Area Forecast Discussion
Issued by NWS Greer, SC

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654
FXUS62 KGSP 190915
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
515 AM EDT TUE MAY 19 2015

.SYNOPSIS...
A COLD FRONT WILL GRADUALLY PUSH ACROSS THE REGION TODAY. SLIGHTLY
COOLER AND DRIER HIGH PRESSURE WILL RETURN ON WEDNESDAY...BUT WITH
BRIEFLY UNSETTLED WEATHER CROSSING THE REGION ON THURSDAY. DRIER
HIGH PRESSURE WILL RETURN TO THE AREA ON FRIDAY AND BUILD OVER THE
WEEKEND INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 500 AM TUE...PATCHY FOG HAS FORMED AT SOME OF THE AREA OBS
SITES...MAINLY ACRS THE UPSTATE AND ADJACENT NC FOOTHILLS. EXPECTING
THIS AREA OF FOG TO DEVELOP EWD INTO THE CHARLOTTE METRO AREA BY
DAWN. A SPECIAL WX STATEMENT FOR LOCALLY DENSE FOG IS IN EFFECT
UNTIL 800 AM HIGHLIGHTING AREAS ALONG I-85 AND US 74 WEST OF
CHARLOTTE. A COUPLE OF WEAK RETURNS ARE SEEN OVER THE MTNS AS
ANTICIPATED...BUT IT LOOKS SAFE TO DELAY THE ONSET OF POPS OVER THE
PIEDMONT UNTIL AFTER DAYBREAK.

TROUGH ASSOCIATED WITH LOW PRESSURE MOVING ACRS QUEBEC IS ALREADY
PRESENT OVER THE PIEDMONT...AND WILL GRADUALLY PUSH EWD TODAY. NW
WINDS BEHIND IT WILL EVENTUALLY BRING DRIER CONTINENTAL AIR TO THE
AREA...BUT SUBSTANTIAL DRYING DOES NOT OCCUR UNTIL TONIGHT. ANOTHER
DAY OF DIURNALLY DRIVEN CONVECTION MAY BE EXPECTED...ALBEIT WITH
LESS COVERAGE THAN MONDAY. SOME GUIDANCE DOES DRY THE COLUMN OUT
ENOUGH OVER THE MTNS THAT ACTIVITY WILL DIMINISH EARLIER THAN USUAL
THERE...BUT COVERAGE IS EXPECTED TO PEAK WITH HEATING OVER THE
PIEDMONT. WEAK CONVERGENCE INVOF THE TROUGH WILL ALSO BE PRESENT
POSSIBLY ACTING AS A FOCUSING MECHANISM. SHEAR REMAINS QUITE WEAK
WITH THE FASTER UPPER FLOW REMAINING NORTH OF THE REGION...AND MOIST
PROFILES STILL POINT MAINLY TO A HEAVY RAIN THREAT.

DRYING TONIGHT IS EXPECTED TO BEGIN A CLEARING TREND AND KEEP SFC
DEWPOINTS LOW ENOUGH TO PREVENT FOG. MINS NEAR MOS VALUES ARE
EXPECTED...BUT STILL A FEW DEGREES ABOVE CLIMO.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 245 AM EDT TUESDAY...ZONAL UPPER LEVEL FLOW WILL BE IN PLACE
ACROSS THE SOUTHEAST WED THROUGH THU...WITH AN 850 MB BAROCLINIC
ZONE STRETCHING FROM THE LOWER OH VALLEY EASTWARD THROUGH THE
VIRGINIAS. DESPITE WEAK OVERALL DRYING IN THE LIGHT W TO NW
FLOW...SHALLOW MOISTURE MAY LINGER WED AFTN ACROSS THE SRN MTNS. LOW
LEVEL CONVERGENCE COULD TRIGGER ISOLD DIURNAL SHOWERS IN THIS AREA.
MAX TEMPERATURES WILL BE ABOUT 5 DEGREES OR MORE ABOVE CLIMO WED
AFTN.

A NRN STREAM SYSTEM WILL CROSS THE GREAT LAKES THROUGH THU. THIS
SYSTEM WILL GENERATE WEAK WAVES ALONG THE STALLED FRONTAL ZONE
THROUGH THE LOWER OH VALLEY AND TRANSLATE UPWARD OMEGA AND BETTER
MOISTURE EASTWARD ALONG THE FRONTAL ZONE TOWARD THE MID ATLANTIC WED
NIGHT INTO THU. THE BEST RH AND DEEPER FORCING SHOULD STAY MAINLY N
OF THE REGION...HOWEVER...ANY SHOWER BANDS WITH THIS SYSTEM LOOK
BEST TIMED FOR THU MORNING ACROSS THE NRN HALF OF THE AREA. THE
INCREASING CLOUDS WILL MAKE FOR A SMALLER DIURNAL RANGE ON
TEMPERATURES...ESPECIALLY ACROSS THE NRN TIER.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 245 AM EDT TUESDAY...A BROAD EASTERN TROUGH WILL DEVELOP THU
NIGHT INTO FRIDAY AS HEIGHTS FALL ACROSS QUEBEC. HOWEVER...ANY
CHANNELED VORTICITY ROUNDING THIS SYSTEM SHOULD STAY MAINLY NORTH OF
OUR FORECAST AREA. THE WEAK FRONTAL ZONE WILL SLIP SE ACROSS THE
REGION THU NIGHT THROUGH FRIDAY...BUT WITH LIMITED SHOWER COVERAGE
GIVEN THE SHALLOW MOISTURE AND LOW LEVEL NW FLOW. TEMPERATURES WILL
COOL AT LEAST A CATEGORY IN MOST PLACES WITH THE WEAK FROPA.

