Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 151834
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
234 PM EDT TUE APR 15 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE OFF THE CAROLINA COAST TONIGHT AS
UNSEASONABLY COLD HIGH PRESSURE BUILDS ACROSS OUR REGION AND REMAINS
INTO FRIDAY. A DEEP UPPER TROUGH ARRIVES FROM THE WEST TO START THE
WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 230 PM EDT TUESDAY...SHOWERS AND A FEW TSTMS WILL MOVE EAST
OF THE FORECAST AREA BY AROUND 6 PM. SO FAR WE HAVE ONLY SEE
GARDEN VARIETY CONVECTION. AS THERE HAS BEEN NO CLEARING AHEAD OF
THE LINE...I/D EXPECT THE SAME THING AT LEAST UNTIL THE STORMS
MOVE EAST OF THE I-77 URBAN CORRIDOR. OVER THE NC MTNS RAIN
SHOWERS HAVE CHANGED OVER TO SNOW SHOWERS IN SEVERAL
AREAS...THOUGH THE PCPN WILL BE ENDING SHORTLY. STILL...SOME OF
THE HIGHER ELEVATIONS MAY SEE AROUND AN INCH OF WET SNOW. THIS IS
NOTHING THAT MERITS AN ADVISORY...BUT IT/S CERTAINLY A SHOCK AFTER
THE RECENT WARM WEATHER.

THE MODELS STILL HAVE AN ADVECTIVE FREEZE FOR MOST OF THE FA
OVERNIGHT. JUST ABOUT EVERY NAM BUFKIT SITE HAS THE SFC TEMPERATURE
FALLING BELOW FREEZING. AND UP TO THIS POINT THE NAM 2M METER RAW
TEMPERATURES HAVE DONE THE BEST JOB WITH THE COLD AIR BEHIND THE
FRONT. THEREFORE...CONFIDENCE REMAINS HIGH IN A FREEZE OVERNIGHT.
CERTAINLY SOME OF THE THERMAL BELT AREAS WILL STAY A LITTLE ABOVE
FREEZING...BUT FOR EVERY SPOT THAT DOES STAY ABOVE FREEZING...JUST A
FEW MILES AWAY THERE WILL BE A LOCATION THAT DOES FALL TO FREEZING.

WE HAVE HAD A FEW REPORTS OF VERY WINDY CONDITIONS IN THE FRENCH
BROAD VALLEY SO FAR THIS AFTN. WE ARE NOT SEEING MAY POWER OUTAGES
AND THE KAVL ASOS HAS GUSTED UP TO 37-38 KTS AT TIMES. ALL OF THIS
IS TYPICAL OF WIND ADVISORY CONDITIONS AND I/LL KEEP THE ADVISORY UP
THROUGH THE EVENING HOURS. CURRENTLY 3 HRLY PRESSURE RISES ARE
GENERALLY RUNNING AROUND 3 MB ACROSS THE MTNS. THIS IS LIKELY TO
INCREASE THIS EVENING AS THE UPPER TROF MOVES ACROSS THE
REGION...BUT THERE IS NOTHING IN THE PRESSURE TRENDS TO INDICATE
THAT WE WILL NEED TO UPGRADE TO HIGH WIND WARNING.

WEDNESDAY WILL SEE MAX TEMPS A GOOD 15 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR...ALBEIT UNDER SUNNY SKIES.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 210 PM TUESDAY...A DRY AND COOL ARIMASS WILL DOMINATE THE
WEATHER THROUGH THURSDAY. AT THE SURFACE...A CP HIGH CENTERED OVER NEW
ENGLAND WILL SLOWLY MOVE NORTHEAST...WITH A DRY WEDGE REMAINING
ALONG THE EAST SLOPES OF THE APPALACHIANS. 12Z MODELS CONTINUE TO
SHOW AN INCREASE IN MOISTURE ON FRI AS A SHORT WAVE TROUGH
APPROACHES FROM THE WEST AND WINDS VEER TO A MORE EASTERLY/UPSLOPE
COMPONENT. ALSO...CYCLOGENESIS IS STILL EXPECTED ALONG THE OLD
FRONTAL ZONE OVER THE CENTRAL GULF AS THE UPPER WAVE APPROACHES.
HOWEVER...WILL DISCOUNT THE CMH SOLUTION OF A MORE NORTHERN
DEVELOPMENT OF THE LOW AND SIGNIFICANT QPF EXTENDING NORTH INTO THE
AREA AND ACCEPT THE IDEA OF THE GFS/ECM THAT THE ASSOCIATED QPF WILL
STAY SOUTH OF THE AREA. THEREFORE EXPECT QPF ON FRIDAY TO BE MINIMAL
OR NON-EXISTANT. WILL HAVE SOME VERY LOW END POPS OVER THE MOUNTAINS
WHERE UPSLOPE FLOW COULD SQUEEZE OUT SOME SPRINKLES. THIS IDEA IS
SUPPORTED BY THE NAM/SREF.

