Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 050252
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
952 PM EST THU FEB 4 2016

.SYNOPSIS...
A COLD FRONT WILL LINGER NEAR THE CAROLINA COAST TONIGHT BEFORE
MOVING OUT OVER THE ATLANTIC THROUGH FRIDAY. LOW PRESSURE IS
EXPECTED TO FORM ON SUNDAY WELL OFFSHORE ALONG THIS FRONT AS ANOTHER
COLD FRONT ARRIVES FROM THE WEST. SNOW SHOWERS WILL BE QUITE
POSSIBLE IN THE MOUNTAINS EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 945 PM EST...WATER VAPOR IMAGERY AND THE LATEST RAP 500 MB
HEIGHT PROGNOSTICS DEPICT THE POTENT UPPER VORTICITY LOBE ON THE
DOORSTEP OF THE SW NC MOUNTAINS LATE THIS EVENING. RADAR CONTINUES
TO PRODUCE SOME INTERMITTENT 5 TO 10 DBZ REFLECTIVITY RETURNS OVER
OUR AREA...BUT WITHOUT ANY COHERENT SHOWERS YET. THIS DEVELOPMENT
APPEARS TO BE SLOWER THAN THE LATEST MESOSCALE MODELS...BUT WITH
MODEL DEVELOPMENT STILL MORE SOLIDLY FOCUSED ON THE 06Z TO 10Z
PERIOD FOR MOST OF THE AREA. MEANWHILE...PROFILES CONTINUE TO SLOWLY
COOL AND NEARLY ALL THE MODELS NOW HAVE SOME MOISTURE DEVELOPING
VERTICALLY TOWARD THE SNOW GROWTH REGION OVERNIGHT AND ALLOWING
SHOWERS TO FORM...WITH A PTYPE MIX OVER TO SNOW UNDER ANY SCATTERED
SHOWERS FROM WEST TO EAST THROUGH THE OVERNIGHT. WILL GENERALLY STAY
THE COURSE ON THE CURRENT FORECAST...EXCEPT FOR YET ANOTHER SLIGHT
UPWARD ADJUSTMENT ON POP INTO A MORE SOLID CHANCE RANGE TOWARD THE
CLT METRO AREA. STILL FEEL A QUICK DUSTING OF SNOW IS POSSIBLE
OVERNIGHT UNDER ANY SCATTERED SHOWERS...BUT MUCH MORE LIKELY IN THE
WESTERN MOUNTAINS WHERE THE MORE PERSISTENT NW FLOW...BETTER
MOISTURE...AND COLDER AIR/SURFACE TEMPERATURES WILL EXIST.

NO CHANGES WILL BE MADE TO THE NORTHERN BLUE RIDGE WIND
ADVISORY...BUT WITH GUSTY CONDITIONS NOW EXPECTED THROUGHOUT MOST OF
THE AREA AS THE PRESSURE GRADIENT TIGHTENS RAPIDLY BETWEEN THE
APPROACHING SFC HIGH PRESSURE FROM THE WEST AND THE DEEPENING NC
COASTAL LOW TO THE EAST.

OTHERWISE...AN UPPER RIDGE AND SURFACE HIGH PRESSURE WILL QUICKLY
BUILD IN FROM THE WEST BY FRIDAY AFTERNOON. THIS SHOULD PROVIDE
SEASONALLY COOL TEMPERATURES AND A SUNNY WINTER DAY. THE WINDS WILL
SLOWLY ABATE THROUGH THE AFTERNOON HOURS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 225 PM THURSDAY...ON SATURDAY...AN AMPLIFIED H5 TROF WILL
RIPPLE TOWARD THE SRN. APPALACHIANS DURING THE DAYLIGHT HOURS. SHORT
RANGE MODELS INDICATE THAT THE TROF MAY CLOSE OFF AND PASS OVER THE
FORECAST AREA DURING THE EVENING AND OVERNIGHT HOURS. GUIDANCE
AGREES THAT THE APPROACH OF THE MID LEVEL LOW WILL SUPPORT
CYCLOGENESIS OFF THE CAROLINA COAST SAT NIGHT. MODELS ALSO AGREE
THAT PRECIPITATION ASSOCIATED WITH THE LOW WILL REMAIN EAST OF THE
FORECAST AREA. I WILL INDICATE A DRY FORECAST FORECAST FOR
SAT...WITH INCREASING SKY COVER. LOW TEMPERATURES SHOULD BEGIN THE
DAY WITH LOW 20S ACROSS THE MTNS TO UPPER 20S EAST. HIGH
TEMPERATURES SHOULD RISE TO THE MID 40S WITHIN MTN VALLEYS TO AROUND
50.

