Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 150230
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1030 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/...
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.


&&

.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 /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT...CEILINGS NEAR 5K FT WILL GRADUALLY LOWER TO 1K TO 2K FT BY
06Z. THEREAFTER... OCCASIONAL CIG NR 8 FT EXPECTED OVERNIGHT AS
NUMEROUS RAIN SHOWERS AFFECT THE AIRFIELD. THUNDER PRESENTLY IS NOT
INCLUDED IN THE TAF UNTIL 11Z... BUT ISOLATED THUNDERSTORMS ARE A
POSSIBILITY BEFORE THAT TIME. WILL MONITOR AND AMEND TAF IF CHANCE
INCREASES SUBSTANTIALLY. STRONG WINDS JUST OFF THE SURFACE IN
ADVANCE OF APPROACHING TROUGH ALOFT AND ASSOCIATED COLD FRONT WILL
RESULT IN LOW LEVEL WIND SHEAR... MOSTLY LIKELY AFTER 06Z. SOUTH
WIND AT 10 TO 15 KT WILL CONTINUE OVERNIGHT AND TUESDAY MORNING.
COLD FRONT WILL CROSS THE TERMINAL BY 18Z ACCOMPANIED BY WIND SHIFT
TO THE NORTHWEST AND BECOMING GUSTY TO 25 KT BY 20Z.

ELSEWHERE...CEILINGS NEAR 5K FT WILL GRADUALLY LOWER TO 1K TO 2K FT
BETWEEN 04Z AND 06Z. THEREAFTER... OCCASIONAL CIG NR 8 FT EXPECTED
OVERNIGHT AS NUMEROUS RAIN SHOWERS CONTINUE. ISOLATED THUNDERSTORMS
ARE A POSSIBILITY... BUT INSTABILITY REMAINS RATHER LIMITED UNTIL
TUESDAY MORNING AS COLD FRONT BEGINS TO MOVE THROUGH THE AREA. IN
ADDITION... AREAS OF FOG WILL LIMIT VISIBILITY TO BELOW 3 MILES
ESPECIALLY IN AREAS OF RAIN. SOUTH WIND NEAR 10 KT WILL CONTINUE
OVERNIGHT. CEILING AND VISIBILITY CONDITIONS WILL IMPROVE FOLLOWING
PASSAGE OF COLD FRONT TUESDAY MORNING... BUT WINDS WILL SHIFT TO THE
NORTHWEST AND BECOME GUSTY TO 25 KT BY EARLY AFTERNOON.

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...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH  89%     HIGH  88%     HIGH  86%     HIGH  98%
KGSP       HIGH  87%     MED   77%     HIGH  85%     HIGH 100%
KAVL       HIGH  94%     HIGH  84%     HIGH  95%     HIGH 100%
KHKY       HIGH  90%     MED   77%     HIGH  83%     HIGH 100%
KGMU       HIGH  87%     MED   79%     HIGH  91%     HIGH 100%
KAND       HIGH  84%     MED   71%     HIGH  82%     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 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...LGL
SHORT TERM...LG
LONG TERM...DEO
AVIATION...LGL






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