Area Forecast Discussion
Issued by NWS Huntsville, AL

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000
FXUS64 KHUN 021153
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
653 AM CDT WED SEP 2 2015

.UPDATE...
FOR 12Z TAFS

&&

.DISCUSSION...
/ISSUED 321 AM CDT WED SEP 2 2015/
WATER VAPOR ANALYSIS LOOKS SIMILAR TO PREVIOUS NIGHTS WITH AN UPPER
LOW SPINNING ALONG THE SE COAST OF TEXAS AND WEAK SURFACE HIGH
PRESSURE AND AN UPPER RIDGE CENTERED OFF TO THE SOUTHEAST OF THE
AREA. THE UPPER LOW IS WHAT WILL BECOME THE FOCUS OF THE FORECAST
CHALLENGE FOR THE DAY. THE LAST FEW NIGHTS MODEL RUNS HAVE KEPT THE
AREA DRY TODAY BUT LATEST RUNS ARE SHOWING A PIECE OF ENERGY MOVING
NORTHWARD FROM THAT AFOREMENTIONED LOW. AS WELL...MODEL INSTABILITY
HAS ALSO INCREASED FROM PREVIOUS RUNS AND THINKING THE COMBO OF THESE
TWO HAVE ALLOWED GUIDANCE TO SHOW SOME SCATTERED SHOWERS THIS
AFTERNOON. THINKING HOWEVER THAT THERE COULD BE SOME CONVECTIVE
FEEDBACK ISSUES WITH EARLIER CONVECTION ASSOCIATED WITH THE WAVE AND
MODELS ARE OVERDOING THE COVERAGE OF THE PRECIP. THIS IS ESPECIALLY
TRUE GIVEN HOW LITTLE MOISTURE IS IN THE COLUMN TODAY AND THE FACT A
CANOPY OF CIRRUS CLOUDS SHOULD HOLD TEMPS/INSTABILITY DOWN TODAY.
THEREFORE...KEPT THE 10 PERCENT CHANCE IN THE FORECAST AND
UPDATES/NOWCASTS CAN BE MADE LATER IN THE DAY IF SHOWERS DO DEVELOP.

THE UPPER RIDGE STRENGTHENS OVER THE LOCAL AREA THURSDAY WITH A DRY
NORTHERLY FLOW IN PLACE. THIS SHOULD HOLD TRUE THROUGH THE DAY ON
FRIDAY WITH NO SHOWER/THUNDERSTORM DEVELOPMENT EXPECTED. THERE ARE
SOME HINTS THAT SHOWERS COULD DEVELOP OVER THE EASTERN PART OF THE
AREA LATE FRIDAY BUT SOUNDINGS STILL SHOW A FAIRLY DRY ATMOSPHERE
AND THERE IS VERY WEAK TO NO LIFT TO SPEAK OF TO DEVELOP THOSE
SHOWERS FROM. WITH LINGERING MID LEVEL MOISTURE AND AFTERNOON
MIXING...MOSTLY TO PARTLY CLOUDY SKIES WILL CONTINUE EACH DAY AND
LINGER THROUGH THE OVERNIGHT HOURS. THIS WILL KEEP HIGH TEMPERATURES
THROUGH FRIDAY IN THE UPPER 80S TO LOWER 90S...SLIGHTLY BELOW
GUIDANCE.

GUIDANCE CONTINUES TO SHOW A BACK DOOR FRONT OF SORTS DEVELOPING
ALONG THE EAST COAST ON SATURDAY...SHIFTING WINDS TO AN EASTERLY
DIRECTION AND USHERING IN A SURGE OF MOISTURE TO THE REGION. THERE
IS NOT A WHOLE LOT OF UPPER SUPPORT FOR THIS SYSTEM AND ANY LIFT
WOULD BE FROM A CONVERGENCE AXIS WITH THE FRONT. THINKING THERE WILL
BE ENOUGH THOUGH TO SUPPORT SCATTERED SHOWERS/THUNDERSTORMS SATURDAY
AND SUNDAY AFTERNOONS WITH ACTIVITY DIMINISHING EACH NIGHT. TEMPS
WILL DECREASE SLIGHTLY AS WELL WITH HIGHS REACHING INTO THE MIDDLE TO
UPPER 80S SAT AND SUN.

THE UPPER RIDGE DOMINATES MUCH OF THE EASTERN U.S. AGAIN FOR THE
NEXT WORK WEEK WITH DISAGREEMENT AMONG GUIDANCE FOR AFTERNOON
SHOWERS/THUNDERSTORMS EACH DAY. THE GFS SHOWS MULTIPLE WAVES
ROTATING AROUND A WEAK UPPER LOW CENTERED OVER THE GULF GIVING THE
AREA ADDITIONAL RAINFALL WITH THE ECMWF BEING DRY AND MORE STABLE.
WILL FOLLOW THE CONSENSUS BLEND WHICH GENERALLY LEAVES THE AREA DRY
UNTIL WED/THU WHEN A COLD FRONT APPROACHES.

LN

&&

.AVIATION...
FOR 12Z TAFS...THICK CANOPY OF CIRROSTRATUS CLOUDS ASSOCIATED WITH
BROAD UPPER LOW NEAR THE NW GULF COAST CONTINUES TO STREAM NEWD
OVER THE REGION...AND THIS HAS LARGELY BEEN RESPONSIBLE FOR REDUCTION
IN BR/FG COMPARED TO PREVIOUS NIGHTS. REGIME SHOULD PERSIST THRU THIS
EVENING...WITH MULTI-LAYERED VFR CIGS ARND 7 AND 20 KFT. THERE ARE
SOME INDICATIONS THAT LIFT ASSOCIATED WITH A WEAK DISTURBANCE ON THE
NRN EDGE OF THE UPPER LOW MAY BE SUFFICIENT TO GENERATE LGT SHRA OR
POCKETS OF LGT RAIN ACROSS THE REGION THIS AFTERNOON/EVENING.
HOWEVER...WILL NOT INCLUDE PCPN IN TAFS ATTM DUE TO UNCERTAINTY
REGARDING BOTH TIMING AND COVERAGE/INTENSITY. COMBINATION OF RESIDUAL
HIGH CLOUDS AND INCREASING NLY SFC FLOW SHOULD PREVENT BR/FG CONCERNS
ONCE AGAIN AT END OF TAF PERIOD.

70/DD

&&

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

&&

$$

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


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