ON SUNDAY...IN THE WAKE OF THE CLOSED MID LEVEL LOW...SHORT WAVE
RIDGING WILL BUILD OVER REGION. AT THE SFC...HIGH PRESSURE CENTERED
OVER THE GULF COAST WILL RIDGE OVER THE WESTERN CAROLINAS. THIS
PATTERN IS EXPECTED TO PROVIDE DRY WEATHER WITH SEASONABLE
TEMPERATURES.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 200 PM THURSDAY...MODELS ARE IN GOOD AGREEMENT ON A POTENT
SHORTWAVE TROF DIGGING INTO THE UPPER MIDWEST TO THE GREAT LAKES
LATE IN THE WEEKEND THRU MONDAY. THIS RESULTS IN A HIGHLY AMPLIFIED
WESTERN CONUS RIDGE AND EASTERN TROF IN THE UPPER LEVELS. AS THE
TROF DIGS ACROSS THE OH AND MID MS VALLEY...STRONG MID AND UPPER
LEVEL Q-VECTOR CONVERGENCE WILL OVERSPREAD THE SOUTHERN
APPALACHIANS...GENERALLY STRONGEST MONDAY MORNING. THE QG FORCING
SHUD SUPPLY DECENT VERTICAL MOTION...AS MID LEVEL LAPSE RATES
STEEPEN SIGNIFICANTLY...WITH 850-500MB RATES ABOVE 7C/KM ON ALL THE
OP MODELS...AND EVEN SOME CONVECTIVE INSTBY IN THE GFS FORECAST
SOUNDINGS. THE LOW PRESSURE SYSTEM WILL BECOME STACKED WITH DEEP
LAYER WEST-SOUTHWESTERLY FLOW ATOP THE CWFA WITHIN THE SE QUADRANT
OF THE CIRCULATION. SO UPSLOPE WILL BE STRONGEST ON SW-FACING SLOPES
OF THE SOUTHERN AND CENTRAL NC MOUNTAINS. TEMPS AND THICKNESSES WILL
START OUT AROUND NORMAL FOR THIS TIME OF YEAR...WITH SNOW LEVELS
LIKELY TO BE MAINLY ABOVE 3500 FT. HOWEVER...IF CONVECTIVE
INSTABILITY AND STRONGER FORCING IS REALIZED...WET-BULB EFFECTS MAY
PRODUCE SOME MEASURABLE SNOW IN THE VALLEYS. EAST OF THE MOUNTAINS
MAY ALSO SEE SOME SHOWERS...BUT WITH TEMPS IN THE MID 40S TO LOWER
50S...NO SNOW IS EXPECTED.

MONDAY NIGHT THRU TUESDAY...THE AXIS OF THE UPPER TROF WILL CROSS
THE CWFA...PRODUCING ANOTHER ROUND OF MID AND UPPER LEVEL
FORCING...AND ALSO STEEP LAPSE RATES. THICKNESSES ARE COOLER THAN
MONDAY...AND FORECAST SOUNDINGS SHOW THAT ANY SHOWERS THAT DEVELOP
WILL LIKELY BE MAINLY SNOW OR PERHAPS A RAIN/SNOW MIX SOUTH/EAST OF
I-85. HOWEVER...STILL EXPECT THE BULK OF ANY QPF TO BE MAINLY IN THE
UPSLOPE AREAS OF THE NC MOUNTAINS. TEMPS ARE EXPECTED TO DROP TO
BELOW NORMAL TUESDAY MORNING...AND STAY WELL BELOW NORMAL FOR
AFTERNOON HIGHS. STORM TOTAL SNOW ACCUMS THRU TUESDAY ARE EXPECTED
TO BE MODERATE ABOVE 3500 FT...AND GENERALLY LIGHT IN THE MOUNTAINS
BELOW 3500 FT. DEPENDING ON HOW THINGS EVOLVE ON TUESDAY...THE NC
FOOTHILLS AND NW PIEDMONT MAY SEE LIGHT ACCUMS AS WELL.

