Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 042051
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
451 PM EDT TUE AUG 4 2015

.SYNOPSIS...
A WEAK COLD FRONT WILL DRIFT SOUTH ACROSS OUR AREA TONIGHT AND
WEDNESDAY BECOMING NEARLY STATIONARY OVER NORTHERN SOUTH CAROLINA.
AS MOISTURE INCREASES ACROSS OUR REGION...A STRONG DISTURBANCE WILL
REACH THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THURSDAY. THIS
DISTURBANCE SHOULD BE EAST OF OUR AREA ON FRIDAY AND DRIER HIGH
PRESSURE WILL BE IN CONTROL OVER THE WEEKEND..

&&

.NEAR TERM /THROUGH WEDNESDAY/...
430 PM UPDATE...EXPECTING THE CONVECTION LEAVING THE NC FOOTHILLS TO
WANE AS IT MOVES INTO MORE STABLE AIR. CAN/T RULE OUT A COUPLE NEW
TOWERS GOING UP ALONG OUTFLOW BOUNDARY HOWEVER. MESO MODELS CONTINUE
TO SHOW LITTLE IN THE WAY OF NEW DEVELOPMENT INTO THE EVENING. TEMPS
ROSE HIGHER THAN PREVIOUS FCST...AND DEWPTS ACCORDINGLY MIXED OUT
FURTHER AS WELL. TRENDS HAVE BEEN REVISED OVER THE NEXT FEW HRS BUT
MINS ARE STILL ON TRACK.

AS OF 225 PM EDT...THE CONVECTION ALLOWING MODELS HAVE TRENDED A BIT
MORE CONSERVATIVE ON SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON
AND EVENING. THE SURFACE COLD FRONT DRAPED NORTH OF THE REGION HAS
NOT PROVIDED MUCH LOW LEVEL FORCING ACROSS THE NORTHERN TIER...AND
SURFACE DEWPOINTS CONTINUE TO MIX OUT INTO THE UPPER 50S AND LOWER
60S EAST OF THE MTNS. HOWEVER...DIFFERENTIAL HEATING ALONG THE
RIDGES ALONG WITH 850 TO 500 MB LAPSE RATES APPROACHING NEARLY 7 DEG
C/KM SHOULD PERMIT SOME ISOLATED TO SCATTERED COVERAGE...ESPECIALLY
ACROSS WESTERN NC THROUGH EARLY EVENING AS THE SURFACE BOUNDARY
SETTLES INTO THE NORTHERN TIER. MEANWHILE...THE SFC LOW PRESSURE
SYSTEM WITH TROPICAL CHARACTERISTICS ALONG THE CAROLINA COASTLINE
WILL CONTINUE TO MOVE SLOWLY NORTHWARD AND KEEP ANY DEEPER MOISTURE
CONFINED TO THE COASTAL PLAIN. WILL DIMINISH ANY LATE AFTN/EVENING
POPS QUICKLY DESPITE THE BOUNDARY LURKING IN THE AREA...WITH
CONTINUED MILD OVERNIGHT MINS.

