Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 191500
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1100 AM EDT TUE AUG 19 2014

.SYNOPSIS...
A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD ACROSS THE
MISSISSIPPI RIVER VALLEY OVER THE NEXT FEW DAYS AND LINGER FOR THE
REST OF THE WORK WEEK...RESULTING IN ABOVE NORMAL TEMPERATURES. A
WEAK COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST LATE
FRIDAY INTO SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1050 AM...SCATTERED SHOWER ACTIVITY ASSOCIATED WITH WEAK
MID-LEVEL SHORT WAVE TROUGH IS IN THE PROCESS OF DISSIPATING ACROSS
THE SC PIEDMONT THIS MORNING. ADDITIONAL SHOWER ACTIVITY IS
PROGRESSING ACROSS CENTRAL GEORGIA ATTM...WITH A TRAJECTORY THAT
WOULD CARRY IT INTO THE SC MIDLANDS THIS AFTERNOON. THE UPSHOT IS
FAIRLY QUIET WEATHER IS ANTICIPATED ACROSS THE AREA OVER THE NEXT
2-4 HOURS. THIS WILL HOWEVER ALLOW FOR SOME DECENT INSOLATION OVER
THE AREA (DESPITE PARTLY/MOSTLY CLOUDY SKIES ASSOCIATED WITH
MID-LEVEL MOISTURE)...WHICH WILL RESULT IN SOME DESTABILIZATION THIS
AFTERNOON. MORNING SOUNDINGS INDICATE LAPSE RATES TENDING STRONGLY
TOWARD MOIST ADIABATIC THROUGH A DEEP LAYER...SUGGESTING ANY
INSTABILITY WILL BE QUITE MODEST...ALTHOUGH PWATS ARE A LITTLE ABOVE
CLIMO. EXPECT SCATTERED DEEP CONVECTION TO DEVELOP OVER THE HIGH
TERRAIN...ESP NEAR THE BLUE RIDGE THIS AFTERNOON...THEN MOVE E/SE.
OVERALL...DECIDED NOT TO ARGUE WITH THE CURRENT 30-40 POPS BEING
ADVERTISED...BUT WOULD NOT BE SURPRISED IF THIS TURNS OUT TO BE A
TAD HIGH...ESP SINCE WE ARE GOING TO SEE AN INCREASE IN LARGE SCALE
WEAK SUBSIDENCE IN THE WAKE OF THE PARTING SHORT WAVE. TEMPS SHOULD
WARM TO WITHIN A DEGREE OR SO OF CLIMO.

1130 UTC UPDATE...POPS AND QPF HAVE BEEN INCREASED IN THE SW
MOUNTAINS AND UPPER UPPER SAVANNA ROVER VALLEY EARLY ON PER RADAR
TRENDS. SKY COVER WAS UPDATED FROM INFRARED SATELLITE IMAGERY...
RESULTING IN A DECREASE IN CLOUD COVER IN THE EAST. WINDS WERE
UPDATED TO INCORPORATE THE 06Z NAM. AREAS OF FOG WERE UPDATED FROM
OBSERVATIONS.

AT 330 AM EDT TUESDAY...AN UPPER TROUGH EXTENDED FROM A CLOSED UPPER
LOW OVER THE GREAT LAKES...TO GA. MEANWHILE...AN UPPER RIDGE AXIS
STRETCHED FROM TX TO THE NORTHER ROCKIES. A STATIONARY FRONT WAS
LOCATED FROM VA TO MO...AND ANOTHER FROM CHESAPEAKE BAY TO THE GREAT
LAKES. SATELLITE IMAGERY SHOWS CLUSTERS OF CLOUD COVER FROM THE
CAROLINAS AND GA TO THE NORTHERN GULF STATES...MAINLY ASSOCIATED
WITH VORT MAXES MOVING THROUGH THE TROUGH AXIS.

