Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS62 KGSP 271510
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1110 AM EDT SUN JUL 27 2014

.SYNOPSIS...
HIGH PRESSURE AND SOUTHERLY FLOW WILL LEAD TO ABUNDANTLY WARM
TEMPERATURES ON SUNDAY AHEAD OF AN APPROACHING COLD FRONT.  THIS
COLD FRONT WILL REACH THE AREA SUNDAY NIGHT AND PUSH EAST ACROSS THE
REGION ON MONDAY. CANADIAN HIGH PRESSURE WILL DOMINATE THE SURFACE
PATTERN THROUGH MIDWEEK LEADING TO WELL BELOW NORMAL TEMPERATURES
AND PLEASANT CONDITIONS.  PRECIPITATION CHANCES WILL RAMP UP YET
AGAIN ON THURSDAY AND FRIDAY AS ATLANTIC MOISTURE SPILLS INTO THE
REGION LEADING TO INCREASED PROBABILITIES FOR SHOWERS AND
THUNDERSTORMS EACH AFTERNOON AND EVENING.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1040 AM...CONVECTIVE COMPLEX HAS MOVED INTO CENTRAL NC AND THE
SC MIDLANDS THIS MORNING...LEAVING THE AREA ESSENTIALLY FREE OF
CONVECTION. OF COURSE...THE MORNING CONVECTION HAS MUDDIED THE
CONVECTIVE PICTURE FOR THIS AFTERNOON...AS EXTENSIVE MID/HIGH CLOUDS
AND RAIN-COOLED AIR HAS OVERTAKEN MUCH OF WESTERN NC. THIS IS
FURTHER COMPLICATED BY THE CONSIDERABLE MORNING CONVECTION
CONTINUING OVER THE OHIO VALLEY AND CENTRAL APPALACHIANS...WHICH IF
IT DOES NOT PUSH AWAY FROM THE MOD RISK AREA SOON IS SERIOUSLY GOING
TO HAMPER THE POTENTIAL FOR ORGANIZED SEVERE CONVECTION TO DEVELOP
UPSTREAM LATER TODAY. HOWEVER...BASED UPON LATEST SATELLITE/RADAR
TRENDS...IT DOES APPEAR THAT MOST OF THIS ACTIVITY AND ASSOCIATED
DEBRIS CLOUD WILL CONTINUE TO SHIFT EAST ACROSS CENTRAL KENTUCKY/
SOUTHERN WV/SOUTHERN VIRGINIA INTO EARLY AFTERNOON. I/D THEREFORE
SAY IT/S A GOOD BET THAT WESTERN NC AND EAST TENN WILL SEE ENOUGH
HEATING TO REALIZE AT LEAST MODERATE LEVELS OF INSTABILITY THIS
AFTERNOON. AS SUCH...CONSIDERING THE APPROACHING FRONTAL ZONE...THE
POTENTIAL OF ESTABLISHMENT OF A DIFF HEATING BOUNDARY THROUGH THE
DAY...AND THE ANOMALOUSLY STRONG LOW-TO-MID LEVEL SHEAR...NE TENN/NW
NC/EXTREME SW VIRGINIA/SOUTHEAST KENTUCKY MAY END UP BEING GROUND
ZERO FOR ORGANIZED DEVELOPMENT OF DEEP CONVECTION LATE THIS
AFTERNOON INTO THE EVENING...WITH DAMAGING WINDS BEING THE PRIMARY
THREAT. POPS WILL BE MAINTAINED AT SOLID CHANCE TO LIKELY NORTH OF
I-40 DURING THIS TIME.

IN ADDITION...CONSIDERING THE AMOUNT OF INSTABILITY EXPECTED...
CANNOT RULE OUT SOME ISLD/SCT DIURNAL CONVECTION DEVELOPING OVER THE
HIGH TERRAIN THIS AFTERNOON...SO SLIGHT/LOW CHANCE POPS HAVE BEEN
EXTENDED SOUTHEAST ACROSS THE HIGH TERRAIN. SLIGHT CHANCE POPS WILL
ALSO BE EXTENDED SOUTH TO THE I-85 CORRIDOR THIS AFTERNOON...WHERE A
DIFFERENTIAL HEATING BOUNDARY SHOULD BECOME ESTABLISHED BETWEEN THE
RAIN-COOLED AIR AND STRONG INSOLATION AREA OVER THE UPSTATE.
(ALTHOUGH THIS WILL BECOME INCREASINGLY DIFFUSE AS THE AIR MASS
RECOVERS ACROSS WESTERN NC).

