Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 312059
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
459 PM EDT THU JUL 31 2014

.SYNOPSIS...
A RIDGE OF HIGH PRESSURE WILL REMAIN WEDGED ACROSS THE AREA THROUGH
THE WEEKEND. TO THE EAST...A FRONT WILL REMAIN NEARLY STATIONARY
ALONG THE COAST. ATLANTIC MOISTURE WILL CONTINUE TO SPREAD INTO THE
AREA WHICH WILL FUEL WIDESPREAD SHOWERS AND THUNDERSTORMS. SOME
LOCALLY HEAVY RAINFALL IS LIKELY. CONDITIONS ARE EXPECTED TO RETURN TO
MORE TYPICAL LATE SUMMER WEATHER BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
415 PM UPDATE...WHILE THE PRECIP SHIELD OVER THE FOOTHILLS REGION
SHOWS SIGNS OF WEAKENING...A BAND OF HEAVY SHOWERS AND A FEW
EMBEDDED TSTMS CURRENTLY ORIENTED E-W ACRS CENTRAL SC IS CREEPING
NORTHWARD INTO OUR SRN ZONES. THIS ACTIVITY IS BEING DRIVEN BY LLVL
CONVERGENCE NEAR THE QUASI-WEDGE BOUNDARY. LATEST HRRR DOES PICK UP
ON THIS ACTIVITY TO SOME EXTENT AND BRINGS IT SLOWLY NWD INTO
MID-EVENING WHEN IT TOO WEAKENS. IT IS SHOWN TO MOVE BASICALLY INTO
THE AREA WHICH IS SEEING LIGHT RAIN ATTM...THOUGH ITS HIGHEST HRLY
ACCUMS ARE OVER THE NC PIEDMONT. THE LLVL FIELDS FROM THE NAM BACK
UP SUCH A FCST...AS THEY SHOW THE CONVERGENCE INCREASING OVER THE
CWFA THOUGH BECOMING LESS DISTINCT WITH TIME. LATEST MESO MODELS
GENERALLY BACK UP THE EARLIER EXPECTATIONS OF THE PRECIP SHIELD
BECOMING MORE ALIGNED ALONG THE BLUE RIDGE BY LATE TONIGHT.

AS OF 210 PM EDT...A POSITIVELY TILTED UPPER TROUGH WILL REMAIN FROM
EASTERN CANADA TO THE GULF COAST TODAY AND TONIGHT. A SHORTWAVE
TROUGH ROUNDING THE BASE OF THIS TROUGH WILL CROSS THE SOUTHERN
APPALACHIANS TONIGHT...AND THE FOOTHILLS AND PIEDMONT ON FRIDAY. LOW
LEVEL UPSLOPE FLOW IS SHOWN TO INCREASE IN MODEL TIME HEIGHTS...
WITH ISENTROPIC UPGLIDE INCREASING AS WELL.

THE COMBINATION OF THESE INGREDIENTS WILL SUPPORT HEAVY
RAINFALL...ESPECIALLY LATE TONIGHT AND EARLY FRIDAY. THE GREATEST
RAINFALL POTENTIAL WILL BE ALONG AND NEAR THE BLUE RIDGE. WITH
ROBUST ANTECEDENT RAINFALL ON THE SC FOOTHILLS...THAT AREA WILL BE
ESPECIALLY VULNERABLE TO FLOODING. THE FLASH FLOOD WATCH FORM AREAS
WEST OF THE INTERSTATE 77 CORRIDOR WILL REMAIN IN PLACE THROUGH
FRIDAY MORNING.

