Area Forecast Discussion
Issued by NWS Greer, SC

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819
FXUS62 KGSP 042354
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
654 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 645 PM EST...RADAR IS STARTING TO SHOW THE FIRST HINTS OF
LIGHT RETURNS OVER THE WESTERN CWA EARLY THIS EVENING AS THE STRONG
UPPER LEVEL SHORTWAVE BEGINS ITS PUSH TOWARD THE BASE OF THE
SOUTHERN APPALACHIANS. UPPER LEVEL SUPPORT WITH THE WAVE WILL REACH
THE SOUTHERN MOUNTAINS BY MIDNIGHT AND THEN TRANSIT QUICKLY OUT
ACROSS THE PIEDMONT THROUGH THE PRE-DAWN HOURS. THE SPEED OF THE
SYSTEM AND THE CURRENT LIMITED MOISTURE IN PROFILES CONTINUE TO BE
THE PRIMARY LIMITING FACTORS FOR ANY SIGNIFICANT SNOW ACCUMULATIONS
OVERNIGHT...BUT TEMPS ARE FALLING QUICKLY FROM THE WEST AND ANY
BURSTS OF SHOWERS UNDER THE PASSING VORT COULD QUICKLY AND EASILY
DROP A DUSTING OF SNOW ON AFFECTED LOCATIONS. WILL PUSH POPS UPWARD
INTO THE MORE SOLID CHANCE RANGE ACROSS THE EASTERN HALF OF THE
FORECAST AREA FROM MIDNIGHT ONWARD...BUT ANY LIGHT ACCUMS SHOULD
REMAIN ALONG THE HIGHER ELEVATIONS WHERE THE GROUND AND NEAR SURFACE
TEMPS ARE ALREADY MUCH COOLER.

WINDS WILL BECOME AN ISSUE OVERNIGHT AS WELL. THE PRESSURE GRADIENT
WILL TIGHTEN RAPIDLY BETWEEN THE APPROACHING SFC HIGH PRESSURE FROM
THE WEST AND THE DEEPENING NC COASTAL LOW TO YIELD SOME MARGINAL
ADVISORY CRITERIA GUSTS ALONG THE NORTHERN BLUE RIDGE OVERNIGHT
THROUGH FRIDAY MORNING. AN ADVISORY HAS BEEN POSTED IN THIS
AREA...AND GUSTS HAVE BEEN BEEFED UP SLIGHTLY ACROSS THE REST OF THE
MOUNTAINS...THE NORTHERN TIER...AND THE EASTERN PIEDMONT.

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 /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT...PESKY MVFR CIGS PERSIST EARLY THIS EVENING...AND THE UPPER
SUPPORT IS STARTING TO ARRIVE FROM THE WEST WHICH PROVIDES SOME
QUESTION WHETHER OR NOT CIGS CAN LIFT OVER THE NEXT COUPLE OF HOURS.
WILL THUS FEATURE MVFR THROUGH THE EVENING. THE MAIN CONCERN WILL BE
THE PASSING SHORTWAVE THAT PEAKS FORCING OVER THE KCLT AREA MAINLY
07Z TO 11Z. GIVEN THE TIME RESTRICTIONS...WILL RAMP UP TO 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 ARE LIKELY AFTER 04Z...CONTINUING THROUGH THE
MORNING HOURS AS THE SFC LOW MOVES UP THE COAST...THEN SLOWLY
ABATING 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 THROUGH MIDNIGHT.
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. 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...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       HIGH  83%     HIGH  85%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   55%     HIGH  92%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  92%     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 FROM 11 PM THIS EVENING TO 10 AM EST FRIDAY FOR
     NCZ033-049-050-501-503-505.
SC...NONE.

&&

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



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