Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 141848
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
248 PM EDT MON APR 14 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 TUESDAY/...
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 /TUESDAY NIGHT 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 /19Z MONDAY THROUGH SATURDAY/...
AT KCLT...MVFR CIGS SHOULD PERSIST OVER THE AIRFIELD FOR THE NEXT
FEW HOURS WITH SOME LIFTING STILL LIKELY AFTER 21Z OR SO. CONFIDENCE
THAT CIGS WILL ACTUALLY BECOME VFR IS NOT VERY HIGH BUT I THOUGHT IT
WAS THE MOST LIKELY OUTCOME. AT ANY RATE...CIGS WILL LOWER AGAIN 4
TO 6 HRS LATER AND REMAIN BELOW VFR THRU THE REST OF THE TAF PERIOD.
I DO NOT CARRY ANY PREVAILING IFR CONDITIONS...HOWEVER SOME
INTERMITTENT PERIODS OF IFR CIGS AND/OR VISBY ARE CERTAINLY POSSIBLE
WITH THE TSRA EXPECTED OVER THE REGION. STILL LOOKING LIKE RAIN WILL
HOLD OFF FOR A FEW MORE HOURS WITH LIKELY CHANCES AFTER 22Z OR SO.
AFTER ABOUT 02Z...I EXPECT PERSISTENT TSRA WITH GUSTY SLY WINDS THRU
THE REST OF THE TAF PERIOD. AS MENTIONED ABOVE...IFR CIGS AND VISBY
ARE CERTAINLY POSSIBLE WITH ANY HEAVIER TSRA.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT...BUT GENERALLY EARLIER ONSET
OF LOWER CIGS AND PRECIP FOR WESTERN SITES. HAVE INCLUDED PRO30
GROUPS AFTER ROUGHLY 07Z AT OTHER SITES FOR PREVAILING TSRA.

OUTLOOK...WIDESPREAD SHOWERS AND RESTRICTIONS WILL CONTINUE INTO
TUESDAY AFTERNOON. A COLD FRONT WILL MOVE EAST OF THE AREA LATE
TUESDAY...WITH MUCH COOLER AND DRIER HIGH PRESSURE SETTLING IN WED
AND PERSISTING THROUGH LATE WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  99%     HIGH  92%     HIGH  94%     MED   70%
KGSP       HIGH  94%     HIGH  82%     MED   77%     HIGH  85%
KAVL       HIGH  89%     MED   73%     HIGH  85%     HIGH  90%
KHKY       HIGH  97%     HIGH  86%     HIGH  84%     HIGH  90%
KGMU       HIGH  94%     HIGH  80%     HIGH  83%     HIGH  82%
KAND       HIGH  91%     MED   74%     MED   71%     MED   73%

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

&&

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






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