NE Georgia Mountain Weather

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Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 301436
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1036 AM EDT WED SEP 30 2009

.SYNOPSIS...
HIGH PRESSURE AND A COOL DRY AIR MASS WILL REMAIN IN CONTROL OF THE
WEATHER THROUGH FRIDAY MORNING. A COLD FRONT WILL CROSS THE AREA
FRIDAY NIGHT INTO EARLY SATURDAY. DRY HIGH PRESSURE WILL BUILD BACK
ACROSS THE AREA DURING THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A RIDGE OF CANADIAN HIGH PRESSURE WILL BUILD ALONG THE MISSISSIPPI
RIVER VALLEY THIS AFTERNOON. AS THE BROAD RIDGE SINKS
SOUTH...UPSLOPE FLOW ACROSS THE TN BORDER COUNTIES SHOULD WEAKEN.
UPSLOPE CLOUDS SHOULD BEGIN TO RETREAT AROUND NOON...LEAVING ONLY A
THIN BAND OF CLOUDS ACROSS THE NRN MTNS AND FEW MTN TOP CU.
ELSEWHERE...SUNNY CONDITIONS WILL PREVAIL. HIGH TEMPERATURES WILL
COMPARE CLOSELY TO YESTERDAY/S VALUES.

ANOTHER CLEAR AND COOL NIGHT ON TAP AS SFC RIDGING BUILDS
INTO THE SOUTHERN APPALACHIANS. WILL BANK OF SKIES REMAINING CLEAR
ENUF FOR HIGH MTN VALLEYS TO BE ABLE TO RADIATE DOWN TO WHERE FROST
DEVELOPMENT BECOMES PROBABLE. CLIMATOLOGICALLY...IT IS A ABOUT A 70
PERCENT PROBABILITY THAT THE FIRST FROST OCCURS BY OCTOBER 1ST ACRS
THESE AREAS.-- End Changed Discussion --


&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 245 AM WEDNESDAY...THU STILL LOOKS LIKE A VERY NICE FALL DAY
AS THE SFC RIDGE MOVES OFF THE SE COAST. SKIES SHOULD BE CLEAR WITH
TEMPS RUNNING AROUND NORMAL FOR THIS TIME OF YEAR. ON FRI THE NAM
AND GFS BRING A PREFRONTAL BAND OF CONVECTION INTO THE MTNS BY LATE
IN THE DAY. THIS APPEARS TO BE THE REMNANTS OF AN MCS THAT DEVELOPS
THU NIGHT OVER THE LOWER MS RIVER VALLEY. THE STORMS WILL WEAKEN AS
THEY ENTER THE MORE STABLE AIR OVER THE SE STATES...BUT MODEL
SOUNDINGS IMPLY ENOUGH INSTABILITY THAT I DID ADD THUNDER TO THE
FORECAST FOR FRI/FRI NIGHT. THE SFC FRONT WILL STRUGGLE TO MAKE IT
INTO THE MTNS FRI NIGHT AS THE INITIAL FORCING LIFTS TO THE NORTH
AND ANOTHER SHORT WAVE WILL ROUND THE BASE OF THE TROUGH...DELAYING
FROPA. THE SREF HAS HIGH RAIN CHANCES FRI NGHT. THE NAM AND GFS BOTH
MAINTAIN LLVL WARM ADVECTION THROUGH THE NIGHT...WITH A FAIR AMOUNT
OF PCPN AS WELL. I/VE UPPED POPS INTO THE LIKELY CAT OVER THE MTNS
AND WRN NC FOOTHILLS AND HIGH CHANCE ELSEWHERE. I IMAGINE POPS WILL
BE RAISED FURTHER IN SUBSEQUENT FORECAST PACKAGES.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 220 AM WEDNESDAY...THE NEW NAM HAS A SHORT WAVE OVER WRN TN
AND THE SFC FRONT STILL OVER NE GA AT 12 UTC SAT...IMPLYING A FAIRLY
WET DAY FOR SAT...THOUGH THAT/S WHERE THE MODEL RUN STOPS. THE GFS
IS SIMILAR IN THAT IT PUSHES THE INITIAL BAND OF PCPN INTO THE FA
FRI AFTN...BUT IT THEN SLOWS THE FRONT DOWN AS ANOTHER SHORT WAVE
DROPS DOWN THE BACK SIDE OF THE UPPER TROF...INCREASING PVA OVER
THE REGION ON SATURDAY. THE OLD RUN OF THE ECMWF WAS FASTER...AND
THE LATEST SREF IMPLIES THAT THE PCPN WILL BE RATHER EAST THAN THE
NAM. I/M A LITTLE SUSPICIOUS OF THE NAM...SO I/LL USE A BLEND OF THE
GFS AND THE PREVIOUS FORECAST WHICH HAS GOOD CHANCE POPS IN THE
MORNING...WITH DRYING SAT AFTN.

THE WEATHER LOOKS GREAT ON SUNDAY AND MONDAY AS THE UPPER LOW LIFTS
QUICKLY INTO SOUTHERN CANADA...REPLACED BY A BROAD RIDGE. SKIES
SHOULD BE CLEAR WITH TEMPS RUNNING A LITTLE BELOW NORMAL. THE FLOW
WILL BECOME INCREASINGLY ZONAL AND STRONGER BY TUE. THE OLD ECMWF
HAS SUFFICIENT LLVL WARM ADVECTION ON TUE FOR A FAIR AMOUNT OF
PCPN. THE GFS HAS A LITTLE MORE RIDING AND IS THEREFORE DRIER WITH
WEAKER WAA. I/VE BUMPED POPS UP A LITTLE ON TUE AS A NOD TO THE
EC...BUT THAT STILL LEAVE THE FOOTHILLS AND PIEDMONT DRY.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...CLEAR SKIES THIS MORNING TO GIVE WAY TO A FEW HIGH BASED CU
THIS AFTERNOON WHICH SHOULD FLATTEN AND PERHAPS LINGER INTO TONIGHT.
WINDS ARE EXPECTED TO REMAIN FROM THE NW...AND INCREASE TO ABT 8 KTS
BY MIDDAY BECOMING LIGHT FROM THE NORTH TONIGHT.

ACRS THE REST OF THE TERMINALS...CLEAR THIS MORNING WITH NW WINDS
INCREASING...PERHAPS BECOMING GUSTY AGAIN AT KAVL...BUT COULD REMAIN
VARIABLE AND LESS THAN 6 KTS AT KGSP THANKS TO LEE TROUGH. LIGHT
WINDS TONIGHT WILL ALLOW AREAS OF MTN VALLEY FOG TO FORM.

OUTLOOK...VFR CONDITIONS EXPECTED THROUGH FRIDAY MORNING. A COLD
FRONT IS EXPECTED TO BRING ANOTHER ROUND OF SHOWERS TO THE REGION
FRIDAY AFTERNOON INTO EARLY SATURDAY.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...FROST ADVISORY FROM 2 AM TO 10 AM EDT THURSDAY FOR NCZ033-049-
050.
SC...NONE.

&&

$$
SYNOPSIS...TJB
NEAR TERM...NED/CSH
SHORT TERM...MCAVOY
LONG TERM...MCAVOY
AVIATION...CSH