEVEL
FORCING FOR ASCENT WILL BE MAINTAINED BY SHORTWAVE TROUGH APPROACHING
SLOWLY FROM THE LOWER MISSISSIPPI VALLEY REGION. ASIDE FROM THESE
FACTORS...CONVECTION MAY ALSO TEND TO REDEVELOP AS THE NOCTURNAL LOW-
LEVEL JET GRADUALLY STRENGTHENS ABOVE A VAST COLD POOL IN PLACE FROM
CURRENT RAINFALL. THE PRIMARY THREATS WITH ANY ACTIVITY DEVELOPING
LATER TONIGHT WOULD BE LOCALLY HEAVY RAINFALL -- WHICH MAY AGGRAVATE
PREEXISTING FLOODING ACROSS THE REGION. TEMPERATURES... DEWPOINTS AND
WINDS APPEAR TO BE ON TRACK AT THIS POINT WITH LITTLE FLUCTUATION IN
TEMPERATURE EXPECTED FOR REMAINDER OF THE NIGHT.

70/DD

&&

.AVIATION...
/ISSUED 658 PM CDT WED MAY 27 2015/
FOR 00Z TAFS...AREA OF WIDESPREAD RA/TSRA CONTINUES TO IMPACT ALL BUT
FAR NE AL/SRN TN EARLY THIS EVENING. THIS ACTIVITY IS SHIFTING EWD
VERY SLOWLY AND WILL MAINTAIN PREVAILING -TSRA THRU 28/05Z WITH TEMPO
FOR +TSRA BTWN 00-03Z. BASED ON OBS...CIGS HAVE BEEN REMAINING VFR
BUT FALLING CLOSE TO MVFR THRESHOLD IN HEAVIER PCPN. HOWEVER...VSBY
WILL LIKELY REMAIN MVFR /3-5 SM/. UPPER-LEVEL WAVE WHICH IS DRIVING
THIS CONVECTIVE EVENT IS FORECAST TO SLOWLY SHIFT NEWD ACROSS REGION
DURING COURSE OF TAF PERIOD...AND SO CURRENT REGIME MAY EITHER
PERSIST FOR MUCH OF TAF PERIOD...OR MAY WEAKEN LATE THIS EVENING AND
REDEVELOP TOWARD 12Z. THUS...WILL KEEP SHRA AS PREVAILING COND FROM
05-18Z AND AMEND IF DRYING TREND BECOMES MORE EVIDENT. SFC FLOW WILL
REMAIN FROM THE SE ARND 5 KTS WITH BKN/OVC VFR CIGS OF 3.5-5 KFT.

70/DD

&&

.PREV DISCUSSION...
/ISSUED 233 PM CDT WED MAY 27 2015/
THE 19Z IR/VISIBLE SATELLITE IMAGERY ANALYSIS INDICATED THAT AN
ELONGATED SHORT WAVE AT 500 MILLIBARS WAS MOVING SLOWLY EASTWARD OUT
OF THE OHIO THROUGH TENNESSEE VALLEYS AND FURTHER SOUTH INTO CENTRAL
MISSISSIPPI. SHOWERS AND STORMS WERE CONTINUING TO DEVELOP TO THE
SOUTHWEST OF THE FORECAST AREA AND UP INTO MIDDLE TENNESSEE IN THE
PVA REGIONS. EXPECT THAT BREAKS IN CLOUDS/INSTABILITY AND PWAT VALUE
INCREASES THIS AFTERNOON/EVENING WILL CONTINUE TO LEAD TO AT LEAST
CHANCE POPS FOR THE FORECAST AREA INTO THE EVENING HOURS. EXPECT THAT
THE ECMWF/NAM SOLUTION INVOLVING LESSENING THE AMOUNT OF PRECIP/LOW
LEVEL MOISTURE ACROSS THE FORECAST AREA AFTER 06Z SHOULD BE THE TREND
TO FOLLOW ALONG WITH INVOLVING TONIGHTS PRECIP CHANCES. WILL CONTINUE
WITH SLIGHT CHANCE POPS DURING TONIGHTS 06Z-12Z TIME FRAME.

THERE WILL STILL BE PLENTY OF LOW LEVEL MOISTURE AVAILABLE ALONG WITH
PWAT VALUES SLIGHTLY ABOVE 1.3 INCHES BY THURSDAY AFTERNOON. AS TEMPS
WARM INTO THE MID 80S AND LIFTED INDICES LOWER TO -3 BY THE
AFTERNOON...WILL CONTINUE WITH A CHANCE POP FOR THE FORECAST AREA
INTO THURSDAY EVENING. THE LOW LEVEL SOUTHEASTERLY FLOW AND STILL
ABUNDANT MOISTURE SHOULD AGAIN RESULT IN A CHANCE POP FOR FRIDAY FOR
THE FORECAST AREA. BY 12Z SATURDAY...A COLD FRONT IS PROGGED BY THE
MODELS TO SLOWLY SHIFT SOUTHEAST THROUGH THE MIDWEST WITH CONTINUED
MAINLY AFTERNOON/EVENING STORMS POSSIBLE ACROSS OUR AREA.

WILL CONTINUE WITH CHANCE POPS FOR THE FORECAST AREA THROUGH SUNDAY
AS THE WEAKENING COLD FRONT IS PROGGED TO SLOWLY MAKE IT SOUTHWARD
THROUGH KENTUCKY AND INTO WEST TENNESSEE. HAVE UPPED PRECIP CHANCES
INTO THE LIKELY CATEGORY FOR SUNDAY DUE TO THE PROXIMITY OF THE COLD
FRONT TO THE FORECAST AREA...PWAT VALUES APPROACHING 1.5 INCHES AND
NEARLY A MODERATELY UNSTABLE AFTERNOON ATMOSPHERE. THE MODELS ARE IN
FAVORABLE AGREEMENT INVOLVING STALLING OUT THE COLD FRONT TO THE
NORTH OF THE FORECAST AREA BY BETWEEN SUNDAY AND INTO MONDAY. THE GFS
AND ECMWF MODELS ARE BOTH SIMILAR INVOLVING ALSO SLOWLY SHIFTING A
WEAK UPPER LOW AT 500 MILLIBARS SOUTHEAST INTO WEST TENNESSEE BY
TUESDAY. THE EFFECTS OF THIS UPPER SYSTEM ALONG WITH ABUNDANT LOW
LEVEL MOISTURE SHOULD CONTINUE TO RESULT IN HIGHER END CHANCE POPS
FOR THE FORECAST AREA INTO WEDNESDAY. HAVE FOLLOWED CLOSER TO THE
SLIGHTLY COOLER GFS TEMPS THROUGH THE EXTENDED FORECAST PERIODS.

TT

&&

.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.