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000
FXUS62 KGSP 211044
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
644 AM EDT MON APR 21 2014

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN OVER THE REGION TODAY. A COLD FRONT WILL
CROSS THE AREA FROM THE WEST ON TUESDAY...WITH DRY HIGH PRESSURE
RETURNING WEDNESDAY THROUGH THURSDAY. ANOTHER COLD FRONT WILL REACH
THE REGION BY FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 645 AM...UPDATED THE T/TD GRIDS WITH THE LATEST OBS...AND
TWEAKED AVIATION GRIDS FOR THE 12Z TAFS. OTHERWISE...FCST LOOKS ON
TRACK AND NO OTHER CHANGES NEEDED.

AS OF 205 AM...A QUIET NEAR TERM IS EXPECTED...AS SHARP UPR RIDGE
AXIS TRANSLATES EAST ACRS THE CWFA. AN INVERTED SFC RIDGE AXIS ALSO
REMAINS INVOF THE REGION...RESULTING IN LGT NE FLOW EAST OF THE MTNS
AND DRY CONDITIONS. THERE MAY BE SOME PATCHY FROST IN THE NORTHERN
MTNS...BUT NOTHING WIDESPREAD ACRS THE REST OF THE HIGH TERRAIN TO
WARRANT A FROST ADVISORY. TEMPS CURRENTLY LOOK ON TRACK.

TEMPS WILL CONTINUE TO REBOUND UNDER SUNNY SKIES AND LIGHT WINDS
TODAY. EXPECTING HIGHS TO BE ABOUT A CATEGORY ABOVE NORMAL...MAINLY
IN THE MID-UPR 70S ACRS THE AREA.

TONIGHT...MID AND UPR LVL HEIGHTS WILL FALL WITH AN APPROACHING
LATITUDINAL TROF AND ASSOCIATED COLD FRONT. THERE WILL BE AN
INCREASE IN MID-HIGH CLOUDS AND EVEN SOME STRATO-CU DEVELOPMENT IN
THE SW NC MTNS OVERNIGHT...KEEPING TEMPS ELEVATED ABOVE NORMAL IN
THE UPR 40S MTNS AN IN THE 50S PIEDMONT. GUIDANCE IN PRETTY GOOD
AGREEMENT ON SCATTERED SHOWERS ALONG/AHEAD OF THE FRONT CROSSING THE
OH/TN VALLEYS. A SLGT CHC TO LOW-END CHC POP WILL CREEP TO THE TN/NC
BORDER BEFORE DAYBREAK TUESDAY. OTHERWISE...IT SHUD BE DRY OVERNIGHT.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
AS OF 205 AM EDT MONDAY...THE UPPER TROUGH THAT WILL CROSS THE ERN
U.S. ON TUE IS NOT PARTICULARLY AMPLIFIED OR COHERENT...BUT IT
SHOULD BE ACCOMPANIED BY SOME DEGREE OF UPPER LEVEL DIVERGENCE TUE
AFTN. THE WEAK UPPER FORCING AND LOW LEVEL CONVERGENCE ALONG THE
PASSING COLD FRONT SHOULD COMBINE WITH MODEST SFC BASED INSTABILITY
TO CREATE SCATTERED TO NUMEROUS COVERAGE OF SHOWERS AND TSTMS
THROUGH TUE AFTN. THE SEVERE TSTM THREAT LOOKS RATHER LIMITED BY THE
TALL SKINNY CAPE IN AREA MODEL PROFILES ALONG WITH MODEST 25 TO 30
KT SFC TO 3 KM SHEAR VALUES IN THE WESTERLY FLOW. HOWEVER...THE SPC
CALIBRATED SREF SEVERE TSTM PROBABILITIES CONTINUE TO POINT TO A NW
NC PIEDMONT MAXIMA...WHERE SFC INSTABILITY HAS JUST ENOUGH OVERLAP
WITH THE BEST WESTERLY SHEAR AND UPPER FORCING FOR A SLIGHTLY
GREATER SVR THREAT. THERE IS NOT ENOUGH CONFIDENCE FOR AN HWO
MENTION OF SEVERE TSTMS AT THIS POINT.

