Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 022150
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
450 PM EST MON MAR 2 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 TUESDAY/...
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 /TUESDAY NIGHT 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 /22Z MONDAY THROUGH SATURDAY/...
AT KCLT...VFR EXPECTED INTO THE MIDDLE PART OF THE EVENING. THINK
LOW CLOUDS WILL DEVELOP THIS AFTERNOON WITH BASES IN THE 035-050
RANGE...WHICH COULD BRING A TEMPORARY CEILING. A WEST WIND AT THE
MOMENT IS MOST LIKELY TO COME AROUND TO NW OR N. THE SITUATION
SHOULD GO DOWNHILL THIS EVENING AS LOW LEVEL MOISTURE RETURNS ALONG
WITH ISENTROPIC LIFT ABOVE A BACK DOOR COLD FRONT EXPECTED TO SLIP
THROUGH FROM THE NE DURING THE EARLY EVENING. EXPECT AN MVFR CEILING
TO DEVELOP NO LATER THAN 03Z...WHICH WILL EVENTUALLY LOWER TO IFR AS
LIGHT PRECIP DEVELOPS AND UPGLIDE INCREASES IN THE PRE-DAWN HOURS.
WINDS SHOULD BE NE FROM EARLY EVENING THROUGH THE END OF THE TAF
PERIOD. THERE SHOULD BE SOME IMPROVEMENT TO CEILINGS...INTO THE
LOWER PART OF MVFR...AROUND MID MORNING ON TUESDAY AS THE BOUNDARY
LAYER WARMS.

ELSEWHERE...AN MVFR CEILING AT KAVL SHOULD BREAK UP DURING THE EARLY
TO MID AFTERNOON. AFTER THAT...THE FCST WILL PROCEED SIMILAR TO KCLT
WITH SOME MINOR TIMING DIFFERENCES. THE BACK DOOR FRONT SHOULD DROP
DOWN TO THE S/SW ACROSS THE REGION IN THE EARLY TO MID EVENING...
BRINGING THE WIND AROUND TO THE N/NE. CLOUDS DEVELOP IN THE MID
EVENING AS THE FRONT GOES THROUGH...FIRST MVFR AND THEN IFR. A
CONCERN WILL BE TEMPS IN THE PRE-DAWN THRU DAYBREAK HOURS. AT THIS
TIME...IT APPEARS THAT ONLY KHKY HAS A CHANCE AT ANY FREEZING
RAIN...AND THAT CHANCE SHOULD BE SMALL AS THE MAIN POTENTIAL IS
ACTUALLY CLOSER TO THE BLUE RIDGE.

OUTLOOK...LOW CIGS AND LIGHT PRECIP/DRIZZLE WILL BE LIKELY ACROSS
MUCH OF THE AREA IN TUESDAY AFTERNOON AND EVENING. A COLD FRONT WILL
MOVE SLOWLY THROUGH THE REGION WED THROUGH THURSDAY...BRINGING
CHANCES FOR HEAVIER RAINFALL TO THE AREA. FRIDAY AND SATURDAY LOOK
VFR.

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 FROM MIDNIGHT TONIGHT TO NOON EST
     TUESDAY FOR NCZ033-049-050-501-503-505.
SC...NONE.

&&

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


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