Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 300305
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1005 PM CDT FRI MAY 29 2015

.UPDATE...
EVENING UPDATE TO PUBLIC FORECAST.

&&

.DISCUSSION...
EARLY EVENING CONVECTION HAS DISSIPATED...AND WITH ONSET OF DIURNAL
COOLING AND LITTLE TO NO SYNOPTIC SCALE FORCING FOR ASCENT
REDEVELOPMENT OVERNIGHT IS NOT EXPECTED. THUS...WILL BE REMOVING POPS
FOR THE REMAINDER OF 00-06Z PERIOD AND IMPROVING SKY CONDITION FOR
ALL AREAS...AS SCATTERED MID-LEVEL CONVECTIVE DEBRIS CLOUDS WILL
CONTINUE TO DISSIPATE. ATTENTION FOR THE EARLY SATURDAY MORNING
PERIOD FOCUSES ON A NEGATIVELY-TILTED 500-MB SHORTWAVE TROUGH AND
ASSOCIATED SURFACE LOW PROGGED TO LIFT NORTHEASTWARD ACROSS ARKANSAS.
CONVECTION ASSOCIATED WITH THIS FEATURE IS EXPECTED TO REMAIN WEST OF
THE AREA THROUGH 12Z SATURDAY...BUT WILL MAINTAIN A SLIGHT CHANCE POP
FOR NW ALABAMA IN THE EVENT THAT ACTIVITY ARRIVES SOONER THAN
CURRENTLY ANTICIPATED. MID-LEVEL CLOUDS ASSOCIATED WITH THIS SYSTEM
WILL BEGIN TO OVERSPREAD REGION FROM THE WEST BEFORE SUNRISE...AND A
BRIEF PERIOD OF LOWER STRATUS CLOUDS MAY ALSO DEVELOP IN SOME
LOCATIONS -- SIMILAR TO PREVIOUS NIGHTS. OTHERWISE...FORECASTED LOW
TEMPERATURES/DEWPOINTS AND WINDS APPEAR TO BE ON TRACK...WITH NO
CHANGES REQUIRED AT THIS TIME.

70/DD

&&

.AVIATION...
/ISSUED 703 PM CDT FRI MAY 29 2015/
FOR 00Z TAFS...VFR CONDS CURRENTLY IN PLACE AT BOTH HSV/MSL...WITH
FEW/SCT HIGH-BASED CU BENEATH SCT/BKN DECK OF AC. SCT SHRA/TSRA ARE
CURRENTLY MVNG NWD IN REGION BTWN THE TWO TERMINALS...BUT TRENDS
SUGGEST SOME ACTIVITY MAY IMPACT MSL EARLY THIS EVENING AND HAVE
INCLUDED VCTS/CB THRU 30/03Z. LINGERING PCPN WILL LKLY DIMINISH BY
03Z...WITH ONLY SCT CI AND LGT SSE FLOW TO PREVAIL THRU SATURDAY
MORNING. SIMILAR TO LAST COUPLE OF NIGHTS...SCT/BKN MVFR STRATUS DECK
MAY DEVELOP PRIOR TO SUNRISE AND HAVE INCLUDED TEMPO FOR THIS BTWN
08-12Z. SCT CU/AC WILL REDEVELOP BY 14Z...WITH SFC WINDS VEERING TO
SSW AND INCREASING TO ARND 10 KTS. COVERAGE OF SHRA/TSRA WILL BE
HIGHEST ARND MSL TOMORROW AS COLD FRONT APPROACHES FROM THE NW...AND
HAVE INCLUDED VCTS BEGINNING LATE TOMORROW MORNING. THREAT WILL BE
SLIGHTLY LOWER AT HSV THRU 31/00Z...BUT MAY INCLUDE VCTS WITH 06Z TAF
ISSUANCE.

