Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270545
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
145 AM EDT WED MAY 27 2015

.SYNOPSIS...
A BERMUDA HIGH PATTERN WILL PERSIST ACROSS THE SOUTHEAST STATES
THROUGH THE END OF THE WEEK. THIS WILL PRODUCE A MOIST SOUTHERLY
FLOW WITH INCREASED CHANCES FOR WIDESPREAD SHOWERS AND THUNDERSTORMS
EACH DAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 145 AM...SHRA HAVE DISSIPATED ACROSS THE AREA AND WILL LIKELY
NOT RETURN BEFORE DAYBREAK. THAT SAID...HI RES GUIDANCE DOES SHOW
SOME LIGHT SHRA REDEVELOPING OVER THE I-77 CORRIDOR AND THE NC MTNS.
HAVE KEPT ISOLATED WORDING FOR THESE AREAS...BEFORE DIURNAL
CONVECTION RETURNS DURING THE DAY. TEMPS ARE QUITE A BIT COOLER THAN
FORECAST AS THE COLD POOL BEHIND THE DIMINISHING CONVECTION SLIDES
ACROSS THE CWFA. HAVE LOWERED LOWS IN RESPONSE. OTHERWISE...GOING
FCST ON TRACK WITH UPDATES MAINLY FOR CURRENT CONDITIONS.

945 PM UPDATE...CONVECTIVE LINE HAS BECOME SOMEWHAT
DISORGANIZED...NOW EFFECTIVELY BEING DISCRETE CELLS LINED UP ALONG
THE LEADING EDGE OF A COLD POOL. IF NOTHING ELSE IT LOOKS LIKE THE
STRUCTURE WILL HOLD UP ENOUGH TO BRING ISOLATED DOWNPOURS TO MOST OF
THE YET UNTOUCHED PART OF THE CWFA OVER THE NEXT COUPLE OF
HRS...INCLUDING THE CHARLOTTE METRO. GUSTS HAVE BECOME WEAKER AND
LESS WIDESPREAD. 00Z RAOB FROM ATLANTA WAS TAKEN IN THE WAKE OF THE
LINE AND REFLECTED A STABLE AIRMASS. LATEST RAP PROGS SUGGEST LITTLE
TO NO REBOUND WILL BE SEEN OVERNIGHT DESPITE MOIST ADVECTION IN THE
CONTINUING SOUTHERLY FLOW. SO NEW POPS REFLECT THE DEPARTURE OF THE
PRESENT ROUND OF CONVECTION LATER IN THE EVENING AND JUST CHANCE
POPS FOR THE AREA AFTER MIDNIGHT. WE WILL STILL SEE THE UPPER
DYNAMIC FEATURES MOVE ACROSS POTENTIALLY KICKING OFF SHOWER
ACTIVITY...BUT HIGH IMPACT STORMS WILL LIKELY BE HISTORY.

AS OF 230 PM EDT...DEEP SOUTHWEST FLOW HAS SET UP OVER THE FORECAST
AREA BETWEEN OFFSHORE HIGH PRESSURE AND A LOW PRESSURE SYSTEM
LIFTING NE FROM THE PLAINS. PRECIPITABLE WATER VALUES CONTINUE TO
INCREASE AND WILL MAXIMIZE AT NEARLY 1.75 INCHES OVER THE HEART OF
THE AREA TONIGHT. MEANWHILE...SEVERAL CONSECUTIVE RUNS OF THE HRRR
HAVE BEEN QUITE ACCURATE IN HANDLING THE WIDESPREAD CONVECTION
DEVELOPING OVER WRN GA THIS AFTN AS AN OUTFLOW BOUNDARY FROM EARLIER
DEEP SOUTH CONVECTION WORKS EAST. THE HRRR SHOWS THIS ACTIVITY
MOVING TOWARD THE UPPER SAVANNAH RIVER REGION AROUND 22Z AND THEN
ACROSS THE UPSTATE AND WRN NC THROUGH THE EVENING HOURS AND EARLY
OVERNIGHT. THIS IS CONSISTENT WITH THE EXPECTED ARRIVAL OF UPPER
DIVERGENCE OVER THE SOUTHERN APPALACHIANS THIS EVENING...ALONG WITH
A WEAK H5 VORTICITY LOBE. INSTABILITY WILL BE MARGINAL IN MOST
AREAS...BUT A LOBE OF BRIEFLY ENHANCED LOW LEVEL BULK SHEAR...AND
ANY OUTFLOW PUSH WITH THE ARRIVAL OF THE CONVECTION...COULD PRODUCE
MARGINALLY SEVERE WINDS INTO FAR SW SECTIONS THIS EVENING WITH ANY
STRONG TSRA. THE ACTIVITY SHOULD WANE OVERNIGHT WITH JUST LINGERING
SCATTERED SHOWERS EXPECTED. ANTICIPATE ANOTHER NIGHT OF VERY WARM
MIN TEMPS AS A BLANKET OF LOW CLOUDS FORMS IN THE MOIST BOUNDARY
LAYER.

