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Area Forecast Discussion

426
FXUS62 KGSP 241418
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1018 AM EDT THU APR 24 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE EASTERN SEABOARD TODAY THROUGH
TONIGHT AS A COLD FRONT AND UPPER LEVEL DISTURBANCE APPROACH FROM
THE WEST. THE COLD FRONT WILL CROSS THE AREA ON FRIDAY...WITH DRY
HIGH PRESSURE RETURNING THROUGH THE WEEKEND. A WET AND POSSIBLY
STORMY PATTERN WILL SET UP MONDAY THROUGH WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 1015 EST THURSDAY...A LOW AMPLITUDE UPPER RIDGE EXTENDED FROM THE
GULF OF MEXICO TO THE GREAT LAKES...WITH TROUGHS OFF THE EAST COAST
AND OVER THE GREAT PLAINS. A STATIONARY FRONT WAS LOCATED ALONG THE
GULF COAST...AND A COLD FRONT OVER THE PLAIN.

SURFACE HIGH PRESSURE WAS LOCATED ALONG THE EASTERN SEABOARD...AND
IS PROJECTED TO PUSH OFF THE COAST THIS AFTERNOON. SATELLITE IMAGERY
SHOWED A CLEAR SKY OVER NE GA AND THE WESTERN CAROLINAS. MODEL TIME
HEIGHTS SUGGEST A SLIGHT INCREASE IN CLOUDS COVER AS WINDS VEER TO
THE SE AND LOW LEVEL MOISTURE STARTS TO INCREASE...BUT NO
PRECIPITATION IS EXPECTED.

HIGH RES MODELS GENERALLY AGREE THAT ORGANIZED CONVECTION ASSOCIATED
WITH THE APPROACHING COLD FRONT WILL MAKE A RUN A THE NC MTNS
OVERNIGHT. THE STORMS LOOK TO TAKE ON A LINEAR MODE...BUT LOSE STEAM
AS THEY CROSS ERN TENN DURING THE WEE MORNING HOURS. THE DAY 1
CONVECTIVE OUTLOOK FROM SPC DOES SHOW A SLGT RISK TO OUR WEST...WITH
GENERAL THUNDER RISK FROM CENTRAL TN TO THE NC MTNS. I WILL KEEP
SOME POPS CREEPING INTO THE WRN ZONES LATE TNGT...WITH THE EXPECTED
ARRIVAL OF AT LEAST WEAKENED SHWRS TO THE SMOKIES BEFORE DAYBREAK
FRIDAY. OTHERWISE...EXPECT AN INCREASE IN CLOUDS...AND TEMPS ONLY
DROPPING INTO THE 50S MOST PLACES.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 300 AM EDT THU...A DEAMPLIFYING BUT COHERENT MID LEVEL
SHORTWAVE TROUGH WILL MOVE QUICKLY EAST THROUGH THE WRN CAROLINAS ON
FRI. DECAYING CONVECTION MAY BE IN PLACE ACROSS THE MOUNTAINS AS THE
PERIOD BEGINS FRI MORNING...BUT ADDITIONAL SHOWER AND TSTM
DEVELOPMENT IS LIKELY ACROSS THE FOOTHILLS AND PIEDMONT THROUGH MID
AFTERNOON PRIOR TO FROPA. THE BEST INSTABILITY SHOULD LINE UP OVER
SE PIEDMONT SECTIONS FRI AFTN...WITH 0 TO 3 KM BULK SHEAR VALUES
AROUND 30 KT. THIS MIGHT BE JUST ENOUGH FOR THUNDERSTORM
ORGANIZATION...BUT PROBABLY NOT ENOUGH FOR A SIGNIFICANT SEVERE WX
THREAT. SCATTERED SHOWERS MAY LINGER ACROSS THE WRN MTNS INTO EARLY
FRI EVENING IN BRIEF MOIST UPSLOPE FLOW.

