Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 050236
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1036 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/...
1015 PM UPDATE...EFFECTIVELY REMOVED ALL POPS FROM THE FCST TONIGHT.
THE REMAINING OUTFLOW BOUNDARIES HAVE WEAKENED ENOUGH THEY ARE NO
LONGER VISIBLE ON RADAR. BANDS OF CIRRUS DEBRIS FROM THE CONVECTION
ALONG THE FRONT ARE PASSING OVERHEAD...BUT THE THICKER CIRRUS WILL
LIKELY STAY MOSTLY TO OUR NORTH TONIGHT. IN LIGHT OF THE RESULTING
EXPECTATION OF BETTER RADIATION...AND IN LIGHT OF THE MUCH HIGHER
DEWPOINTS IN THE MTNS COMPARED TO THOSE LAST NIGHT AT THIS TIME...I
DID CHOOSE TO ADD BACK A PATCHY FOG MENTION IN THE VALLEYS. REVISED
MIN TEMPS SLIGHTLY WARMER ALSO.

AS OF 225 PM EDT...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 /03Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR. FRONTAL BOUNDARY REMAINS STALLED JUST N OF THE REGION
TONIGHT WITH WEAK COASTAL LOW SE OF THE FIELD. DUBIOUS PRESSURE
PATTERN OVERALL...BUT WINDS SHOULD STAY NELY INTO WED MRNG. THEN
THEY BACK TO SW FOR THE BULK OF THE DAY. MRNG RESTRICTIONS NOT
EXPECTED DUE TO RELATIVELY DRY AIRMASS...GOOD MIXING TUE AFTN...AND
POTENTIALLY CIRRUS DEBRIS LIMITING COOLING. AN OUTSIDE CHANCE OF A
TSRA WED AFTN EXISTS...BUT TOO LOW TO MENTION.

ELSEWHERE...OUTFLOW BOUNDARIES FROM CONVECTION OVER NW NC AND SW VA
WILL WORK SWD THRU KAVL AND KHKY THIS EVENING BUT NO ADDITIONAL
CONVECTIVE DEVELOPMENT IS EXPECTED ALONG THEM. ON RECENT MORNINGS
THE BEST VERIFYING VSBY/CIG GUIDANCE HAS COME FROM THE HIGHER
RESOLUTION DETERMINISTIC MODELS...NAMELY THE RAP/HRRR...AND AGAIN
TONIGHT THESE ARE PROGGING VFR. DEWPTS LIKELY MIXED OUT ENOUGH TUE
AFTN TO PRECLUDE ANY SUCH DEVELOPMENT ANYWAY. CONVECTION WED AFTN
MAY BE SLIGHTLY MORE WIDESPREAD THAN IT WAS TUE...WITH SLIGHTLY
BETTER LAPSE RATES ALOFT. HOWEVER THE ONLY SITE WITH A MENTIONABLE
CHC IS KAVL...WHICH HAS A PROB30. MAINLY NLY WINDS TONIGHT WILL BACK
TO SW IN THE PIEDMONT WED...REMAINING GENERALLY NW AT KAVL. HOWEVER
THAT SITE MIGHT SEE SOME VARIABILITY NEAR MIDDAY.

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...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     MED   70%     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...WIMBERLEY


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