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Area Forecast Discussion

206
FXUS62 KGSP 311825
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
225 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/...
AT 210 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 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 MIANLY JUST WIDELY SCATTERED AFTERNOON
CONVECTION OVER THE MOUNTAINS WED AND THU.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  99%     MED   62%     HIGH  86%
KGSP       MED   65%     MED   71%     MED   68%     HIGH  91%
KAVL       MED   72%     MED   70%     HIGH  88%     MED   76%
KHKY       MED   66%     HIGH  99%     MED   70%     MED   62%
KGMU       MED   66%     HIGH  81%     MED   62%     HIGH  94%
KAND       MED   63%     HIGH  84%     MED   76%     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...LG
NEAR TERM...JAT
SHORT TERM...LG
LONG TERM...LG
AVIATION...JAT






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