Area Forecast Discussion
Issued by NWS Greer, SC

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434
FXUS62 KGSP 041942
AFDGSP

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

.SYNOPSIS...
A COLD FRONT WILL LINGER NEAR THE CAROLINA COAST EARLY 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 THROUGH MID WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 245 PM...THE WESTERN EDGE OF THE LIGHT PRECIP HAS BEEN SHUNTED
OFF TO THE EAST...CLOSE TO THE EDGE OF UNION COUNTY NC...BUT NOT
CLOSE ENOUGH TO KEEP ANYTHING MORE THAN A CHANCE OVER THE EASTERN
HALF OF UNION COUNTY AND A SLIGHT CHC OVER THE SE PART OF THE CLT
METRO AREA. CLOUDS CONTINUE TO THIN OUT OVER THE WRN PIEDMONT AND
FOOTHILLS. HIGH TEMPS LOOK LIKE THEY SHOULD WORK OUT JUST FINE.

THE SITUATION GETS INTERESTING THIS EVENING WITH THE ARRIVAL OF A
STRONG SHORT WAVE SEEN ON WATER VAPOR IMAGERY CURRENTLY ABOUT TO
CROSS THE MISSISSIPPI R. THE SHORT WAVE WILL BRING A SHOT OF STRONG
MID-LEVEL FORCING IN THE FORM OF DPVA AND WARM ADVECTION. AT THE
SAME TIME...SOME WEAK UPPER DIVERGENCE MOVES OVERHEAD...ALONG WITH A
TROPOPAUSE FOLD THAT SHOULD INJECT SOME STRATOSPHERIC VORTICITY INTO
THE MIX. THIS WILL GREATLY HELP CYCLOGENESIS OFF THE COAST OF NC
LATE TONIGHT...BUT MAY ALSO FORCE THE DEVELOPMENT OF LIGHT PRECIP
MAINLY OVER THE PIEDMONT IN THE MID- TO LATE-EVENING. WHAT IT LACKS
IS LOW LEVEL FORCING...WHICH IS MERELY WEAK IF THE 850MB LOW MOVES
AS PLANNED TO THE NORTH. THE GEFS IS PARTICULARLY INSISTENT THAT AT
LEAST THE NC PIEDMONT WILL SEE SOME PRECIP LATE THIS EVENING. THE
HRRR AND WRF-NMM AGREE...WHILE THE ARW IS NOT AS IMPRESSED. EVEN THE
NEW ECMWF AND 15Z RUN OF THE SREF AGREE IN PRINCIPLE WITH LIGHT
PRECIP DEVELOPING OVER THE NW PIEDMONT. SO...THE FCST WILL FOLLOW A
TREND IN THAT DIRECTION WITH A LARGER AREA OF CHANCE POP OVER THE NC
WRN PIEDMONT. KEEP AN EYE ON THE CAM GUIDANCE AND 18Z RUNS...AS THIS
MIGHT HAVE TO BE BUMPED UP CONSIDERABLY LATER THIS AFTERNOON OR
EVENING IF THE TREND CONTINUES. ASSUMING THE PRECIP DEVELOPS...THE
RACE BETWEEN IT AND THE COLD AIR WILL BE UNDERWAY. THICKNESS WILL
DROP AS COLD AIR MOVES IN BEHIND THE DEVELOPING SURFACE LOW LATE
TONIGHT...SUCH THAT ANY REMAINING PRECIP WILL CHANGE OVER FROM N TO
S BETWEEN 06Z AND 09Z. RIGHT NOW...THAT LEAVES OPEN ONLY THE
NARROWEST OF WINDOWS TO SEE ANY SNOW. THE CHANCE IS TOO LOW AND THE
TIMING TOO SHORT TO EXPECT ANY ACCUMULATION...AND CONFIDENCE IS TOO
LOW TO MENTION IN THE HWO. BUT THERE IS A CHANCE IT COULD ACCUMULATE
OVER THE EAST TOWARD MORNING. TEMPS WILL BOTTOM OUT IN THE LOW 30S.

