Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 232054
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
454 PM EDT WED APR 23 2014

.SYNOPSIS...
DRY HIGH PRESSURE...CENTERED NEAR THE GREAT LAKES...WILL CONTROL OUR
WEATHER THROUGH THURSDAY. A WEAK COLD FRONT WILL CROSS THE FORECAST
AREA ON FRIDAY...WITH A REINFORCING FRONT STALLING IN THE VICINITY
OF THE REGION OVER THE WEEKEND. A WET AND POSSIBLY STORMY PATTERN
WILL SET UP FOR EARLY NEXT WEEK...FOLLOWED BY COOLER WEATHER.

&&

.NEAR TERM /THROUGH THURSDAY/...
AT 445 PM... HIGH PRESSURE CENTERED TO OUR NORTH AND UPPER LEVEL
RIDGE TO THE WEST CONTINUE THE FAIR WEATHER ACROSS THE REGION.
REMAINING GUSTINESS IN THE SURFACE WINDS WILL DIMINISH QUICKLY
AROUND SUNSET. ONLY CHANGES TO FORECAST AT THIS TIME TAKE INTO
ACCOUNT CURRENT TEMPERATURES AND DEWPOINTS.

PREVIOUS DISCUSSION...
AS OF 150 PM...WEAKENING PRESSURE GRADIENT HAS RESULTED IN MID TO
UPPER TEEN WIND GUSTS ACROSS THE MTNS AND NC FOOTHILLS/PIEDMONT THIS
AFTERNOON. LATEST OBSERVATIONS INDICATED A NOTICEABLE DROP IN RH
VALUES ACROSS THE REGION...ESPECIALLY ACROSS PIEDMONT AREAS. THE
FIRE DANGER STATEMENT CONTINUES TO LOOK WELL PLACED AND TIMED ACROSS
THE NC ZONES.

OVERNIGHT...DRY HIGH PRESSURE WILL RIDGE ACROSS THE WESTERN
CAROLINAS AS A COLD FRONT SLIDES ACROSS OK/TX. WINDS ARE FORECAST TO
REMAIN LIGHT FROM THE NE OR BECOME CALM DURING THE PRE DAWN HOURS.
THE LIMITED MIXING AND CLEAR/MOSTLY CLEAR SKY COVER WILL FAVOR
RADIATIONAL COOLING. HOWEVER...SOUTH H85 WINDS AROUND 15KTS AND LOW
AMPLITUDE RIDGING MAY PROVIDE WEAK LLVL WAA ACROSS THE SOUTHERN
APPALACHIANS. GIVEN THE WEAK WAA...I WILL INDICATE A SLIGHT INVERSE
LAPSE RATE IN THE MIN TEMPERATURE ACROSS THE MTNS. BLENDING OF THE
PREFERRED GUIDANCE SUPPORTS MIN TEMPERATURES BETWEEN 3 TO 6 DEGREES
BELOW NORMAL. I WILL INDICATE UPPER 30S ACROSS THE MTNS AND NC
FOOTHILLS...WITH LOW 40S ACROSS THE I-40 CORRIDOR...WITH MID TO
UPPER 40S ACROSS THE UPPER SAVANNAH RIVER VALLEY AND UPSTATE. PATCHY
FROST IS POSSIBLE WITHIN THE MTNS VALLEYS...BUT BELOW FROST ADVISORY
CRITERIA.

