Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010235
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1035 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/...
1015 PM UPDATE...WIDESPREAD LIGHT RAIN EXTENDS IN A SHIELD FROM
METRO ATLANTA NEWD INTO THE CENTRAL NC PIEDMONT...ON THE COOL SIDE
OF THE FIXED BOUNDARY ACROSS THE LOWER SC MIDLANDS. SELY FLOW
CONTINUES OVER THE BOUNDARY WITH PWAT VALUES HAVING STEADILY
INCREASED TODAY AS A RESULT. THIS SHOULD CONTINUE OVERNIGHT AND
LATEST GUIDANCE STILL FEATURES INCREASING PRECIP RATES ACRS THE CWFA
INTO EARLY FRIDAY. CONVECTION HAS WANED WITHIN THE RAIN SHIELD OVER
THE PAST COUPLE HRS THOUGH 00Z KGSO RAOB SUGGESTS FAIRLY STRONG
LAPSE RATES REMAIN ABOVE THE NOCTURNAL INVERSION. THIS BACKS UP THE
EXPECTATION THAT WE WILL SEE INCREASING AMOUNTS OF PRECIP OVERNIGHT
WITH SHORTWAVE ENERGY APPROACHING FROM THE GULF STATES. FLOOD THREAT
CURRENTLY IS RATHER LOW WITH HRLY RATES OF ONE OR TWO TENTHS PER
HOUR AT MOST SITES. WITHOUT CONVECTION IT IS UNLIKELY FLASH FLOODING
WILL OCCUR...BUT THE LONG DURATION OF RAIN IN AREAS WHICH RECEIVED
HEAVY RAIN EARLIER WILL LIKELY BECOME A CONCERN. PORTIONS OF
ANDERSON AND GREENVILLE COUNTIES GOT 4-6 INCHES OF RAIN THIS AFTN
AND THESE AREAS WILL BE CLOSELY MONITORED.

IN GENERAL...RAISED POPS UNDERNEATH THE CONTIGUOUS AREA OF
PRECIP...HOLDING ONTO CATEGORICAL WORDING UNTIL AFTER MIDNIGHT WHEN
UPSLOPING IS SUGGESTED TO INCREASE ITS INFLUENCE. TEMPS ARE TRICKY
WITH HRLY TRENDS SUGGESTIVE OF RAIN COOLING...BUT I REVISED
OVERNIGHT TRENDS/LOWS BASED ON THE LATEST OBS AND LAMP TRENDS.

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 /03Z FRIDAY THROUGH TUESDAY/...
AT KCLT...BAND OF MODERATE TO HEAVY RAINFALL WILL SLOWLY MOVE NWD
ACRS THE FIELD THIS EVENING. PERIODS OF MVFR TO IFR VSBY WILL
ACCOMPANY THE HEAVIER SHOWERS...AND A RUMBLE OF THUNDER CANNOT BE
RULED OUT. THERE MAY BE A LULL IN PRECIP COVERAGE IN THE VERY LATE
EVENING. PRECIP ACTIVITY PICKS UP AGAIN IN THE EARLY MRNG AS LIFT
FROM MOIST SELY FLOW ALOFT IS ENHANCED BY A PASSING SHORTWAVE.
ELEVATED INSTABILITY IS PROGGED BY GUIDANCE SO BETTER THUNDER
CHANCES WILL COME THEN. WITH THE PROLONGED RAIN THIS EVENING AND THE
WARM ADVECTION CONTINUING JUST ABOVE THE SFC...IFR CIGS ARE A GOOD
BET OVERNIGHT. SOME FOG LIKELY AS WELL BUT THE CIGS WILL BE MORE
RESTRICTIVE. THE PATTERN CHANGES SO LITTLE INTO FRI THAT IMPROVEMENT
IN CATEGORY WILL BE SLOW AND MVFR WILL PREVAIL THRU THE AFTN.
THUNDER RETURNS WITH DIURNAL INSTABILITY IN THE AFTN. NE WINDS ARE
EXPECTED TO PREVAIL DURING THE PERIOD THOUGH SELY GUSTS MAY OCCUR
DURING THE EVENING SHRA.

ELSEWHERE...NUMEROUS AREAS OF RAIN WILL PROGRESS NWD THRU THE NC
PIEDMONT EARLY THIS EVENING...WITH MORE SCATTERED ACTIVITY FURTHER
W. A SHORTWAVE WILL MOVE ACRS OVERNIGHT WHICH IS EXPECTED TO ENHANCE
LIFT FROM LLVL WARM UPGLIDE...SO AN UPTICK IN COVERAGE IS IN THE
FCST OVERNIGHT. PROFILES BECOME MORE FAVORABLE FOR THUNDER TOWARD
DAWN SO VCTS IS ADDED AT THAT TIME. IFR CIGS SHOULD DEVELOP AT ALL
SITES WITH IFR FOG ACCOMPANYING IT IN PLACES. IMPROVEMENT TO MVFR
SHOULD OCCUR LATER THAN USUAL GIVEN THE MOIST...WEDGE-LIKE SETUP
OVER THE AREA. MOST SITES WILL REMAIN MVFR THRU THE END OF THE DAY.

OUTLOOK...MOISTURE WILL CONTINUE TO INCREASE THROUGH FRIDAY AS MOIST
SOUTHERLY FLOW CONTINUES INTO THE REGION OVER A STALLED FRONTAL
BOUNDARY. UNSETTLED WEATHER WITH ENHANCED PRECIPITATION CHANCES
ALONG WITH MORNING FOG/STRATUS ARE EXPECTED THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH  92%     HIGH  80%     HIGH  86%     HIGH  92%
KGSP       HIGH  86%     HIGH  86%     HIGH  88%     HIGH  87%
KAVL       HIGH  91%     HIGH  92%     HIGH  90%     MED   74%
KHKY       HIGH  88%     HIGH  85%     HIGH  94%     HIGH  93%
KGMU       HIGH  84%     HIGH  84%     HIGH  88%     HIGH  93%
KAND       HIGH  87%     HIGH  83%     MED   79%     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/WIMBERLEY
SHORT TERM...LG
LONG TERM...LG
AVIATION...WIMBERLEY






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