Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270732
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
332 AM EDT SUN JUL 27 2014

.SYNOPSIS...
HIGH PRESSURE AND SOUTHERLY FLOW WILL LEAD TO ABUNDANTLY WARM
TEMPERATURES ON SUNDAY AHEAD OF AN APPROACHING COLD FRONT.  THIS
COLD FRONT WILL REACH THE AREA SUNDAY NIGHT AND PUSH EAST ACROSS THE
REGION ON MONDAY. CANADIAN HIGH PRESSURE WILL DOMINATE THE SURFACE
PATTERN THROUGH MIDWEEK LEADING TO WELL BELOW NORMAL TEMPERATURES
AND PLEASANT CONDITIONS.  PRECIPITATION CHANCES WILL RAMP UP YET
AGAIN ON THURSDAY AND FRIDAY AS ATLANTIC MOISTURE SPILLS INTO THE
REGION LEADING TO INCREASED PROBABILITIES FOR SHOWERS AND
THUNDERSTORMS EACH AFTERNOON AND EVENING.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM...MCS TO THE NW IS WEAKENING AS IT MOVES EAST TOWARD
THE AREA. HOWEVER...THERE IS ENUF ELEVATED INSTABILITY AND FORCING
FOR CONVECTION TO FORM AHEAD OF THIS SYSTEM. EXPECT THIS
CONVECTION...AND THE MCS ITSELF...TO SPREAD INTO THE NC MTNS AND
I-40 CORRIDOR BEFORE DAYBREAK. THE PRECIP THEN DISSIPATES DURING THE
MORNING BEFORE RETURNING FROM THE NW AS CONVECTION DEVELOPS AHEAD OF
A COLD FRONT MOVING IN. THE ATMOS AHEAD OF THE FRONT IS VERY
UNSTABLE AND BECOMES HIGHLY SHEARED AS A LOW LEVEL JET MOVES IN WITH
THIS SYSTEM. ALTHOUGH INSTABILITY WILL BE SIGNIFICANT ACROSS THE
CWFA...THE BEST SHEAR WILL BE ACROSS THE NC MTNS INTO THE I-40
CORRIDOR. ALTHOUGH SPEED SHEAR IS VERY STRONG...THERE IS LITTLE
VEERING OF THE WINDS AS THE LOW LEVEL WINDS DO NOT BACK AHEAD OF THE
COLD FRONT AND REMAIN SWLY. THE FORECAST SOUNDINGS ALSO SHOW LOW
LEVEL CIN...AND THE DEBRIS CLOUDS FROM THE MCS COULD KEEP HEATING
FROM REACHING MAXIMUM POTENTIAL. HOWEVER THIS WILL EASILY BE
OVERCOME WITH THE STRONG FORCING DEVELOPING. THEREFORE...LOOKS LIKE
A DECENT CHC OF SEVERE STORMS WITH DAMAGING WINDS AND LARGE
HAIL...IN EITHER MULTICELL OR SQUALL LINE FORM...DEVELOPING ACROSS
THE NC MTNS INTO THE I-40 CORRIDOR...BUT THE ISOLATED TORNADO
CHC...WHILE THERE...LOOKS LIMITED WITH BETTER CHC TO OUR NORTH. SVR
CHC...AND EVEN CHC OF CONVECTION...WILL DROP OFF QUICKLY ACROSS THE
SRN CWFA AS SHEAR AND FORCING WILL BE LIMITED. WILL UPDATE HWO FOR
THESE CONCERNS. HIGHS TODAY WILL BE ABOVE NORMAL...BUT NOT AS WARM
AS SOME OF THE MOS GUIDANCE. LOWS TONIGHT WILL BE ABOVE NORMAL AS
WELL.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 225 AM EDT SUNDAY...THE SHORT TERM PERIOD INITIALIZES MONDAY
MORNING WITH A STRONG FRONTAL BOUNDARY PUSHING THROUGH THE REGION.
EXPECTING THE BOUNDARY TO BE LAID ALONG OR JUST SOUTH OF INTERSTATE
85 BY AROUND 12Z...THEN QUICKLY PUSH EAST SOUTHEAST INTO THE
MIDLANDS BY NLT 18Z.  00Z NAM/GFS SOLUTIONS ARE IN GOOD AGREEMENT
REGARDING THIS FROPA TIMING WHICH WOULD GREATLY IMPACT CHANCES FOR
ANY ENHANCED CONVECTION ACROSS THE PIEDMONT REGIONS OF NC/SC.  AS A
MATTER OF FACT...LATEST NAM/GFS CONS FORECAST SOUNDINGS INDICATE
SUBSTANTIAL LOW LEVEL INHIBITION IN PLACE ACROSS THE
PIEDMONT...WHICH ANY UPDRAFTS WILL STRUGGLE TO OVERCOME.  THAT
SAID...HAVE LOWERED POPS FOR THE EASTERN TIER OF THE FORECAST AREA
WITH ONLY SLIGHT CHANCE POPS BEING HIGHLIGHTED THROUGH MIDDAY MONDAY
ALONG WITH LINGERING UPSLOPE SHOWERS ALONG THE HIGH TERRAIN.
DESPITE A NARROW WINDOW OF OPPORTUNITY...STILL CANNOT COMPLETELY
RULE OUT SEVERE THUNDERSTORM THREAT LATE MONDAY MORNING AS THERE
WILL BE A MODERATELY UNSTABLE AIRMASS IN PLACE OUT AHEAD OF FRONTAL
FORCING.  THAT SAID...THE OVERALL THREAT DOES LOOK TO BE DIMINISHING
AS THE FROPA HAS SPED UP SIGNIFICANTLY OVER THE LAST FEW MODEL
RUNS.