THE HIGHEST IMPACT WEATHER THROUGH THE SHORT TERM WILL BE THE COLD
TEMPS AGAIN WED NIGHT. WITH VERY FAVORABLE RADIATIONAL COOLING
CONDITIONS ALONG WITH THE DRY AIRMASS...FROST/FREEZE CONDITIONS ARE
EXPECTED EARLY THU. FREEZING TEMPS ARE A GOOD BET ACROSS ALL OF THE
MOUNTAINS/FOOTHILLS AND PORTIONS OF THE PIEDMONT. WILL BE POSTING A
FREEZE WATCH FOR THE WESTERN NC COUNTIES AND EASTERN UPSTATE FOR WED
NIGHT BASED ON CURRENT MIN TEMP GRID. COULD BE SOME FREEZING TEMPS
IN THE NORMALLY COLDER UPSTATE AREAS OUTSIDE THE THERMAL BELT...BUT
PREFER NOT TO HAVE A SWISS CHEESE LIKE WWA. WILL INSERT FROST FOR
MOST AREAS WED NIGHT...THOUGH THE LOW DEWPOINTS/WIND WILL LIMIT THE
AMOUNT OF ACTUAL FROST. WITH INCREASING CLOUDS THU NIGHT...FROST
POTENTIAL SHOULD MINIMAL DESPITE CHILLY TEMPS ACROSS THE NORTH.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 200 PM TUESDAY...MEDIUM RANGE GUIDANCE INDICATES THAT A 500MB
TROF AXIS WILL SLOWLY CROSS THE SOUTHEAST STATES FROM WEST TO EAST
TO START THE WEEKEND. THE PASSAGE OF THE TROUGH MAY RESULT IN A
PERIOD OF UNSETTLED WEATHER FOR FRIDAY NIGHT AND SATURDAY.
HOWEVER...BOTH THE GFS AND ECMWF INDICATE THAT A LOW MAY DEVELOP OFF
THE SOUTHEAST COAST LATE FRIDAY AND SATURDAY...WITH A SECOND AREA OF
LOW PRESSURE ACROSS THE UPPER OHIO RIVER VALLEY. THE CANADIAN
CONTINUES TO BE THE WETTEST MODEL WITH A BROADER EXPANSE OF PRECIP
FROM THE LOW TO OUR SE GIVING AT LEAST A HALF INCH RAIN LATE FRIDAY
AND MOVING IT OUT BY LATE FRIDAY NIGHT. THE GFS AND ECMWF HAVE
LITTLE IF ANY PRECIP FOR THIS EVENT FOR OUR ENTIRE FORECAST AREA.
HIGH PRESSURE TRANSITIONING FROM THE NRN GREAT LAKES TO NRN NEW
ENGLAND WILL BE IN CONTROL OF OUR WEATHER SATURDAY AND SUNDAY.

