Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 230658
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
258 AM EDT WED JUL 23 2014

.SYNOPSIS...
EXPECT A BRIEF RETURN TO MORE TYPICAL SUMMER WEATHER ON WEDNESDAY
BEFORE A FRONT APPROACHES AND MOVES ACROSS THE REGION ON THURSDAY.
THE PASSAGE OF THE FRONT WILL NOT BRING COOLER AIR...BUT IT SHOULD
BRING DRIER AIR FOR FRIDAY AND INTO THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 250 AM...I WILL UPDATE THE FORECAST TO INCREASE THE FOG
MENTION WITHIN THE MTN VALLEYS AND I-77 CORRDIOR...BASED ON HRRR AND
NAM CONDENSATION PRESSURE DEFICITS.

AS OF 1020 PM...ONLY A FEW SHRA REMAIN ACROSS VARIED PARTS OF THE
CWFA THIS EVENING. ISOLATED SHRA MAY CONTINUE UNTIL SHORTLY AFTER
MIDNIGHT BUT SHUD END SHORTLY THEREAFTER. CURRENTLY MUCH LESS
CLOUDINESS THAN THE MDLS WERE SUGGESTING. HAVE BACKED OFF ON CLOUDS
THIS EVENING...BUT ALLOW SOME CLOUDS TO DEVELOP AFTER MIDNIGHT. LOWS
LOOK ON TRACK.

AS OF 740 PM...CONVECTIVE COVERAGE BEGINNING TO WANE WITH THE LOSS
OF HEATING. COVERAGE WILL CONTINUE TO DIMINISH THRU THE EVENING WITH
MOST CELLS GONE BY MIDNIGHT. HAVE UPDATED POP FOR THESE TRENDS. HAVE
BACKED OFF ON CLOUDS EARLY AS WELL GIVEN SAT PIX...BUT STILL EXPECT
LOW CLOUDS TO RETURN OVERNIGHT. OTHERWISE...GOING FORECAST ON TRACK
WITH UPDATES MAINLY FOR CURRENT CONDITIONS.

AS OF 420 PM...CONVECTION DEVELOPING ALONG AND SOUTH OF THE I-85
CORRIDOR AND SLOWLY MOVING NE. EXPECT THESE TRENDS TO CONTINUE INTO
THE EVENING WITH GREATEST COVERAGE OUTSIDE OF THE MTNS EARLY...THEN
ACROSS THE MTNS NEAR SUNSET. CONVECTION SHUD THEN SLOWLY TAPER OFF
WITH ONLY ISOLATED COVERAGE EXPECTED AFTER MIDNIGHT. HAVE UPDATED
POP...MAINLY EARLY...FOR THESE TRENDS. REST OF THE FCST LOOKS TO BE
IN GOOD SHAPE WITH ONLY UPDATES FOR CURRENT CONDITIONS NEEDED.

AT 230 PM EDT TUESDAY... FOR THE REMAINDER OF THE AFTERNOON AND
EVENING... SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL PERSIST
IN A MOIST BUT ONLY MODESTLY UNSTABLE AIR MASS. NO SIGNIFICANT
SURFACE FEATURES EXIST IN THE CWA TO PROVIDE AN OBVIOUS FOCUS FOR
CONVECTIVE DEVELOPMENT. EXPECT SHOWERS TO DRIFT SLOWLY TO THE
NORTHWEST WITH PERHAPS A SLIGHT PREFERENCE FOR ENHANCEMENT AND BEST
COVERAGE THIS EVENING IN AREAS WITH UPSLOPE FLOW. WINDS ALOFT
THROUGH THE EVENING WILL REMAIN QUITE LIGHT IN THE COL REGION OF THE
MID AND UPPER TROPOSPHERIC HEIGHT FIELD... SO SLOW MOVEMENT OF
CONVECTIVE CELLS IS LIKELY. OVERNIGHT FOG IS POSSIBLE... BUT MODELS
AT THIS TIME ARE NOT DEFINITIVE IN INDICATING WIDESPREAD LOW
VISIBILITY CONDITIONS. NONETHELESS... THE POTENTIAL BEARS WATCHING
OVERNIGHT. THE PRIME AREA FOR SIGNIFICANT FOG WILL BE IN THE
MOUNTAIN VALLEYS AND ACROSS THE NORTHERN FOOTHILLS INTO THE
NORTHWEST PIEDMONT OF NC.