THE STALLED FRONT WILL LIKELY BEGIN LIFTING NORTHWARD AS A WARM
FRONT AGAIN THROUGH WEDNESDAY. WILL KEEP POPS FOCUSED MAINLY OVER
THE MOUNTAINS THROUGH WED AFTN AS HEIGHTS FALL SLIGHTLY FROM THE
WEST...BUT WILL ADVERTISE ISOLATED CHANCES OUT OVER THE PIEDMONT
WITH STEEP MID LEVEL LAPSE RATES EXPECTED...ALONG WITH POSSIBLY
BETTER LOW LEVEL PIEDMONT WIND FIELD CONVERGENCE. WED MAX TEMPS
SHOULD BE FAIRLY COMPARABLE TO TUE...WITH HEAT INDEX VALUES
REMAINING BELOW 100 GIVEN THE DEWPOINT MIXING.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AT 215 PM EDT TUESDAY...12Z SUITE OF GUIDANCE INDICATES THAT THE
WEAK BOUNDARY WILL REMAIN IN THE VICINITY WED NIGHT INTO THURSDAY.
THE NAM PUSHES THE BOUNDARY NORTH OF THE AREA BY LATE THURSDAY WHILE
THE GFS MOVES IT NO FARTHER NORTH THAT THE NC/SC BORDER. REGARDLESS
OF THE SOLUTION...THE WEAK CONVERGENCE ALONG THE BOUNDARY MAY
TRIGGER SOME WIDELY SCT SHOWERS/THUNDERSTORMS WED NIGHT WITH MORE
NUMEROUS SHOWERS/THUNDERSTORMS THURSDAY AFTERNOON AS THE AIRMASS
DESTABALIZES. ALSO...SYNOPTIC FORCING STEADILY IMPROVES THURSDAY AS
A WELL DEFINED SHORT WAVE IN THE MODEL GUIDANCE APPROACHES FROM THE
WEST. THIS FEATURE IS FORECAST TO MOVE ACROSS THE AREA THURSDAY
NIGHT. THE NAM GENERATES A WELL DEFINED SURFACE LOW WHICH MOVES
ACROSS THE CENTRAL APPALACHIANS THURSDAY NIGHT...WHILE THE GFS HAS A
WEAKER LOW MOVING ESSENTIALLY ALONG ITS STALLED FRONTAL BOUNDAY FROM
NE GA EASTWARD ALONG THE NC/SC BORDER. A MORE WELL DEFINED SFC LOW
SEEMS MORE REASONABLE BASED ON THE AMOUNT OF UPPER FORCING EXPECTED.
PLUS...THE EC AND SREF ARE MORE MORE LIKE THE NAM...SO WILL LEAN
TOWARDS THE NAM SOLUTION. THE MODELS HAVE QUITE A BIT OF QPF
RESPONSE ACROSS THE AREA FROM LATE THURSDAY INTO THURSDAY NIGHT. ALL
THE MODELS THEN DRIVE THE COLD FRONT SOUTH OF THE AREA ON FRIDAY AS
THE SURFACE LOW MOVES TO THE COAST. THIS WILL ALLOW DRYER AIR TO
OVERSPREAD THE AREA FRIDAY AIDED BY DOWNSLOPE FLOW. MAX TEMPS ARE
FORECAST TO BE NEAR CLIMO THURSDAY AND FRIDAY WITH MIN TEMPS A
LITTLE ABOVE NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AT 230 PM EDT TUESDAY...STARTING AT 00Z SATURDAY...500MB TROUGH HAS
AXIS OVER THE CAROLINAS FRIDAY NIGHT WITH 500MB RIDGE CENTERED OVER
TEXAS.  THE AXIS OF THE TROUGH MOVES TO JUST OFF THE ATLANTIC
SEABOARD BY MONDAY WITH THE RIDGE BUILDING EAST OVER THE GULF
STATES.  HOWEVER...IN MID WEEK THE PATTERN BECOMES MORE AMPLIFIED
WITH DEEPER TROUGH RETROGRADING A BIT WEST TO OVER THE APPALACHIANS
AND RIDGE CENTERED OVER WEST TEXAS AND NEW MEXICO.