MAX TEMPS WERE LOWERED ABOUT A CATEGORY ACROSS MUCH OF WESTERN NC IN
LIGHT OF THE CONTINUING CLOUD COVER...WHILE TEMPS LOOK VERY MUCH ON
TRACK TO REACH THE MID-90S ACROSS THE UPSTATE AND NORTHEAST GEORGIA.

AS OF 650 AM...CONVECTION DID DISSIPATE AS IT CROSSED THE MTNS.
HOWEVER...MCV ASSOCIATED WITH THIS CONVECTION IS HELPING KICK OFF
RENEWED CONVECTION ACROSS THE FOOTHILLS INTO THE PIEDMONT. THIS
CONVECTION WILL SWING ACROSS THE PIEDMONT AND EAST OF THE AREA BY
MID MORNING...WITH A FEW TSRA DEVELOPING. ANOTHER ROUND OF
CONVECTION ACROSS KY IS MOVING TOWARD THE AREA ON A SIMILAR
TRAJECTORY. THIS CONVECTION SHUD REACH THE NC MTNS BY MID MORNING
AND THE PIEDMONT AROUND NOON. THIS CONVECTION IS ALREADY SHOWING
SOME DISSIPATING TRENDS...SO WILL HAVE TO SEE IF IT FOLLOWS A
SIMILAR RESOLUTION AND REDEVELOPS AS IT MOVES OUT OF THE MTNS AND
INTO THE FOOTHILLS. HAVE UPDATED THE POPS TO SHOW THESE TRENDS. WILL
HAVE TO SEE IF THIS CONVECTION AND ASSOCIATED DEBRIS CLOUDS AFFECT
HIGHS FOR THE DAY. HAVE KEPT HIGHS AS IS FOR NOW.

