Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030614
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
114 AM EST TUE MAR 3 2015

.SYNOPSIS...
COOL CANADIAN HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH
TUESDAY...BUT MOIST AND MILDER AIR SHOULD BE BACK ON WEDNESDAY OUT
AHEAD AN APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS
THROUGH THE AREA ON THURSDAY...DRYING US OUT BY THURSDAY NIGHT.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 105 AM...RADAR ECHOES CONTINUE TO BE LIMITED TO LIGHT/PATCHY
RETURNS EARLY THIS MORNING...AND THUS FAR THIS ACTIVITY IS
DEVELOPING FARTHER NORTH THAN PREVIOUSLY ANTICIPATED...GENERALLY
ACROSS THE NC MTNS AND FAR NORTHERN UPSTATE. HIGHER POPS HAVE BEEN
DELAYED...BUT THESE UPGLIDE ONSET/MOISTURE RETURN PRECIP EVENTS HAVE
A HABIT OF BLOSSOMING RATHER ABRUPTLY...SO POPS HAVE NOT BEEN
DELAYED TOO MUCH...AND WE WILL RETAIN LIKELIES ACROSS ROUGHLY THE SW
THIRD OF THE CWFA BY DAYBREAK. VERY DRY AIR...CONSIDERABLY DRIER AIR
THAN THE MODELS WERE FORECASTING...HAS NOSED ITS WAY INTO THE FAR
NORTHERN ZONES ON NE FLOW. THIS SHOULD EVENTUALLY SUPPORT WET BULB
TEMPS AT OR BELOW FREEZING ACROSS THE NORTHERN NC MTNS/BLUE RIDGE
AREA...WITH INCREASING CHANCES FOR FZRA/FZDZ EXPECTED TOWARD
DAYBREAK AND THEREAFTER.

EVENING UPDATE...SFC WEDGE DEVELOPING FARTHER SW ACROSS THE CWFA IS
ALLOWING FOR BETTER ISENT LIFT -SHRA COVERAGE ACROSS THE WRN ZONES.
MOISTURE FLUX WILL CONTINUE FROM THE GOM/ATL OVERNIGHT AND MOST
AREAS WILL SEE -RA BY 08Z OR SO. THE LATEST SOUNDINGS INDICATE A
PRONOUNCED WARM NOSE AND SFC MINS WILL DROP OFF JUST ENUF ACROSS THE
NRN BLUE RIDGE FOR POCKETS OF -FZRA JUST BEFORE AND AFTER
SUNRISE...SO NO ADJ WERE MADE TO THE FZ.Y.

AS OF 630 PM...MADE UPWARD ADJ/S TO HR/LY TEMP TRENDS WHICH ARE
STILL AFFECTED BY THE WARM AFTERNOON HEATING. WILL LIKELY BUMP UP
TONIGHT/S MIN TEMPS A LITTLE AND RUN NEW DIURNAL CURVE...EVEN
WITH WEDGE BNDRY BEGINNING TO PUSH IN.

AS OF 430 PM...UPDATED THE GRIDS TO ACCOUNT FOR PEAK TEMPS ACROSS
THE AREA RUNNING WARMER THAN THE FCST GRIDS. OBSERVED WINDS ARE A
CAT OR SO STRONGER ACROSS THE NC PIEDMONT ASSOCIATED WITH THE
BACKDOOR FRONT AND HAVE BEEN UPDATED. STILL EXPECT ISOL/SCT -RA TO
REACH THE SW/RN ZONES BY 00Z.

AS OF 230 PM...THE TARDY BACK DOOR COLD FRONT CONTINUES TO WREAK
HAVOC UPON THE TEMPERATURE FORECAST THIS AFTERNOON...WITH TEMPS ONCE
AGAIN RUNNING ABOUT TWO CATEGORIES WARMER THAN FCST AS OF 19Z. WILL
SIGNIFICANTLY BUMP TEMPS UP ONCE MORE...AND ADJUST TO THE TREND THAT
WAS TAKEN FROM A SUPER-BLEND OF GUIDANCE STARTING EARLY THIS
EVENING. NOT SEEING MUCH IN THE WAY OF PRECIP DEVELOPMENT YET...SO
POP TREND WAS ALSO KNOCKED DOWN.