INSTABILITY WILL BE SUFFICIENT FOR CONVECTION...MAINLY DURING
MAXIMUM DAYTIME HEATING EACH AFTERNOON. MODEL SOUNDINGS INDICATE
THAT THERE MAY BE A BRIEF PEAK OF ELEVATED INSTABILITY LATE TONIGHT
AS THE SHORTWAVE MOVES OVERHEAD. THIS OVERNIGHT PEAK APPEARS TO
COINCIDE WITH SOME LOW LEVEL SHEAR...BUT THE TWO INDICES DO NOT
APPEAR TO OVERLAP IN HEIGHT. THE DIURNAL TEMPERATURE RANGE WILL BE
LIMITED BY MOISTURE AND CLOUDS COVER.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AT 2 PM EDT THURSDAY...THE WET PATTERN WILL CONTINUE THROUGH THE
WEEKEND. AN UPPER TROUGH WILL REMAIN WEST OF THE APPALACHIANS WHICH
WILL SEND A SERIES OF IMPULSES THROUGH THE AREA. AT THE SURFACE...
AN OSCILLATING QUASI-STATIONARY FRONT WILL REMAIN JUST EAST OF THE
AREA AS WAVES OF LOW PRESSURE RIPPLE NE ALONG IT. ALSO...ISENTROPIC
LIFT WILL CONTINUE OVER A WEDGE BOUNDARY LOCATED ALONG THE EAST
SLOPES OF THE MOUNTAIN CHAIN. THERE MAY BE A LULL/DOWN TICK IN
COVERAGE OF RAIN EARLY SATURDAY EAST OF THE MOUNTAINS AS A WAVE OF
LOW PRESSURE INDUCES THE FRONT TO MOVE EASTWARD SOMEWHAT. HOWEVER...
GUIDANCE POPS REMAIN HIGH SO EXPECT THAT AREAS OF RAIN/DRIZZLE WILL
REMAIN AND UPSLOPE FLOW IN THE MOUNTAINS WILL CONTINUE TO PRODUCE
EVEN MORE WIDESPREAD SHOWER COVERAGE THERE. ANOTHER WAVE ON THE
FRONT IS LIKELY TO DEVELOP BY SUN MORNING OVER EASTERN SC WHICH WILL
PRODUCE INCREASED ISENTROPIC UPGLIDE AND MORE WIDESPREAD SHOWERS SAT
NIGHT THROUGH SUN. PW`S WILL REMAIN ELEVATED THROUGH THE PERIOD...SO
AREAS OF HEAVY RAINFALL ARE A GOOD BET. RAINFALL IN THE 1-2 INCH
RANGE IS LIKELY MOST PLACES....WITH LOCALLY HEAVIER AMOUNTS. MAX
TEMPS WILL REMAIN WELL BELOW NORMAL.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 145 PM THURSDAY...THE UPPER AIR PATTERN WILL GRADUALLY
TRANSITION FROM A TROUGH WEST OF THE APPALACHIANS TO A ZONAL FLOW
OVER THE REGION. THIS WILL OCCUR WHEN EARLY IN THE NEW WORK WEEK THE
NORTHERN PART OF THE UPPER TROF IS FORECAST TO SLIDE EAST OF THE
AREA LEAVING A WEAK UPPER LOW OVER THE TN VALLEY WHICH MOVES SLOWLY
SW INTO THE LOWER MS VALLEY BY MIDWEEK. THAT WILL ALLOW ZONAL FLOW
TO DEVELOP WHICH WILL PRODUCE A DRYER AIRMASS OVER THE FORECAST AREA
BY MIDWEEK. AT THE SFC...THE WEAK FRONT  WILL REMAIN NEAR THE COAST
WITH A WAVE OF LOW PRESSURE OVER THE EASTERN CAROLINAS WHICH WILL
TRACK NE INTO THE MID-ATLANTIC REGION ON MONDAY. AS THE LOW MOVES
AWAY...WEAK HIGH PRESSURE WILL DEVELOP OVER THE SOUTHERN
APPALACHIANS.