AS OF 330 AM...MCS TO THE NW IS WEAKENING AS IT MOVES EAST TOWARD
THE AREA. HOWEVER...THERE IS ENUF ELEVATED INSTABILITY AND FORCING
FOR CONVECTION TO FORM AHEAD OF THIS SYSTEM. EXPECT THIS
CONVECTION...AND THE MCS ITSELF...TO SPREAD INTO THE NC MTNS AND
I-40 CORRIDOR BEFORE DAYBREAK. THE PRECIP THEN DISSIPATES DURING THE
MORNING BEFORE RETURNING FROM THE NW AS CONVECTION DEVELOPS AHEAD OF
A COLD FRONT MOVING IN. THE ATMOS AHEAD OF THE FRONT IS VERY
UNSTABLE AND BECOMES HIGHLY SHEARED AS A LOW LEVEL JET MOVES IN WITH
THIS SYSTEM. ALTHOUGH INSTABILITY WILL BE SIGNIFICANT ACROSS THE
CWFA...THE BEST SHEAR WILL BE ACROSS THE NC MTNS INTO THE I-40
CORRIDOR. ALTHOUGH SPEED SHEAR IS VERY STRONG...THERE IS LITTLE
VEERING OF THE WINDS AS THE LOW LEVEL WINDS DO NOT BACK AHEAD OF THE
COLD FRONT AND REMAIN SWLY. THE FORECAST SOUNDINGS ALSO SHOW LOW
LEVEL CIN...AND THE DEBRIS CLOUDS FROM THE MCS COULD KEEP HEATING
FROM REACHING MAXIMUM POTENTIAL. HOWEVER THIS WILL EASILY BE
OVERCOME WITH THE STRONG FORCING DEVELOPING. THEREFORE...LOOKS LIKE
A DECENT CHC OF SEVERE STORMS WITH DAMAGING WINDS AND LARGE
HAIL...IN EITHER MULTICELL OR SQUALL LINE FORM...DEVELOPING ACROSS
THE NC MTNS INTO THE I-40 CORRIDOR...BUT THE ISOLATED TORNADO
CHC...WHILE THERE...LOOKS LIMITED WITH BETTER CHC TO OUR NORTH. SVR
CHC...AND EVEN CHC OF CONVECTION...WILL DROP OFF QUICKLY ACROSS THE
SRN CWFA AS SHEAR AND FORCING WILL BE LIMITED. WILL UPDATE HWO FOR
THESE CONCERNS. HIGHS TODAY WILL BE ABOVE NORMAL...BUT NOT AS WARM
AS SOME OF THE MOS GUIDANCE. LOWS TONIGHT WILL BE ABOVE NORMAL AS
WELL.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 225 AM EDT SUNDAY...THE SHORT TERM PERIOD INITIALIZES MONDAY
MORNING WITH A STRONG FRONTAL BOUNDARY PUSHING THROUGH THE REGION.
EXPECTING THE BOUNDARY TO BE LAID ALONG OR JUST SOUTH OF INTERSTATE
85 BY AROUND 12Z...THEN QUICKLY PUSH EAST SOUTHEAST INTO THE
MIDLANDS BY NLT 18Z.  00Z NAM/GFS SOLUTIONS ARE IN GOOD AGREEMENT
REGARDING THIS FROPA TIMING WHICH WOULD GREATLY IMPACT CHANCES FOR
ANY ENHANCED CONVECTION ACROSS THE PIEDMONT REGIONS OF NC/SC.  AS A
MATTER OF FACT...LATEST NAM/GFS CONS FORECAST SOUNDINGS INDICATE
SUBSTANTIAL LOW LEVEL INHIBITION IN PLACE ACROSS THE
PIEDMONT...WHICH ANY UPDRAFTS WILL STRUGGLE TO OVERCOME.  THAT
SAID...HAVE LOWERED POPS FOR THE EASTERN TIER OF THE FORECAST AREA
WITH ONLY SLIGHT CHANCE POPS BEING HIGHLIGHTED THROUGH MIDDAY MONDAY
ALONG WITH LINGERING UPSLOPE SHOWERS ALONG THE HIGH TERRAIN.
DESPITE A NARROW WINDOW OF OPPORTUNITY...STILL CANNOT COMPLETELY
RULE OUT SEVERE THUNDERSTORM THREAT LATE MONDAY MORNING AS THERE
WILL BE A MODERATELY UNSTABLE AIRMASS IN PLACE OUT AHEAD OF FRONTAL
FORCING.  THAT SAID...THE OVERALL THREAT DOES LOOK TO BE DIMINISHING
AS THE FROPA HAS SPED UP SIGNIFICANTLY OVER THE LAST FEW MODEL
RUNS.

