Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 281543
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1043 AM EST SUN DEC 28 2014

.SYNOPSIS...
A COLD FRONT WILL SLOWLY CROSS OUR REGION THROUGH MONDAY...THOUGH
SOME MOISTURE WILL LINGER UNTIL TUESDAY. DRIER AND COOLER HIGH
PRESSURE WILL MOVE ACROSS THE AREA WEDNESDAY AND THURSDAY. ANOTHER
LOW PRESSURE SYSTEM THEN SHOULD BEGIN TO TAKE SHAPE AT THE END OF
THE WEEK...BRINGING PRECIPITATION BACK TO THE AREA BY FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1045 AM EST UPDATE...A BAND OF LIGHT TO MODERATE RAIN CURRENTLY OVER
THE SOUTHERN TIER OF THE CWA IS EXPECTED TO EXIT EAST OF THE AREA BY
NOON...WITH A DRY SLOT MOVING IN THRU THE REST OF THE REGION THRU
THIS AFTERNOON. HENCE...POPS WERE LOWERED INTO THE SLIGHT CHANCE
RANGE OVER THE PIEDMONT...AND LOW END CHANCE RANGE IN THE MTNS ZONES
BETWEEN 18Z AND 00Z SUN...BEFORE RAMPING BACK UP FROM NW TO SE THRU
TONIGHT AS ANOTHER BAND OF PRECIP ASSOCIATED WITH AN UPPER TROUGH
AXIS APPROACHES FROM THE WEST.

910 AM EST UPDATE...HAVE RAISED POPS TO 90/100 RANGE THIS MORNING
OVER THE SOUTHERN HALF OF THE CWA PER LATEST RADAR TREND. THIS IS
WELL IN LINE WITH THE LATEST HRRR WHERE THE HEAVIEST RAIN BAND WILL
MOVE ACROSS ALONG AND SOUTHEAST OF THE I-85 THIS MORNING THRU
MIDDAY. ALSO...HAVE INCLUDED AREAS OF PATCHY FOG TO ACCOUNT FOR THE
LATEST SURFACE OBS.

AS OF 645 AM...RAIN SHIELD HAS MADE VERY LITTLE NORTHWARD PROGRESS
ABOVE (ROUGHLY) I-85 THIS MORNING...AND AM BEGINNING TO WONDER IF
THE PRECIP ISN/T GOING TO JUST FIZZLE MORE OR LESS IN PLACE...AS
UPGLIDE WEAKENS...AND THE MID-LEVELS DRY OUT. WILL CONTINUE TO
FEATURE HIGH POPS (60-80) ACROSS OUR NC ZONES...BUT THESE HAVE BEEN
SCALED BACK FROM THE EARLIER FORECAST. OTHERWISE...TEMPS ARE
EXPECTED TO REMAIN MORE OR LESS STEADY THIS MORNING UNDER DENSE
CLOUD COVER.

AREA OF MODERATE RAIN IS FINALLY PUSHING ACROSS THE UPPER SAVANNAH
RIVER VALLEY THIS MORNING. IN GENERAL...THIS IS FARTHER SOUTH THAN
WHAT THE MODELS HAVE RECENTLY BEEN DEPICTING...AND THE HIGHEST QPF
FOR THIS MORNING HAS BEEN ADJUSTED TO THE UPSTATE AND NORTHEAST
GA...WHERE RAINFALL AMOUNTS THIS MORNING SHOULD RANGE FROM ONE
QUARTER TO ONE HALF INCH...WITH LOCALLY HIGHER AMOUNTS. THE PRECIP
SHIELD IS EXPECTED TO SHIFT NORTHWARD WITH TIME...AS THE BROAD BAND
OF ISENTROPIC LIFT TRANSLATES NORTHEAST TOWARD THE MID-ATLANTIC.
THEREFORE...THE MOUNTAINS AND FOOTHILLS OF WESTERN NC MAY YET SEE UP
TO A HALF INCH OF RAINFALL THIS MORNING...WITH LIGHTER AMOUNTS
TOWARD THE I-77 CORRIDOR.

AS UPGLIDE SHUTS OFF AND MID-LEVELS DRY OUT THIS AFTERNOON...PRECIP
SHOULD COME TO AN END...ALTHOUGH THE LOW LEVELS WILL REMAIN VERY
MOIST AND THERE MAY BE PATCHES OF DRIZZLE OR LIGHT RAIN LINGERING.
POPS WILL THEREFORE BE KEPT IN THE TOKEN CHANCE RANGE IN MOST AREAS
THROUGH THE AFTERNOON. WITH PRECIP FALLING INTO A DRY AIR MASS THIS
MORNING...FOLLOWED BY ABUNDANT LOW CLOUD COVER THROUGH THE
AFTERNOON...A WEAK IN-SITU CAD EVENT MAY RESULT...AND MAX TEMPS ARE
EXPECTED TO END UP BEING RATHER CLOSE TO CLIMO...DESPITE HIGH
THICKNESS VALUES FOR THE TIME OF YEAR.