THURSDAY...THE COLD FRONT WILL SWEEP EAST ACROSS THE
ARKLATX...GRADUALLY INCREASING THE RETURN FLOW ACROSS THE FORECAST
AREA. DEWPOINTS ARE FORECAST TO RECOVER 5 TO 10 DEGREES FROM THIS
AFTERNOON. HIGH TEMPERATURES ARE FORECAST TO RANGE WITHIN 1 TO 2
DEGREES OF NORMAL...RESULTING IN RH VALUES IN THE 30S.
OVERALL...CONDITIONS SHOULD REMAIN DRY WITH MOSTLY SUNNY CONDITIONS.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 240 PM WED...A RELATIVELY STRONG SHORT WAVE APPROACHES THE
AREA THU NITE AND CROSSES THE AREA FRI. THIS WAVE WILL PUSH A COLD
FRONT ACROSS THE AREA FRIDAY AS WELL. MOISTURE AND ISENTROPIC LIFT
INCREASE THU NITE...BRINGING CHC POP TO THE MTNS AND FOOTHILLS AFTER
MIDNIGHT. GOOD FORCING MOVES IN FRI MORNING WITH THE FRONT AND SHORT
WAVE...BRINGING LIKELY POP TO THE MTNS AND GOOD CHC POP TO THE I-40
CORRIDOR. FORCING AND DEEP MOISTURE IS A LITTLE LOWER OVER NE GA AND
THE WESTERN UPSTATE. THEREFORE...HAVE LIMITED POP TO 40 PERCENT OVER
ALL BUT THE MOUNTAIN PORTIONS. BEST CHC POP SHIFTS TO THE I-77
CORRIDOR FOR THE AFTERNOON AS THE FRONT MOVES INTO THAT AREA. THE
GFS STILL HAS MORE INSTABILITY THAN THE NAM...BUT ITS VALUES HAVE
DECREASED. WHILE THERE WILL BE SOME SHEAR GIVEN THE STRENGTH OF THE
SHORT WAVE AND COLD FRONT...IT GENERALLY REMAINS IN THE LIGHT RANGE.
THEREFORE...ALTHOUGH SCT THUNDERSTORMS WILL DEVELOP...SEVERE STORM
POTENTIAL IS LOW. QPF AMOUNTS ARE NOT EXPECTED TO BE EXCESSIVE
EITHER. TEMPS WILL BE AROUND 5 DEGREES ABOVE NORMAL.

PRECIP WILL QUICKLY TAPER OFF EARLY FRI EVENING AS THE FRONT MOVES
EAST OF THE AREA. A LOW AMPLITUDE UPPER TROF WILL CROSS THE AREA SAT
AS AN UPPER LOW MOVES FROM THE GREAT LAKES INTO NEW ENGLAND. AT THE
SFC...HIGH PRESSURE BUILDS IN BRIEFLY BEFORE A WEAK BACK DOOR COLD
FRONT APPROACHES FROM THE NORTH BY THE END OF THE DAY. THE RESULT
WILL BE DRY WX AND MOSTLY SUNNY SKIES. LOWS WILL RANGE FROM NEAR
NORMAL TO 5 DEGREES ABOVE NORMAL. HIGHS WILL BE 5 TO 10 DEGREES
ABOVE NORMAL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 240 PM EDT WED...THE EXTENDED PART OF THE FORECAST STARTS WITH
A DEEP-LAYER SHORTWAVE RIDGE TRANSLATING ACROSS THE REGION. THIS
SHOULD BRING FAIR AND MILD WEATHER. HOWEVER...THE MODELS HAVE BEEN
TRADING OFF RUN TO RUN AS TO WHETHER A BACK DOOR COLD FRONT CROSSES
THE REGION...BRINGING WITH IT COOLER AND POTENTIALLY CLOUDY WEATHER
IN THE FORM OF COLD AIR DAMMING. FOR NOW I STAYED WITH THE WARMER
AND DRIER EC SOLUTION.