HEIGHTS WILL RISE SHARPLY OVER THE SE SAT THROUGH MON...WITH A 592
DM 500 MB HIGH CENTER OVER THE SE COAST BY 18Z MON. ON SATURDAY...A
SE ATLANTIC FETCH COULD BRING MOISTURE BACK TO THE EXTREME SRN
APPALACHIANS. DEEPER MOISTURE WILL THEN FLIRT WITH THE SRN
APPALACHIANS SUNDAY THROUGH MONDAY...BUT WITH THE BEST AXIS OF
MOISTURE AND INSTABILITY GENERALLY WRAPPING WEST OF THE MTN CHAIN
AROUND THE RIDGE. WILL FEATURE MAINLY SCATTERED DIURNAL POPS EXCEPT
FOR IMPROVING CHANCE COVERAGE IN THE MOUNTAINS ON MONDAY...WITH
WARMING TEMPERATURES THROUGH THE PERIOD.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
AT KCLT /09Z UPDATE/...AS FLOW BEGINS TO SHIFT TO NW AHEAD OF
INCOMING SFC COLD FRONT AND HIGH PRESSURE...LLVL CONVERGENCE HAS
MANAGED TO DEVELOP AN AREA OF IFR CIGS AND SOME FOG THAT WILL ADVECT
THRU BY 11-12Z. PREVAILED IFR TO START THE TAF...BUT THINK THE PATCH
OF LOW CIGS IS LIKELY TO MOVE OUT RATHER THAN BURN OFF. BRIEF
PERIODS OF IFR VSBY ARE POSSIBLE. SIGNIFICANT DRYING WILL OCCUR
TONIGHT BEHIND THE FRONT...BUT NOT IN TIME TO PRECLUDE DIURNAL
CONVECTION TODAY. LOW VFR CU WILL DEVELOP BY LATE MRNG. THOUGH
CHANCES DO NOT LOOK AS GOOD AS MONDAY A PROB30 IS STILL WARRANTED
DURING PEAK HEATING. HEAVY RAIN ONCE AGAIN IS THE MAIN THREAT. THE
DRIER CONDITIONS SHOULD PRECLUDE RESTRICTIONS TONIGHT. SFC WINDS
SHOULD GO NW ONCE THEY COME UP AFTER DAWN AND STAY THERE INTO
TONIGHT. LEE TROUGH MAY BACK WINDS TO WNW FOR A TIME DURING THE AFTN.

ELSEWHERE...ALL THE SITES SAW SOME RAIN MON AFTN...THE UPSTATE SC
SITES HAVING GOTTEN SOAKED MORE EFFECTIVELY THAN KAVL/KHKY. DEWPOINT
DEPRESSIONS WILL BE SMALL OVERNIGHT...POSING A THREAT OF FOG. ON THE
OTHER HAND LIGHT BREEZES AND A LACK OF SATURATION ABOVE THE SFC WILL
LIKELY KEEP FOG PATCHY WITH POTENTIALLY UP-AND-DOWN VSBY. HAVE
INCLUDED A TEMPO FOR MVFR EXCEPT PREVAILING AT KAVL WHICH WILL SEE
BETTER MOISTURE ALOFT. LOW VFR CU WILL BREAK OUT WITH PRECIP CHANCES
AT ALL SITES...THOUGH NOT HIGH ENOUGH TO PREVAIL. WINDS WILL FAVOR
NW TODAY BUT REMAIN LIGHT...WITH RESTRICTIONS LOOKING UNLIKELY AS
THE DRIER AIR FILTERS IN.

OUTLOOK...THE PASSAGE OF A WEAK COLD FRONT SHOULD BRING BACK
SOMEWHAT DRIER CONDITIONS FOR WEDNESDAY. ANOTHER FRONT WILL CROSS
THE AREA THURSDAY...WITH A LITTLE MORE COVERAGE OF MAINLY AFTN SHRA
AND TSRA. DRY WX RETURNS FOR THE UPCOMING WEEKEND.

CONFIDENCE TABLE...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       HIGH  85%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   41%     HIGH  96%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  98%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

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...HG/WIMBERLEY
NEAR TERM...WIMBERLEY
SHORT TERM...HG
LONG TERM...HG
AVIATION...WIMBERLEY



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