000
FXUS62 KGSP 052340
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
640 PM EST MON JAN 5 2009

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN ACROSS THE WESTERN CAROLINAS DOWN TO
LOUISIANA THROUGH WEDNESDAY. AREAS OF LOW PRESSURE WILL MOVE
NORTHEAST ACROSS THE FRONT TONIGHT AND AGAIN TUESDAY NIGHT. THE
FRONT WILL MOVE EAST OF THE REGION WEDNESDAY...FOLLOWED BY COOL HIGH
PRESSURE FOR THE REMAINDER OF THE WORK WEEK.

.NEAR TERM /THROUGH TUESDAY/...
AT 1930Z...DOWNSLOPE CLEARING YIELD MOSTLY TO PARTLY SUNNY
CONDITIONS ACROSS MOST OF THE FOOTHILLS AND WESTERN PIEDMONT.
AFTERNOON ISOLATION HAS PUSHED TEMPERATURES TO RECORD
TERRITORY...WITH GSP MATCHING THE RECORD HIGH OF 72 SET IN 1955. THE
18Z LAPS ANALYSIS OF CAPE INDICATES THAT 200-400 J/KG COVER MUCH OF
THE SC UPSTATE AND ALONG THE EAST FACING SLOPES OF THE MTNS. IT
REMAINS POSSIBLE THAT A ISOLATED TSRA MAY DEVELOP ALONG THE COLD
FRONT OVER NE GA OR THE EASTERN UPSTATE LATE THIS AFTERNOON TO EARLY
THIS EVENING.

THE COLD FRONT SHOULD STALL ACROSS THE EASTERN THIRD OF THE CWA THIS
EVENING. SHORT RANGE MODELS AGREE THAT A FRONTAL WAVE WILL DEVELOP
OVER THE SOUTHERN MISSISSIPPI RIVER VALLEY LATE THIS AFTERNOON AND
TRACK NORTHEAST TONIGHT. AS THE LOW APPROACHES...THE CENTER OF HIGH
PRESSURE WILL PUSH OVER THE MID ATLANTIC REGION...WITH SFC RIDGING
EXTENDING SW ACROSS THE CWA. THIS PATTERN WILL YIELD A DEVELOPING
CAD EVENT LATE TONIGHT AND TUESDAY. OVERNIGHT...ISENTROPIC LIFT AND
UPSLOPE FLOW WILL SUPPORT INCREASING COVERAGE OF SHRA THIS EVENING
ACROSS THE UPPER SAVANNAH RIVER VALLEY AND CAROLINA MTNS. AFTER
9Z...THE AXIS OF LLVL FRONTOGENESIS AND LOW EPV VALUES WILL MOVE
ACROSS THE MOUNTAINS. A BAND OF LIGHT TO MODERATE SHRA ACROSS THE
REGION LATE TONIGHT INTO TOMORROW. IT APPEARS THAT UPSLOPE FLOW AND
FORCING WILL YIELD MODERATE RAINFALL RATES ACROSS THE MTNS LATE
TONIGHT AND TOMORROW. WE WILL CONTINUE TO HIGHLIGHT THE REGION WITH
A FLASH FLOOD WATCH STARTING A 6Z TUES.

TUESDAY...AMPLIFYING H5 TROF WILL RIPPLE EAST TOWARD THE SOUTHEAST
DURING THE DAY. LLVL FORCING ALONG THE FRONT WILL DEEPEN WITHIN A
VERY MOIST PW AIRMASS...PWS RANGING FROM 1-1.3 INCHES. THE GREATEST
LIFT WILL LIKELY REMAIN OVER THE MTNS AND I-40 CORRIDOR THROUGH THE
DAY. MESOSCALE MODELS INDICATE A SURGE IN HIGH PRESSURE ACROSS THE
NC FOOTHILLS AND PIEDMONT ASSOCIATED WITH CAD. TEMPERATURES MAY
SLOWLY COOL ACROSS THE I-40 CORRIDOR EAST OF THE MTNS AFTER SUNRISE.
ELSEWHERE...WIDESPREAD CLOUD COVER AND COVERAGE OF MODERATE SHRA
WILL LIMIT DIURNAL HEATING TO WITHIN 5-8 DEGREES OF MORNING
LOWS...WITH NEAR 50 AROUND KHKY TO NEAR 60 AROUND KAND.