THEREFORE...THE SENSIBLE WEATHER WILL FEATURE SOME LINGERING SHOWERS
EARLY IN THE PERIOD...BUT IN GENERAL THE WEATHER SHOULD RETURN TO A
MORE NORMAL SUMMERTIME PATTERN. TEMPERATURES WILL REBOUND TO NEAR
NORMAL BY MIDWEEK WITH MAINLY JUST WIDELY SCATTERED AFTERNOON
CONVECTION OVER THE MOUNTAINS WED AND THU.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
AT KCLT...A BREAK IN PRECIP WILL COME THIS AFTERNOON PERHAPS WITH
PEEKS OF SUNSHINE AS WELL...BUT A BAND OF SHRA WILL LIFT NWD TOWARD
THE FIELD THIS AFTN. THIS WILL BRING WIDESPREAD RAIN WITH EMBEDDED
DOWNPOURS THRU EARLY EVENING. ANY SUNSHINE AT/NEAR THE FIELD PRIOR
TO THIS BAND MAY FIRE UP ADDITIONAL SHRA/TSRA. IN GENERAL PRECIP
CHANCES WILL INCREASE AS AN UPPER LEVEL SYSTEM APPROACHES THIS
EVENING. MOIST INFLOW FROM THE SW WILL SUPPORT MORE WIDESPREAD LOW
CLOUDS OVERNIGHT...EVENTUALLY BECOMING IFR BY DAWN. GUIDANCE FAVORS
MVFR VSBY BEFORE DAWN AS WELL. CONDITIONS MAY BE SLOW TO IMPROVE ON
FRIDAY...EVEN AS PRECIPITATION BEGINS TO DECREASE...AS THE LOW
LEVELS REMAIN VERY MOIST FROM OVERNIGHT RAINFALL. CONVECTIVE CHANCES
WILL BE BEST IN THE AFTERNOON. WINDS WILL REMAIN LIGHT OUT OF THE NE.

ELSEWHERE...PRECIPITATION IS EXPECTED TO INCREASE AT ALL SITES AS
MOIST SE LOW LEVEL FLOW INCREASES INTO THE HIGHER TERRAIN. GUIDANCE
TAKES CIGS DOWN FROM LOW VFR THIS AFTERNOON...TO MVFR THIS
EVENING...THEN IFR BEFORE DAWN...AND EVEN LIFR AT KAVL. VSBY WILL
FOLLOW ABOUT THE SAME TREND...WITH SOME SITES IFR AT DAYBREAK...AND
OTHERS MVFR. IMPROVEMENT MAY BE QUITE SLOW FRIDAY MORNING WITH VERY
MOIST LOW LEVELS. WINDS WILL FAVOR THE NE...EXCEPT CHANNELING FROM
THE SE AT KAVL. CONVECTIVE CHANCES WILL BE BEST THIS AFTERNOON.

OUTLOOK...MOISTURE WILL CONTINUE TO INCREASE THROUGH THE
REMAINDER OF THE WORK WEEK AS A WARM FRONT APPROACHES FROM THE EAST
AND SOUTHEASTERLY FLOW CONTINUES. UNSETTLED WEATHER WITH ENHANCED
PRECIPITATION CHANCES ALONG WITH MORNING FOG/STRATUS ARE EXPECTED
THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH 100%     HIGH  80%     HIGH  86%     HIGH  95%
KGSP       HIGH  85%     LOW   59%     HIGH  91%     HIGH  93%
KAVL       MED   77%     HIGH  84%     HIGH  95%     MED   65%
KHKY       HIGH  87%     HIGH  93%     HIGH  80%     MED   62%
KGMU       HIGH  94%     MED   64%     HIGH  95%     HIGH  87%
KAND       HIGH  87%     MED   60%     HIGH 100%     HIGH  87%

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...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR GAZ010-017-018-
     026-028-029.
NC...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR NCZ033-048>053-
     058-059-062>065-501>510.
SC...FLASH FLOOD WATCH THROUGH FRIDAY MORNING FOR SCZ001>007-
     010>012-019.

&&

$$
SYNOPSIS...LG
NEAR TERM...JAT/WIMBERLEY
SHORT TERM...LG
LONG TERM...LG
AVIATION...JAT/WIMBERLEY





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