000
FXUS62 KGSP 172355
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
755 PM EDT FRI MAY 17 2013

.SYNOPSIS...
A MID LEVEL DISTURBANCE WILL DRIFT ACROSS THE REGION THIS
WEEKEND... TRIGGEREING SHOWERS AND THUNDERSTORMS THROUGH THE
BEGINNING OF NEXT WEEK. SOUTHERLY FLOW WILL KEEP THE AIRMASS WARM
AND MOIST... AND THE PATTERN WILL REMAIN UNSETTLED UNTIL A FRONTAL
SYSTEM APPROACHES THE WESTERN CAROLINAS LATE NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 745 PM EDT FRIDAY...SCATTERED STRONG THUNDERSTORMS HAVE
FINALLY LIFTED NORTH OF THE FORECAST AREA. THERE ISN/T MUCH FORCING
FOR PCPN UNTIL LATE TONIGHT WHEN AN MVC WILL SPREAD LIGHT STRATIFORM
PCPN AND A FEW HEAVIER SHRA/TSTMS INTO THE FA FROM THE SOUTHWEST.
UPSLOPE AND PROXIMITY TO THE POT VORT ANOMALY - AS SEEN ON THE 18
UTC GFS - WILL YIELD THE GREATEST COVERAGE OVER THE SOUTHWEST AND
CENTRAL MTNS AS WELL AS THE NE GA AND THE WRN UPSTATE. I/VE RAISED
POPS TO LIKELY IN THIS AREA...BUT NOT UNTIL AROUND 5 AM. EVERYTHING
ELSE LOOKS GOOD FOR THIS UPDATE.

AS OF 515 PM EDT FRIDAY...A FEW SHOWERS AND THUNDERSTORMS HAVE
DEVELOPED OVER THE WRN NC PIEDMONT...ESPECIALLY ACROSS ROWAN COUNTY.
THIS IS AN AREA OF WEAK MOISTURE AND SPEED CONVERGENCE. I/D EXPECT
CONVECTION TO CONTINUE ACROSS THIS AREA AND EXTENDING BACK INTO THE
SW NC FOOTHILLS FOR A FEW MORE HOURS. CONVECTION WILL ALSO PERSIST
OVER THE CENTRAL AND NRN MTNS. FARTHER SOUTH AND WEST LAPS ISN/T
SHOWING MUCH INSTABILITY AND MID AND HIGH LEVEL CLOUDS ARE SPREADING
IN WHICH SHOULD ALSO LIMIT CONVECTION. MUCH LATER
TONIGHT...HOWEVER...CONVECTION MAY SPREAD IN FROM THE SOUTHWEST AS
THE UPPER LOW APPROACHES. NOT SEEING A LOT OF ELEVATED INSTABILITY
BUT SHOWERS AND EVEN SOME STRATIFORM RAIN IS POSSIBLE. INTERESTINGLY
THERE IS SOME ELEVATED INSTABILITY OVER THE NC PIEDMONT. OUR
WORKSTATION WRF-ARW MODEL SHOWS CONVECTION DEVELOPING IN THAT AREA
AFTER MIDNIGHT. I WON/T BE THAT AGGRESSIVE...BUT IT/S SOMETHING TO
KEEP IN MIND.