THE REST OF THE FCST LOOKS RELATIVELY BORING. AN UPPER RIDGE WILL
QUICKLY BUILD IN FROM THE WEST BY FRIDAY AFTERNOON WITH HIGH
PRESSURE RIDGING IN FROM THE WEST. THIS SHOULD GIVE US A SEASONALLY
COOL AND SUNNY WINTER DAY. WIND COULD BE QUITE GUSTY ACROSS THE
RIDGETOPS IN THE MORNING...AND TO THE LEE OF THE NRN MOUNTAINS...
BUT NOT QUITE ENOUGH RIGHT NOW TO WARRANT A WIND ADVISORY.

&&

.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...IT 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 /20Z THURSDAY THROUGH TUESDAY/...
AT KCLT...BKN MVFR CEILING REMAINED ACROSS THE WRN PIEDMONT...BUT
DRIER AIR WAS SLOWLY FILTERING IN FROM THE WEST. THINK THAT BY MID
AFTERNOON THE LOW CLOUDS WILL SCATTER AND VFR WILL PREVAIL WITH A
MAINLY MID-LEVEL CEILING. HAVE KEPT A TEMPO FOR THE MVFR CEILING
THRU THE AFTERNOON...BUT THIS COULD BE FOR TOO LONG OF A PERIOD.
WIND SHOULD REMAIN NE TO N INTO THE MID EVENING. THINGS GET MURKY
LATER THIS EVENING. AS AN AREA OF LOW PRESSURE ORGANIZES AND DEEPENS
OFF THE COAST THIS EVENING IN RESPONSE TO THE ARRIVAL OF A STRONG
SHORT WAVE ALOFT...THE MODELS INDICATE THE DEVELOPMENT OF SOME LIGHT
PRECIP ACROSS THE PIEDMONT. DEEP LAYER FORCING LOOKS ADEQUATE FOR
PRECIP PRODUCTION FROM MAINLY A VFR CLOUD DECK. THIS SHOULD BE IN A
LIQUID FORM IF IT HAPPENS BEFORE 06Z WHEN THE STRONGEST FORCING
MOVES THRU AND TEMPS HAVE NOT COOLED EXCESSIVELY IN THE BOUNDARY
LAYER. IF ANY PRECIP PERSISTS PAST 06Z...IT WOULD BE IN THE FORM OF
SNOW SHOWERS. FOR THE TIME BEING...THE CHANCE OF PRECIP DOES NOT
APPEAR TO BE HIGH ENOUGH TO INCLUDE IN THE TAF. HOWEVER...A FEW SNOW
SHOWERS ARE WITHIN THE REALM OF POSSIBILITIES AT KCLT BETWEEN 06Z
AND 12Z FRIDAY. SKY SHOULD CLEAR QUICKLY AROUND DAYBREAK.
THEREAFTER...WITH A DEEPENING BOUNDARY LAYER AND COLD ADVECTION...WE
SHOULD HAVE A STRONG AND GUSTY NW WIND.

ELSEWHERE...VFR THRU THE PERIOD. CLOUDS MAY REDEVELOP THIS EVENING
BUT SHOULD HAVE BASES AT LEAST 050. WIND WILL COME AROUND TO N AND
NW. ON FRIDAY...EXPECT A STRONG AND GUSTY NW WIND.

OUTLOOK...LARGE HIGH PRESSURE WILL SLOWLY BUILD ACROSS THE REGION
THROUGH THE WEEKEND...GRADUALLY PUSHING OUT THE LINGERING MOISTURE
LATE THU INTO EARLY FRIDAY. UNRESTRICTED CONDITIONS ARE THEN
EXPECTED THROUGH THE WEEKEND. A STRONG UPPER AIR DISTURBANCE COULD
BRING ENOUGH MOISTURE TO WRING OUT A FEW RAIN OR SNOW SHOWERS ON
MONDAY.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       HIGH  80%     HIGH  93%     HIGH  97%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     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 100%     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...NONE.
SC...NONE.

&&

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



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