STRONG NORTHWEST FLOW DOWN THE DESCENDING BRANCH OF ANOMALOUSLY DEEP
UPPER TROF WILL ADVECT A SHALLOW LAYER OF WESTERN GREAT LAKES
MOISTURE INTO THE SOUTHERN/CENTRAL APPS MONDAY NIGHT.  THUS...POPS
WILL RAMP UP YET AGAIN TO SLIGHT CHANCE LEVELS ACROSS THE NC
MOUNTAINS AS SAID MOISTURE POOLS ON THE WESTERN SLOPES OF THE APPS
AND IS LIFTED MECHANICALLY.  POPS WILL REMAIN ELEVATED AT THOSE
LEVELS THROUGH TUESDAY AFTERNOON WITH A DRY FORECAST ELSEWHERE AS
HIGH PRESSURE BUILDS FOR THE REMAINDER OF THE PERIOD.  TEMPERATURES
THROUGH THE SHORT TERM WILL COOL SIGNIFICANTLY BEHIND THE FROPA WITH
HIGHS NEARLY TEN DEGREES BELOW NORMAL FOR SOME LOCATIONS ON TUESDAY
AFTERNOON.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 AM EDT SUNDAY...THE EXTENDED RANGE PORTION OF THE
FORECAST INITIALIZES WEDNESDAY MORNING WITH A PERSISTENT EAST COAST
UPPER TROF IN PLACE.  CANADIAN HIGH PRESSURE AT THE SURFACE WILL
YIELD A DRY FORECAST THROUGH THE DAY ON WEDNESDAY AS NORTHERLY FLOW
PREVAILS.  THE ABOVE MENTIONED UPPER TROF WILL REMAIN IN PLACE
THROUGH THE PERIOD LEADING TO NO CHANGE IN DEEP LAYER FLOW.  AT THE
SURFACE HOWEVER...HIGH PRESSURE WILL SLIDE NORTHEAST ALLOWING AN
EASTERLY SHIFT TO LOW LEVEL FLOW LEADING TO INCREASING MOISTURE
ACROSS THE AREA FROM THE WESTERN ATLANTIC.  THE FORECAST WILL
RESPOND WITH INCREASING POPS ON THURSDAY WITH THE HIGHEST CHANCE
POPS ALONG THE CLIMO FAVORED UPSLOPE REGIONS OF THE MOUNTAINS WITH
ONLY SLIGHT CHANCE POPS SPREAD ACROSS THE REMAINDER OF THE FORECAST
AREA.  POPS WILL INCREASE FURTHER ON FRIDAY AS NORTHEAST SURFACE
RIDGE EXTENDS DOWN THE LEE SIDE OF THE APPS IN A WEDGE LIKE PATTERN
LEADING TO UPGLIDE POTENTIAL ACROSS THE REGION.  THEREFORE...CHANCE
POPS WILL BE FEATURED REGION-WIDE ON FRIDAY INTO SATURDAY MORNING.
TEMPERATURES THROUGH THE PERIOD WILL REMAIN BELOW NORMAL WITH
GRADUAL MODERATION EXPECTED INTO WEEKS END.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT KCLT...CONVECTION REDEVELOPING OVER THE PIEDMONT ASSOCIATED WITH
AN MCV THAT DROVE CONVECTION INTO THE MTNS. LOOKING INCREASINGLY
LIKELY THAT THIS CONVECTION WILL CROSS NEAR THE AIRFIELD AROUND 12Z
BEFORE MOVING EAST OF THE AREA. THUNDER HAS BEEN ASSOCIATED WITH A
FEW OF THESE CELLS...SO WILL HAVE TO KEEP A WATCH ON THIS FOR TAF
ADDITION OR WWA ISSUANCE. ONCE THIS CONVECTION MOVES THRU...ANOTHER
ROUND IS POSSIBLE AROUND 16Z AS CONVECTION CURRENTLY MOVING THRU KY
ON THE SAME TRAJECTORY MOVES INTO OR NEAR THE AREA. TIMING THIS WILL
BE TROUBLE...SO WILL HAVE TO KEEP AN EYE ON ITS EVOLUTION FOR LATER
INCLUSION WITH MID MORNING AMD. BETWEEN THESE FEATURES...VFR
CONDITIONS EXPECTED WITH INCREASINGLY STRONG AND GUSTY SWLY WINDS. A
FINAL ROUND OF CONVECTION IS POSSIBLE OVERNIGHT AS A COLD FRONT
MOVES INTO THE AREA. AGAIN...TIMING WILL BE PROBLEMATIC. GUSTS END
THIS EVENING BUT SWLY WINDS REMAIN IN PLACE THRU THE NITE.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT. EXCEPT BETTER CONVECTION CHC
AT KAVL AND KHKY. AS WITH KCLT...TIMING IS PROBLEMATIC AND AMD WILL
LIKELY BE NECESSARY AS THE FEATURES APPROACH AND TIMING IS BETTER
ANTICIPATED. KAVL ALSO DIFFERENT WITH NLY WINDS TURNING SWLY FOR THE
AFTERNOON THEN BACK TO NLY DURING THE EVENING.

OUTLOOK...A FEW THUNDERSTORMS ARE POSSIBLE WITH THE COLD FRONT AS IT
CROSSES THE REGION INTO MONDAY. VFR CONDITIONS WILL RETURN BY LATE
MONDAY...THEN LINGER THROUGH AT LEAST MID WEEK.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     MED   78%     MED   77%
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 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...CDG
NEAR TERM...JDL/RWH
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...RWH





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.