TUESDAY NIGHT THRU THURSDAY...THE UPPER FLOW DEAMPLIFIES...BUT REMAIN
IN A WESTERN RIDGE-EASTERN TROF SETUP THRU THE REST OF THE MEDIUM
RANGE. TEMPS WILL BE QUITE CHILLY TUESDAY NIGHT THRU WEDNESDAY...AS
AN ARCTIC AIR MASS SETTLES INTO THE REGION...THEN SHUD GRADUALLY
MODERATE BACK TOWARD NORMAL LATE IN THE WEEK.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
AT KCLT...PESKY MVFR CIGS FINALLY LET GO EARLY THIS EVENING.
HOWEVER...APPROACHING UPPER SUPPORT FROM THE WEST ALONG WITH SLOWLY
DEEPENING MOISTURE SHOULD LOCK LOWER END VFR CIGS IN PLACE
OVERNIGHT. THE MAIN CONCERN WILL BE THE PASSING SHORTWAVE THAT PEAKS
FORCING OVER THE KCLT AREA MAINLY 07Z TO 11Z. WILL CONTINUE TO
FEATURE A TEMPO FOR SNOW SHOWERS AS THE COLDER THICKENESSES/TEMPS
SHOULD BE ARRIVING FROM THE WEST BY THAT TIME...ALONG WITH SOME
EVAPORATIVE COOLING UNDER ANY SHOWERS. THE NRLY FLOW GRADIENT WILL
STEADILY INCREASE AS WELL...AND GUSTS WILL CONTINUE THROUGH THE
MORNING HOURS AS THE SFC LOW MOVES UP THE COAST...THEN SLOWLY ABATE
THROUGH THE AFTN. SOME LIGHT DAYBREAK SNOW ACCUMULATIONS CANNOT BE
COMPLETELY RULED OUT UNDER ANY BRIEFLY HEAVY SHOWERS...BUT THE EVENT
DURATION WILL BE TOO SHORT FOR ANY ADVISORY/AIRPORT WEATHER WARNING
PRODUCTS AT PRESENT.

ELSEWHERE...VFR CIGS WILL DEVELOP AND LOWER AS THE PASSING UPPER
WAVE RAPIDLY INCREASES FORCING IN THE COLUMN INTO THE EARLY MORNING
HOURS. ENOUGH MOISTURE WILL WRAP WESTWARD FROM THE COASTAL SYSTEM TO
PERMIT ISOLD TO SCATTERED SHOWERS...MAINLY SNOW...AT TIMES OVERNIGHT
ACROSS THE FOOTHILLS. HOWEVER...CONFIDENCE IS TOO LOW FOR ANYTHING
MORE THAN A VCSH MENTION AT THIS POINT. NW FLOW MOISTURE COULD ALLOW
SNOW SHOWERS TO FLIRT WITH KAVL AS WELL...BUT THESE SHOULD STAY
CLOSER TO THE TN BORDER. WIND GUSTS WILL STEADILY DEVELOP AS THE
PRES GRADIENT TIGHTENS TONIGHT...WITH GUSTS 25 TO 30 POSSIBLE AT
KAVL AND INTO THE 20S ACROSS THE FOOTHILLS. THE GRADIENT WILL SLOWLY
RELAX THROUGH FRIDAY...WITH SKIES CLEARING.

OUTLOOK...LARGE HIGH PRESSURE WILL SLOWLY BUILD ACROSS THE REGION
THROUGH THE WEEKEND WITH UNRESTRICTED CONDITIONS EXPECTED. A STRONG
UPPER AIR DISTURBANCE COULD BRING ENOUGH MOISTURE TO WRING OUT A FEW
RAIN OR SNOW SHOWERS ON MONDAY.

CONFIDENCE TABLE...

            03-09Z        09-15Z        15-21Z        21-00Z
KCLT       HIGH  85%     HIGH  88%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   55%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  85%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WIND ADVISORY UNTIL 10 AM EST FRIDAY FOR NCZ033-049-050-501-
     503-505.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...HG
SHORT TERM...NED
LONG TERM...ARK
AVIATION...HG


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