.SHORT TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 245 PM MONDAY...LLVL ISENTROPIC UPGLIDE AND MOISTURE TRANSPORT
INCREASE AGAIN TUESDAY EVENING. THE BEST UPPER DIVERGENCE AND H7
FRONTOGENESIS IS LOCATED ALONG AND JUST TO THE WEST OF THE
MOUNTAINS. HOWEVER...THE STRONGEST LLVL WARM ADVECTION AND
FRONTOGENESIS AOB H8 WILL BE ALONG AND JUST EAST OF THE
MOUNTAINS...AND HEAVY RAINFALL IS LIKELY TO CONTINUE OVERNIGHT OVER
THE MOUNTAINS AND FOOTHILLS. I WILL NOT EXPAND THE FLASH FLOOD WATCH
FARTHER TO THE NORTHEAST YET...BUT LATER SHIFTS WILL PROBABLY HAVE
TO EXPAND IT TO COVER THE REST OF THE NC MOUNTAINS AND FOOTHILLS.
DESPITE THE BETTER FORCING BEING OFF TO THE WEST...THE WEAK WEDGE
OVER THE NC PIEDMONT STILL HAS ME CONCERNED. WITH THE STRONG SW FLOW
ORIENTED NEARLY ORTHOGONAL TO THE BNDRY...THERE COULD BE ENOUGH LIFT
TO GENERATE HEAVY RAIN OVER THE PIEDMONT AND EVEN INTO THE CHARLOTTE
METRO AREA.

A SFC WAVE WILL MOVE UP THE FRONT TUE NGHT AS WELL. THE GFS IS A
LITTLE FASTER WITH THE TRANSLATION OF THE WAVE AND IT IS SEVERAL MB
DEEPER WITH THE LOW THAN THE NAM. CONSIDERING THE OVERALL POSITIVE
TILT TO THE UPPER TROUGH...A BLEND OF THE TWO IS A GOOD BET. WARM
SECTOR INSTABILITY WILL BE MINIMAL THOUGH THERE WILL BE VERY STRONG
SHEAR OVER THE REGION. ATTM I THINK THE SEVERE THREAT IS VERY
SMALL...BUT IF SOME MOISTURE CAN POOL ALONG THE WEAK WEDGE...THEN
THERE COULD STILL BE A CHANCE OF AN ISOLATED SEVERE STORM...OR EVEN
TORNADO OVER THE NRN UPSTATE OR SRN PIEDMONT.

THE STRONG LLVL JET WILL MOVE EAST OF THE FA AFTER 12 UTC WED...BUT
THE TRAILING SRN STREAM SHORT WAVE WILL RESULT IN STRONG DIV-Q ON
WED AND A POSSIBLE CONTINUATION OF LIGHTER PCPN AT LEAST THROUGH THE
MORNING HOURS. H8 TEMPS ARE LOOKING WARMER THAN ON PAST RUNS...AND I
DON/T HAVE MUCH SNOW OVER THE MTNS DURING THE DAY. THERE WILL BE
STRONG WIND GUST POTENTIAL IMMEDIATELY BEHIND THE FRONT ON WED OWING
TO DEEP MIXING AND STRONG PRESSURE RISES.

THE NAM IS NOT AS COLD OR AS TIGHT WITH THE GRADIENT AS THE GFS
BEHIND THE FRONT WED NIGHT. I WENT WITH A BLEND OF THE
TWO...POPULATING MY GRIDS WITH THE SREF WHERE I COULD. THIS KEEPS
POPS GENERALLY IN THE CHANCE RANGE WED NGHT AND INTO EARLY THURSDAY
OVER THE TENNESSEE BORDER COUNTIES WITH VERY LIGHT NORTHWEST FLOW
SNOWFALL AMOUNTS AS MODEL SOUNDINGS DON/T SHOW AND AMOUNT OF
SATURATE AIR IN THE GOOD SNOW CRYSTAL GROWTH AREA.

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM MONDAY...THE PRESSURE GRADIENT AND ASSOCIATED WINDS
WILL RELAX THURSDAY NIGHT AS A FLAT UPPER RIDGE BUILDS IN AND
PERSISTS THROUGH FRIDAY.