AT THE SURFACE...THE COLD FRONT MOVES TO SOUTH GEORGIA OVER THE
WEEKEND AS THE NEXT COLD FRONT APPROACHES FROM THE UPPER MISSISSIPPI
VALLEY. VERY LOW INSTABILITY OVER THE WEEKEND WITH SLIGHTLY HIGHER
AMOUNTS AROUND THE SOUTHERN FRINGE FROM SW NC MTNS TO UPPER
SAVANNAH.  THE LATEST GFS HAS A RATHER VIGOROUS FRONT APPROACHING ON
TUESDAY WITH CAPES FROM NORTHERN MISSISSIPPI TO EAST TENNESSEE OVER
3000 AND SOME WIND SHEAR IN THE LOW TO MID LEVELS.  THE CURRENT
ECMWF IS LESS IMPRESSIVE BUT DOES SHOW A SHORTWAVE COMING DOWN FROM
KY AND TN ON TUES.  THEREFORE...AFTER THE WEEKEND LULL IT DOES
APPEAR TUES WILL BE MORE ACTIVE THAN SHOWN IN PREVIOUS MODEL RUNS.
WITH THE LOWER HEIGHTS...SHEAR AND OTHER FACTORS...APPEARS TO BE
SOME THREAT FOR STORMS TO PRODUCE HAIL AND STRONG WIND. A FIRST
SHORTWAVE CROSSES LATE MONDAY AND THEN THE BIGGER SHORTWAVE LATE
TUESDAY...IF THE TIMING STAYS THE SAME AS AFTER ALL IT IS A WEEK
AWAY FROM NOW.  TEMPS WILL BE NEAR NORMAL OVER THE WEEKEND. THE OLD
FRONT TO OUR SOUTH SLOWLY DISSIPATES LATE IN THE WEEKEND OR MONDAY.
SOUTHERLY NEAR SURFACE FLOW LATE MONDAY WILL SHIFT TO SW ON TUES
AHEAD OF THE APPROACHING COLD FRONT AS TEMPS WILL BE AT LEAST A
CATEGORY ABOVE NORMAL.

&&

.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
AT KCLT...NW WINDS WILL CONTINUE THIS AFTN...PARTICULARLY IN
LIGHT OF TS OUTFLOW MOVING INTO THE PIEDMONT POTENTIALLY BRINGING A
FEW GUSTS. A FEW TCU OR CB MIGHT GO UP NEARBY ALONG THE BOUNDARY BUT
CHC OF TS AT THE FIELD REMAINS TOO LOW TO MENTION. WINDS BECOME MORE
LIGHT AND VARIABLE TO STEADY LIGHT NE OVERNIGHT. WILL NOT MENTION
ANY FOG RESTRICTIONS AGAIN WED MORNING SINCE THE CROSSOVER TEMPS ARE
FAIRLY LOW. ANY PIEDMONT STRATUS SHOULD ONCE AGAIN STAY CONFINED
EAST OF THE AREA. EXPECT WINDS TO COME UP SLIGHTLY FROM THE SW WITH
MIXING MID TO LATE WED MORNING. ANY CLOUDS WILL GENERALLY BE FEW TO
SCT HIGH BASED CUMULUS WITH SCT TO BKN DEBRIS TYPE CIRRUS.

ELSEWHERE...ISOLD CONVECTION ALONG A COLD FRONT SETTLING INTO
WESTERN NC THROUGH THE EVENING...BUT CHC OF TS HAS PEAKED AT BOTH
KAVL AND KHKY. LIGHT WINDS WILL BE PREDOMINANTLY NW AT THE NC TAF
SITES AND MORE SW TO WSW AT THE UPSTATE TAFS WITH WEAK LEE TROUGHING
THERE. WILL OMIT ANY FOG MENTION DUE TO LOW CROSSOVER TEMPS...BUT
HINT AT VALLEY FOG WITH 6SM AT KAVL. NO RESTRICTIONS ARE THUS
EXPECTED THROUGH THE CURRENT PERIOD.

OUTLOOK...GRADUALLY INCREASING PRECIPITATION/RESTRICTION CHANCES ARE
EXPECTED THROUGH LATE WEEK AS MOISTURE RETURNS...A FRONT STALLS IN
OUR VICINITY...AND AN UPPER WAVE MOVES THROUGH THU NIGHT. EXPECT
SOME DRYING LATE FRI INTO THE WEEKEND.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-18Z
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 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...DEO
NEAR TERM...HG/WIMBERLEY
SHORT TERM...LG
LONG TERM...DEO
AVIATION...HG/WIMBERLEY


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