Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 281124
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
624 AM CDT THU MAY 28 2015

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 327 AM CDT THU MAY 28 2015/
WATER VAPOR ANALYSIS AS OF 08Z IS STILL SHOWING A WEAK SHORTWAVE
MAKING ITS WAY THROUGH WESTERN MISSISSIPPI VERY SLOWLY. THIS WAVE
WAS PARTIALLY RESPONSIBLE FOR THE WIDESPREAD RAINFALL THAT OCCURRED
ON WEDNESDAY. PLENTY OF MOISTURE ACROSS THE AREA HAS KEPT DEW POINTS
IN THE UPPER 60S WITH TEMPS NOT MUCH HIGHER SO PATCHY FOG MAY BE
POSSIBLE THROUGH THE MORNING HOURS.

THE PREVIOUSLY MENTIONED WAVE IS SHOWING UP IN MODEL GUIDANCE AT
500/700MB AS WELL AND LOOKS TO CONTINUE SLOWLY MOVING EAST THROUGH
THE DAY TODAY. RIDGING IS APPARENT AT 850 BUT THIS LOOKS TO JUST
HELP CONTINUE THE MOISTURE FEED FROM THE SOUTH. THE WAVE LOOKS TO BE
THE MAIN FOCUS OF SHOWER AND THUNDERSTORM DEVELOPMENT AGAIN TODAY
ALONG WITH CONTINUED MOISTURE AND AFTERNOON INSTABILITY. NONE OF THE
HIRES MODELS DID A GOOD JOB WITH ENDING THE RAINFALL LAST NIGHT SO
NOT SURE HOW MUCH FAITH CAN BE PLACED IN THEM FOR THE MORNING HOURS
EITHER. THINKING IS THAT WE SHOULD BE DRY THROUGH THE EARLY MORNING
HOURS BUT AS THE ATMOSPHERE STARTS TO HEAT UP THE WAVE WILL HELP
INITIATE SHOWERS ONCE AGAIN. TODAY MAY BE SIMILAR TO
YESTERDAY...WITH SCATTERED SHOWERS AND THUNDERSTORMS BECOMING MORE
WIDESPREAD BY THE AFTERNOON THEN TURNING INTO MORE OF A RAIN EVENT
LATER IN THE DAY. CANNOT RULE OUT A STRONG THUNDERSTORM BUT THE
THREAT IS MORE OF LOCALLY HEAVY RAIN AND SMALL HAIL...MAYBE SOME
GUSTY WINDS.

THEREFORE...DID MOVE THE POPS UP TO THE LIKELY CATEGORY FOR MUCH OF
THE AREA AFTER 12Z BUT THINKING THAT AFTER 15Z IS REALLY WHEN THE
HIGHEST CHANCES WILL BE AND OBVIOUSLY AS THE DAY PROGRESSES AND
HEATS UP THE HIGHEST CHANCES WILL BE IN THE LATE AFTERNOON.
RAIN/THUNDERSTORM CHANCES WILL THEN DIMINISH ONCE AGAIN TONIGHT.

A BACKDOOR FRONT/SURFACE WAVE LOOKS TO BUILD IN FROM THE EAST ON
FRIDAY WHICH SETS UP A CONVERGENCE BOUNDARY OVER THE CWA OR AT LEAST
FOR THE EASTERN PART. THERE IS A WEAK WAVE ALOFT AGAIN BUT NOT AS
SUBSTANTIAL AS THE ONE FOR TODAY SO THINKING THAT THE SURFACE
BOUNDARY MAY BE THE FOCUS OF SHOWER/THUNDERSTORM DEVELOPMENT. EVEN
WITH A SLIGHT DRYING OF LOWER LEVELS...THERE IS STILL PLENTY OF
MOISTURE AVAILABLE FOR SHOWERS AS WELL AS DEW POINTS REMAINING IN THE
MIDDLE 60S. WITH LOW CONFIDENCE IN THE COVERAGE OF THESE
SHOWERS...WILL GO WITH JUST A CHANCE OF SHOWERS/THUNDERSTORMS FOR THE
AFTERNOON AND EVENING. ONCE AGAIN NOT LOOKING AT SEVERE THUNDERSTORMS
BUT WITH A DRY MID LEVEL...GUSTY WINDS ARE PROBABLY THE MAIN THREAT
FOR ANY STORMS ON FRIDAY.

THERE IS SOME DISAGREEMENT IN TERMS OF LOW TEMPS/DEW POINTS THROUGH
FRIDAY. LOOKING BACK AT PREVIOUS DAYS AND NOTICING THE AMOUNT OF
MOISTURE ACROSS THE AREA...GOING TO LEAN TOWARDS THE GUIDANCE WITH
THE WARMER DEW POINTS AND THE WARMER LOWS. HIGHS SEEMS TO BE IN
AGREEMENT IN THE LOWER TO MIDDLE 80S.