THE TROUGH AXIS IS EXPECTED TO MOVE VERY SLOWLY TO THE CAROLINA
COAST BY TONIGHT. A SHORTWAVE NOW OVER AL WILL REACH THE UPPER
SAVANNAH RIVER BY DAYLIGHT...BUT AT A TIME OF MINIMUM INSTABILITY.
SHOWER ACTIVITY IN N AL MAY SURVIVE TO REACH OUR AREA BY DAWN.

THE SHORTWAVE WILL MOVE EAST OF OUR AREA BY AFTERNOON...WHILE A
WEAKER SHORTWAVE MOVES ACROSS AL AND GA. CONVECTIVE ACTIVITY WILL BE
BEST DURING MAXIMUM HEATING THIS AFTERNOON...BUT THE TIMING OF THE
TWO SHORTWAVES MAY NOT LEND IDEAL SUPPORT. MODEL SOUNDINGS SHOW A
VERY MOIST COLUMN FROM 850 MB UP TO 500 MB...WITH A DRY LAYER
BENEATH...BUT CAPE IS EXPECTED TO BE UNDER 1000 J/KG...LIMITING THE
CHANCES OF SEVERE WEATHER. STEERING FLOW SHOULD BE SUFFICIENT TO
KEEP CELLS MOVING ALONG. MAXIMUM TEMPERATURES WILL RUN NEAR NORMAL.

THE GA SHORTWAVE MOVES BY TO OUR S TONIGHT...WHILE ONLY MODEST
ELEVATED INSTABILITY REMAINS. MODEL SOUNDINGS SHOW DRYING THROUGH
THE COLUMN...PARTICULARLY ABOVE 700 MB. STEERING FLOW WILL BECOME
WEAKER IN THE LOWER LEVELS...BUT PRECIPITATION SHOULD DECREASE IN
COVERAGE AND INTENSITY. MINIMUM TEMPERATURES WILL RUN NEAR NORMAL.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 300 AM TUESDAY...A LARGE UPPER RIDGE WILL BUILD OVER THE
SOUTHEAST AND LWR-MID MS VALLEY WEDNESDAY AND THURSDAY.
MEANWHILE...A CLOSED UPPER LOW WILL DRIFT SOUTHEAST AND OPEN INTO A
DEEPER TROF ALONG THE EAST COAST. THIS WILL PLACE THE CWFA WITHIN
INCREASING NWLY MID-UPR FLOW. MODELS DISAGREE ON INDIVIDUAL EMBEDDED
SHORTWAVES RIDING OVER THE TOP OF THE BUILDING RIDGE AND DIVING
SOUTHEAST ACRS THE OH VALLEY TO THE MID ATLANTIC. IN ANY
CASE...EXPECT ABOVE NORMAL TEMPS BOTH DAYS...WITH PLENTY OF
INSTABILITY FOR AT LEAST SCATTERED MTN CONVECTION AND ISOLD ACRS THE
PIEDMONT. THERE IS SOME CONCERN THAT THE FLOW WILL PLACE THE AREA
WITHIN A FAVORED MCS TRACK. HOWEVER...CONFIDENCE IS STILL LOW...SUCH
THAT I DID NOT TRY TO ADJUST POPS BASED ON THAT (THE HIGHEST POPS
ARE ALREADY ALONG THE TN/NC BORDER BOTH DAYS). WITH THAT SAID...IF A
DECENT CLUSTER OF STORMS DEVELOPS TO OUR NW...THERE MAY BE ENUF
SHEAR TO ALLOW STRONG TO SEVERE STORMS AT LEAST REACHING THE
MTNS...IF NOT CROSSING THEM. THE NEW DAYS 2 AND 3 OUTLOOKS...HAVE A
MENTION OF POSSIBLE ORGANIZED CONVECTION ACRS THE MID MS AND OH
VALLEYS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 315 AM TUESDAY...THE 00Z MODEL SUITE (EXCEPT FOR THE
CMC)...HAVE TRENDED TO THE EAST WITH THE UPPER RIDGE AXIS...KEEPING
HIGHER HEIGHTS OVER THE CWFA THIS WEEKEND INTO EARLY NEXT WEEK. THIS
ACTUALLY RESULTS IN EVEN MORE PRONOUNCED BACKDOOR COLD FRONT AND
ENSUING WEDGE.