WHAT WE HAVE OVER THE NEXT 24 HOURS IS ANOTHER NUISANCE-TYPE
SITUATION DEVELOPING EARLY TUESDAY MORNING...MAINLY OVER THE NRN
FOOTHILLS AND NRN MTNS OF NC. IN THE BIGGER PICTURE...A BROAD UPPER
RIDGE WILL BUILD IN FROM THE WEST TONIGHT...WITH THE UPPER RIDGE
AXIS MOVING OVERHEAD MIDDAY ON TUESDAY. A WEAK UPPER WAVE WILL TOP
THE RIDGE AND MOVE THROUGH ON TUESDAY MORNING. THE MAIN PROBLEM
ARISES WHEN THE UPPER RIDGE CARRIES A COLD DRY SURFACE HIGH PAST TO
THE N THIS EVENING AND THEN INTO A POSITION OVER THE MID ATLANTIC ON
TUESDAY MORNING TO SUPPORT A HYBRID COLD AIR DAMMING EVENT. LOW
LEVEL MOISTURE RETURN AND ISENTROPIC UPGLIDE COMMENCE ON THE BACK
SIDE OF THE HIGH AND OVER THE TOP OF THE OLD BACK DOOR COLD FRONT
LATE TONIGHT. PRECIP MAY DEVELOP AS EARLY AS THIS EVENING ACROSS THE
SAVANNAH RIVER BASIN/UPSTATE/SRN NC MTNS AS THE UPGLIDE BEGINS. WILL
START WITH A CHANCE POP THERE AND GRADUALLY EXPAND/INCREASE THE
POP...FAVORING THE BLUE RIDGE. AS IN THE PREVIOUS FCST...THERE WILL
BE A SLIVER OR AREA OF TEMPS THAT DROP DOWN TO SOMETHING SUB-
FREEZING MAINLY NEAR THE BLUE RIDGE N OF I-40 AFTER MIDNIGHT. PRECIP
AMTS WILL BE LESS THAN ONE TENTH OF AN INCH AND PROBABILITY IS
LIKELY AT BEST...BUT THE PRECIP TYPE WOULD BE FREEZING RAIN/DRIZZLE.
THINK IT BEST TO RAISE A FREEZING RAIN ADVISORY FOR THAT REGION FOR
LATE TONIGHT/TUESDAY MORNING. TEMPS WILL RISE ABOVE FREEZING BY LATE
MORNING. THE REST OF AREA SHOULD REMAIN ABOVE FREEZING. WILL HOLD
ONTO A LIKELY POP FOR THE BALANCE OF TUESDAY MAINLY OVER THE WEST...
WITH A CHC OVER THE EASTERN FRINGE. TEMPS ON TUESDAY WILL SEEM LIKE
A CRUEL JOKE...NEARLY 20 DEGREES COLDER THAN TODAY...WITH A NE WIND.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AT 300 PM EST MONDAY...THE SHORT TERM FCST PERIOD INITIALIZES
TUESDAY EVENING AMONGST WEAK UPPER RIDGING ALOFT OVER THE
EAST...WHILE A TROF SLIDES THROUGH THE NORTHERN PLAINS.  AT THE
SURFACE...A POTENT COLD FRONT WILL BE SLIDING THROUGH THE OHIO
VALLEY WHILE A MODEST WARM SECTOR ESTABLISHES ITSELF OVER THE
SOUTHEAST AIDED BY SOUTHERLY FLOW AROUND WESTERN ATLANTIC SURFACE
RIDGE.  THE FCST INITIALIZES WITH LIKELY POPS ACROSS THE MTNS DUE TO
SOUTHERLY UPSLOPING WHILE LOWER MID RANGE CHANCE POPS ARE FEATURED
FURTHER EAST.  POPS WILL DECREASE THROUGH THE OVERNIGHT ACROSS THE
EASTERN TIER OF THE FCST AREA WHILE SOLID LIKELY POPS REMAIN OVER
THE HIGH TERRAIN INTO WEDNESDAY.

