Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 251825
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
225 PM EDT SAT APR 25 2015

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL MOVE EAST FROM KENTUCKY AND
TENNESSEE TO NORTH CAROLINA TONIGHT...THEN OFF THE COAST ON
SUNDAY.  COOL AND DRY HIGH PRESSURE DROPS DOWN FROM CENTRAL
CANADA SUNDAY AND WILL BE OUR WEATHER MAKER FOR THE FIRST HALF OF
THE WEEK.  EXPECT LOW PRESSURE TO MOVE EAST FROM TEXAS IN MID WEEK
AND BRING MORE RAIN WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
AT 230 PM EDT SATURDAY...A LOW AMPLITUDE UPPER TROUGH WAS LOCATED
OVER THE SOUTHERN APPALACHIANS THIS AFTERNOON...WHILE A CLOSED LOW
WAS OVER THE MID MS RIVER VALLEY.  THE TROUGH IS EXPECTED TO
DEAMPLIFY THIS EVENING WHILE THE CLOSED UP FILLS...RESULTING IN
ZONAL FOR OVER THE SE. SHORTWAVES MOVING THROUGH THIS FLOW WILL
CROSS OUR AREA THIS EVENING...AND AGAIN ON SUNDAY MORNING.

AT THE SURFACE...A STATIONARY FRONT WAS LOCATED FROM THE NORTHERN NC
MOUNTAINS TO THE NC OUTER BANKS EARLY THIS AFTERNOON. ALTHOUGH MOIST
ISENTROPIC UPGLIDE AND LOW CLOUDS REMAIN OVER MOST OF OUR AREA...THE
BULK OF PRECIPITATION HAS MOVES EAST OF THE AREA WITH A DEPARTING
SHORTWAVE. PRECIPITATION CHANCES ARE EXPECTED TO INCREASE AGAIN THIS
EVENING THE FRONT TO OUR NORTH DROPS SOUTH...EVEN AS UPGLIDE
WEAKENS. INSTABILITY AND SHEAR BOTH INCREASE ABOVE A LOW LEVEL
INCREASE OVERNIGHT...BEFORE A DECREASE TOWARD DAWN...INCREASING
SUPPORT FOR ELEVATED ORGANIZED CONVECTION. MINIMUM TEMPERATURES WILL
RUN ABOVE NORMAL UNDER CLOUD COVER. AS THE COLD FRONT MOVES SOUTH
ACROSS OUR AREA ON SUNDAY...A DRYING DOWNSLOPE FLOW WILL FOLLOW IN
ITS WAKE...RESULTING IN WARMING TEMPERATURES.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 210 PM SATURDAY...AS COLD FRONT SAGS SOUTH ACROSS THE AREA...
ISLD/SCT SHOWERS WILL REMAIN POSSIBLE ACROSS SOUTHERN PIEDMONT AREAS
INTO SUNDAY EVENING. MEANWHILE...A RELATIVELY MODEST/MOIST NW FLOW
COULD YIELD SOME SCATTERED SHOWERS NEAR THE TENNESSEE BORDER AS
WELL. POPS WILL GENERALLY BE CONFINED TO THOSE AREAS DURING THE
EVENING HOURS.

