Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 051441
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1041 AM EDT THU MAY 5 2016

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE REGION EARLY IN THE DAY AND WILL
USHER IN MORE COOL AIR FROM THE NORTHWEST. THE WEATHER WILL REMAIN
UNSETTLED BEHIND THE FRONT AS A DEEP UPPER LOW CENTER MOVES DOWN
ACROSS THE CAROLINAS TODAY AND TONIGHT...AND THEN MOVES AWAY TO THE
NORTHEAST ON FRIDAY. ANOTHER FRONT IS EXPECTED TO STALL JUST TO OUR
NORTH ON SATURDAY AND SUNDAY. THE FRONT SHOULD LIFT BACK TO THE
NORTH ON MONDAY...AS HIGH PRESSURE OFF THE SOUTHEAST COAST EXPANDS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM...CENTER OF 500MB LOW CURRENTLY CENTERED INVOF THE
KY/VA/TN INTERSECTION...AND IS STILL PROGGED TO SWING ACROSS THE
WESTERN CAROLINAS AND NE GA THIS AFTERNOON. ONE OF THE VORT LOBES
CIRCLING THE LOW PRODUCED SHOWERS OVER THE I-77 CORRIDOR MUCH OF
THE MORNING SO FAR...BUT AS THIS FEATURE MOVES EAST THE SHOWERS
ARE FOLLOWING SUIT. A SCATTERING OF SHOWERS OVER EAST TN AND THE
CUMBERLAND PLATEAU IS EXPECTED TO MOVE SEWD INTO THE NC MTNS
AND THEN INTO THE SAVANNAH RIVER VALLEY AND WRN UPSTATE LATER
THIS AFTN. HRRR AND OTHER CAMS CONTINUE TO DEPICT SCT SHRA/TSRA
CONCENTRATING IN THE LATTER AREAS DURING PEAK HEATING. I REVISED
POP TRENDS INTO TONIGHT ACCORDINGLY.

NAM INDICATES THAT MIXED LAYER WILL LIKELY EXCEED 10 KFT ACROSS
PIEDMONT LOCATIONS THIS AFTERNOON. THE DEEP MIXING COMBINED WITH
A 4 TO 5 MB PRESSURE GRADIENT WILL RESULT IN GUSTY WINDS BY MID
MORNING...REMAINING INTO THE EARLY EVENING ACROSS THE MTNS. 25-30
KT GUSTS WILL CONTINUE OVER THE MTNS TODAY. I WILL INCLUDE A
HEADLINE FOR CAUTION ON MTN LAKES THROUGH EARLY THIS EVENING.
OTHERWISE...THE FORECAST CHALLENGE WILL BE THE PLACEMENT AND
TIMING OF SHOWERS AND THUNDERSTORMS TODAY. CAMS TO THE SPECTRAL
INDICATE THE GREATEST COVERAGE ACROSS THE UPPER SAVANNAH RIVER
VALLEY...MTNS...AND I-40 CORRIDOR THIS AFTERNOON AND EVENING. NAM
SHOWS A FIELD OF 300-500 J/KG CAPE DEVELOPING DURING THE HEAT
OF THE AFTERNOON...YIELDING SMALL HAIL PRODUCING SHOWERS AND
STORMS. HIGH TEMPERATURES ARE FORECAST TO REMAIN AROUND 10 DEGREES
BELOW NORMAL...WITH MID 50S NEAR KAVL TO LOW TO MID 60S ALONG AND
EAST OF I-85.

