Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 302350
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
750 PM EDT TUE SEP 30 2014

.SYNOPSIS...
DRIER HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH THURSDAY. A
COLD FRONT WILL THEN ARRIVE FROM THE NORTHWEST ON FRIDAY AND MOVE
OFFSHORE BY EARLY SATURDAY. IN THE FRONTS WAKE...A COOL AND DRY
AIRMASS WILL MOVE BACK OVER THE SOUTHEAST AND REMAIN IN PLACE OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 750 PM...CONVECTIVE CLOUDS DISSIPATING WITH LOSS OF HEATING
BUT CIRRUS MOVING IN FROM THE WEST. GUIDANCE AND FCST SOUNDINGS NOT
AS FAVORABLE FOR DENSE FOG OUTSIDE OF THE MTNS. SHUD SEE PATCHY FOG
THOUGH...ESPECIALLY NEAR BODIES OF WATER. FCST STILL LOOKS GOOD FOR
DENSE MTN VALLEY FOG OVERNIGHT...SO HAVE ADDED THAT TO THE FCST.
OTHERWISE...GOING FCST STILL LOOKS GOOD...SO UPDATES MAINLY FOR
CURRENT CONDITIONS.

AS OF 420 PM...STILL NO SIGN OF DEEP CONVECTION WITH ONLY SHALLOW CU
FORMING. FCST GENERALLY ON TRACK...SO ONLY MINOR CHANGES FOR CURRENT
CONDITIONS.

AT 215 PM EDT TUESDAY...A CLOSED UPPER LOW WILL MOVE FROM THE
EASTERN GREAT LAKES THIS AFTERNOON...TO SOUTHERN NEW ENGLAND BY
WEDNESDAY EVENING...WHILE THE TROUGH TO ITS SOUTH DEAMPLIFIES.
MEANWHILE...AN UPPER RIDGE AXIS WILL PROGRESS FORM THE MS RIVER
VALLEY TO THE OH AND TN RIVER VALLEYS. A COLD FRONT NOW IN THE OH
RIVER VALLEY WILL STALL TO OUR NORTH...WHILE WEAK HIGH PRESSURE
REMAINS OVER THE CAROLINAS AND GA.

MODEL TIME HEIGHTS SHOW LIMITED MOISTURE IN THE LOWER LEVELS...AND
SCATTERED CLOUD COVER IS EXPECTED WITH HEATING THIS AFTERNOON.
ALTHOUGH MODEL TIME HEIGHTS SHOW SOME WEAK INSTABILITY...A MID LEVEL
SUBSIDENCE INVERSION SHOULD PREVENT CONVECTION FROM DEVELOPING.
GUIDANCE SUPPORTS ANOTHER ROUND OF FOG IN THE MORNING...BUT OUTSIDE
THE MOUNTAINS...GENERALLY DOES NOT SUPPORT DENSE FOG. WEDNESDAY
FEATURES CONDITIONS MUCH LIKE TODAY...WITH SOME SCATTERED LOW CLOUDS
AND A CAPPING INVERSION ABOVE. THE ONE CAVEAT WOULD BE IF THE FRONT
TO THE NORTH CAN DROP INTO THE INTERSTATE 40 CORRIDOR BEFORE
STALLING...WHICH WOULD RESULT IN A FEW MORE CLOUDS AND A WIND
SHIFT FROM LIGHT SW TO LIGHT NE. TEMPERATURES ARE EXPECTED TO RUN A
FEW DEGREES ABOVE NORMAL AS HEIGHTS SLOWLY RISE ALOFT.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 215 PM TUESDAY...AN UPPER RIDGE AXIS WILL REMAIN ACRS THE CWFA
ON THURSDAY...KEEPING THE AREA DRY WITH ABOVE NORMAL TEMPS.

HEIGHTS BEGIN TO FALL IN EARNEST THURSDAY NIGHT...AS A POTENT
SHORTWAVE TROF DIVES INTO THE MIDWEST. IN THE LLVLS...S/SWLY FLOW
WILL INCREASE...TRANSPORTING GULF MOISTURE INTO THE AREA. THERE MAY
BE SOME UPSLOPE-ENHANCED SHOWER ACTIVITY DEVELOPING OVERNIGHT
THURSDAY NIGHT IN THE WESTERN ZONES. OTHERWISE...SHUD BE GENERALLY
DRY WITH INCREASING RETURN FLOW AND CLOUD COVER...TEMPS WILL BE WELL
ABOVE NORMAL...MAINLY IN THE 60S.

MODELS ARE STILL IN GOOD AGREEMENT ON THE TIMING OF A COLD FRONT TO
CROSS THE AREA ON FRIDAY. A PRE-FRONTAL BAND OF CONVECTION IS LIKELY
TO CROSS THE AREA DURING THE DAYLIGHT HOURS...WITH THE SFC FRONT
COMING THRU FRIDAY EVENING. AS AN 500 MB LOW CLOSES OFF INVOF MN...A
VORT LOBE SHUD LIFT NE ACRS THE SRN APPALACHIANS...PROVIDING
DEEP-LAYER Q-VECTOR CONVERGENCE. GUIDANCE ALSO SHOWS PLENTY OF UPPER
DIVERGENCE WITH THE BAND OF PRECIP. SO CONFIDENCE IS INCREASING ON
THE POP FOR FRIDAY. I HAVE CATEGORICAL POP IN THE MTNS AND LIKELY
ACRS THE PIEDMONT...THEN TAPERING OFF FRIDAY NIGHT.