ALTHOUGH THE H5 PATTERN WILL FLATTEN OUT SOMEWHAT THROUGH
WED...ADDITIONAL WEAK SHORTWAVES WILL MOVE OVER THE AREA IN THE
BROAD SW FLOW ALOFT...WITH DEEP MOISTURE PERSISTING. HEATING WILL
GET OFF TO A SLOW START AGAIN ON WED WITH THE ABUNDANT MORNING
CLOUDS...BUT SBCAPE VALUES SHOULD RISE TO 1500 J/KG OR BETTER BY WED
AFTN WITH ANY BREAKS GIVEN THE ELEVATED DEWPOINTS. ANTICIPATE HIGH
SCATTERED TO LOW LIKELY SHRA/TSRA COVERAGE IN THE MOIST AIRMASS ON
WED AFTN...BUT LOW LEVEL CONVERGENCE WILL LEAD TO THE BEST COVERAGE
OVER THE NC MTNS. TEMPS WILL STRUGGLE THROUGH THE 70S AGAIN TO MAX
OUT NEAR 80 EAST OF THE MTNS...LOWER 80S IN THE PIEDMONT.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
AT 200 PM EDT TUESDAY...ON WEDNESDAY EVENING HIGH PRESSURE WILL BE
CENTERED OFF THE EAST COAST...WHILE WEAK UPPER TROUGHING WILL BE
OVER THE WESTERN USA...AND A SHORTWAVE MOVES ACROSS THE GREAT LAKES
AND OH RIVER VALLEY. THE SHORTWAVE MOVES OFF THE NEW ENGLAND COAST
ON THURSDAY...FOLLOWED BY RISING HEIGHTS ALOFT INTO FRIDAY.

AT THE SURFACE...ATLANTIC HIGH PRESSURE MAINTAINS A FOOTHOLD OVER
THE CAROLINAS AND GA FROM WEDNESDAY EVENING INTO FRIDAY...WHILE LOW
LEVEL MOISTURE REMAINS BANKED UP AGAINST THE SOUTHERN APPALACHIANS.
INSTABILITY IS EXPECTED TO BE SOMEWHAT LIMITED UNDER THE UPPER
RIDGE. WITH A LACK OF ISENTROPIC UPGLIDE...AND ONLY MODEST LOW LEVEL
UPSLOPE FLOW...PRECIPITATION SHOULD BE RATHER MODEST...AND GREATEST
NEAR THE BLUE RIDGE. TEMPERATURES WILL EXHIBIT A REDUCED DIURNAL
TREND DUE TO CLOUD COVER AND MOISTURE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AT 200 PM EDT TUESDAY...ON SATURDAY MORNING...HIGH PRESSURE WILL BE
CENTERED SOUTHEAST OF NEW ENGLAND AND ATLANTIC CANADA...WHILE UPPER
TROUGHING WILL EXTEND FROM HUDSON BAY TO THE SOUTHERN US PLAINS. THE
UPPER HIGH WILL VERY SLOWLY BREAKS DOWN....WHILE THE UPPER TROUGH
SLOWLY PROGRESSES...SUCH THAT BY TUESDAY THE UPPER TROUGH CROSSES
THE MS RIVER VALLEY.

