Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 311717
AFDGSP

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

.SYNOPSIS...
A RIDGE OF CANADIAN HIGH PRESSURE REMAINS OVER THE AREA INTO THE
WEEKEND AS A FRONT MOVES NORTH TO THE COAST. MOISTURE
INCREASES BETWEEN THESE TWO SYSTEMS INCREASING THE CHANCES OF
WIDESPREAD SHOWERS AND THUNDERSTORMS. CONDITIONS RETURN TO THOSE
MORE TYPICAL OF LATE SUMMER BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 115 PM EDT THURSDAY...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 MODEST ISENTROPIC UPGLIDE CONTINUING AS WELL. THE
COMBINED LIFT OF ALL THREE 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...HOWEVER 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 THROUGH SATURDAY NIGHT/...
AS OF 330 AM...IT IS LOOKING MORE AND MORE LIKELY THAT THE FIRST
PART OF THE WEEKEND WILL BE WET. SWLY UPPER FLOW INCREASES THRU THE
PERIOD AS A TROF AXIS TO THE WEST SHARPENS AND THE ATLANTIC
SUB-TROPICAL ANTI-CYCLONE MOVES WEST TOWARD THE COAST. SHORT WAVES
MOVE THRU THE FLOW AND ACROSS THE AREA KEEPING Q-VECTOR CONVERGENCE
IN PLACE. IN ADDITION...UPPER LEVEL DIVERGENCE REMAINS OVER THE AREA
AS THE RIGHT ENTRANCE REGION OF AN UPPER JET BECOMES PARKED NEARBY.
A SERIES OF H85 LOWS MOVE OVER THE AREA BRINGING PERIODS OF SELY LOW
LEVEL FLOW. THESE KEEP LOW LEVEL AND DEEP MOISTURE ACROSS THE AREA
AS WELL. BEST POP WILL BE ALONG THE BLUE RIDGE WHERE UPSLOPE FLOW
MAXIMIZES. HOWEVER...LIKELY POP WILL BE FEATURED ALL AREAS GIVEN THE
MOISTURE AND FORCING. SCT TSRA SHUD ALSO DEVELOP...MAINLY ALONG AND
SOUTH OF I-85 AS ELEVATED INSTABILITY DEVELOPS. FCST HODOGRAPHS SHOW
QUITE A BIT OF SPEED AND DIRECTIONAL SHEAR DEVELOPS. RIGHT NOW...
INSTABILITY REMAINS RELATIVELY WEAK AND ELEVATED...BUT WILL HAVE TO
KEEP AN EYE ON THIS.

SATURDAY WILL BE SIMILAR TO FRIDAY EXCEPT FOR THE WEAKENING SFC
RIDGE LEADING TO INCREASED INSTABILITY AND BETTER CHC OF SCT TSRA
ACROSS THE AREA. ALTHOUGH INSTABILITY WILL BE GREATER...SHEAR WILL
BE MUCH LESS. STILL TOO EARLY TO TELL IF AREAS OF HEAVY RAIN WILL
DEVELOP EITHER DAY...BUT IT CANNOT BE RULED OUT. HIGHS FRIDAY WILL
BE 10 TO 15 DEGREES BELOW NORMAL...THEN RISE ABOUT 5 DEGREES ON SAT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 145 PM THURSDAY...THE UPPER AIR PATTERN WILL GRADUALLY
TRANSITION FROM A TROUGH WEST OF THE APPALACIANS TO A ZONAL FLOW.
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. AT THE SFC... A WEAK FRONT  WILL
REMAIN ALONG THE COAST WITH A WAVE OF LOW PRESSURE OVER THE EASTERN
CAROLIANS WHICH WILL TRACK NE INTO THE MID-ATLANTIC REGION. 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 WITH MIANLY JUST WIDELY SCATTERED AFTERNOON CONVECTION OVER
THE MOUNTAINS WED AND THU.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...
AT KCLT...PRECIPITATION CHANCES WILL INCREASE AS AN UPPER LEVEL
SYSTEM APPROACHES THIS AFTERNOON INTO TONIGHT. MOIST INFLOW FROM THE
SW WILL SUPPORT MORE WIDESPREAD LOW CLOUDS...WITH A LOW VFR CIG THIS
AFTERNOON...MVFR THIS EVENING...AND EVENTUALLY 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...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     MED   70%     HIGH  90%
KGSP       MED   78%     HIGH  88%     MED   64%     HIGH  91%
KAVL       HIGH  91%     HIGH  87%     HIGH  89%     HIGH  85%
KHKY       HIGH  91%     HIGH 100%     MED   79%     MED   77%
KGMU       HIGH  91%     HIGH  95%     MED   60%     HIGH  91%
KAND       HIGH  83%     HIGH  91%     MED   70%     HIGH  91%

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...RWH
NEAR TERM...JAT
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...JAT






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