70/DD

&&

.PREV DISCUSSION...
/ISSUED 320 PM CDT FRI MAY 29 2015/
THE 20Z IR/SATELLITE AND 88-D IMAGES INDICATED THAT SCATTERED SHOWERS
AND A FEW STORMS WERE DEVELOPING MAINLY EAST OF INTERSTATE 65 IN THE
FORECAST AREA. TEMPS WERE IN THE UPPER 70S TO AROUND 80 DEGREES. WILL
KEEP IN A CHANCE OF SHOWERS/STORMS INTO THE EVENING HOURS TONIGHT...
AND WILL LIMIT CHANCES INTO THE SLIGHT CHANCE CATEGORY AFTER 06Z
TONIGHT.

THE NEXT COLD FRONT AND ASSOCIATED UPPER LEVEL TROUGH IS PROGGED BY
THE SHORT TERM MODELS TO MOVE INTO THE LOWER OHIO VALLEY REGION BY
00Z SUNDAY. EXPECT THAT SCATTERED SHOWERS/STORMS ON THE LOWER END OF
THE CHANCE CATEGORY WILL BE POSSIBLE BY AFTERNOON AND INTO SATURDAY
EVENING. THE MODELS FURTHER SAG THE COLD FRONT THROUGH MIDDLE
TENNESSEE BY 12Z SUNDAY AND INTO THE NORTHERN SECTIONS OF THE
FORECAST AREA BY SUNDAY AFTERNOON. PWAT VALUES WILL REMAIN IN THE 1.6
TO 1.7 INCH RANGE THROUGH THE DAYTIME HOURS ON SATURDAY AND INTO
SUNDAY AND EXPECT CAPE VALUES TO INCREASE IN THE AFTERNOONS TOWARD
2000 J/KG ALONG WITH LIFTED INDICES IN THE -5 RANGE. WITH THE COLD
FRONT IN VICINITY OF THE FORECAST AREA ON SUNDAY...INCREASED POPS
LOOK TO BE IN ORDER AND THE FORECAST AREA WILL BE IN THE MARGINAL
SEVERE WEATHER RISK. THE GFS MODEL IS QUICKER INVOLVING THE SOUTHEAST
MOVEMENT OF THE COLD FRONT...COMPARED TO THE SLIGHTLY SLOWER ECMWF
MODEL.

THE GFS MODEL HANGS UP THE SOUTHEAST MOVING COLD FRONT JUST TO THE
SOUTH OF THE FORECAST AREA BY TUESDAY AFTERNOON...COMPARED TO THE
MORE PROGRESSIVE ECMWF MODEL...WHICH MOVES IT MUCH FARTHER SOUTHEAST.
HAVE LOWERED POPS ON TUESDAY AND WEDNESDAY SOMEWHAT TO ACCOUNT FOR
MORE DRIER AIR MOVING SOUTHEAST INTO THE REGION. HAVE FOLLOWED CLOSER
TO THE COOLER ECMWF MODEL TEMP GUIDANCE THROUGH WEDNESDAY.

THE GFS MODEL IS MUCH MORE PRONOUNCED IN DEVELOPING AN UPPER LOW OFF
OF THE TEXAS/LOUISIANA COAST BY WEDNESDAY...WITH INCREASING LOW LEVEL
MOISTURE TRANSPORT NORTHWARD TOWARD THE FORECAST AREA. THE ECMWF
MODEL DOES NOT PICK UP ON THIS FEATURE NEARLY AS MUCH AS THE GFS
MODEL IN THE EXTENDED PORTION OF THE FORECAST. FOR NOW...WILL GO MORE
IN LINE WITH PERSISTENCE...AS THERE SHOULD STILL BE SCATTERED MAINLY
AFTERNOON/EVENING SHOWERS/STORMS AS WE CONTINUE TO BE IN THIS MOIST
PATTERN THROUGH THE END OF THE EXTENDED FORECAST PERIODS. WILL
CONTINUE TO FOLLOW CLOSER TO THE ECMWF MODEL TEMP GUIDANCE 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.



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