Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 150545
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
145 AM EDT TUE APR 15 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE MOUNTAINS EARLY TUESDAY AND THE PIEDMONT
AROUND MID DAY.  UNSEASONABLY COLD HIGH PRESSURE WILL BE IN CONTROL
OF OUR WEATHER FROM TUESDAY NIGHT INTO FRIDAY. A DEEP UPPER TROUGH
ARRIVES FROM THE WEST TO START THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 145 AM...WIDESPREAD SHOWERS MOVING BACK ACROSS THE AREA.
EXPECT THESE TO CONTINUE THRU THE MORNING BEFORE ENDING FROM SW TO
NE THRU THE AFTERNOON. INSTABILITY REMAINS LIMITED...BUT A RUMBLE OF
THUNDER OR TWO CANNOT BE RULED OUT...ESPECIALLY ALONG AND JUST WEST
OF THE I-77 CORRIDOR.

AT 1030 PM EDT... RAIN SHOWER COVERAGE WAS QUITE EXTENSIVE ACROSS
THE CENTRAL AND EASTERN CWA. ONLY PATCHY LIGHT RAIN WAS EVIDENT ON
RADAR OVER THE MOUNTAINS... BUT MORE SUBSTANTIAL RAIN TO THE WEST
WAS SPREADING INTO NORTH GEORGIA AND ADVANCING STEADILY TOWARD THE
SOUTHERN APPALACHIANS. PRUDENT COURSE OF ACTION AT THIS POINT IS TO
CONTINUE HIGH POPS DURING THE REMAINDER OF THE NIGHT. THUNDER CHANCE
FOR MOST OF THE AREA IS MINIMAL. HOWEVER... A SMALL AREA OF MUCAPE
GREATER THAN OR EQUAL TO 500 J/KG WAS JUST TO OUR EAST AND THE
WESTERN EDGE OF THE HIGHER VALUES HELPED TO DEFINE A WEAK BOUNDARY
OVER THE EXTREME EASTERN PORTION OF THE FORECAST AREA WHERE SEVERAL
SMALL CONVECTIVE CELLS HAVE DEVELOPED DURING THE PAST THREE OR FOUR
HOURS. MOST OF THE CONVECTIVE CELL DEVELOPMENT WAS NORTH OF THE
CHARLOTTE METRO... IN ROWAN... IREDELL... AND DAVIE COUNTIES.  BRIEF
HEAVY RAIN AND A PERIOD OF GUSTY WIND WILL ACCOMPANY THESE SMALL
STORMS. ADDITIONAL DEVELOPMENT IS POSSIBLE OVERNIGHT IN THE
FAVORABLE ENVIRONMENT AHEAD OF THE APPROACHING UPPER LEVEL TROUGH
AND SURFACE FRONT. HODOGRAPHS DISPLAY IMPRESSIVE SURFACE TO 3-KM
HELICITY... BUT THE LACK OF CAPE IS HINDERING STRONG UPDRAFT
FORMATION. NONETHELESS... THE FAVORABLE LOW-LEVEL WIND FIELD CAN
CONTRIBUTE TO SMALL CONVECTIVE CELL ORGANIZATION FROM CHESTER AND
YORK COUNTIES NORTHEAST THROUGH THE CHARLOTTE AREA TO DAVIE COUNTY
THROUGH THE OVERNIGHT HOURS.

AT 730 PM... GENERAL TREND LEADING TOWARD HIGH POPS OVERNIGHT
CONTINUES.  HOWEVER... HAVE LOWERED THE POPS SLIGHTLY FOR THE FIRST
FEW HOURS OF THE NEAR TERM TO REFLECT THE FACT THAT VERY LITTLE
PRECIPITATION IS OCCURRING ACROSS THE WEST. BOTH THE NAM AND THE GFS
ARE QUITE INSISTENT THAT ISENTROPIC LIFT COMBINED WITH GOOD MOISTURE
INFLOW WILL RESULT IN RAINFALL SPREADING ACROSS THE AREA IN ADVANCE
OF THE APPROACHING COLD FRONT. INSTABILITY REMAINS ON THE LOW SIDE
BUT HAVE HELD ON TO AT LEAST SMALL PROBABILITIES OF THUNDER
OVERNIGHT.

AT 430 PM... LATE AFTERNOON ISSUANCE INCLUDED ONLY MINOR CHANGES TO
ACCOUNT FOR CURRENT CONDITIONS. PRIMARY PRECIPITATION WAS A LINE OF
SHOWERS EXTENDING FROM NEAR LENOIR SOUTH TO NEAR FOREST CITY THEN
SOUTHWARD INTO SPARTANBURG AND LAURENS COUNTIES. BRIEF HEAVY  RAIN
WILL ACCOMPANY THIS FEATURE AS IT PROGRESSES ACROSS THE EASTERN
PORTION OF THE CWA DURING THE REST OF THE AFTERNOON. ONLY A COUPLE
OF LIGHTNING OBSERVATIONS HAVE OCCURRED THIS AFTERNOON. CAPE REMAINS
ON THE MARGINAL SIDE FOR SIGNIFICANT CONVECTION... BUT ISOLATED
THUNDERSTORMS SHOULD BE EXPECTED THROUGH THE EVENING.