A SHORT WAVE TROUGH EJECTING FROM TEXAS/THE LOWER MISS VALLEY
TONIGHT WILL DAMPEN AS IT ENCOUNTERS THE CONFLUENT UPPER FLOW ACROSS
THE EASTERN CONUS. NEVERTHELESS...A CONSENSUS OF MODEL GUIDANCE
DEPICTS WEAK CYCLOGENESIS OCCURRING ALONG A BAROCLINIC ZONE ACROSS
GEORGIA AND THE CAROLINAS...SUPPORTING ANOTHER ROUND OF RAINFALL
LATE TONIGHT INTO EARLY MONDAY...AND WARRANTING CATEGORICAL POPS IN
ALL AREAS ONCE AGAIN. ANOTHER ROUND OF .25-.50 INCH QPF APPEARS
LIKELY IN MOST AREAS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM SUNDAY...PESKY FRONTAL ZONE FINALLY DOES LOOK TO BE
FORCED SOUTH AND EAST OF THE CWFA MONDAY AS A CANADIAN AIRMASS
EXPANDS OVER MOST OF THE ERN CONUS. COOLER AND DRIER AIR DO START TO
FILTER IN BY MONDAY NIGHT...BUT SOME LLVL MOISTURE DOES LINGER INTO
TUE. THE SOUTHEAST REMAINS UNDER BROADLY CYCLONIC FLOW THROUGH THAT
TIME...WITH AN EMBEDDED SHORTWAVE PROGGED TO MOVE FROM THE MID
MISSISSIPPI VALLEY TO THE DELMARVA BY TUE NIGHT. A WEAK BOUNDARY
ASSOCIATED WITH THIS WAVE WILL ENHANCE COLD ADVECTION AND LLVL LIFT
MON NIGHT/EARLY TUE...IN TIME TO ENCOUNTER THE MOISTURE. THUS POPS
EXHIBIT A SECONDARY PEAK TUE MRNG. AS WINDS VEER TO NW AROUND THAT
TIME...SOME UPSLOPE ENHANCEMENT IS ALSO EXPECTED WITH POPS TAKING A
LITTLE LONGER TO TAPER OFF TUE NEAR THE TENN BORDER. TEMPS ARE
EXPECTED TO REMAIN ABOVE CLIMO THROUGH TUE MRNG. PROFILES INDICATE AN
ACCORDINGLY WARM COLUMN...AND THE MOISTURE WILL BE CONCENTRATED IN
THE LOW TO MID LEVELS. ICE NUCLEATION AND SNOW PRODUCTION ARE
UNLIKELY...SO WITH TEMPS REMAINING ABOVE FREEZING THROUGHOUT THE CWFA
MON NIGHT NO MENTION OF WINTRY PRECIP HAS BEEN MADE.

