FXUS62 KGSP 250828
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
328 AM EST FRI DEC 25 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL CONTINUE TO MOVE NORTHWARD AND INTO THE
UPPER MIDWEST TODAY AS A COLD FRONT SWEEPS ACROSS THE FORECAST AREA.
BEHIND THIS FRONT WEAK HIGH PRESSURE WILL BUILD IN ACROSS THE
SOUTHEAST THROUGH SUNDAY. ANOTHER MUCH STRONGER AREA OF HIGH
PRESSURE WILL BUILD IN FROM THE NORTHWEST THROUGH EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AN UPPER LEVEL SHORTWAVE WILL CROSS OUR AREA TODAY AS IT ROUNDS AN
UPPER LOW TO THE NORTHWEST. STRONG ISENTROPIC UPGLIDE WILL BE IN
PLACE UNTIL MIDDAY...SETTING UP HEAVY RAIN OVER THE AREA THAT WILL
BE ENHANCED BY TERRAIN ALONG THE BLUE RIDGE ESCARPMENT...ESPECIALLY
IN NC WHERE SURFACE WINDS WILL HAVE THE BEST UPSLOPE COMPONENT. A
FLASH FLOOD WATCH WILL NOT BE ISSUED AT THIS TIME...AS THE HEAVIEST
RAIN SHIFT EASTWARD FORM THE SC MOUNTAINS TO THE NC BLUE RIDGE.
WET BULB TEMPERATURES SUPPORT FREEZING RAIN IN NC UNTIL LATE MORNING
FROM THE NORTHERN MOUNTAINS AND NORTHERN FOOTHILLS TO THE SOUTHERN
BLUE RIDGE. THE ICE STORM WARNING WILL BE EXTENDED SOUTH INTO THE
SOUTHERN NC MOUNTAINS AND BLUE RIDGE...AND EAST INTO THE PIEDMONT.
THE FREEZING RAIN ADVISORY WILL BE EXTENDED INTO HAYWOOD
COUNTY...AND DAVIE COUNTY. STRONG 850 MB WINDS SUPPORT A HIGH
WIND WARNING IN THE SOUTHWEST NC MOUNTAINS... WITH A CONTINUATION OF
THE WIND ADVISORY IN THE MOUNTAINS TO THE EAST AND SOUTH. THE LAKE
WIND ADVISORY IN UPSTATE SC WILL BE EXTENDED TO THE I-77 CORRIDOR OF
NC.
THE GOOD NEWS IS THAT BY AFTERNOON...THE BEST LIFT AND WINDS WILL BE
EXITING THE AREA...WHILE TEMPERATURES WARM ABOVE FREEZING AND GET TO
WITHING A COUPLE OF CATEGORIES OF NORMAL. CLOUDS DECREASE AND WINDS
BECOME LIGHT FROM THE WEST BY EVENING...AND MINIMUM TEMPERATURES
WILL BE NEAR NORMAL.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY/...
AS OF 325 AM FRI...AN INTENSE UPPER LOW WILL ROTATE ACROSS THE
WESTERN GREAT LAKES STATES SAT AND SAT NITE. THE CWFA WILL BE UNDER
A STRONG SOUTHWESTERLY UPPER LEVEL FLOW...THOUGH THE AIRMASS WILL BE
QUITE DRY OVERALL. HIGHS SAT WILL BE ABOVE NORMAL WITH HIGHER
THICKNESSES AND MOSTLY SUNNY SKIES. LOWS SHOULD BE NEAR OR SLIGHTLY
BELOW NORMAL.
BY SUNDAY THE UPPER LOW WILL WILL BEGIN TO BE PICKED BACK UP BY THE
WESTERLIES...MOVING BRIEFLY TO THE SOUTH BEFORE LIFTING OFF TO THE
NORTH. AS THIS HAPPENS...SOME UPPER DIVERGENCE DEVELOPS OVER THE
AREA AS A SHORT WAVE SHOOTS ACROSS THE REGION. A WEAK GULF LOW
DEVELOPS AND MOVES EASTWARD. THIS BRINGS SOME MOISTURE INTO THE
AREA. HOWEVER...THE MOST OF THE GUIDANCE HAS NO TO VERY LOW POP. THE
EXCEPTION IS THE SREF WHICH HAS VERY HIGH POP WITH VERY LOW QPF.
WILL KEEP THE FCST DRY FOR NOW. HIGHS A LITTLE COOLER...BUT STILL
ABOVE NORMAL.
A STRONGER SHORT WAVE ROTATES AROUND THE DEPARTING LOW AND INTO THE
AREA SUN NITE. MOST OF THE AREA WILL REMAIN DRY. HOWEVER...IT WILL
BE THE BEST PERIOD FOR NW FLOW SNOW AS LOW LEVEL MOISTURE AND NWLY
FLOW INCREASE ACROSS THE MTNS. FOR NOW...HAVE KEPT POP IN THE CHC TO
SLIGHT CHC RANGE OVER THE USUAL AREAS. THE SNOW SHOWERS END BY
AFTERNOON MONDAY. RIGHT NOW...IT LOOKS LIKE LIGHT ACCUMULATIONS ARE
POSSIBLE. LOWS AND HIGHS BELOW NORMAL.