THE REMAINDER OF THE SHORT TERM WILL BE PLEASANTLY COOL AND DRY
UNDER THE INFLUENCE OF A BROAD LONG WAVE TROUGH ALONG THE EAST
COAST/WESTERN ATLANTIC...WITH A COUPLE OF PERIODIC SHORT WAVE
TROUGHS ONLY ACTING TO REINFORCE THE BELOW CLIMO TEMPS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 215 PM SATURDAY...CHANCES FOR PRECIPITATION WILL GRADUALLY
INCREASE THROUGH MID-WEEK...AS A SOUTHERN STREAM AREA OF LOW
PRESSURE WOBBLES OUT OF THE FOUR CORNERS REGION/TEXAS AND OPENS UP
ACROSS THE SOUTHEAST. THIS WILL CREATE COMPLICATIONS TO THE UPPER
PATTERN IN TERMS OF HOW THE NORTHERN AND SOUTHERN STREAMS WILL
INTERACT (IF AT ALL)...AND INDEED GLOBAL MODEL SOLUTIONS ARE QUITE
DISPARATE REGARDING THE SYNOPTIC DETAILS FOR MID-WEEK...ESP
REGARDING SOUTHEAST COASTAL LOW PRESSURE. NEVERTHELESS...ALL GLOBAL
MODELS AND ENSEMBLE SOLUTIONS DEPICT AT LEAST A WEAK WAVE OF LOW
PRESSURE ACROSS THE NORTHERN GULF BY TUE AFTERNOON...THUS CHANCE
POPS WILL SPREAD INTO THE AREA FROM THE SOUTHWEST TUE NIGHT INTO
WEDNESDAY. UNCERTAINTY REALLY EXPLODES AFTER WED...WHEN
DETERMINISTIC MODEL SOLUTIONS DIVERGE CONSIDERABLY (WITH THE ECMWF
DEVELOPING AN INTENSE/MILLER-A CYCLONE OFF THE CAROLINA COAST BY
THURSDAY...WHILE THE GFS BARELY DEPICTS A WEAK WAVE IN THIS AREA).
NEVERTHELESS...ENSEMBLE GLOBAL ENSEMBLE MEAN SOLUTIONS SUPPORT
MAINTAINING LOW POPS INTO THURSDAY. DRY AND SEASONABLY WARM
CONDITIONS ARE EXPECTED TO RETURN FOR LATE WEEK.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
AT KCLT...LOW CONFIDENCE FORECAST...WITH MODEL GUIDANCE QUITE
DIVERGENT. OBSERVATIONS SHOW IFR CIG RESTRICTION...BUT VSBY HAS
IMPROVED BEHIND DEPARTING RAINFALL. MODEL TIME HEIGHTS SUPPORT BRIEF
CIG IMPROVEMENT TO LOW VFR THIS EVENING BEFORE LOWERING TO AT LEAST
MVFR LATE TONIGHT INTO SUNDAY MORNING. GUIDANCE SUPPORTS AN MVFR
VSBY LATE THIS EVENING...BUT SUGGEST A RETURN TO VFR TOWARD DAWN...
OSTENSIBLY DUE TO NE WINDS THAT SET UP OVERNIGHT AS A COLD FRONT
ARRIVES FROM THE N. CONVECTIVE CHANCES APPEAR BEST OVERNIGHT AS THE
FRONT APPROACHES.

ELSEWHERE...CONFIDENCE IS LIMITED AS TRENDS DEPART FORM PREVIOUS
FORECAST...AND MODEL SOLUTIONS DIVERGE. OBSERVED CIG RESTRICTIONS
MAY IMPROVE THIS EVENING BASED ON MODEL TIME HEIGHTS...BUT PROBABLY
NOT AS MUCH AS A MODEL BLEND WOULD SUGGEST. VSBY IMPROVEMENT HAS
BEEN NOTED AS RAINFALL MOVES OFF TO THE EAST...AND THIS TREND IS
EXPECTED OT CONTINUE. TIME HEIGHTS SHOW CIGS LOWERING AGAIN TOWARD
DAWN...AND REMAINING LOW INTO SUNDAY MORNING. VSBY RESTRICTIONS
APPEAR TO RETURN AT KHKY LATE THIS EVENING...THEN END AS A BACK DOOR
COLD FRONT ARRIVES BEFORE DAWN VEERING THE WIND TO THE NE. MODEL
DATA SUPPORTS KAND HAVING A DAYBREAK VSBY RESTRICTION...BUT MODEL
WINDS REMAIN UP...FAVORING VFR. CONVECTIVE CHANCES NOW APPEAR TO BE
BEST OVERNIGHT AHEAD OF THE COLD FRONT.

OUTLOOK...A COLD FRONT WILL SWEEP ACROSS THE REGION SUNDAY
NIGHT...FOLLOWED BY DRY HIGH PRESSURE THROUGH TUESDAY. ANOTHER LOW
PRESSURE SYSTEM MAY TRACK ACROSS THE DEEP SOUTH WEDNESDAY AND
THURSDAY.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  97%     LOW   54%     MED   61%     MED   76%
KGSP       HIGH  83%     HIGH  90%     MED   67%     MED   60%
KAVL       MED   72%     MED   64%     LOW   57%     MED   75%
KHKY       HIGH  97%     LOW   55%     MED   68%     HIGH  85%
KGMU       HIGH  82%     HIGH  86%     MED   66%     MED   60%
KAND       HIGH  84%     HIGH  98%     MED   67%     MED   62%

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...JAT
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...JAT


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