AS OF 220 PM...EXPANSIVE STRATUS DECK...WITH SOME INTERMITTENT
POCKETS OF STRATOCU...CONTINUES TO STREAM ACROSS THE AREA THIS
AFTERNOON. HEAVIER BANDS OF PRECIP HAVE ALSO BEEN MOVING OVER OUR
WESTERN ZONES SINCE ABOUT 1PM OR SO. PRECIP COVERAGE IS EXPECTED TO
GRADUALLY INCREASE OVER THE NEXT SEVERAL HOURS WITH LIKELY TO
CATEGORICAL POPS OVER THE ENTIRE CWFA JUST AFTER 00Z TUES. STILL
ANTICIPATE THAT THE BULK OF THE QPF WILL FALL BETWEEN 00 AND 12Z
TUES WITH TOTAL AMOUNTS DECREASED ABOUT 20% OR SO COMPARED TO THE
PREVIOUS FCST. THE MAIN CONCERN OVER THE NEXT 24 HRS STILL REVOLVES
AROUND THE POTENTIAL FOR SOME SVR TS TO DEVELOP LATER THIS EVENING
AND OVERNIGHT. THE AMPLE UPPER LVL FORCING COMBINED WITH THE LATEST
MODEL PROFILES CONTINUE TO GENERATE MEAN CAPE VALUES FROM 250 TO
ABOUT 800 J/KG ACROSS NE GA AND THE UPSTATE...WITH LESSER AMOUNTS
OVER NC...ESPECIALLY OVER THE NORTHERNMOST NC ZONES. SOUNDINGS ALSO
DISPLAY MODERATE AMOUNTS OF BULK SHEAR AND HELICITY COINCIDING WITH
THE INSTABILITY. IT APPEARS THAT THE MOST LIKELY SVR THREAT WILL BE
DAMAGING STRAIGHT LINE WINDS WITH LARGE HAIL LESS LIKELY. SOME WEAK
TORNADOES CANNOT BE RULED OUT...BUT THE CHANCES ARE LESS THAN 5%
OVER THE AREA. THE COLD FRONT WILL MOVE ACROSS THE REGION TOMORROW
AND SHOULD BE JUST SOUTH OF THE CWFA BY EARLY WED. IN ITS WAKE...SIG
CAA SURGES INTO THE AREA AND TEMPS PLUMMET TO WELL BELOW MID APRIL
VALUES. WIDESPREAD BELOW FRZ VALUES ARE LIKELY ACROSS THE NC MTS AND
NEAR FRZ VALUES ARE ALSO LIKELY ACROSS THE SC UPSTATE AND NC
FOOTHILLS AND PIEDMONT.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 200 PM MONDAY...MAIN STORY WILL BE THE UNSEASONABLY COLD
AIRMASS THAT WILL ADVECT INTO THE AREA TUE NIGHT. TEMPERATURES EARLY
WED WILL BE ON THE ORDER OF 3 STANDARD DEVIATIONS BELOW NORMAL FOR
THIS TIME OF YEAR WITH RETURN INTERVALS ON THE ORDER OF 30 YRS.
LOOKS LIKE AN ADVECTIVE FREEZE WILL OCCUR TUE NIGHT IN MOST...IF NOT
ALL COUNTIES IN THE WESTERN CAROLINAS AND NE GA. THEREFORE...WILL BE
ISSUING A FREEZE WATCH FOR TUE NIGHT. THE EXCEPTION BE IN THE
NORTHERN MOUNTAIN COUNTIES OF AVERY...MITCHELL AND YANCEY WHERE THE
FROST/FREEZE SEASON HAS NOT YET BEEN TURNED ON. CURRENT GUIDANCE
SUGGEST LOWS WILL BE IN THE 20-25 DEGREE RANGE IN THE MOUNTAINS...
AND FROM AROUND 30 TO THE LOWER 30S ELSEHWERE. MIN TEMPS PROBABLY
WILL NOT REACH RECORD LEVELS OUTSIDE THE MOUNTAINS...THOUGH THEY
WILL MAKE A RUN AT THE CLT RECORD. LOOKS LIKE THE AVL MIN TEMP
RECORD IS IN PLAY. (SEE CLIMO SECTION) THE CP SURFACE HIGH WILL
MIGRATE FROM THE MIDWEST TUE NIGHT TO NEW ENGLAND WED NIGHT. IT WILL
TAKE ON A DRY WEDGE CONFIGURATION WITH DRY WX AND BELOW NORMAL TEMPS
CONTINUING THROUGH THU. ANOTHER COLD NIGHT IS IN STORE WED NIGHT
WITH FROST AND/OR FREEZING TEMPS OVER MUCH OF THE CWA.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 210 PM MONDAY...THE DEPARTING COOL HIGH PRESSURE WILL BE
CENTERED NEAR MAINE THURSDAY NIGHT WITH LOW LEVEL WIND FLOW
GENERALLY FROM THE EAST THURSDAY NIGHT INTO FRIDAY. TEMPERATURES
WILL BE SLOWLY MODERATING AND MORE CLOUDS THURSDAY NIGHT WILL AID IN
BRINGING MINS ABOVE FREEZING. A STRONG SHORTWAVE WILL CROSS THE MID
TO UPPER MISSISSIPPI VALLEY LATE FRIDAY AND MOVE NE OVER THE GREAT
LAKES FRIDAY NIGHT. ALSO LATE FRIDAY AND FRIDAY NIGHT...LOW PRESSURE
IS EXPECTED TO CROSS FLORIDA AND MOVE NE ALONG OR OFF THE CAROLINA
COAST ON SATURDAY. MODELS ARE NOT IN AGREEMENT ON WHICH SYSTEM WILL
BE THE GREATER SOURCE OF ANY PRECIP OR IF ALL SYSTEMS WILL LEAVE US
DRY. THE CANADIAN MODEL GIVES US THE MOST PRECIP AS BOTH SYSTEMS
CONTRIBUTE TO NEARLY AN INCH OF RAIN ON THE OLD RUN MAINLY OVER
FOOTHILLS AND PIEDMONT FROM THE COASTAL LOW.  THE LATEST CANADIAN
GIVES US ABOUT A HALF INCH. SOME LIGHT RAIN SHOWERS MAY LINGER ON
SATURDAY WITH THE PASSAGE OF THE SHORTWAVE...MAINLY OVER HIGHER
TERRAIN IN NC.