UPPER LEVEL RIDGING WILL THEN BUILD OVER THE ERN CONUS AND
STRENGTHEN THROUGH THE WEEKEND. THERE SEEMS TO BE SLIGHTLY BETTER
CONSENSUS ON AN APPROACHING BACK DOOR COLD FRONT STALLING N OF THE
REGION OVER VA THROUGH SUNDAY. DESPITE THE WEAK FROPA ON FRI...MAXES
WILL BE HIGHER SAT AND SUNDAY IN BETTER INSOLATION.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 300 AM EDT THU...A DEEP LOW PRESSURE SYSTEM OVER THE CENTRAL
PLAINS BY THE END OF THE WEEKEND WILL GRADUALLY FILL AS IT WOBBLES
EWD TOWARD THE MIDWEST MON THROUGH WED. THE DOWNSTREAM RIDGE AXIS
WILL MOVE TO THE ERN SEABOARD SUNDAY NIGHT...WITH HEIGHTS FALLING
THROUGH THE REMAINDER OF THE LONG TERM PERIOD. GRADUALLY BUILDING SW
FLOW AND BANDS OF MOISTURE AND LIFT EJECTING EASTWARD FROM THE DEEP
VORTEX WILL BE HARD TO TIME THROUGH THE PERIOD. THE BEST MOISTURE
AND UPPER SUPPORT SHOULD LEAN TOWARD THE TUE THROUGH WED PERIOD AS A
BETTER UPPER JET STRUCTURE EAST OF THE CLOSED SYSTEM WILL LIKELY BE
IN PLACE NEAR THE APPALACHIANS. PERIODS OF HEAVY RAIN WILL BE
POSSIBLE AT SOME POINT...PROBABLY TUE OR WED...BUT THAT TIMING
CANNOT BE PINNED DOWN YET. EXPECT SLIGHTLY ABOVE NORMAL TEMPS ON
MONDAY...NEAR CLIMO TUE...AND LOWER THAN NORMAL MAXES BY WED.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
KCLT AND ELSEWHERE...VFR CONDITIONS TODAY AND INTO THIS EVENING...AS
DRY HIGH PRES SLIDES EAST ACRS THE AREA. THE WINDS WILL VEER FROM NE
TO SE AROUND MIDDAY OR EARLY AFTN. WINDS SHUD REMAIN FAIRLY
LIGHT...GENERALLY UNDER 10 KTS. OTHER THAN OCCASIONAL FILAMENTS OF
CIRRUS...IT SHUD BE SKC THRU THIS AFTN. THEN CLOUDS WILL INCREASE IN
COVERAGE AND THICKNESS EARLY THIS EVENING THRU THE OVERNIGHT...AS A
COLD FRONT APPROACHES FROM THE WEST. MODEL GUIDANCE SEEMS TO AGREE
ON MVFR STRATUS DEVELOPING WITHIN INCREASING SWLY LLVL FLOW AHEAD OF
THE FRONT BEFORE DAYBREAK FRIDAY. A BAND OF SHWRS AND DECAYING TSTMS
IS PROGGED TO CROSS THE TENN VALLEY OVERNIGHT...AND ENTER THE NC
MTNS BEFORE 12Z. CONFIDENCE ON ANY PRECIP AT KAVL BEFORE END OF TAF
PERIOD TOO LOW TO ADD TO THE TAF FOR NOW.

OUTLOOK...A COLD FRONT WITH POTENTIAL FOR SHOWERS/TSTMS IS EXPECTED
TO CROSS THE REGION FRIDAY. THEN DRY HIGH PRES RETURNS SATURDAY THRU
SUNDAY. INCREASED MOISTURE RETURNS TO THE REGION EARLY NEXT WEEK.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-14Z
KCLT       HIGH 100%     HIGH 100%     HIGH  95%     HIGH  89%
KGSP       HIGH 100%     HIGH 100%     HIGH  94%     HIGH  98%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  88%
KHKY       HIGH 100%     HIGH 100%     HIGH  94%     HIGH  96%
KGMU       HIGH 100%     HIGH 100%     HIGH  95%     HIGH  98%
KAND       HIGH 100%     HIGH 100%     HIGH  90%     HIGH  88%

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/JAT
SHORT TERM...HG
LONG TERM...HG
AVIATION...ARK






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