TONIGHT...SHOWERS WILL REMAIN ACROSS THE MTNS AND NC FOOTHILLS AND
PIEDMONT OVERNIGHT. OMEGA BLOCK WILL LINGER ACROSS THE CONUS AS THE
EASTERN CLOSED LOW LIFTS NORTH OVER THE MID ATLANTIC STATES. LOW
TEMPERATURES WILL REMAIN COOL...WITH 30S TO LOW 40S ACROSS THE
MTNS AND UPPER 40S ACROSS THE FOOTHILLS AND PIEDMONT.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 AM THURSDAY...THE MODEL GUIDANCE KEEPS THE UPPER LOW IN
CLOSE ENOUGH PROXIMITY ON FRIDAY THAT THE MID LEVEL COOL POOL WILL
REMAIN OVER THE EASTERN ZONES WHILE WEAK VORT CENTERS DROP DOWN FROM
THE NORTH. THE COLD AIR ALOFT WILL KEEP ENOUGH INSTABILITY ACROSS
THE EASTERN HALF OF THE FORECAST AREA TO ACCOUNT FOR ISOLATED TO
SCATTERED SHOWERS....WHILE UPSLOPE FLOW WILL FORCE SOME SHOWER
ACTIVITY MAINLY OVER THE NRN MOUNTAINS. AS THE UPPER LOW PULLS
OUT...THE PRECIP CHANCES SHOULD DIMINISH THROUGH FRIDAY NIGHT. TEMPS
ARE EXPECTED TO BEGIN A REBOUND AS THE LOW PULLS AWAY...AND THEN GET
BACK CLOSE TO NORMAL ON SATURDAY. SOME OF THE MODEL GUIDANCE SHOWS
PRECIP ENCROACHING ON THE NRN ZONES ON SATURDAY AND THIS WAS KEPT IN
THE FCST ON OUR NRN FRINGES BASED ON NEIGHBORING FCSTS. PRECIP
CHANCES WILL START CREEPING UP FROM THE NORTH AS A COLD FRONT SAGS
DOWN TOWARD THE AREA SATURDAY NIGHT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 315 AM THURSDAY...THE MODELS INDICATE A CHANGE IN THE
MID/UPPER LEVEL PATTERN THAT FAVORS A RETURN TO SOMETHING MORE
TYPICAL OF MID/LATE SPRING. THE DEEP UPPER TROF OVER THE NORTHEAST
SHOULD LIFT OUT ON SUNDAY AND SUNDAY NIGHT ALLOWING A FLAT UPPER
RIDGE TO MOVE IN FROM THE LOWER MS VALLEY. THIS SHOULD HELP LIFT A
SURFACE BOUNDARY BACK TO THE NORTH EARLY IN THE PERIOD AND SET THE
STAGE FOR TEMPS TO RETURN TO SOMETHING ON THE ORDER OF FIVE DEGREES
ABOVE NORMAL. FROM THE EARLY PART OF THE WEEK ONWARD...THE SOUTHEAST
WILL BE UNDER A WSW OR NEARLY ZONAL UPPER FLOW WITH SURFACE HIGH
PRESSURE OFF THE COAST THAT WILL PROVIDE FOR RETURN MOISTURE FROM
THE GULF. WHAT REMAINS TO BE SEEN IS THE EXTENT OF ANY DIURNALLY-
DRIVEN CONVECTION FROM TUESDAY ONWARD. THE FCST CONTINUES TO REFLECT
A MORE ECMWF-LIKE SOLUTION WITH THE PRECIP CHANCE OVER THE MTNS...
WHILE THE GFS HAS A CHANCE ACROSS THE WHOLE AREA. TEMPS WILL REMAIN
ABOVE NORMAL.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE EAST OF THE MTNS...VFR CONDITIONS WILL
GENERALLY CONTINUE THRU THE PERIOD. AT THE MID LEVELS...THE CORE OF
A CLOSED LOW WILL PASS OVER THE WESTERN CAROLINAS THIS
AFTERNOON...PASSING EAST THIS EVENING. AS THE LOW APPROACHES THIS
MORNING...SCT SHRAS WILL REMAIN NEAR KHKY AND KCLT DURING THE EARLY
DAYLIGHT HOURS. AT THE SFC...THE FOOTHILLS AND PIEDMONT WILL REMAIN
BETWEEN LOW PRESSURE CENTERED NEAR THE NC OUTERBANKS AND HIGH
PRESSURE OVER THE GREAT PLAINS. THIS PATTERN WILL PROVIDE THE REGION
WITH NW WINDS AND DEEP MIXING. MOMENTUM TRANSFER FROM AS DEEP AS 10
KFT APPEARS POSSIBLE THIS AFTERNOON. I WILL FEATURE GUSTS FOR ALL
SITES 3 TO 4 HOURS FOLLOWING SUNRISE. STEEP LAPSE RATES AND MARGINAL
FORCING MAY YIELD SCT SHRAS DURING THE AFTERNOON TO EARLY
EVENING...I WILL HIGHLIGHT WITH A PROB30 OR TEMPO. WINDS ARE FORECAST TO
WEAKEN TO 6 TO 10 KTS BETWEEN 23Z TO 2Z.

AT KAVL...NNW WINDS WILL INCREASE RAPIDLY AFTER SUNRISE...WITH
FREQUENT GUSTS INTO THE MID 20S KTS. SCT SHRAS MAY OCCASIONALLY PASS
OVER THE TERMINAL DURING THE AFTERNOON...WITH MVFR VIS AND CEILINGS.
GUSTY NNW WINDS MAY CONTINUE INTO THE MID EVENING...THEN SETTLE TO
10KTS TO 14 KTS BY 3Z.

OUTLOOK...THE UPPER LOW MOVES EAST OF THE AREA FRIDAY...BUT MOISTURE
AND INSTABILITY LINGER BRINGING SHRA AND TSRA MAINLY ACROSS THE NC
SITES. DRY HIGH PRES RETURNS SATURDAY...WHILE ANOTHER COLD FRONT
APPROACHES FROM THE NORTH THRU SUNDAY.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  82%
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 SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...PM
NEAR TERM...NED/WIMBERLEY
SHORT TERM...PM
LONG TERM...PM
AVIATION...NED


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