000
FXUS64 KHUN 241608
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1108 AM CDT FRI MAY 24 2013

.UPDATE...
MORNING UPDATE TO PUBLIC FORECAST.

&&

.DISCUSSION...
THE SHORT TERM FORECAST IS IN GOOD CONDITION THIS MORNING...WITH NO
SIGNIFICANT CHANGES REQUIRED. DID UPDATE SKY COVER GRIDS AND HOURLY
TEMPERATURES/DEWPOINTS BASED ON CURRENT TRENDS IN SATELLITE DATA AND
SURFACE OBSERVATIONS. HIGH TEMPERATURES APPEAR TO BE ON TRACK TO
REACH THE LOWER/MID 70S...BUT IT WILL BE A BATTLE BETWEEN LOW-LEVEL
COLD ADVECTION AND STRONG INSOLATION.

70/DD

&&

.AVIATION...
/ISSUED 625 AM CDT FRI MAY 24 2013/
FOR 12Z TAFS...LOW STRATUS DECK WILL CONTINUE TO IMPACT BOTH
TERMINALS FOR THE NEXT SEVERAL HOURS...BREAKING UP AND LIFTING
NEARING 15Z. WINDS WILL THEN INCREASE OUT OF THE NORTH AND
PERIODICALLY GUST TO NEAR 18KT THROUGH THE AFTERNOON HOURS. WINDS
WILL CONTINUE TO VEER TO THE NNE AND SLACKEN AFTER SUNSET...WITH VFR
CONDITIONS EXPECTED THROUGH THE END OF THE PERIOD.

CCC

&&

.PREV DISCUSSION...
/ISSUED 151 AM CDT FRI MAY 24 2013/
A FAIRLY SIGNIFICANT UPPER FLOW PATTERN CHANGE IS IN STORE FOR THIS
FORECAST PACKAGE, AS THE OMEGA BLOCK THAT HAS MOVED OVER CENTRAL
NORTH AMERICA BEGINS TO BREAK. THE MID-UPPER LOW THAT BROUGHT SEVERE
WEATHER FROM THE PLAINS TO THE SOUTHEAST HAS FINALLY LIFTED OFF TO
THE GREAT LAKES. MEANWHILE, THE WESTERN PORTION OF THE OMEGA BLOCK
CONSISTS OF AN UPPER LOW OVER THE PACIFIC NORTHWEST PROVIDING STRONG
TO SEVERE THUNDERSTORMS ACROSS MT/WY/DAKOTAS. IN BETWEEN THESE TWO
LOWS IS A BUILDING RIDGE OVER THE PLAINS. AT THE SFC, THE CYCLONE
OVER THE GREAT LAKES HAS PUSHED A CP AIRMASS SOUTHWARD ACROSS THE
SOUTHEAST.

THE SFC COLD FRONT AND ENSUING INCREASED PRESSURE GRADIENT WILL
BRING A GUSTY N/NE WIND ALONG WITH DRIER AND COOLER CONDITIONS FOR
TODAY. IN FACT, DAYTIME HIGHS WILL BE SOMEWHAT BELOW NORMAL IN THE
LOW TO MID 70S. ADDITIONAL CLOUD COVER APPROACHING FROM THE NORTH
(OH RIVER VALLEY) AND CIRRUS CANOPY FROM TX CONVECTION WILL RESULT
IN PARTLY CLOUDY CONDITIONS TODAY. AS THE PRESSURE GRADIENT RELAXES
WHILE THE SFC HIGH PRESSURE SYSTEM SINKS SOUTHWARD FROM THE OHIO
RIVER VALLEY, WINDS SHOULD GRADUALLY RELAX THIS EVENING. THIS
COUPLED WITH A GENERALLY CLEAR SKY SHOULD MEAN A DROP IN TEMPS INTO
THE MID TO UPPER 40S BY EARLY SATURDAY MORNING. BY SATURDAY, THE
UPPER LOW OVER THE GREAT LAKES WILL SHIFT SE ACROSS THE NEW ENGLAND
SEABOARD RESULTING IN NW FLOW ALOFT ACROSS THE SOUTHEAST. AS A
RESULT, A COUPLE OF PRONOUNCED EDDIES/MID-LEVEL SHORTWAVE TROUGHS
ROTATING AROUND THE RIDGE TO THE WEST MAY DEVELOP MCS/QLCS FEATURES
ACROSS THE MID MS RIVER VALLEY ON SATURDAY NIGHT WHICH WITH THE
PREVAILING NW STEERING FLOW MAY IMPACT THE TN VALLEY BY EARLY SUNDAY
MORNING. THUS, HAVE INCREASED POPS SLIGHTLY FOR THAT TIME PERIOD
ALTHOUGH IT WOULD LIKELY BE A RAPIDLY MOVING FEATURE (DIFFICULT TO
TIME AT THIS POINT). LINGERING CIRRUS/CLOUD COVER FROM THE MCS ON
SUNDAY MAY HAMPER RAPID WARMING ON SUNDAY AFTERNOON, AND COULD
CONTRIBUTE TO ISOLATED THUNDERSTORMS (OUTFLOW BOUNDARIES). THUS,
FURTHER ADJUSTMENTS MAY BE NECESSARY.

THE MODELS INDICATE ANOTHER POSSIBLE MCS EPISODE (WITH THE SOUTHEAST
IN PREVAILING NW FLOW ALOFT) ON MONDAY, BUT IS STILL DIFFICULT TO
TIME. FOR NOW, WILL MAINTAIN SCHC POPS MAINLY DURING THE AFTERNOON
AND EVENING. AN AMPLIFYING TROUGH OVER THE WEST COAST ALONG WITH THE
EXITING EAST COAST UPPER LOW WILL TRANSLATE TO A RIDGE GRADUALLY
BUILDING OVER THE SOUTHEAST BY LATE IN THE FORECAST PERIOD. THIS
WILL RESULT IN MOST (IF NOT ALL) OF THE MID TO UPPER EXTRA-TROPICAL
CYCLONES TRANSLATING NORTH ATOP THE RIDGE OVER THE NORTHERN PLAINS
INTO ONTARIO. SO, A RETURN TO HOT AND HUMID CONDITIONS LOOKS LIKELY
ON TUESDAY THROUGH THURSDAY (WITH THURSDAY LIKELY BEING THE HOTTEST
DAY)ACROSS THE SOUTHEAST. FURTHERMORE, DUE TO LARGE SCALE SUBSIDENCE
CENTERED ALMOST ATOP THE TN VALLEY, AM HESITANT TO PLACE AFTERNOON
THUNDERSTORMS IN THE FORECAST FOR TUESDAY THROUGH THURSDAY. COULD
SEE SOME OROGRAPHIC PULSE-LIKE ACTIVITY ON TUESDAY DUE TO THE
PREVAILING FLOW AND CONVECTIVE TEMPERATURE BEING REACHED, BUT NOT
ENOUGH CONFIDENCE TO INCLUDE IN THE FORECAST YET. OTHERWISE, MADE
TWEAKS TO THE DAYTIME HIGHS IN THE MID TO UPPER 80S AND OVERNIGHT
LOWS WARMING INTO THE UPPER 60S.

SL.77

&&

.HUN WATCHES/WARNINGS/ADVISORIES...

AL...NONE.

TN...NONE.

&&

$$

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