IN THE WAKE OF THE BOUNDARY DEEPER DRYING BEGINS LATER TUE AND
CONTINUES THROUGH MID-WEEK...WITH SKIES TRENDING CLEARER. MAX TEMPS
WILL RETURN TO AROUND CLIMO TUE FOLLOWED BY SIMILARLY NORMAL TEMPS
FOR WED MRNG. DESPITE THE COLD ADVECTION...NOTABLY GUSTY WINDS ARE
NOT EXPECTED WITH THE LEADING EDGE OF THE AIRMASS HAVING ALREADY
PUSHED THROUGH.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 AM SUNDAY...REMARKABLY STRONG SFC HIGH PRESSURE OVER THE
CENTRAL PLAINS GETS SHUNTED SWD AS NRN STREAM SHORTWAVE DIVES INTO
THE MIDWEST AND PATTERN BEGINS TO REAMPLIFY OVER THE EAST. DRY AND
SEASONABLY COOL WEATHER WILL CONTINUE FOR OUR AREA WED-THU WITH TEMPS
NEAR CLIMO. THE SFC HIGH MOVES OVER THE SOUTHEAST BY THU NIGHT
INITIATING RETURN FLOW INTO THE WRN GULF STATES AS THE CUTOFF LOW
OVER THE DESERT SOUTHWEST PICKS UP SPEED. EVENTUALLY THAT WILL TRACK
ACRS THE MIDDLE OR LOWER MISSISSIPPI VALLEY...SPINNING UP A NEW
SYSTEM.  AGREEMENT BETWEEN THE 28/00Z RUNS OF THE GFS AND EC IS
GENERALLY GOOD...NOW ONLY SHOWING MINOR DIFFERENCES IN THE SFC LOW
TRACK. REGARDLESS OF THE PRECISE TRACK PRECIP CHANCES BEGIN TO
INCREASE THU NIGHT BEFORE PEAKING SATURDAY. MODELS HINT AT SOME PTYPE
CONCERNS EARLY IN THE EVENT WITH A POSSIBLE IN-SITU CAD EVENT
DEVELOPING...BUT THE BULK OF THE PRECIP SHOULD BE RAIN WITH TEMPS
TRENDING ABOVE NORMAL BEYOND FRIDAY.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
AT KCLT...-RA HAS BEEN SLOW TO MATERIALIZE OVER THE TERMINAL THIS
MORNING...REMAINING SOUTHWEST THROUGH SOUTHEAST OF THE TERMINAL THUS
FAR. STILL EXPECT PERIODS OF -RA TO DEVELOP THIS MORNING...AS THE
LOW LEVEL LIFT RESPONSIBLE FOR THE PRECIP GRADUALLY SHIFTS NORTH.
HOWEVER...WITH SOME UNCERTAINTY REGARDING THE PRECIP POTENTIAL...
THERE IS ALSO UNCERTAINTY AS TO HOW MUCH CIGS WILL LOWER LATER THIS
MORNING. THE LATEST GUIDANCE HAS COME IN A LITTLE MORE OPTIMISTIC
REGARDING THE IFR POTENTIAL...AND WE WILL CONTINUE TO HOLD OFF IFR
CIGS UNTIL THE AFTERNOON. IN FACT...I/M BECMG LESS CONFIDENT THIS
WILL EVEN WORK OUT...BUT DO NOT HAVE ENOUGH CONFIDENCE TO REMOVE THE
IFR CIGS ALTOGETHER. EXPECT CONDITIONS TO IMPROVE TO MVFR OR VFR BY
THIS EVENING. HOWEVER...CIGS WILL BEGIN TO LOWER AGAIN LATE TONIGHT
AS LIFT INCREASES AGAIN IN RESPONSE TO APPROACHING UPPER AIR
DISTURBANCE. MVFR CONDITIONS APPEAR TO BE A GOOD BET AFTER
MIDNIGHT...AND WOULD NOT BE SURPRISED TO SEE IFR DEVELOP BY THE END
OF THE PERIOD. WINDS SHOULD REMAIN LIGHT S/SW THROUGH MUCH OF THE
PERIOD.

ELSEWHERE...IFR OR EVEN LIFR CONDITIONS ARE EXPECTED TO PERSIST AT
KAND THROUGH THE MORNING...ALONG WITH OCCL MVFR VISBY IN -RA. THESE
CONDITIONS ARE EXPECTED TO DEVELOP AT KGSP/KGMU BY 15Z OR SO. THINGS
ARE A BIT MORE UNCERTAIN AT THE NC TERMINALS...AS -RA HAS BEEN SLOW
TO MATERIALIZE. IT APPEARS THAT -RA SHOULD EVENTUALLY DEVELOP AT
KAVL...BUT WHETHER THIS WILL BE ENOUGH TO BRING THE CIGS DOWN INTO
THE IFR RANGE IS UNCERTAIN. NEVERTHELESS...GUIDANCE CONTINUES TO
INSIST THAT IFR CIGS WILL DEVELOP THERE...SO A TEMPO HAS BEEN
INCLUDED DURING LATE MORNING. AT KHKY...FEEL A BIT MORE CONFIDENT IN
HOLDING OFF ON THE IFR CONDITIONS UNTIL 18Z. EXPECT CONDITIONS TO
IMPROVE TO MVFR OR VFR BY THIS EVENING. HOWEVER...CIGS WILL BEGIN TO
LOWER AGAIN LATE TONIGHT AS LIFT INCREASES AGAIN IN RESPONSE TO
APPROACHING UPPER AIR DISTURBANCE. MVFR CONDITIONS APPEAR TO BE A
GOOD BET AFTER MIDNIGHT...AND WOULD NOT BE SURPRISED TO SEE IFR
DEVELOP BY THE END OF THE PERIOD.

OUTLOOK...PERIODS OF LIGHT RAIN AND FLIGHT RESTRICTIONS MAY LINGER
MONDAY AND MONDAY NIGHT BEFORE GRADUAL IMPROVEMENT OCCURS THROUGHOUT
TUESDAY. DRY HIGH PRESSURE SHOULD RETURN BY MID-WEEK.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       MED   69%     MED   72%     LOW   52%     HIGH 100%
KGSP       MED   69%     MED   66%     LOW   38%     HIGH  90%
KAVL       MED   63%     LOW   58%     LOW   49%     MED   73%
KHKY       HIGH  80%     MED   61%     LOW   38%     MED   70%
KGMU       HIGH  83%     MED   72%     LOW   44%     HIGH  83%
KAND       HIGH  83%     LOW   47%     LOW   33%     HIGH  86%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...JDL/JOH
SHORT TERM...WIMBERLEY
LONG TERM...ARK/WIMBERLEY
AVIATION...JDL



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