Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 311903
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
303 PM EDT FRI OCT 31 2014

.SYNOPSIS...
A DEEP LOW PRESSURE SYSTEM WILL CROSS THE AREA FROM THE WEST
TONIGHT THROUGH SATURDAY. THIS SYSTEM WILL BE ACCOMPANIED BY COLD
TEMPERATURES AND VERY WINDY CONDITIONS. DRY AND COLD HIGH PRESSURE
WILL RETURN SUNDAY THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 245 PM EDT...WATER VAPOR IMAGERY REVEALS A DEEPENING
CIRCULATION DIVING SWD FROM THE GREAT LAKES THIS AFTERNOON. THIS
H5 LOW CENTER WILL MOVE QUICKLY SWD THROUGH THE OH VALLEY AS IT
DEEPENS FURTHER THIS EVENING AND THEN CROSSES THE EXTREME SRN
APPALACHIANS OVERNIGHT. THE CUTOFF LOW WILL BOTTOM OUT OVER THE
UPPER SAVANNAH RIVER AREA BY DAYBREAK. DEEP LAYER QG FORCING WILL
RAMP UP RAPIDLY LATE THIS AFTN AND EVENING AND THEN BECOME QUITE
INTENSE FROM 06Z TO 12Z...ESPECIALLY OVER THE EASTERN TWO THIRDS
OF THE CWFA. MEANWHILE...SNOW LEVELS WILL CRASH QUICKLY STARTING
IN THE SMOKIES THIS EVENING...WITH ZERO C 850 MB TEMPS WRAPPING
INTO THE FOOTHILLS OVERNIGHT AND ACROSS THE REGION BY MID MORNING
SAT. A STRONG 3 TO 5 PVU SATURATED EQUIVALENT GEOSTROPHIC
POTENTIAL VORT LOBE WILL MOVE OVER THE SRN APPALACHIANS AND DOWN
THE SAVANNAH RIVER AREA AROUND 12Z SAT. COMBINED WITH STEEP 850 TO
500 MB LAPSE RATES...A FEW THUNDERSTORMS CANNOT BE RULED OUT. IN
ADDITION...WITH AN 850 MB LOW CENTER BOMBING OUT JUST S OF
KCLT...THERE IS GROWING CONCERN FOR STRONG FRONTOGENESIS TO CREATE
A SECONDARY MAXIMUM OF PRECIP OVER THE ERN UPSTATE AND CLT METRO
AREA. THE RATES THERE MAY BE ENOUGH FOR PRECIP TO CHANGE OVER TO
SNOW AT TIMES DESPITE THE SFC WARM LAYER...UNDER BOTH THE
DEFORMATION FORCING AND THE UPPER POT VOT. ALL TOLD...THE MTN
WINTER STORM WARNING LOOKS WELL PLACED GIVEN THE ANTICIPATED QPF
AND SNOW TO LIQUID RATIOS IN THE LOW TEENS. THE ONLY CHANGE WILL
BE TO ADD GRAHAM CO. WILL ALSO POST A SNOW ADVISORY TIER FARTHER
TO THE SE IN THE HIGH TERRAIN. THE FOOTHILLS AND PIEDMONT REMAIN
QUITE UNCERTAIN...AS SNOW COULD MIX IT AT TIMES. THE H5 LOW CENTER
WILL TRANSITION OFF THE CAROLINA COAST QUICKLY THROUGH SATURDAY
AFTN...BUT THE LOW LEVEL DEFORMATION FORCING WILL BE SLOWER TO
EXIT.