THE NEXT CLIPPER SYSTEM WILL DIG THROUGH THE MIDWEST FRIDAY...WITH
THE RESULTING BROAD UPPER TROUGH AXIS LIKELY CROSSING THE REGION ON
SATURDAY. THE ECM IS QUITE A BIT SLOWER THAN THE OPERATIONAL GFS IN
BRINGING THE MOISTURE ALONG THE FRONTAL ZONE INTO THE AREA ON
SATURDAY. THIS SLOWER ECM SOLUTION IS CLOSER TO THE ENSEMBLE MEANS
AND IS PREFERRED. THIS WILL MEAN LESS OF A CHANCE OF FZRA AHEAD OF
THE SYSTEM SAT MORNING...WITH LOWER QPF. AND...SOME DEGREE OF POPS
WILL BE CARRIED THROUGH SAT NIGHT WITH THE SLOWER DEPARTURE OF THE
FRONTAL ZONE.

UPPER HEIGHTS THEN BRIEFLY RISE ON SUNDAY...WITH STRONG MODEL
DIFFERENCES DEVELOPING IN THE HANDLING OF LOW PRESSURE UPSTREAM IN
THE UPPER MIDWEST. ANY MOISTURE RETURN IN THE SW FLOW AHEAD OF THIS
SYSTEM SHOULD HOLD OFF UNTIL MON AFTN.

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AT KCLT...WINDS WILL REMAIN OUT OF THE S/SW GENERALLY AT 5-10 KTS
THROUGH THE PERIOD. RATHER CHALLENGING FORECAST OVERNIGHT...AS LOW
LEVEL MOISTURE REMAINS QUITE HIGH...BUT UNTIL PRECIP MOVES IN AFTER
MIDNIGHT...THERE WON/T BE MUCH OF A MECHANISM TO FORCE LOW CLOUDS.
MEANWHILE...LINGERING CLOUD COVER WILL HINDER FOG DEVELOPMENT. WILL
FEATURE A GRADUAL DETERIORATION TO MVFR CONDITIONS BY MIDNIGHT.
PRECIP SHOULD THEN MOVE IN BETWEEN MIDNIGHT AND SUNRISE...WITH IFR
CONDITIONS EXPECTED TO ACCOMPANY THE RAINFALL. PERIODS OF HEAVY
RAIN/FURTHER REDUCED VISBY WILL BE POSSIBLE. AS A WARM FRONT LIFTS
NORTH OF THE AREA TOMORROW...RAINFALL SHOULD BECOME MORE SHOWERY/
INTERMITTENT IN NATURE BY AFTERNOON.

ELSEWHERE...SCATTERED SHOWERS WILL BE POSSIBLE AT THE UPSTATE
TERMINALS AND KAVL EARLY THIS EVENING...WITH BRIEF PERIODS OF MVFR
RESTRICTIONS POSSIBLE. WIDESPREAD/PERSISTENT RAIN WILL HOLD OFF
UNTIL MIDNIGHT OR SO...WITH IFR CONDITIONS EXPECTED TO ACCOMPANY THE
PRECIP. THE ONSET OF RAIN WILL BE DELAYED A COUPLE OF HOURS AT KHKY.
NOT MUCH IMPROVEMENT IS EXPECTED DURING THE DAY TOMORROW...BUT MOST
LOCATIONS SHOULD SEE MVFR BY AFTERNOON...WITH A FEW LOCATIONS
PERHAPS SEEING VFR BY EVENING.

OUTLOOK...SHOWERS AND PERHAPS A THUNDERSTORM WILL REMAIN POSSIBLE
TUE NIGHT...MAINLY ACROSS THE MTNS. A COLD FRONT WILL BRING ANOTHER
CHANCE OF WIDESPREAD RAINFALL/FLT RESTRICTIONS TO THE REGION EARLY
WEDNESDAY.

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLASH FLOOD WATCH FROM MIDNIGHT EST TONIGHT THROUGH WEDNESDAY
     EVENING FOR GAZ010-017-018.
NC...FLASH FLOOD WATCH FROM MIDNIGHT EST TONIGHT THROUGH WEDNESDAY
     EVENING FOR NCZ048-051053-058-059-062065.
SC...FLASH FLOOD WATCH FROM MIDNIGHT EST TONIGHT THROUGH WEDNESDAY
     EVENING FOR SCZ001006.

SYNOPSIS...MCAVOY
NEAR TERM...NED
SHORT TERM...MCAVOY
LONG TERM...HG
AVIATION...JDL