AS FOR HOW ROBUST THE CONVECTION WILL BE...THERE LOOKS TO BE ABOUT
1000-1500 J/KG OF SBCAPE FOR THE LINE TO WORK WITH...WITH 0-6 KM
BULK SHEAR OF 40-50 KTS. CERTAINLY ENUF FOR AT LEAST A LOW-TOPPED
QUASI-LINEAR CONVECTIVE SYSTEM (QLCS). WE ARE NOT CURRENTLY
MENTIONING SEVERE WX IN THE HWO...BUT I WOULDN/T BE SURPRISED IF SPC
PLACES SOME AREA IN A SLGT FOR THE NEW DAY 3 TONIGHT FOR FRIDAY...IF
MODEL TRENDS HOLD.

TEMPS WILL BE NEAR OR SLIGHTLY BELOW NORMAL FRIDAY AND FRIDAY NIGHT
WITH THE PRECIP...AND PASSING COLD FRONT.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 150 PM TUESDAY AFTERNOON...THE MEDIUM RANGE FCST PICKS UP AT
12Z ON SATURDAY WITH A STEEP UPPER TROF TO OUR NORTH AND BROAD UPPER
RIDGING BUILDING OVER THE WEST COAST. AS WE MOVE INTO THE LATTER
PART OF THE WEEKEND...THE TROF AXIS LIFTS NE YET WE LIKELY WILL
REMAIN UNDER BROAD UPPER TROFFING THRU THE END OF THE PERIOD. THE
ECMWF CONTINUES TO REAMPLIFY THE TROF MORE THAN THE GFS ON DAYS 6
AND 7 WITH CONSIDERABLY LOWER HEIGHTS OVER THE FCST AREA ON NEW DAY
7...TUES. THE LATEST GFS DEVELOPS A VERY LARGE CLOSED H5 LOW OVER
ONTARIO AND THUS MAINTAINS A MUCH LONGER WAVELENGTH TROF THRU NEW
DAY 7.

AT THE SFC...IN THE WAKE OF THE FROPA ON FRI AFTERNOON AND
EVENING...COOL AND DRY HIGH PRESSURE WILL SPREAD OVER THE CWFA AND
REMAIN THRU THE WEEKEND. THE MODELS CONTINUE TO DEVELOP SOME SORT OF
GREAT LAKES LOW EARLY NEXT WEEK AND MOVE A SECOND COLD FRONT OVER
OUR AREA. THE GFS HAS THE FROPA ON MON WHILE THE ECMWF IS ABOUT 24
HRS SLOWER WITH THE FROPA ON TUES. BOTH MODELS SUGGEST A FAIRLY
QUICK AND MOSTLY DRY FROPA WITH LITTLE IN THE WAY OF QPF. AS FOR THE
SENSIBLE FCST...WE CAN EXPECT MOSTLY DRY AND COOL CONDITIONS THRU
THE PERIOD WITH JUST SOME SLIGHT CHANCE POPS ON MON AFTERNOON THRU
TUES TO ACCOUNT FOR THE NEXT FROPA. TEMP GUIDANCE HAS BEEN TRENDING
COOLER WITH HIGHS IN THE UPPER 60S TO LOW 70S OVER THE WEEKEND AND
WARMING BETWEEN 1 AND 2 CATEGORIES EARLY NEXT WEEK.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...CONVECTIVE CU DISSIPATING WITH LOSS OF HEATING WHILE
CIRRUS WILL SPREAD INTO THE AREA OVERNIGHT. GUIDANCE HAS GREATLY
DECREASED THE CHC OF FOG OVERNIGHT WITH LITTLE TO NO LOW CLOUD CHC.
HAVE GONE VFR GIVEN THE LOW CHC. THAT SAID...MVFR LIKELY AT THE
NORMALLY FOGGIER SITES NEAR THE AREA. EXPECT ANOTHER ROUND OF
CONVECTIVE CU WED AFTERNOON. WINDS WILL BE CALM OVERNIGHT BECOMING
VERY LIGHT SLY BY AFTERNOON.

ELSEWHERE...SIMILAR CONDITIONS AS KCLT...ESP KGSP/KGMU. KHKY/KAND
SHUD SEE MVFR FOG OVERNIGHT...WITH LITTLE TO NO CHC OF LOW CLOUDS.
KAVL THE MAJOR EXCEPTION...AS USUAL...WITH ANOTHER ROUND OF VLIFR
EXPECTED. STATISTICAL GUIDANCE AND FCST SOUNDINGS ARE IN LINE WITH
THE RESTRICTIONS. SHUD BE A QUICK RETURN TO VFR WED MORNING...WITH
CONVECTIVE CU DEVELOPING ONCE AGAIN ALL AREAS. LIGHT WIND BECOMES
CALM OVERNIGHT THEN SSW WED AFTERNOON. KAVL WILL SEE NLY WIND DURING
THE MORNING AND SLY WIND FOR THE AFTERNOON.

OUTLOOK...FOG/VSBY CONCERNS REMAIN THURSDAY. A FRONT WILL APPROACH
ON FRIDAY WHICH COULD TRIGGER SOME SHOWERS AND THUNDERSTORMS...WITH
ASSOCIATED RESTRICTIONS POSSIBLE. VFR RETURNS ON SATURDAY.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH  94%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     MED   74%     MED   69%     HIGH 100%
KHKY       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH  97%     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...JPT
NEAR TERM...JAT/RWH
SHORT TERM...ARK
LONG TERM...JPT
AVIATION...RWH






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