Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 190608
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
208 AM EDT SAT APR 19 2014

.SYNOPSIS...
A MOIST LOW PRESSURE SYSTEM WILL MOVE SLOWLY ACROSS SOUTHERN GEORGIA
AND OFF THE SOUTH CAROLINA COAST THROUGH SUNDAY. HIGH PRESSURE WILL
BRIEFLY BUILD IN MONDAY...BEFORE A COLD FRONT CROSSES EAST ON
TUESDAY. A BROAD AND DRY AREA OF HIGH PRESSURE WILL THEN BUILD SOUTH
WEDNESDAY AND LINGER THROUGH THE END OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 150 AM EDT...SATELLITE IMAGERY SHOWED AN UPPER LEVEL CLOSED
LOW MOVING ACROSS SW GA AND THE FL PANHANDLE VERY EARLY THIS
MORNING. WHILE IR IMAGERY INDICATED VERY COLD CLOUD TOPS ACROSS OUR
REGION...SOME DEGREE OF DRY SLOTTING WRAPPING IN FROM THE SW WAS
EVIDENT WHICH SHOULD ALLOW SRN ESCARPMENT AREAS TO DRY A BIT THROUGH
DAYBREAK. THE SFC LOW UNDER THE CLOSED UPPER SYSTEM WILL MOVE EWD
ALONG THE GA/FL BORDER TODAY AND THEN OFF THE COAST BY THIS EVENING.
UNTIL THEN...PRECIPITABLE WATER VALUES IN LAPS SOUNDINGS ON THE
ORDER OF 1.25 INCHES SHOULD PERSIST IN MOST AREAS. ALTHOUGH UPPER
LEVEL DIVERGENCE WILL GRADUALLY WEAKEN TODAY...DEEP LAYER QG FORCING
WILL CROSS THE FORECAST AREA BETWEEN 12Z AND 18Z BEFORE DIMINISHING
FROM THE W. IN ADDITION...AN AXIS OF STRONG FRONTOGENESIS WILL
CONTINUE THROUGH THE HEART OF THE FORECAST AREA THIS MORNING BEFORE
WEAKENING THIS AFTERNOON AND DIMINISHING TONIGHT AS THE LOW PRESSURE
SYSTEM MOVES AWAY OFFSHORE. THIS FRONTOGENESIS MAX MAY PIVOT ACROSS
PIEDMONT SECTIONS TO PRODUCE THE HEAVIEST RAINFALL GOING FORWARD
ACROSS THE CHARLOTTE METRO AREA. SERIOUS CONSIDERATION HAS BEEN
GIVEN TO A FLOOD WATCH ACROSS CLT METRO...BUT GIVEN THE WEAK
RAINFALL RATES THUS FAR...AND THE FFG AND HEADWATER GUIDANCE
VALUES...IT APPEARS THAT ANY HYDRO PROBLEMS SHOULD BE FAIRLY
ISOLATED. WILL CONTINUE THE HWO MENTION FOR HEAVY RAINFALL...BUT
ADDRESS ANY HYDRO PROBLEMS AS THEY ARISE WITH SHORTER FUSE PRODUCTS.

IN ADDITION TO THE RAINFALL...THE TIGHTENING PRES GRADIENT WILL
CAUSE NE WINDS TO PICK UP...WITH GUSTS WELL INTO THE 20S AND
POSSIBLY ABOVE 30 MPH AT TIMES THIS AFTN ACROSS THE PIEDMONT. SFC
CAD REMAINING IN PLACE THROUGH TONIGHT WILL KEEP THE DIURNAL TEMP
RANGE FAIRLY SMALL. PRECIPITATION SHOULD GRADUALLY END FROM THE WEST
TONIGHT AS THE MOISTURE AND FORCING DIMINISH.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
AS OF 200 PM FRI...STACKED SFC AND UPPER LOW WILL DEPART THE SRN
ATLANTIC COAST SATURDAY EVENING...SLOWLY PROGRESSING EAST AND FURTHER
OFFSHORE THRU SUNDAY. WHILE A FAIR AMOUNT OF LLVL MOISTURE WILL
REMAIN OVER THE AREA SATURDAY NIGHT...THE BEST FORCING WILL HAVE
MOVED EAST WITH THE SYSTEM. HOWEVER NELY 925-850MB WINDS WILL STILL
BE STRONG...BRINGING SOME VERY WEAK LIFT FROM WARM ADVECTION BUT
PERHAPS MORE SIGNIFICANT UPSLOPE FORCING INTO THE BLUE RIDGE. VARIOUS
MODELS CONTINUE TO PRODUCE LIGHT QPF OVERNIGHT. THUS POPS AND CLOUD
COVER ARE SLOW TO TRAIL OFF...LASTING INTO THE MRNG HRS SUNDAY. MIN
TEMPS SUN MRNG WILL BE NEAR NORMAL.