IN ADDITION...A 50 TO 55 KT 850 JET WILL PEAK ALONG THE BLUE RIDGE
AND SRN/ERN ESCARPMENT DURING THE DAY SAT. HIGH END ADVISORY
CRITERIA GUSTS WILL LIKELY MIX DOWN INTO THE MTNS THROUGH THE DAY.
NORMALLY...WE WRAP WIND HAZARDS INTO WINTER PRODUCTS...BUT THERE IS
ENOUGH DIFFERENCE IN TIMING AND AREAL EXTENT THAT WE WILL ISSUE A
SEPARATE NPW PRODUCT. ALSO...THE EXISTING FREEZE WARNING FOR TONIGHT
WILL BE UNTOUCHED.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM EDT FRIDAY...LONG WAVE TROUGH WITH A DEEP UPPER LOW
MOVING THROUGH ITS BASE WILL BE ORIENTED ALONG THE ATLANTIC COAST
SAT EVENING WITH A BOMBING SFC LOW EAST OF CAPE HATTERRAS. THE SFC
LOW WILL MOVE QUICKLY NE SAT NIGHT ALLOWING COLD HIGH PRESSURE TO
BEGIN RIDGING OVER THE AREA. SCT TO NUMEROUS NW FLOW SNOW SHOWERS
WILL BE ONGONG SAT EVENING CONFINED MAINLY TO THE TENNESSEE BORDER
COUNTIES....BUT AS THE SFC HIGH MOVES EASTWARD A DIMINISHING TREND
IN THE SNOW SHOWERS WILL COMMENCE OVERNIGHT AND END BY SUNDAY
MORNING. THE GFS WOULD SUGGEST LESS THAN 1/2 INCH OF ADDITIONAL
ACCUMULATION WITH THE NAM IN THE 1-3 INCH RANGE. A COMPROMISE
SOLUTION WILL BE AROUND 1 INCH WHICH IS CLOSE TO THE CURRENT
FORECAST. GUSTY WINDS WILL CONTINUE SAT EVENING BUT GRADUALLY
DIMINISH OVERNIGHT AS THE PRESSURE GRADIENT RELAXES. HOWEVER...
FORECAST SOUNDINGS INDICATE THAT THE ATMOSPHERE SHOULD REMAIN
MIXED ENOUGH SO THAT MIN TEMPS GO NO LOWER THAN THE LOWER TO
MIDDLE 30S OUTSIDE OF MOST MOUNTAIN LOCATIONS. THE MOUNTAINS WILL
BE A DIFFERENT STORY WITH MIN TEMPS REACHING THE LOWER TO MIDDLE
20S. THE COLD HIGH PRESSURE WILL SLOWLY BUILD EAST AND SETTLE OVER
THE REGION SUNDAY NIGHT. THE HIGH IS OF ARCTIC ORIGIN SO TEMPS
WILL BE WELL BELOW CLIMO. ALMOST IDEAL RADIATIONAL COOLING
OCNDITIONS SUN NIGHT WILL ALLOW FRO FREEZING TEMPS ACROSS MOST IF
NOT ALL OF THE AREA. AS THE HIGH MOVES TO THE SE ON MON...WINDS
BECOMIE SW WHICH WILL ALLOW FOR MODERATING TEMPS...BUT STILL A
LITTLE BELOW CLIMO.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM EDT FRIDAY...LATEST MEDIUM RANGE GUIDANCE CONTINUES
WITH THE IDEA THAT AN UPPER RIDGE WILL BUILD ACROSS THE AREA EARLY
NEXT WEEK AND THEN TRANSITION OFF THE EAST COAST BY MIDWEEK.
ANOTHER TROUGH IS THEN FORECAST TO DEVELOP OVER THE EASTERN CONUS
BY LATE WEEK. HIGH PRESSURE WILL DOMINATE THE WEATHER THROUGH WED
WITH TEMPS MODERATING SLOWLY TO NEAR OR EVEN SLIGHTLY ABOVE CLIMO.
A SURFACE COLD FRONT IS FORECAST TO CROSS THE AREA ON THU. IT
LOOKS LIKE THE FRONT WILL BE LOSING MOISTURE FLUX AS IT APPROACHES
AND ANY SHOWERS MAY BE CONFINED TO THE MOUNTAINS ONLY. DRY HIGH
PRESSURE THEN RETURNS FOR FRIDAY.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...PESKY MVFR/LOWER VFR CLOUDS CONTINUE IN THE VICINITY OF
KCLT THIS AFTN AND SLOW IMPROVEMENT WILL CONTINUE BEFORE CIGS
START HEADING SOUTH WITH INCREASING MOISTURE AHEAD OF THE STRONG
LOW AGAIN THIS EVENING. ANTICIPATE DEEP LAYER Q VECTOR FORCING
ARRIVING DURING THE OVERNIGHT. ALTHOUGH A SFC BASED WARM LAYER
WILL REMAIN IN PLACE...STRONG DYNAMICAL FORCING SAT MORNING FROM
THE UPPER LOW AND LOW LEVEL FRONTOGENESIS WILL LIKELY CAUSE PRECIP
TO MIX OVER TO SNOW SHOWERS AT TIMES. WILL FEATURE MAINLY MVFR
VSBY/CIGS DURING THAT PERIOD. WINDS WILL INCREASE AND BECOME NW
AND GUSTY STARTING AROUND DAYBREAK.

ELSEWHERE...THE STRONG LOW PRESSURE SYSTEM WILL BE ACCOMPANIED BY
SUFFICIENTLY DEEP MOISTURE TO GENERATE INCREASING SHOWERS FROM THE
WEST TONIGHT. CIGS WILL TRANSITION DOWN QUICKLY TO MVFR THIS
EVENING...WITH SNOW LEVELS CRASHING TO PRODUCE SNOW SHOWERS AT KAVL
STARTING 04Z TO 07Z. THE FEELING IS THAT UPPER LEVEL FORCING WILL
BECOME STRONG ENOUGH TO ALLOW SNOW TO MIX IN WITH THE RAIN SHOWERS
AT THE SFC ACROSS THE FOOTHILL TAFS AS WELL SAT MORNING. EXPECT
MAINLY LINGERING MVFR CIGS UNTIL THE PRECIP TAPERS OFF TOWARD THE
END OF THE PERIOD. AN INCREASING NW FLOW GRADIENT WILL ALSO GENERATE
ROBUST WIND GUSTS...PARTICULARLY AT KAVL WHERE SOME 40KT WILL NOT BE
OUT OF THE QUESTION BY MID DAY.

OUTLOOK...DRYING HIGH PRES WILL BUILD IN LATE THIS WEEKEND THROUGH
EARLY NEXT WEEK.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT
     SATURDAY FOR GAZ010-017.
     WIND ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT SATURDAY FOR
     GAZ010-017.
     FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR GAZ010-017-018-026-028-029.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT SATURDAY
     FOR GAZ010.
NC...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT
     SATURDAY FOR NCZ053-059-062>065-501-503-505.
     WIND ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT SATURDAY FOR
     NCZ033-035-048>053-058-059-062>065-501>510.
     FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR NCZ065-068-507>510.
     WINTER STORM WARNING FROM 8 PM THIS EVENING TO 8 PM EDT
     SATURDAY FOR NCZ033-048>052-058.
     FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT SATURDAY
     FOR NCZ033-049-050-053-063>065.
SC...WIND ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT SATURDAY FOR
     SCZ001>003.
     FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR SCZ001>008-010>013-019.

&&

$$
SYNOPSIS...HG
NEAR TERM...HG
SHORT TERM...LG
LONG TERM...LG
AVIATION...HG



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