STRONG NORTHWEST FLOW DOWN THE DESCENDING BRANCH OF ANOMALOUSLY DEEP
UPPER TROF WILL ADVECT A SHALLOW LAYER OF WESTERN GREAT LAKES
MOISTURE INTO THE SOUTHERN/CENTRAL APPS MONDAY NIGHT.  THUS...POPS
WILL RAMP UP YET AGAIN TO SLIGHT CHANCE LEVELS ACROSS THE NC
MOUNTAINS AS SAID MOISTURE POOLS ON THE WESTERN SLOPES OF THE APPS
AND IS LIFTED MECHANICALLY.  POPS WILL REMAIN ELEVATED AT THOSE
LEVELS THROUGH TUESDAY AFTERNOON WITH A DRY FORECAST ELSEHWERE AS
HIGH PRESSURE BUILDS FOR THE REMAINDER OF THE PERIOD.  TEMPERATURES
THROUGH THE SHORT TERM WILL COOL SIGNIFICANTLY BEHIND THE FROPA WITH
HIGHS NEARLY TEN DEGREES BELOW NORMAL FOR SOME LOCATIONS ON TUESDAY
AFTERNOON.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 245 AM EDT SUNDAY...THE EXTENDED RANGE PORTION OF THE
FORECAST INITIALIZES WEDNESDAY MORNING WITH A PERSISTENT EAST COAST
UPPER TROF IN PLACE.  CANADIAN HIGH PRESSURE AT THE SURFACE WILL
YIELD A DRY FORECAST THROUGH THE DAY ON WEDNESDAY AS NORTHERLY FLOW
PREVAILS.  THE ABOVE MENTIONED UPPER TROF WILL REMAIN IN PLACE
THROUGH THE PERIOD LEADING TO NO CHANGE IN DEEP LAYER FLOW.  AT THE
SURFACE HOWEVER...HIGH PRESSURE WILL SLIDE NORTHEAST ALLOWING AN
EASTERLY SHIFT TO LOW LEVEL FLOW LEADING TO INCREASING MOISTURE
ACROSS THE AREA FROM THE WESTERN ATLANTIC.  THE FORECAST WILL
RESPOND WITH INCREASING POPS ON THURSDAY WITH THE HIGHEST CHANCE
POPS ALONG THE CLIMO FAVORED UPSLOPE REGIONS OF THE MOUNTAINS WITH
ONLY SLIGHT CHANCE POPS SPREAD ACROSS THE REMAINDER OF THE FORECAST
AREA.  POPS WILL INCREASE FURTHER ON FRIDAY AS NORTHEAST SURFACE
RIDGE EXTENDS DOWN THE LEE SIDE OF THE APPS IN A WEDGE LIKE PATTERN
LEADING TO UPGLIDE POTENTIAL ACROSS THE REGION.  THEREFORE...CHANCE
POPS WILL BE FEATURED REGIONWIDE ON FRIDAY INTO SATURDAY MORNING.
TEMPERATURES THROUGH THE PERIOD WILL REMAIN BELOW NORMAL WITH
GRADUAL MODERATION EXPECTED INTO WEEKS END.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
AT KCLT...BKN HIGH DEBRIS CLOUDS WILL REMAIN ACROSS THE AREA INTO
THE MORNING. THE CLOUDS WILL COMBINE WITH BOUNDARY LAYER DRYING TO
LIKELY KEEP LOW CLOUDS AND RESTRICTIONS FROM THIS MORNING. ANOTHER
MCS COULD MAKE A RUN INTO THE SRN APPALACHIANS...BUT WITH LITTLE
MORE THAN ADDITIONAL MID AND HIGH CLOUDS REACHING THE KCLT TERMINAL
AREA. THE FORECAST WILL THUS REMAIN DRY AS THESE SYSTEMS
DISSIPATE...AND ANY UPSTREAM CONVECTION WITH THE NEXT APPROACHING
FRONT STAYS WEST OF THE PIEDMONT THROUGH LATE DAY. LIGHT SW WINDS
WILL INCREASE WITH MIXING AND AN INCREASING PRES GRADIENT DURING THE
AFTERNOON...WITH GUSTS OF 18 KT OR BETTER ARE LIKELY. GUSTS DIMINISH
DURING THE EVENING...BUT SWLY WINDS REMAIN UP THRU THE NITE. BKN
LOWER VFR CLOUDS LIKELY DEVELOP LATE IN THE EVENING AS WELL.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT. KAVL THE EXCEPTION WHERE NLY
WINDS AND VFR FOG EXPECTED THRU THE MORNING. MESOSCALE MODELS DEPICT
VERY LITTLE TSRA ACTIVITY SURVIVING THE TRIP ACROSS THE MTNS...SO NO
SHOWERS OR THUNDERSTORMS WILL BE FEATURED THROUGH THE MORNING...BUT
KAVL WOULD SEE THE BEST CHC OF SHRA/TSRA IF SOMETHING DID MAKE IT.
WSW FLOW WILL INCREASE THROUGH THE DAY AS THE PRESSURE GRADIENT
IMPROVES FROM FALLING HEIGHTS TO THE WEST. HAVE INCLUDED AFTERNOON
PROB30 AT KHKY/KAND WHERE TSRA CHC BEST.EXPECT GUSTS AT ALL BUT KAVL
DURING THE AFTERNOON...WITH WINDS REMAINING UP DURING THE EVENING.
KAVL WILL SEE A RETURN TO NLY WIND DURING THE EVENING.

OUTLOOK...SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED TO
ACCOMPANY THE COLD FRONT AS IT CROSSES THE REGION INTO MONDAY. VFR
CONDITIONS WILL RETURN BY LATE MONDAY...THEN LINGER THROUGH AT LEAST
MID WEEK.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...CDG
NEAR TERM...RWH
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...RWH





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