BY MONDAY PW/S BEGIN TO INCREASE ON THE GFS AND LLVL ISENTROPIC
UPGLIDE AND UPSLOPE FLOW DEVELOPS. THE ECMWF IS A LITTLE
SLOWER...THOUGH IT HAS BASICALLY THE SAME SOLUTION. AGAIN...THERE
ISN/T MUCH TO DISAGREE WITH CONCERNING THE WPC GRIDS AND I HAVE
MOSTLY CLOUDY SKIES AND A CHANCE OF SHOWERS. INSTABILITY WILL BE
LIMITED AND ONLY A SMALL CHANCE OF TSTMS IS EXPECTED. BY MONDAY
NIGHT AND TUESDAY THE GFS PW/S INCREASE TO ALMOST 1.75 INCHES AND
THERE IS A CONSIDERABLE INCREASE IN THE LLVL FLOW. WE SHOULD ALSO BE
UNDER STRONG UPPER DIVERGENCE AS A UPPER TROPOSPHERIC JET MAX SHIFTS
EASTWARD UNDER A BROAD UPPER LOW THAT WILL BE CENTERED OVER
MISSOURI. THE POTENTIAL EXISTS FOR HEAVY RAIN LATER MONDAY INTO
TUESDAY. THERE MAY ALSO BE A SEVERE THREAT...THOUGH THE MOIST
WORKED-OVER AIRMASS AND GENERALLY VEERED LLVL FLOW DOESN/T SEEM
CONDUCIVE TO THE HIGH END SEVERE THREAT THAT WILL AFFECT THE PLAINS
WITH THE SYSTEM OVER THE WEEKEND. OF COURSE IT IS STILL QUITE EARLY
TO GET TOO CUTE WITH THE CHANCES OF SEVERE WEATHER FOR THE MON/TUE
PART OF THE FORECAST.

CONFIDENCE IN THE DAY 7 PART OF THE FORECAST IS LOW AS THERE WILL BE
SEVERAL CHUNKS OF SHORT WAVE ENERGY EMBEDDED WITHIN THE BROAD UPPER
LOW THAT WILL SLOWLY CROSS INTO THE EASTERN CONUS. ALL THE MODELS
AGREE THAT THERE WILL BE CONSIDERABLE DOWNSTREAM BLOCKING...SO THE
TROUGH SHOULD DEFINITELY PARK OVER THE REGION FOR A FEW DAYS.
HOWEVER...DEPENDING ON THE TIMING AND HOW ADVECTIVE INDIVIDUAL SHORT
WAVES ARE...THERE MIGHT BE A CHANCE FOR SOME ORGANIZED SEVERE
WEATHER WITH THE COOLING HEIGHTS.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
KCLT AND ELSEWHERE...VFR. THE CENTER OF CANADIAN HIGH PRESSURE
LOCATED OVER THE GREAT LAKES REGION THIS EVENING WILL LIKELY SPLIT
TONIGHT...WITH THE SOUTHERN CENTER REACHING THE CAROLINA COAST BY
18Z THURSDAY. THIS PATTERN WILL YIELD VEERING WINDS THROUGH THE
PERIOD...RANGING FROM NW THIS AFTERNOON TO SE BY THURSDAY AFTERNOON.
WIND SPEEDS MAY REMAIN AROUND 10 KTS UNTIL SUNSET THIS
EVENING...BECOMING LIGHT NE TO CALM TONIGHT...THEN INCREASING 5 TO
10 KTS THURSDAY MORNING. FEW CIRRUS CLOUDS AND CONTRAILS EXPECTED ON
THURSDAY.

OUTLOOK...ANOTHER COLD FRONT WITH POTENTIAL FOR SHOWERS/TSTMS IS
THEN EXPECTED TO CROSS THE REGION FRIDAY...DRYING OUT BY SATURDAY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
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

&&

.FIRE WEATHER...
THE FIRE DANGER STATEMENT WILL REMAIN IN PLACE UNTIL EXPIRATION AS
THE VERY LOW RH VALUES AND LOW END WIND GUSTS CONTINUE INTO THE
EARLY EVENING. RH VALUES SHOULD RECOVER THU WITH LOWER TEMPS AND
INCREASED DEW POINTS.

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...LGL/NED
SHORT TERM...RWH
LONG TERM...MCAVOY
AVIATION...LGL/NED
FIRE WEATHER...






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