Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010542
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
142 AM EDT FRI AUG 1 2014

.SYNOPSIS...
A RIDGE OF HIGH PRESSURE WILL REMAIN WEDGED ACROSS THE AREA TO THE
EAST OF THE MOUNTAINS THROUGH THE WEEKEND AS AN UPPER TROUGH
CONTINUES OVER THE EASTERN STATES. 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 A FEW
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 TODAY/...
130 AM EDT UPDATE...PRECIP SHIELD AROUND IS SHIFTING JUST ENOUGH TO
PRECLUDE MUCH OF A HYDRO THREAT THIS MORNING. SOME CELLS ARE
PRODUCING INSTANTANEOUS RATES ON THE ORDER OF 1 IN/HR OVER THE EAST
CENTRAL UPSTATE...BUT 3-HR FFG RATIOS REMAIN 50 PERCENT OR LESS PER
DUAL POL. THE 02Z HRRR HAS INITIALIZED PRETTY WELL WITH THE LLVL MASS
FIELDS AND WILL LEAN TOWARD THE GENERAL IDEA OF THE PRECIP FOCUS
ALIGNING ALONG THE BLUE RIDGE AND NC FOOTHILLS OVER THE NEXT SEVERAL
HRS. THE OP MODELS ALSO HAVE THIS SAME GENERAL QPF TREND. THERE
COULD BE ENUF RAINFALL ACROSS THE CENTRAL UPSTATE TO WARRANT AN SPS
OR POSSIBLY AN ADVISORY OVER THE NEXT FEW HRS....ESP OVER AREAS THAT
RECEIVED HIGH AMOUNTS YESTERDAY. POPS WERE CUT BACK SIGFNTLY ACROSS
THE FAR WRN ZONES WHERE VERY SHALLOW MOISTURE IS CURRENTLY WORKING
IN. TEMPS AND TDS ARE IN GOOD SHAPE WITH STEADY STATE CONDS.

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 /TONIGHT 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 1220 AM FRIDAY...THIS MEDIUM RANGE PERIOD BEGINNING AT 12Z
MONDAY WITH THE UPPER AIR PATTERN WITH A TROUGH AXIS WEST OF THE
APPALACHIANS. THIS TROUGH WILL GRADUALLY TRANSITION INTO MORE ZONAL
WEST TO EAST FLOW IN MID WEEK. AS THE TROUGH BREAKS DOWN...A WEAK
UPPER LOW WILL BE LEFT OVER THE LOWER MISSISSIPPI VALLEY. AS THE
GENERAL WESTERLY FLOW INCREASES IN MID WEEK...OUR AIRMASS WILL
BECOME DRIER AND TEMPS WILL RETURN TO NEAR NORMAL. ON MONDAY...THE
STALLED OUT SURFACE FRONT FROM NRN FL TO ALONG THE CAROLINA COAST
WILL HAVE WEAK LOWS RIDING NE ALONG THE FRONT.  IT APPEARS THE
TROPICAL LOW BERTHA IS FORECAST TO BE EAST OF THE CAROLINAS OUT
TOWARD BERMUDA ON TUESDAY AS IT TURNS FROM NW TO N THEN NE AVOIDING
THE EAST COAST. BY WED AND THUR WE CAN EXPECT A TYPICAL SUMMERTIME
PATTERN OF PM TSTORMS FAVORING THE MTNS WITH LESS OUT OVER THE
PIEDMONT. SOME UPPER ENERGY WILL BE APPROACHING FROM THE NW LATE
THURS...BUT MOST EFFECTS SHOULD HOLD OFF UNTIL AFTER THE END OF THE
CURRENT FORECAST.

MONDAY HIGH TEMPS WILL BE AROUND 7 DEGREES BELOW NORMAL THEN REBOUND
TO NEAR NORMAL WED AND THURS.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AT KCLT...LIGHT TO MODERATE RAIN SHIELD WILL CONTINUE TO COME AND GO
AT CLT THIS MORNING AND A GRADUAL LOWERING OF CIGS TO IFR ARND 10Z.
NOT MUCH IMPROVEMENT TIL 15Z OR SO AS SFC HEATING WILL BE SLOW. THE
TAF REMAINS PESSIMISTIC WITH MVFR CIGS EXPECTED MOST OF THE DAY THEN
A DROP BACK IFR LATE ARND 03Z. THUNDER CHANCES REMAIN HIGH ENOUGH
FOR PROB30 MENTION AFT 18Z.

ELSEWHERE...A MIXED BAG OF CIGS/VSBY THIS MORNING DEPENDING ON THE
INTENSITY AND LOCATION OF RAINFALL. ALL SITES SHOULD DROP TO LOW
MVFR IF NOT IFR THIS MORNING MAINLY FOR CIGS. KAND WILL SEE THE
QUICKEST IMPROVEMENT BY 15Z TO POSSIBLY VFR CONDS AS PRECIP SHIELD
PUSHES NORTH. OTHER SITES WILL LIKELY TEMPO MVFR/VFR THROUGH THE
DAY...WITH LOWERING CIGS TO IFR LATE IN THE TAF PERIOD. THUNDER
CHANCES REMAIN HIGH ENOUGH FOR PROB30S AND VCTS THIS AFTERNOON.

OUTLOOK...UNSETTLED WEATHER WITH ENHANCED PRECIPITATION CHANCES
ALONG WITH MORNING FOG/STRATUS ARE EXPECTED THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       MED   71%     MED   78%     HIGH  94%     HIGH  80%
KGSP       HIGH  89%     MED   76%     HIGH  86%     MED   69%
KAVL       MED   78%     HIGH  80%     MED   76%     MED   78%
KHKY       HIGH  82%     HIGH  80%     HIGH  99%     HIGH  91%
KGMU       HIGH  86%     MED   72%     HIGH  85%     MED   71%
KAND       HIGH  85%     MED   73%     MED   67%     MED   69%

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

&&

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






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