AS OF 230 PM...LOOKING AT LATEST WV IMAGERY...WEAKENING UPPER
LEVEL TROF CONTINUES TO MOVE EASTWARD ACROSS THE TENNESSEE
VALLEY...THUS SPREADING MOISTURE THRU THE SOUTHEASTERN UNITED
STATES.  WITH THIS...SOME SHOWER AND THUNDERSTORMS ACTIVITY IS
PRESENT ON RADAR ACROSS PORTIONS OF NORTHEAST MISSISSIPPI AND
NORTHWEST ALABAMA.  LOCALLY...MID TO UPPER LEVEL CLOUD COVER
CONTINUES TO INCREASE ACROSS THE REGION AS A CONSEQUENCE OF DEEP
MOISTURE ADVECTION ALOFT.  HEIGHTS WILL CONTINUE FALL ACROSS
NORTHEAST GEORGIA AND THE CAROLINAS THROUGH THE NEXT 24 HOURS AS
REMNANTS OF UPPER LEVEL TROF MOVE THROUGH.  LATEST MESOANALYSIS
INDICATES A MODERATELY UNSTABLE AIRMASS ACROSS THE REGION THIS
AFTERNOON.  STILL EXPECTING THE MAJORITY OF CONVECTIVE ACTIVITY TO
BE IN THE HIGHER TERRAINS AS UPSLOPE FLOW WILL PROVIDE ENOUGH LIFT
TO OVERCOME ANY CAPPING...THEREFORE KEPT LIKELY POPS ACROSS NORTHERN
MOST PORTIONS OF THE NC MOUNTAINS AND HIGHER END CHANCE POPS
ELSEWHERE IN THE HIGH TERRAIN.  POPS DECREASE TO THE SOUTHEAST AS
LOCATIONS NEAR AND ALONG THE I85 CORRIDOR WILL HAVE THE MOST
DIFFICULT TIME OVERCOMING ANY INVERSION.  THUS...WENT WITH SLIGHT
CHANCE POPS ACROSS THIS REGION.

TONIGHT AND TOMORROW...MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH
REGARDS TO DECREASE IN CONVECTIVE ACTIVITY DURING THE OVERNIGHT
HOURS AS DAYTIME HEATING DISSIPATES.  HOWEVER...AFTER SUNRISE
TOMORROW THE ABOVE MENTIONED UPPER LEVEL WAVE WILL BE CENTERED OVER
THE SOUTHERN APPALACHIANS.  PRECIPITATION CHANCES WILL INCREASE ONCE
AGAIN DURING THE LATE MORNING HOURS ACROSS THE ENTIRE REGION.  SOME
SHOWER AND THUNDERSTORM ACTIVITY COULD BE STRONG TOMORROW AFTERNOON
AND EVENING AS THERMAL PROFILES INDICATE SLIGHTLY DEEPER INSTABILITY
THAN PREVIOUS DAYS.  LIKEWISE...SOME OF THESE SHOWERS AND
THUNDERSTORMS COULD PRODUCE LOCALLY HEAVY RAINFALL AS PRECIPITABLE
WATER VALUES EXCEED 1.5 INCHES THROUGHOUT THE PROFILE.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AT 200 PM FRIDAY...A WEAKNESS WILL PERSIST IN THE UPPER HEIGHT FIELD
OVER THE SOUTHEAST THROUGH MUCH OF THE PERIOD...ALTHOUGH IT WILL
CONTINUE TO GRADUALLY FILL. MOISTURE WILL REMAIN DEEP AND ABUNDANT
ACROSS THE REGION THROUGH THE PERIOD...AS PWATS WILL RUN IN THE
NEIGHBORHOOD OF 1.5 INCHES THROUGH AT LEAST SUNDAY NIGHT. THIS
SHOULD PROMOTE DEVELOPMENT OF NUMEROUS SHOWERS AND THUNDERSTORMS
ACROSS THE AREA DURING THE AFTERNOONS AND EVENINGS. LOW LEVEL FOCI
FOR INITIATION SHOULD GENERALLY BE LIMITED TO DIFFERENTIAL
HEATING/TERRAIN EFFECTS AS WELL AS OUTFLOW BOUNDARIES. HOWEVER...IT
APPEARS A WEAK/QUASI-CAD BOUNDARY WILL BE DRAPED ACROSS THE
CAROLINAS DURING THIS TIME AS WELL. WITH RELATIVELY WEAK DEEP LAYER
FLOW EXPECTED TO PREDOMINATE...SLOW MOVING...TRAINING AND/OR
ANCHORING CELLS PRODUCING LOCALLY EXCESSIVE RAINFALL WILL BE THE
PRIMARY THREATS. ISOLATED PULSE SEVERE STORMS OR SMALL CLUSTERS WILL
BE POSSIBLE... BUT THE SEVERE WEATHER THREAT WILL HINGE LARGELY UPON
THE DEGREE OF INSTABILITY AND THEREFORE THE MAGNITUDE OF HEATING WE
SEE...WHICH WILL PROBABLY NOT AMOUNT TO MUCH CONSIDERING THE MOIST
ADIABATIC LAPSE RATES/PROBABLE WIDESPREAD AND PERSISTENT CLOUD
COVER. MIN TEMPS WILL AVERAGE WELL ABOVE NORMAL AND MAXES SLIGHTLY
BELOW CLIMO OWING TO THE VERY MOIST AIR MASS.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AT 225 PM FRIDAY...AN UPPER LEVEL RIDGE WILL DOMINATE THE EASTERN
U.S INTO THE MIDDLE PART OF NEXT WEEK. AT THE SURFACE...THE WESTERN
EXTENSION OF THE BERMUDA HIGH WILL BE OVER THE SE STATES.
THEREFORE...EXPECT TEMPERATURES TO BE ABOVE CLIMO TUE AND WED.
DIURNALLY DRIVEN SCATTERED CONVECTION WILL OCCUR TUE AND WED WITH THE
GREATEST COVERAGE OVER THE MOUNTAINS. AN UPPER TROUGH WILL APPROACH
THE AREA FROM THE WEST LATE IN THE WEEK WITH THE ASSOCIATED COLD
FRONT MOVING THROUGH THE AREA LATE THU INTO FRI. THEREFORE...PRECIP
CHANCES WILL BE ON THE INCREASE THU...AND THEN DIMINISH ON FRI AS
THE FRONT MOVES TO THE EAST. TEMPERATURES WILL LOWER BACK TO
SEASONAL VALUES BY FRIDAY. STAYED CLOSE TO WPC GUIDANCE TEMPS/POPS.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...A FEW CUMULUS CLOUDS WILL LINGER ACROSS THE REGION THROUGH
THE OVERNIGHT...THOUGH ANY CIGS SHOULD BE OF THE MID AND UPPER LEVEL
VARIETY. THE CIGS MAY LOWER TO AROUND 10KFT LATE TONIGHT AS AN UPPER
LOW APPROACHES FROM THE WEST. STARTING AT MID MORNING AN AREA OF
PCPN WILL BEGIN TO MOVE INTO THE REGION. IT/S REALLY QUESTIONABLE
HOW QUICKLY IT MOVES EAST. I SUSPECT WE WILL HAVE TO WAIT FOR AFTN
HEATING TO KICK IN BEFORE SHRA/TSTMS BEGIN IN EARNEST...WHICH IS
WHAT I/VE CARRIED IN THE TAF. WINDS WILL GENERALLY BE OUT OF THE S
TO SW THROUGH THE PERIOD.

