Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270249
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1049 PM EDT TUE APR 26 2016

.SYNOPSIS...
WARM ATLANTIC HIGH PRESSURE WILL PERSIST OVER THE SOUTHEAST THROUGH
MIDWEEK. AFTER A WEAK COLD FRONT MOVES IN FROM THE WEST THURSDAY
NIGHT...WEAK HIGH PRESSURE WILL RETURN BRIEFLY ON FRIDAY. A LOW
PRESSURE SYSTEM WILL MOVE IN FROM THE WEST OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 1025 PM...ISOLATED SHOWERS WERE HOLDING ON ACROSS PARTS OF THE
MTNS...BUT THIS IS STILL EXPECTED TO DISSIPATE. TEMP TRENDS WERE
RUNNING A BIT WARMER THAN FCST...AND THAT WILL PROBABLY CONTINUE AS
THE CIRRUS BLOWOFF FROM CONVECTION OVER THE OH/MS RIVER VALLEYS
ARRIVES DURING THE LATE EVENING. THINK THAT CONVECTION TO THE N AND
NW WILL MAKE A RUN BUT SHOULD ULTIMATELY DIE BEFORE REACHING THE NC
MTNS IN THE EARLY MORNING HOURS.

A WEAK SHORT WAVE MOVES THROUGH THE FLAT RIDGE OVER THE SOUTHEASTERN
US TONIGHT PUSHING A BACK DOOR COLD FRONT SOUTH TOWARD THE AREA. THE
FRONT STALLS NEAR THE VIRGINIA-NORTH CAROLINA BORDER AND REMAINS
THERE THROUGH THE DAY WEDNESDAY. THIS SHOULD PROVIDE LOW LEVEL
CONVERGENCE TO HELP INITIATE DEEP CONVECTION. MODERATE INSTABILITY
DEVELOPS ON WEDNESDAY ACROSS THE ENTIRE AREA WITH BULK SHEAR
INCREASING...BUT NOT QUITE REACHING MODERATE LEVELS. THEREFORE...
EXPECT AN INCREASING CHANCE OF CONVECTION...BUT STILL FAVOR THE NC
COUNTIES WHERE THE COMBINATION OF INSTABILITY AND FORCING IS
GREATER. WILL HAVE TO KEEP AN EYE ON SHEAR VALUES ACROSS THE
NORTHERN TIER. IF MODERATE SHEAR CAN DEVELOP...THEN THE CHANCE OF
SEVERE STORMS WILL INCREASE AS WELL. LOWS TONIGHT AND HIGHS
WEDNESDAY WILL AGAIN BE AROUND 10 DEGREES ABOVE NORMAL.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM TUE...WEDNESDAY NIGHT OUR AREA WILL REMAIN IN THE WARM
SECTOR OF THE WEAKENING CENTRAL CONUS SYSTEM. GENERALLY MODELS
INDICATE NEARLY STATIONARY WARM FRONT EXTENDING FROM THE CORN
BELT TO THE DELMARVA REGION...AND COLD FRONT MOVING THRU THE LOWER
OHIO/TENN VALLEYS. THE COLD FRONT IS RATHER ILL-DEFINED. THERE IS
SOME NOTABLE SPREAD AS TO HOW MUCH INSTABILITY WILL BE AVAILABLE
OVER THE CWFA WED NIGHT...AND THAT MAY DEPEND ON HOW MUCH THE
ATMOSPHERE IS WORKED OVER WED AFTN. I WILL ALLOW POPS TO DIMINISH
SLOWLY OVERNIGHT. THE COLD FRONT WILL CONTINUE TO APPROACH THRU
THURSDAY...BUT NWLY WINDS AND LO-LEV DRYING DO NOT DEFINITIVELY
OCCUR UNTIL THU NIGHT. SLIGHTLY BETTER CAPE IS EXPECTED TO DEVELOP
DIURNALLY THU...AND WITH THE SYSTEM HAVING MOVED CLOSER SHEAR
PARAMETERS ARE STRONGER THAN WED. ON THAT NOTE POPS WILL RISE
INTO THE LIKELY RANGE OVER A GREATER SHARE OF THE AREA THU...AND
CURRENT INCLUSION OF THE AREA IN MARGINAL RISK ON THE SPC DAY 3
OUTLOOK SEEMS APPROPRIATE.