THE NEXT SHORTWAVE WILL APPROACH SUNDAY NIGHT FROM THE WEST WITH THE
GFS BEING MOST PROGRESSIVE HAVING TROF AXIS NEAR NASHVILLE AT 12Z
MONDAY WHILE ECMWF HAS IT OVER FAR EASTERN OKLAHOMA AT THAT TIME.
THE TROF AXIS ON THE GFS WILL REACH OUR AREA AROUND 00Z TUES WHILE
THE ECMWF AXIS WILL NOT ARRIVE UNTIL DAYTIME TUESDAY. GFS GIVES NC
MTNS AT LEAST AN INCH QPF FROM SUNDAY NIGHT THROUGH MONDAY EVENING
WHILE ECMWF SLOWLY DISSIPATES ALL PRECIP WITH TOTAL LESS THAN A
QUARTER INCH FOR MTNS. THERE SHOULD BE A GOOD SOUTHERLY LOW LEVEL
WIND FLOW AHEAD OF THE TROF AXIS AND THIS WOULD ENHANCE UPSLOPE
SHOWERS. THUS HAVE HIGHER POPS IN UPSLOPE AREAS FROM RABUN COUNTY TO
HENDERSON COUNTY. DEPENDING ON THE MODEL...ALL PRECIP SHOULD BE EAST
OF OUR AREA BY TUESDAY NIGHT. THE GFS INDICATES ENOUGH CAPE ON
TUESDAY TO PRODUCE A LITTLE THUNDER FROM ELBERTON TO GREENWOOD AND
EVEN A LITTLE SW OF CLT LATE TUESDAY.

TEMPERATURES NEAR NORMAL THROUGH PERIOD FOR HIGHS AND A BIT ABOVE
NORMAL FOR LOWS DUE TO CLOUD COVER.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AT KCLT...A LINE OF SHOWERS AND TSTMS WILL CROSS THE AIRFIELD
BETWEEN 18-20 UTC. EXPECT GUSTY AND ERRATIC WINDS AND VERY HEAVY
RAIN AS THE LINE PASSES. WINDS WILL SHIFT TO THE NORTHWEST BEHIND
THE LINE AS A COLD FRONT CROSSES THE AIRFIELD. MVFR CIGS ARE
EXPECTED TO PERSIST FOR A COUPLE HOURS AFTER THE FRONTAL PASSAGE.
WINDS WILL GUST UP TO 28-30 KTS INTO THE EVENING HOURS. LATER
TONIGHT THE WINDS WILL VEER TO THE NORTHEAST AS HIGH PRESSURE MOVES
INTO THE MID-ATLANTIC STATES.

ELSEWHERE...A COLD FRONT WITH ASSOCIATED SHRA/TSTMS WAS CROSSING THE
AIRFIELDS AT KGSP/KGMU AT ISSUANCE TIME. WINDS WILL SHIFT TO THE
NORTHWEST BEHIND THE LINE OF STORMS...THOUGH SCT SHOWERS AND MVFR
CIGS AREA EXPECTED TO PERSIST FOR A COUPLE HOURS BEHIND THE FRONT.
WINDS MAY GUST AS HIGH AS 30 KTS INTO THE EVENING HOURS. WINDS AT
KAVL WILL BE STRONGER...GUSTING ALMOST TO 40KTS FROM THE NW INTO THE
EVENING HOURS.

OUTLOOK...HIGH PRESSURE WILL PRODUCE VFR WEATHER WEDNESDAY AND
THURSDAY. CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND
SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE
SYSTEM DEVELOPS ALONG THE COAST.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  89%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  94%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  88%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH  88%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  92%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  94%     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

&&

.CLIMATE...
RECORD LOWS FOR WEDNESDAY APRIL 16...

AVL...26 IN 1943
CLT...29 IN 2008
GSP...24 IN 1907

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     MORNING FOR GAZ010.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR GAZ010-017-018-026-028-029.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR GAZ010-017.
NC...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     MORNING FOR NCZ035>037-048-051>053-056>059-062>065-
     068>072-082-501>510.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR NCZ035>037-048-051>053-056>059-062>065-068>072-082-
     501>510.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR NCZ033-048>053-
     058-059-062>065-501-503-505-507-509.
SC...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     MORNING FOR SCZ008-009-014.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR SCZ001>014-019.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR SCZ001>003.

&&

$$
SYNOPSIS...DEO
NEAR TERM...MCAVOY
SHORT TERM...LG
LONG TERM...DEO
AVIATION...MCAVOY
CLIMATE...






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