ELSEWHERE...AN AREA OF SHOWERS...THUNDERSTORMS AND RAIN WILL SLOWLY
MOVE INTO THE WESTERN CAROLINAS LATE TONIGHT. KAVL WILL SEE PCPN
FIRST...FOLLOWED BY THE UPSTATE SITES AND KHKY. CIGS AND VSBYS WILL
FALL LATE TONIGHT...BUT THIS WILL PRIMARILY BE CONFINED TO THE
MOUNTAINS AND IMMEDIATE FOOTHILLS. WHILE THERE WON/T BE MUCH
HEATING...THERE SHOULD STILL BE A FAIR AMOUNT OF SHOWERY PCPN IN THE
AFTN ON SATURDAY...SOME OF WHICH WILL EVOLVE INTO TSTMS. THEREFORE
I/VE ADDED TEMPO THUNDER IN THE AFTN AT MOST SITES. NO WIND SHIFTS
THIS PERIOD WITH THE FLOW GENERALLY OUT OF THE S TO SW.

OUTLOOK...SHOWERS AND THUNDERSTORMS...AND ASSOCIATED RESTRICTIONS...
WILL PERSIST THROUGH MONDAY. FAIR WEATHER MAY RETURN BY TUESDAY.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  87%     HIGH  86%
KHKY       HIGH 100%     HIGH 100%     HIGH  98%     HIGH  94%
KGMU       HIGH 100%     HIGH 100%     HIGH  91%     HIGH 100%
KAND       HIGH 100%     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...LEV
NEAR TERM...CDG/MCAVOY
SHORT TERM...JDL
LONG TERM...LG
AVIATION...MCAVOY