EXPECT BREEZY TO WINDY CONDITIONS POST FROPA TUE NIGHT INTO WED
MORNING. BROAD RIDGING WILL THEN RETURN WED THROUGH THU WITH DRY
CONDITIONS AND NEAR CLIMO MAXES AND MINS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
AS OF 205 AM EDT MONDAY...A NRN TIER VORTEX CROSSING THE GREAT LAKES
ON FRI WILL NOT PROVIDE MUCH AMPLIFICATION TO THE TROUGH OVER THE
SRN TIER STATES. IN ADDITION...MOISTURE LOOKS SOMEWHAT LIMITED WITH
THE FRI SFC FRONT/TROUGH PASSAGE. HOWEVER...INSTABILITY IS RATHER
ROBUST ON BOTH THE GFS AND ECMWF SOLUTIONS ACROSS THE PIEDMONT FRI
AFTN AND ABOUT 40 KT OF DEEP LAYER SHEAR IS EVIDENT IN PROFILES.
LITTLE CHANGE WILL BE MADE TO THE LATE WEEK FORECAST...WITH CHC POPS
FOR TSRA THROUGHOUT THE REGION ON FRI.

BROAD TROUGHING WILL LIKELY LINGER INTO SAT OVER THE EAST...WITH A
SECONDARY COLD FRONT FEATURING A BETTER THERMAL CONTRAST APPROACHING
FROM THE N. THIS FRONT WILL LIKELY STALL IN OR NEAR THE FORECAST
AREA OVER THE WEEKEND. THE POSITION OF THE BOUNDARY WILL DETERMINE
WHERE INSTABILITY LINGERS/RETURNS AND THIS WILL BE DIFFICULT TO
PROJECT THAT FAR OUT IN THE FORECAST. WILL KEEP MAINLY ISOLD TO SCT
DIURNAL CONVECTIVE CHANCES GOING OVER THE WEEKEND FOR PRIMARY MTN
AND SW SECTIONS.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED FOR THE NEXT 24
HOURS AT ALL TAF SITES...AS SFC HIGH PRES AXIS TRANSLATES EAST ACRS
THE AREA. IT SHUD BE GENERALLY SKC OR FEW/SCT250 INTO EARLY
AFTN...THEN HIGH CLOUDS WILL BEGIN TO THICKEN/LOWER WITH APPROACH OF
AN UPR DISTURBANCE AND COLD FRONT. THE WINDS WILL BE LIGHT AND FAVOR
A N/NE DIRECTION UNTIL ABOUT NOON...THEN SHIFT TO FAVORING SW FOR
THE AFTN/EVE. MID CLOUDS OR HIGH-BASED STRATO-CU ARE EXPECTED TO
BEGIN DEVELOPING ACRS THE REGION TONIGHT...AS MOISTURE INCREASES
FROM THE WEST. SO NOT EXPECTING MUCH FOG POTENTIAL TONIGHT.
SCATTERED SHOWERS WITH THE FRONT WILL APPROACH THE NC MTNS...BUT NOT
EXPECTED TO REACH KAVL UNTIL AFTER 12Z TUESDAY.

OUTLOOK...A FAIRLY WET FRONTAL SYSTEM...WITH PIEDMONT
THUNDERSTORMS...IS EXPECTED ON TUE. DRY HIGH PRES RETURNS FOR
WEDNESDAY/THURSDAY. ANOTHER COLD FRONT WITH POTENTIAL FOR
SHOWERS/TSTMS IS THEN EXPECTED TO CROSS THE REGION FRIDAY.

CONFIDENCE TABLE...

            10-16Z        16-22Z        22-04Z        04-10Z
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...HG
NEAR TERM...ARK
SHORT TERM...HG
LONG TERM...HG
AVIATION...ARK