SOME DISAGREEMENT AMONG THE MODELS ON WHAT WILL HAPPEN LATE IN THE
WEEKEND AND ON MONDAY. FOR NOW WE WILL HAVE SLIGHT TO VERY LOW
CHANCE POPS ON MONDAY THEN CLEARING US OUT FOR MONDAY NIGHT. THE GFS
NOW HAS A SOUTHERN STREAM LOW PASSING OVER GSP AROUND 00Z MONDAY
WITH AN INCH OR MORE QPF AT THAT TIME. THE ECMWF HAS A DISSIPATING
RAIN SHIELD WITH THE PASSING SHORTWAVE LATE MONDAY AND MONDAY NIGHT
WITH A TENTH AN INCH OR LESS.

TEMPERATURES WILL BE ABOUT TEN DEGREES BELOW NORMAL FRIDAY AND THEN
AROUND OR SLIGHTLY ABOVE NORMAL SATURDAY THROUGH MONDAY.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...MVFR CONDITIONS WILL BECOME IFR AS SHRA MOVE IN OVERNIGHT.
IFR CONTINUES THRU THE MORNING AS SHRA CONTINUE. MVFR EXPECTED THRU
MUCH OF THE AFTERNOON AS SHRA CONTINUE AND TSRA BECOME POSSIBLE. SLY
WINDS BECOME SWLY AROUND NOON THEN NWLY AND GUSTY BY MID AFTERNOON
AS A COLD FRONT MOVES THRU. GUSTY NW WIND AND CLEARING SKIES
EXPECTED THIS EVENING.

ELSEWHERE...IFR ALREADY IN PLACE OVER THE NON-MTN TAFS. EXPECT THE
IFR TO CONTINUE THRU THE MORNING...OR DEVELOP AT KAVL BY DAYBREAK.
CONDITIONS IMPROVE TO MVFR BY EARLY AFTERNOON THEN VFR BY MID
AFTERNOON AS DRIER AIR MOVES IN BEHIND THE COLD FRONT AND SHRA END.
DID NOT MENTION ANY TSRA AS CHC IS QUITE LOW. THAT SAID...A BRIEF
RUMBLE OF THUNDER CANNOT BE RULED OUT. S TO SW WIND CONTINUES THRU
THE MORNING...BECOMING W NEAR NOON THEN NW AND VERY GUSTY FOR THE
AFTERNOON. GUSTY N TO NW WIND AND CLEARING SKIES EXPECTED THIS
EVENING.

OUTLOOK...HIGH PRESSURE WILL PRODUCE VFR WEATHER WEDNESDAY AND
THURSDAY. CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND
SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE
SYSTEM DEVELOPS ALONG THE COAST.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH  90%     MED   68%     HIGH  86%     HIGH 100%
KGSP       HIGH  84%     HIGH  85%     HIGH  92%     HIGH 100%
KAVL       HIGH  89%     MED   75%     HIGH  93%     HIGH 100%
KHKY       HIGH  86%     MED   77%     HIGH  92%     HIGH 100%
KGMU       MED   76%     MED   74%     HIGH  94%     HIGH 100%
KAND       LOW   57%     MED   64%     HIGH  95%     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

&&

.CLIMATE...
RECORD LOWS FOR WEDNESDAY APRIL 16...

AVL...26 IN 1943
CLT...29 IN 2008
GSP...24 IN 1907

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     GAZ010-017-018-026-028-029.
NC...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     NCZ035>037-048-051>053-056>059-062>065-068>072-082-
     501>510.
SC...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     SCZ001>014-019.

&&

$$
SYNOPSIS...DEO
NEAR TERM...JPT/LGL/RWH
SHORT TERM...LG
LONG TERM...DEO
AVIATION...RWH
CLIMATE...






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