ON SATURDAY...A WEAK UPPER TROUGH STARTS TO DEEPEN AND MOVE TO THE
SOUTHEAST WITH A COLD FRONT STRETCHING THROUGH THE MIDWEST. THIS
UPPER WAVE MAY INITIATE SOME SHOWERS AND THUNDERSTORMS ACROSS THE
AREA FOR THE AFTERNOON WITH THE DAYTIME HEATING BUT COVERAGE LOOKS
TO BE LIMITED AT MOST...WITH HIGHEST CHANCES IN THE WESTERN PARTS OF
THE AREA. SATURDAY NIGHT LOOKS TO BE DRY AS INSTABILITY DECREASES.
THE WAVE THEN OPENS UP OVER WESTERN MISSISSIPPI ON SUNDAY WITH A COLD
FRONT MAYBE MAKING ITS WAY ACROSS THE CWA. THE RECENT MODEL RUNS
WANTS TO KEEP IT TO THE WEST OR STALL NEAR THE AREA WITH A LOW
DEVELOPING ALONG IT. GFS IS STILL MORE BULLISH WITH THE CONVECTION
BUT THE UNCERTAINTY IS TOO HIGH TO HAVE LIKELY SHOWERS/THUNDERSTORMS
IN THERE AT THIS TIME.

AFTER THE FRONT ON SUNDAY...THINGS GET A LITTLE MORE COMPLICATED IN
TERMS OF THE SYNOPTIC SET UP FOR THE WEEK. THE UPPER TROUGH THAT
HELPED PUSH THE COLD FRONT TO THE SOUTHEAST...CUTS OFF AN UPPER LOW
RIGHT OVER THE SOUTHEAST. SOME GUIDANCE HAS IT OPENING BACK UP AT
TIMES BUT OVERALL IT IS ACTING LIKE A CUT OFF LOW. BOTH THE ECMWF
AND GFS SHOW THIS GENERAL IDEA AS WELL AS A STRENGTHENING RIDGE TO
THE EAST HELPING TO KEEP THE LOW IN PLACE. THE TIMING AND PLACEMENT
OF THE LOW WILL BE THE MAJOR FACTOR IN HOW MUCH PRECIPITATION WE
GET. AS WELL...THE GFS (WITH THE ECMWF HINTING AT THIS) IS
DEVELOPING A SURFACE LOW OVER THE GULF AND BRINGING IT UP INTO THE
SOUTHEAST AROUND THE UPPER LOW. THIS WILL BE SOMETHING TO WATCH AS
THIS SOLUTION WOULD BRING MORE CLOUD COVER/PRECIP THAN FORECAST.

SOUNDINGS LOOK SIMILAR EACH DAY NEXT WEEK WITH MORE OF A MOIST
SOUNDING AND A TALL SKINNY CAPE PROFILE. EACH AFTERNOON WITH
AFTERNOON MIXING AND THE COLD POOL ALOFT...LAPSE RATES DEEPEN AND
CAPE INCREASES...TYPICAL OF A SUMMER LIKE CONVECTION PATTERN WITH
VERY WEAK SHEAR AND DEW POINTS INTO THE UPPER 60S. THIS MEANS THAT
EACH AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE...WITH
SMALL HAIL AND GUSTY WINDS BEING THE PRIMARY FACTORS ALONG WITH
LOCALLY HEAVY RAINFALL. CANNOT RULE OUT A STRONG STORM WITH THESE
CONDITIONS BUT IT WILL BE HARD FOR A STORM TO REMAIN STRONG WITH
SUCH LITTLE SHEAR. WILL GO WITH JUST A SLIGHT CHANCE OF THUNDER EACH
NIGHT BECAUSE ANY DAYTIME THUNDERSTORMS SHOULD DIMINISH WITH SUNSET.

OVERALL..TEMPERATURES SATURDAY THROUGH FRIDAY WILL BE NEAR NORMAL
WITH HIGHS IN THE LOWER 80S AND LOWS IN THE MIDDLE 60S.

LN

&&

.AVIATION...
FOR 12Z TAFS...A WEAK UPPER TROF WILL MOVE ACROSS THE TN VALLEY
TODAY. ALSO A MCV OVER MID TN WILL PRODUCE SCT SHRA AT KHSV THRU
ARND 15Z. STLT ALSO WAS SHOWING A BAND OF IFR CLOUDS PUSHING INTO NW
AL ATTM. THUS IFR CONDITIONS WILL BE POSSIBLE AT KMSL THRU 15Z AND
KHSV UNTIL 17Z. WILL GO WITH A TEMPO GROUP FOR TSRA BETWEEN 20Z AND
01Z. NAM TIME SECTIONS DO SHOW THAT MORE LOW CLOUDS (MVFR) COULD BE
POSSIBLE AFTER 06Z TONIGHT.

007

&&

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

$$

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



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