THICKNESSES REBOUND SOMEWHAT THRU THE DAY AS SHORT UPPER RIDGE STARTS
TO BUILD IN THE WAKE OF THE LOW. HOWEVER EAST COAST HIGH PRESSURE
WILL MAINTAIN NELY WINDS AND MAX TEMPS A CATEGORY OR TWO BELOW
NORMAL. THE UPPER RIDGE BUILDS OVERHEAD SUNDAY NIGHT THOUGH IT IS
SOON IMPINGED UPON BY HEIGHT FALLS OVER THE MISSISSIPPI VALLEY
MONDAY. BETWEEN THAT TROUGH AND THE ATLANTIC LOW THE DEGREE OF RETURN
FLOW IS LIMITED BUT SOME MOISTURE DOES ARRIVE SUNDAY NIGHT IN THE
MTNS...ENOUGH TO BRING BACK CLOUD COVER. SOME GUIDANCE DEVELOPS QPF
RESPONSE MONDAY...ALONG WITH SOME DIURNAL INSTABILITY...THOUGH ASCENT
WILL BE HINDERED BY POOR LOW LEVEL LAPSE RATES UNDER THE RIDGE. HAVE
KEPT PRECIP CHANCES BELOW MENTIONABLE VALUES MONDAY. MAX TEMPS RETURN
TO SLIGHTLY ABV CLIMO.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 215 PM FRIDAY...THERE IS FAIRLY GOOD AGREEEMENT IN THE MEDIUM
RANGE AMONGST THE GLOBAL MODELS IN REGARD TO THE UPPER AIR PATTERN
AND RESULTANT SURFACE FEATURES. AN UPPER RIDGE OVER THE REGION
INITIALLY WILL TRANSLATE EASTWARD MON NIGHT WITH A SHORT WAVE
TROUGH TRAVERSING THE AREA ON TUE ALONG WITH A SURFACE COLD FRONT.
MODEL SOUNDINGS DO PRODUCE SOME SBCAPE ON THE ORDER OF 500J/KG TUE
AFTERNOON SO WILL CONTINUE TO MENTION THUNDER. WIND FIELDS DO NOT
LOOK PARTICULARILY STRONG...SO SEVERE THREAT LOOKS MINIMAL AT THIS
JUNCTURE. ANOTHER UPPER RIDGE IS FORECAST TO BUILD OVER THE AREA BY
LATE NEXT WEEK. IN THE MEAN TIME...SURFACE HIGH PRESSURE WILL
MIGRATE FROM THE UPPER MIDWEST ON WED...TO OFF THE CAROLINA COAST BY
LATE THU. AFTER TUE...DRY AND MILD WEATHER IS EXPECTED INTO
FRI...WITH JUST A LOW END CHANCE FOR SOME SCATTERED MOUNTAIN SHOWERS
FRI AFTERNOON WITH INCREASING UPSLOPE FLOW.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...IFR TO MVFR LEVEL CLOUDS ARE FILLING IN AROUND THE KCLT
AIRFIELD...BUT GUIDANCE INSISTS ON KCLT REMAINING AN ISLAND OF
MAINLY MVFR TO VFR CIGS. STILL THINK THAT MOISTURE AND RAINFALL WILL
EVENTUALLY OVERCOME THE BOUNDARY LAYER TO PRODUCE AT LEAST TEMPO IFR
CONDITIONS AFTER 08Z. ANTICIPATE MAINLY MVFR CIGS THROUGH THE DAY
WITH PERIODS OF MODERATE RAINFALL AS THE FRONTOGENESIS MAX PIVOTS
OVERHEAD. ADDITIONAL TEMPO IFR CIGS WILL LIKELY BE NEEDED IN LATER
ISSUANCES. THE TIGHTENING PRES GRADIENT SHOULD EASILY PRODUCE GUSTS
INTO THE 20S THROUGH THE TAF PERIOD.

AT KAVL AND KHKY...THE WESTERN NC TAF SITES WILL BE THE FARTHEST
FROM THE DEEPER MOISTURE WITH THE SE LOW...AND THE LEAST LIKELY TO
EXPERIENCE ANY EXTENDED PERIODS OF IFR CIGS. IFR CIGS ARE
POSSIBLE...BUT FOLLOWING A MOS CONSENSUS OF MAINLY MVFR TO LOWERING
VFR SEEMS REASONABLE. BRIEF N TO NE WIND GUSTS ARE LIKELY AS
WELL...BUT WITH LESS MAGNITURE THAN TAF LOCATIONS FARTHER SE.

AT THE UPSTATE TAF SITES...IFR CIGS SHOULD CERTAINLY MAKE A RUN AT
THE AIRFIELDS THROUGHOUT THE MORNING HOURS IN LIGHT TO MODERATE
RAINFALL. THE MOST PRUDENT COURSE WILL BE TO TEMPO IFR CIGS IN AFTER
08Z AND THEN FEATURE MAINLY MVFR CIGS THROUGH THE COURSE OF THE DAY.
NE FLOW WILL STEADILY INCREASE AS THE PRES GRADIENT TIGHTENS...AND
GUSTS TO BETTER THAN 25 KT WILL BE LIKELY TODAY THROUGH THIS
EVENING. RAIN SHOULD TAPER OFF FROM THE WEST LATE IN THE PERIOD.

OUTLOOK...CEILING RESTRICTIONS MAY WELL LINGER INTO SUNDAY MORNING
BEFORE MOISTURE PULLS AWAY WITH THE SLOWLY DEPARTING OFFSHORE LOW
PRESSURE SYSTEM. DRY HIGH PRES WILL DEVELOP THROUGH MONDAY...WITH A
FAIRLY WET FRONTAL SYSTEM EXPECTED ON TUE.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  94%     HIGH  98%     HIGH  85%     HIGH  86%
KGSP       HIGH  82%     HIGH  94%     HIGH  92%     HIGH  81%
KAVL       HIGH  97%     HIGH  94%     MED   68%     HIGH  82%
KHKY       HIGH 100%     HIGH  81%     MED   64%     HIGH  94%
KGMU       MED   75%     HIGH  89%     HIGH  83%     MED   79%
KAND       HIGH  83%     HIGH  90%     HIGH  96%     HIGH  92%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...LG
AVIATION...HG






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