UPPER LEVEL PATTERN ACROSS THE AREA WILL UNDERGO A TRANSITION
TONIGHT AND WEDNESDAY. THE CUTOFF LOW OVER GULF COAST STATES WILL
CONTINUE A SLOW DRIFT TO THE WEST AND HEIGHTS WILL FALL TO OUR NORTH
IN ADVANCE OF SIGNIFICANT TROUGH DIGGING INTO THE EAST. AS TROUGH
HEADS ACROSS THE GREAT LAKES TOWARD THE ATLANTIC COAST... THE
SURFACE RIDGE THAT HAS EXTENDED FROM THE MID-ATLANTIC INTO THE
CAROLINAS FOR A COUPLE OF DAYS WILL DISAPPEAR. IN ITS PLACE WE ARE
LIKELY TO HAVE A LEE TROUGH RETURN TO THE PIEDMONT PORTION OF THE
CWA BY WEDNESDAY AFTERNOON. THE FALLING HEIGHTS AND APPROACHING
DIGGING TROUGH WEDNESDAY AFTERNOON WILL BE ACCOMPANIED BY A WESTERLY
WIND FLOW ALOFT AND SOUTH TO SOUTHWEST WIND IN THE BOUNDARY LAYER.
THE RESULT WILL BE A RETURN TO A MORE DIURNAL PATTERN OF CONVECTION
WITH THE HIGHEST POPS OVER AND NEAR THE HIGHER TERRAIN. WITHOUT A
MAJOR CHANGE IN AIR MASS... SIGNIFICANT TEMPERATURE CHANGES WILL NOT
OCCUR. TUESDAY MORNING LOWS ARE EXPECTED TO BE NEAR 70 WITH 60S IN
THE MOUNTAIN VALLEYS. WEDNESDAY AFTERNOON TEMPERATURES WILL BE
BETWEEN 85 AND 90 EXCEPT IN THE LOWER AND MIDDLE 80S IN THE MOUNTAIN
VALLEYS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
AS OF 200 PM EDT TUESDAY...ALL NUMERICAL GUIDANCE IS FORECASTING A
STRONG SHORT WAVE TO MOVE THROUGH THE GREAT LAKES WED NIGHT INTO THU
WHICH WILL DRIVE A SURFACE COLD FRONT SOUTHEASTWARD INTO THE
SOUTHEAST STATES. THE NAM AND GFS HAVE SETTLED ON SIMILAR TIMING
IN REGARD TO THE FRONT WITH BOTH MODELS BRINGING IT TO JUST NW OF
THE NC MOUNTAINS BY 12Z THU...AND THEN BRINGING IT ACROSS THE
MOUNTAINS INTO THE LOWER PIEMDONT BY THURSDAY EVENING. THE FRONT IS
THEN FORECAST TO CLEAR THE AREA BY MIDNIGHT. A DRYER AND MORE STABLE
AIR MASS IS EXPECTED TO OVERSPREAD THE AREA ON FRIDAY AS HIGH
PRESSURE RIDGES SOUTHEASTWARD FROM THE OHIO VALLEY.

IN REGARD TO SENSIBLE WEATHER...SOME LINGERING SHOWERS AND STORMS
MAY BE OVER THE AREA WED EVENING...BUT THEY SHOULD DISSIPATE WITH
LOSS OF HEATING WED NIGHT. HOWEVER...WILL NEED TO RAMP POPS UPWARD
LATE THURSDAY NIGHT AS SOME PREFRONTAL SHOWERS MAY REACH THE
MOUNTAINS BY SUNRISE THURSDAY. WILL CONTINUE TO ADVERTISE LIKELY
POPS IN PORTIONS OF THE MOUNTAINS AND ALSO IN NC PIEDMONT ON THU
AFTERNOON...BUT CONVECTION SHOULD BE SCATTERED ELSEWHERE AS WINDS IN
PROFILES ARE DECIDELY DOWNSLOPE IN NATURE. THERE SHOULD BE PLENTY OF
INSTABILITY THU AFTERNOON WITH CAPES POOLING TO 1500-2000J OVER THE
PIEMDONT. HENCE...A FEW SEVERE STORMS ARE POSSIBLE. WILL FORECAST
DECREASING POPS THU NIGHT AND THEN A DRY DAY ON FRI. MAX TEMPS WILL
BE BELOW CLIMO BOTH THU AND FRI IN THE MOUNTAINS...BUT NEAR CLIMO
OUTSIDE THE MOUNTAINS ON THU AND THEN ABOUT A CATEGORY BELOW CLIMO
ON FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...THE MEDIUM RANGE GUIDANCE SUGGESTS THAT THE
EASTERN U.S. TROUGH WILL FLATTEN AS HEIGHTS RISE IN RESPONSE TO
ANOTHER STRONG UPPER WAVE DIGGING INTO THE NORTHERN PLAINS OVER THE
WEEKEND. THIS WAVE IS FORECAST TO SWING ACROSS THE GREAT LAKES AND
RE-ESTABLISH THE EASTERN U.S TROUGH BY MONDAY.