HEIGHTS WILL RISE OVER THE SOUTHEAST FRIDAY UNDER A SHORTWAVE
RIDGE. MODELS AGREE THAT A POTENT SHORTWAVE /THE REMNANT OF THE
DEFUNCT PLAINS LOW/ WILL ROUND THE CREST OF THE RIDGE DURING THE
DAY...BUT VARY WIDELY IN THE PRECISE LOCATION. THE EC IS STRONGEST
AND FASTEST IN ITS DEPICTION OF THE WAVE EVOLUTION...AND WOULD
SUGGEST IT WILL CROSS JUST TO OUR NORTH FRI AFTN. COMPARE THIS TO
THE NAM WHICH EXPECTS THE WAVE TO BE OVER LAKE HURON AT 00Z SAT. IF
THE EC SOLUTION WERE TO VERIFY...OUR NC FOOTHILLS/PIEDMONT ZONES
MIGHT EXPERIENCE SOME ISOLD TSTMS. FOR NOW THE BETTER CONSENSUS
IS FOR A DRY FCST. TEMPS WILL BE WARMER FRI UNDER CLEARER SKIES
AND HIGHER PARTIAL THICKNESS VALUES.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 210 PM TUESDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
SATURDAY WITH UPPER RIDGING AMPLIFYING OVER THE SE CONUS WHILE A
WELL DEFINED EMBEDDED UPPER SHORTWAVE MOVES OFF THE NC COAST. AT THE
SAME TIME...DEEP AND PERSISTENT UPPER TROFFING OVER MOST OF THE
WESTERN CONUS WILL GRADUALLY LIFT NORTHEASTWARD AS MULTIPLE CLOSED
LOWS SPIN UP OVER THE WEEKEND. MOST OF THE UPPER LEVEL ENERGY
ASSOCIATED WITH THE TROF WILL LIKELY REMAIN WEST OF THE CWFA AS THE
RIDGE PERSISTS INTO NEXT WEEK...HOWEVER SOME PVA COULD REACH THE
WESTERN CAROLINAS BY THE END OF THE PERIOD.

AT THE SFC...WEAK LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL BE
MOVING OFF THE ATLANTIC COAST BY LATE FRI/EARLY SAT. IN ITS
WAKE...ANOTHER CANADIAN HIGH WILL BEGIN TO PUSH BACK INTO THE REGION
FROM THE NORTH AND ESTABLISH A WEAK CAD PATTERN OVER THE CAROLINAS.
AT THE SAME TIME...A LOW DEVELOPS OVER THE SOUTHERN PLAINS AND MOVES
NE TOWARDS THE SOUTHERN GREAT LAKES. AS THE LOW MOVES TO OUR NW IT
WILL WEAKEN THE CAD AS IT PUSHES THE HIGH NE. IT WILL ALSO ALLOW
MOIST SELY FLOW TO OVERSPREAD THE FCST AREA BY EARLY NEXT WEEK. THE
COLD FRONT ASSOCIATED WITH THE LOW APPEARS TO AT LEAST PARTIALLY
WASH OUT AS IT MOVES INTO THE CWFA SO IT PROBABLY WON`T HAVE MUCH
IMPACT ON TEMPS. AS FOR THE SENSIBLE FCST...THINGS SHOULD START OUT
DRY WITH POPS STEADILY INCREASING THRU THE DAY ON SAT AND SUN. BY
SUN AFTERNOON...SCATTERED TO WIDESPREAD SHOWERS AND TS WILL LIKELY
DEVELOP ACROSS THE FCST AREA. THEY COULD LINGER WELL INTO MON...BUT
THE CHANCES ARE LOWER FOR ANY WIDESPREAD COVERAGE. I KEPT A SOLID
CHANCE OVER THE CWFA FOR THE REST OF THE PERIOD WITH CONTINUED MOIST
SLY FLOW IN THE BNDY LAYER. TEMPS SHOULD MODERATE OVER THE
WEEKEND...HOWEVER VALUES ARE EXPECTED TO REMAIN ABOVE CLIMO FOR LATE
APRIL.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...SAT PIX AND OBS SHOW FEW HIGH BASED CU
ACROSS THE PIEDMONT WITH SCT/BKN COVERAGE OVER THE MOUNTAINS AND
FOOTHILLS. A FEW SHOWERS HAVE POPPED UP OVER THE MTNS AND ONE COULD
IMPACT KAVL THIS EVENING. EXPECT THE SHOWERS TO DIMINISH BY 02Z. SW
WIND SHOULD BECOME LIGHT AFTER SUNSET...AND CONVECTIVE CLOUDS WILL
DIMINISH. ON WEDNESDAY...SOME CONVECTIVE DEBRIS CLOUDS COULD MOVE
OVERHEAD IN THE MORNING HOURS AND THIS IS NOT ADDRESSED IN THE TAFS
AS IT WOULD BE MID/HIGH CLOUDINESS. WIND WILL COME UP FROM THE SW BY
MID-MORNING BUT NOT AS STRONG AS TODAY. CONVECTION SHOULD DEVELOP IN
THE AFTERNOON WITH BETTER COVERAGE THAN TODAY...BUT PREVAILING SKY
CONDITION SHOULD STAY SCT. ALL SITES HAVE A CHANCE OF STORMS IN THE
MID TO LATE AFTERNOON AS THE ATMOSPHERE DESTABILIZES SO A PROB30 WAS
EMPLOYED.

OUTLOOK...PRECIPITATION CHANCES AND ASSOCIATED RESTRICTIONS SHOULD
INCREASE INTO THURSDAY AHEAD OF A COLD FRONT APPROACHING FROM THE
NORTHWEST. SOME DRYING IS EXPECTED ON FRIDAY WITH VFR CONDITIONS
BEFORE UNSETTLED WEATHER RETURNS FROM THE WEST OVER THE WEEKEND.
MORE RESTRICTIONS ARE POSSIBLE STARTING SATURDAY NIGHT.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     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 SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

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

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...PM/RWH
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...PM



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