AT THE SURFACE...ON SATURDAY HIGH PRESSURE WILL EXTEND FROM THE
WESTERN ATLANTIC TOT HE SOUTHERN APPALACHIANS....WHILE MODEST GULF
INFLOW EXISTS OVER THE GULF STATES...AND A COLD FRONT CROSSES THE
GREAT LAKES...MID MS RIVER VALLEY...AND SOUTHERN PLAINS. HIGH
PRESSURE STARTS TO WEAKEN OVER THE CAROLINAS AND GA ON SUNDAY...
WHILE THE APPROACHING FRONT STRETCHES FROM NEW ENGLAND TO THE OH
RIVER VALLEY. THE EASTERN PORTION OF THE FRONT STALLS TO OUR N ON
MONDAY...WHILE THE SOUTHERN PORTION MOVES INTO THE LOWER MS RIVER
VALLEY. MOIST INFLOW FROM THE ATLANTIC IMPROVES AHEAD OF THIS FRONT.
ON TUESDAY THE FRONT STALLS TO OUR N AND W.

WITH HEIGHTS FALLING ALOFT...AND INSTABILITY AND MOISTURE
INCREASING...CONVECTIVE CHANCES SHOULD IMPROVE WITH TIME. MOIST
INFLOW NEVER REALLY GETS ROBUST...SO PRECIPITATION IS NOT EXPECTED
TO BE EXCESSIVE ON A GRAND SCALE. TEMPERATURES WILL RUN WITHIN A FEW
DEGREES OF NORMAL.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...SHRA HAVE DISSIPATED AND SHUD NOT RETURN THIS MORNING.
HOWEVER...A FEW LIGHT SHRA OR SPRINKLES ARE POSSIBLE. GUIDANCE STILL
SUGGESTS MVFR THEN IFR CIGS DEVELOPING BY DAYBREAK AS IS OCCURRING
TO THE WEST. HAVE GONE WITH THESE TRENDS AS WELL. EXPECT A RETURN TO
MVFR BY MID MORNING...THEN LOW VFR BY NOON. AFTERNOON TSRA EXPECTED
AGAIN...AND HAVE INCLUDED PROB30 DURING THIS TIME. S TO SW WINDS
THRU THE PERIOD.

ELSEWHERE...IFR ALREADY DEVELOPED ACROSS THE SC SITES...BUT HAS BEEN
IN AND OUT THE LAST FEW HOURS. EXPECT IFR TO BE THE PREDOMINANT
FLIGHT CATEGORY THIS MORNING...SO HAVE STARTED IFR BUT KEPT TEMPO
VFR EARLY FOR THE BRIEF SCATTERING. KAVL AND KHKY SHUD SEE MVFR THEN
IFR BEFORE DAYBREAK. SHUD SEE A SLOW RISE TO LOW VFR AFTER DAYBREAK.
DIURNAL CONVECTION EXPECTED AGAIN...SO HAVE INCLUDED PROB30. HAVE
KEPT LOW VFR FOR THE EVENING...BUT RESTRICTIONS COULD RETURN BEFORE
THE END OF THE PERIOD. S TO SW WINDS THRU THE PERIOD.

OUTLOOK...MOIST SW FLOW WILL CONTINUE TO AFFECT THE TERMINAL
FORECAST AREA RIGHT THROUGH THE UPCOMING WEEKEND...AS A COLD FRONT
LAYS OVER TO THE NORTH OF THE AREA. EXPECT MORNING STRATUS TO RESULT
EACH DAY...WITH CONTINUED BETTER THAN CLIMATOLOGICAL CHANCES OF
AFTN/EVENING SHRA/TSRA EACH DAY.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       HIGH 100%     HIGH  90%     HIGH  90%     HIGH 100%
KGSP       MED   69%     LOW   55%     MED   65%     HIGH 100%
KAVL       LOW   56%     MED   70%     MED   60%     LOW   57%
KHKY       HIGH 100%     LOW   55%     HIGH  95%     HIGH 100%
KGMU       MED   62%     LOW   43%     MED   60%     HIGH 100%
KAND       MED   69%     MED   70%     MED   70%     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...JPT
NEAR TERM...HG/RWH/WIMBERLEY
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...RWH


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