I BLENDED IN THE 00Z WPC GUIDANCE (THE SUPERBLEND GRIDS) FOR THE
DAYS 4 THRU 7. FRIDAY LOOKS TO STILL BE ABOVE NORMAL WITH DIURNAL
ISOLD TO SCATTERED CONVECTION. THE BACKDOOR COLD FRONT PUSHES IN
FRIDAY AFTN/EVE...WHICH COOLS THE NW NC PIEDMONT SLIGHTLY. THEN
SATURDAY AND SUNDAY...TEMPS RETURN TO NORMAL OR EVEN SLIGHTLY BELOW
NORMAL IN SPOTS...WITH INCREASED CLOUD COVER AND LIGHT E/NELY SFC
FLOW. POPS RAMP UP TO MORE WIDESPREAD CHC OVER THE WEEKEND. THEN THE
GFS AND ECMWF DIVERGE ON WHETHER WE DRY OUT ON MONDAY...WITH THE GFS
SHOWING THE WEDGE ENDING...WITH MUCH WARMER TEMPS. I HAVE LOWER POPS
AND SLIGHTLY WARMER TEMPS FOR MONDAY.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...THE DEW POINT DEPRESSION IS STILL A BIT HIGH FOR FOG
FORMATION THIS MORNING...AND NONE WILL BE CARRIED IN THE TAF. THE
BULK OF LOW CLOUDS REMAIN OFF THE THE SE WITH AN APPROACHING MID
LEVEL SYSTEM...BUT LOW VFR CIGS ARE EXPECTED BY MIDDAY...LASTING
THROUGH THE AFTERNOON. CONVECTIVE CHANCE WILL PEAK THIS AFTERNOON
WITH THE BEST HEATING. CLOUDS COVER DECREASES TONIGHT IN THE WAKE OF
THE DEPARTING SYSTEM. GUIDANCE FAVORS MVFR VSBY BY DAYBREAK
WEDNESDAY. LIGHT WINDS WILL VEER TO WNW TODAY..THEN GO VARIABLE
TONIGHT.

ELSEWHERE...GUIDANCE WAS A BIT TOO PESSIMISTIC WITH VSBY THIS
MORNING...SO FEW RESTRICTIONS WILL BE CARRIED..PER OBSERVATIONS. LOW
CLOUDS MOVING IN FROM GA WITH A MID LEVEL SYSTEM WILL SET UP LOW VFR
CIGS BY MIDDAY....THAT LAST UNTIL LATE AFTERNOON...WHEN THE SYSTEM
AND CLOUDS DEPART. CONVECTIVE CHANCES WILL BE BEST THIS AFTERNOON
WITH MAXIMUMS HEATING. GUIDANCE IS VERY PESSIMISTIC WITH CIGS
WEDNESDAY MORNING. WITH CONFIDENCE LIMITED...BLENDED GUIDANCE VSBYS
HAVE BEEN RAISED BY ONE MILE...WHICH STILL YIELDS IFR AT KAVL...AND
MVFR AT ALL OTHER SITES BY KGMU. WINDS WILL VEER FORM WSW TO W
TODAY...THEN GO VARIABLE TONIGHT....EXCEPT AT KAVL WERE WINDS WILL
CHANNELED UPVALLEY FROM THE NW.

OUTLOOK...SCT AFTERNOON CONVECTION AND PATCHY EARLY MORNING FOG WILL
REMAIN IN THE FORECAST THROUGH THE WEEK. THERE WILL ALSO BE
INCREASING CHANCES FOR ORGANIZED CONVECTION APPROACHING THE AREA
FROM THE NW DURING THE LATE NIGHT/EARLY MORNING HOURS.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  87%
KAND       HIGH  98%     HIGH 100%     HIGH  95%     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...ARK
NEAR TERM...JAT/JDL
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...JAT






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