MODELS CONTINUE TO INDICATE SOME DESTABILIZATION IN THE WARM SECTOR
ACROSS THE MTNS ON WEDNESDAY AHEAD OF THE FRONT...THUS ADDED MENTION
OF THUNDER WHERE NEEDED ALTHOUGH NO DEEP ORGANIZED CONVECTION IS
FCST.  OUTSIDE OF THE MTNS ONLY SHOWERS WERE MENTIONED. POPS WILL
GRADUALLY INCREASE ACROSS THE ENTIRE REGION WEDNESDAY NIGHT INTO
THURSDAY AS THE FROPA OCCURS LEADING TO SOLID LIKELY POPS BY EARLY
MORNING THURSDAY.  AT THAT POINT...THE PRIMARY FOCUS OF THE PERIOD
BECOMES WINTRY WEATHER CONCERNS ALONG THE NC MTN ZONES NEAR THE TN
LINE.   MODELS INDICATE A PERIOD WHEN THERMAL PROFILES YIELD A
SUBFREEZING LAYER NEAR THE SURFACE...AHEAD OF THE DEEPER COLD
ADVECTION ALOFT.  THE NAM BEING THE MOST AGGRESSIVE WITH SUCH WOULD
YIELD A PROLONGED PERIOD OF FZRA ACROSS THE SPINE OF THE
APPS...BEFORE A CHANGE OVER TO ALL SNOW.  THE GFS LEANED TOWARDS A
FASTER COLD ADVECTION PATTERN...THUS A SHORTER PERIOD OF FZRA.
OPTED FOR THE GFS SOLUTION...WHICH HAPPENED TO BE MUCH ALIGNED WITH
THE NEW ECMWF.  THEREFORE...FCST FEATURES A PERIOD OF FZRA ALONG THE
TN LINE ON THURSDAY MORNING...BEFORE A PHASE CHANGE OCCURS TO
SLEET...THEN ALL SNOW.  TOTAL SNOW AND ICE ACCUMULATIONS REMAIN
BELOW ADVISORY CRITERIA AT THIS POINT THEREFORE WILL NOT MENTION IN
HWO. FURTHER EAST ALONG THE FRONT...PROFILES WILL REMAIN SUPPORTIVE
OF ALL RAIN PROCESSES WITH POPS DECREASING INTO THE LATE AFTERNOON
HOURS.  TEMPERATURES ON WEDNESDAY WILL BE ABOVE NORMAL AMONGST WAA
REGIME...WHILE BELOW NORMAL TEMPERATURES RETURN POST FROPA ON
THURSDAY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MON...SFC FRONT WILL DEPART THE AREA TO THE EAST THU
NIGHT AS SPRAWLING CANADIAN HIGH PRESSURE FILLS IN FROM THE NW. LLVL
PROFILES ALONG THE TENN BORDER INDICATE A LOW CHANCE OF LINGERING
SNOW SHOWERS IN NW FLOW...BUT THIS DIMINISHES QUICKLY. GLOBAL MODELS
NOW IN STRONG CONSENSUS THAT THE HIGH WILL CONTINUE TO PUSH THE
FRONTAL BOUNDARY TO THE FLA PANHANDLE. DRY CONDITIONS WILL PREVAIL
FRI-SAT AS A RESULT. MAX TEMPS 10 TO 15 DEGREES BELOW CLIMO FRIDAY
BEFORE AIRMASS MODIFIES AND TOP OUT AROUND 5 BELOW CLIMO SATURDAY.
HOWEVER COOL TEMPS ARE REINFORCED BY A SECOND COLD FRONT SATURDAY
NIGHT. WHILE THE FROPA ITSELF APPEARS GENERALLY DRY EXCEPT POSSIBLY
ALONG THE TENN BORDER...THE 02/00Z EC AND A HANDFUL OF NAEFS
ENSEMBLE MEMBERS SUGGEST A WAVE COULD DEVELOP ALONG THE OLD
STATIONARY FRONT OVER THE CENTRAL GULF STATES AND LIFT INTO THE AREA
SUN OR SUN NIGHT. POPS WERE ALLOWED TO RAMP BACK UP FROM THE SW
BEGINNING SUNDAY. TEMPS SUN NIGHT WILL BE COOL ENOUGH THAT A
RAIN/SNOW MIX COULD RESULT OVER PARTS OF THE AREA. FURTHER
MODERATION IN TEMPS IS IN STORE FOR MONDAY AS SKIES BEGIN TO CLEAR.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...FINALLY SEEING SOME EXPANSION OF MVFR CIGS
ACROSS PORTIONS OF UPSTATE SC AND FAR WESTERN NC...BUT THE ONSET OF
SAID LOWER CIGS HAS BEEN DELAYED AT KHKY/KCLT UNTIL 08-10Z.
OTHERWISE...AREAS OF PATCHY -RA AND DZ WILL GRADUALLY EXPAND ACROSS
THE AREA THROUGH THE MORNING...WITH VISBY RESTRICTIONS BECOMING MORE
LIKELY BY DAYBREAK AT THE SC TERMINALS AND KAVL. CIGS ARE ALSO
EXPECTED TO  LOWER TO IFR...BUT NOT UNTIL AFTER SUNRISE AT MOST
TERMINALS... ALTHOUGH A TEMPO FOR BKN008 HAS BEEN INCLUDED AT KAND
AFTER 11Z. ONCE DETERIORATION TO IFR OCCURS...CIGS WILL REMAIN LOW
THROUGH THE DAY AND INTO TUE EVENING...ACCOMPANIED BY OCCL -RA/DZ
AND REDUCED VISBY...AS COLD AIR DAMMING EVENT BECOMES ESTABLISHED.
IN FACT...LIFR CONDITIONS WILL LIKELY BECOME ESTABLISHED AT SOME
POINT...ALTHOUGH THE EXACT TIMING OF THAT IS DIFFICULT TO PIN DOWN
ATTM. OTHERWISE...NE WINDS WILL PERSIST THROUGH THE PERIOD. WITH
FLOW TURNING RAPIDLY TOWARD THE SW ABOVE THE COOL WEDGE...THERE WILL
BE ENHANCED LL WIND SHEAR...BUT NOT QUITE REACHING CRITERIA FOR A
TAF MENTION.

OUTLOOK...A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION WED
THROUGH THURSDAY...BRINGING CHANCES FOR HEAVIER RAINFALL AND LOW
CIGS/VSBYS TO THE AREA. VFR CONDITIONS ARE EXPECTED TO RETURN
FOR FRIDAY AND SATURDAY.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     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 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...FREEZING RAIN ADVISORY UNTIL NOON EST TODAY FOR NCZ033-049-050-
     501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...CSH
NEAR TERM...JDL/PM/SBK
SHORT TERM...CDG
LONG TERM...WIMBERLEY
AVIATION...JDL



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