LOOKS LIKE WE SHOULD BE ABLE TO SQUEEZE OUT ONE MORE NICE DAY ON
SATURDAY BEHIND THE THURSDAY FRONTAL PASSAGE AS HIGH PRESSURE
REMAINS WEEKLY RIDGED OVER THE AREA AND MOISTURE LEVELS REMAIN
RELATIVELY LOW. HOWEVER...IT LOOKS LIKE THE FIRST PART OF NEXT
WEEK WILL TURN STORMY. ALL THE MEDIUM RANGE MODELS HINT AT A
POSSIBLE MCS MAKING A RUN AT THE SOUTHERN APPALACHIANS ON SUNDAY. IT
IS DIFFICULT TO SAY WHETHER ANY OF THE PARENT STORMS WILL MAKE IT
ACROSS THE MOUNTAINS...BUT THE OUTFLOW MAY TRIGGER ADDITIONAL STORMS
ACROSS THE PIEDMONT SUNDAY AFTERNOON AND NIGHT. ALSO..AS THE UPPER
TROUGH DIGS OVER THE GREAT LAKES EARLY NEXT WEEK A COLD FRONT IS
FORECAST TO ARRIVE ON MONDAY PROVIDING THE TRIGGER FOR MORE
THUNDERSTORMS. SEVERE STORMS ARE A POSSIBILITY FROM SUNDAY INTO
MONDAY.

THE FRONT IS FORECAST TO CLEAR THE AREA MONDAY NIGHT WHICH SHOULD
ALLOW FOR DRYER AND MORE STABLE AIR TO OVERSPREAD THE AREA FROM THE
NW ON TUESDAY. MAX TEMPS ARE FORECAST TO BE NEAR OR EVEN SLIGHTLY
ABOVE CLIMO SAT THROUGH MONDAY...AND THEN BELOW CLIMO ON TUE BEHIND
THE COLD FRONT

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...LATEST OBSERVATION INDICATE THAT THE DEWPOINT DEPRESSION
WAS AROUND ONE DEGREE. HRRR AND NAM INDICATE THAT CONDENSATION
PRESSURE DEFICITS WILL FALL ACROSS THE CLT METRO AREA TO LESS THAN 1
MB BETWEEN 9Z TO 12Z. I WILL HIGHLIGHT THE FOG POTENTIAL WITH A
TEMPO GROUP FOR MVFR FOG BETWEEN 9Z TO 12Z. SHORTLY AFTER
SUNRISE...SW WINDS SHOULD DEVELOP WITH VFR CLOUD COVER. SCT COVERAGE
OF LATE AFTERNOON TSRA ARE POSSIBLE 18Z TO 24Z.

ELSEWHERE...THE PRIMARY CONCERN FOR THE REST OF THE NIGHT WILL BE THE
DENSITY AND PLACEMENT OF FOG. KAVL WILL SEE THE GREATEST POTENTIAL
FOR VLIFR FOG AND CEILINGS. ELSEWHERE...I WILL HIGHLIGHT THE FOG
POTENTIAL WITH A TEMPO GROUP FOR MVFR FOG BETWEEN 9Z TO 12Z. SHORTLY
AFTER SUNRISE...SW WINDS SHOULD DEVELOP WITH VFR CLOUD COVER. SCT
COVERAGE OF LATE AFTERNOON TSRA ARE POSSIBLE 18Z TO 24Z

OUTLOOK... SHOWERS AND THUNDERSTORMS THURSDAY WITH THE PASSAGE OF A
COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS MAINLY DURING THE
AFTERNOONS AND EVENINGS THROUGH THE END OF THE WEEK.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       MED   74%     HIGH  92%     HIGH 100%     HIGH 100%
KGSP       MED   78%     HIGH  89%     MED   78%     HIGH 100%
KAVL       HIGH  86%     MED   67%     HIGH 100%     HIGH 100%
KHKY       HIGH  91%     HIGH  97%     HIGH 100%     HIGH 100%
KGMU       MED   79%     HIGH  91%     HIGH 100%     HIGH 100%
KAND       MED   74%     HIGH  91%     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...CSH
NEAR TERM...NED
SHORT TERM...LG
LONG TERM...LG
AVIATION...NED





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