&&
.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
AS OF 315 AM FRIDAY...STILL NO SIGNIFICANT CHANGES TO THE GOING
MEDIUM RANGE FORECAST. THE FIRST PART OF THE PERIOD WILL GENERALLY
BE QUIET AS HIGH PRESSURE BUILDS IN FROM THE WEST UNDER RIDGING
ALOFT. MODEL SOLUTIONS RAPIDLY DIVERGE FROM TUESDAY NIGHT
ONWARD...PRIMARILY WITH THEIR HANDLING OF THE NEXT SOUTHERN STREAM
SYSTEM. THE COLLECTION OF GFS...ECMWF...AND GEM ALL HANDLE THE MID
AND UPPER LEVEL ENERGY DIFFERENTLY ESPECIALLY WITH REGARD TO TRACK
AND TIMING. THE GFS CONTINUES TO KEEP THE DEVELOPING GULF LOW
PRESSURE SYSTEM SUPPRESSED TO THE SOUTH AND KEEPS ACCUMULATING
PRECIP SOUTH AND EAST OF THE FA. HOWEVER...THE ECMWF TAKE THE LOW
SLOWLY ACROSS THE NORTHERN GULF AND UP THE EAST COAST SPREADING
PRECIP INTO THE WESTERN CAROLINAS AS EARLY AS WEDNESDAY. WITH THIS
SIGNIFICANT TIMING DIFFERENCE IN MIND THE END OF THE FORECAST
CONTINUES TO BE VERY LOW CONFIDENCE. I HAVE KEPT THE CHANCE POP IN
THE FORECAST FOR WEDNESDAY AND WEDNESDAY NIGHT WITH IT DRY UP TO
THAT POINT. AT THIS POINT...ATTEMPTING TO PREDICT PTYPE FOR SUCH A
LOW CONFIDENCE FORECAST IS SUCH A FUTILE EXERCISE THAT I WILL
HANDLE WX AS RAIN OR SNOW FOR NOW.
&&
.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
AT KCLT...ISENTROPIC UPGLIDE IS EXPECTED TO INCREASE DRAMATICALLY BY
DAWN...AND IFR RESTRICTIONS ARE STILL EXPECTED TO DEVELOP AS THE
HEAVIER RAIN NO IN GA ARRIVES. NORTHEAST WINDS ARE EXPECTED TO
BECOME GUSTY AS THE PRESSURE GRADIENT TIGHTENS BETWEEN AN
APPROACHING FRONT AND THE EAST COAST RIDGE. WINDS WILL VEER TO THE
SOUTHEAST AROUND NOON AS THE SURFACE RIDGE IS DISPLACED...WITH
CONDITIONS BEGINNING TO IMPROVE AS THE BEST UPGLIDE MOVES OFF TO THE
NORTHEAST. BY EVENING A SOUTHWEST WIND AND VFR ARE EXPECTED BEHIND
THE FRONT.
ELSEWHERE...CONDITIONS WILL DETERIORATE TO IFR BY DAWN AS LOW LEVEL
LIFT INCREASES WITH STRONG WINDS ALOFT...AND HEAVIER PRECIPITATION
ARRIVES FROM GA. WET BULB TEMPERATURES STILL SUPPORT FREEZING RAIN
AT NC SITES BEFORE DAWN. GUSTY EAST NORTHEAST WINDS ARE EXPECTED IN
A TIGHTENING PRESSURE GRADIENT..EXCEPT AT KAVL WHERE WINDS WIL BE
CHANNELED DOWN VALLEY FROM THE SOUTH. IMPROVEMENT IS EXPECTED AT
MIDDAY AS THE SURFACE RIDGE LOSES ITS GRIP AND WINDS VEER TO THE
SOUTHEAST OR SOUTH. BY EVENING VFR SHOULD RETURN TO SC SITES IN THE
MID LEVEL DRY SLOT BEHIND THE FRONT. VFR WILL RETURN TO SC SITES A
FEW HOURS LATER.
OUTLOOK...VFR CONDITIONS EXPECTED SAT THROUGH TUE. A WEAK COLD FRONT
WILL APPROACH THE AREA WED AND POSSIBLY LOWER CIGS TO MVFR ACROSS
MOST TAF SITES THROUGHOUT THE DAY. HIGH PRESSURE AND DRIER AIR WILL
MOVE IN QUICKLY WED NIGHT RETURNING FLIGHT CATS TO VFR FOR THU.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...LAKE WIND ADVISORY UNTIL NOON EST TODAY FOR GAZ018-026-028-029.
WIND ADVISORY UNTIL NOON EST TODAY FOR GAZ010-017.
NC...ICE STORM WARNING UNTIL NOON EST TODAY FOR NCZ033-035-036-049-
050-053-056-064-065-068-069-501>510.
LAKE WIND ADVISORY UNTIL NOON EST TODAY FOR NCZ057-070>072-082.
FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR NCZ037-052.
HIGH WIND WARNING UNTIL NOON EST TODAY FOR NCZ048-051-058-059-
062-063.
SC...LAKE WIND ADVISORY UNTIL NOON EST TODAY FOR SCZ001>014-019.
&&
$$
SYNOPSIS...BSH
NEAR TERM...JAT
SHORT TERM...RWH
LONG TERM...BSH
AVIATION...JAT
