Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261801
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
201 PM EDT TUE MAY 26 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 WEDNESDAY/...
AS OF 145 PM EDT...A 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 ALONG THE AL/GA BORDER THIS AFTN AS AN OUTFLOW
BOUNDARY FROM CONVECTION OVER THE DEEP SOUTH 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 VORITICITY 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 IN 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
DEVELOPS 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 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 /WEDNESDAY NIGHT 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 /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...ANTICIPATE MAINLY VFR CIGS THROUGH LATE DAY AS CONVECTIVE
CUMULUS ABOUNDS. THE HRRR TIMES CONVECTION OVER GA THIS AFTN TO MAKE
A RUN ACROSS THE SC UPSTATE AND THREATEN THE KCLT AIRFIELD BY 03Z.
THERE IS QUITE A BIT OF UNCERTAINTY OVER INSTABILITY IN THE
IMMEDIATELY UPSTREAM AREAS...BUT A PROB30 FOR TSRA AFTER 03Z STILL
SEEMS REASONABLE. OTHERWISE...WIDESPREAD MVFR CIGS SHOULD DEVELOP
ONCE AGAIN IN THE MOIST BOUNDARY LAYER...WITH A WINDOW OF DAYBREAK
IFR ONCE AGAIN POSSIBLE. CANNOT RULE OUT A LINGERING SHOWER IN THE
VICINITY AT JUST ABOUT ANY TIME DURING THE TAF PERIOD. EXPECT STEADY
S TO SW FLOW AT 10 KT OR LESS.

ELSEWHERE...LOWER VFR TO SPOTTY MVFR CIGS WILL PERSIST AROUND THE
REGION WITH ABUNDANT CONVECTIVE CUMULUS FORMING AT 3 TO 4 KFT. THE
HRRR SHOWS THE UPSTREAM CONVECTION OVER GA MAKING A RUN ACROSS THE
SW HALF OF THE FORECAST THIS EVENING BEFORE GRADUALLY WEAKING ACROSS
THE NE PART OVERNIGHT. GIVEN THE TIMING...AND THE RELATIVE
CONSISTENCY OF THE HRRR SOLUTIONS...WILL PUSH THE TSRA INTO A TEMPO
GROUP FOR GENERALLY 00Z TO 04Z...A LITTLE SOONER AT KAVL...AND WITH
JUST SHRA AT KHKY. EXPECT A QUICK TRANSITION TO MVFR
OVERNIGHT...ESPECIALLY IF WIDESPREAD RAINFALL DEVELOPS...WITH A
PERIOD OF DAYBREAK IFR EXPECTED. SCATTERED SHOWERS MAY CONTINUE TO
AFFECT THE AIRFIELDS AT JUST ABOUT ANY TIME THROUGHOUT THE TAF
PERIOD GIVEN THE MOIST PROFILES AND SW FLOW..

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  99%     HIGH  81%     HIGH  84%
KGSP       HIGH  97%     HIGH 100%     HIGH  85%     HIGH  95%
KAVL       HIGH  80%     HIGH  89%     HIGH  85%     HIGH  95%
KHKY       HIGH 100%     HIGH 100%     HIGH  85%     HIGH  90%
KGMU       HIGH  99%     HIGH 100%     HIGH  84%     HIGH  95%
KAND       HIGH  93%     HIGH  99%     MED   76%     HIGH  94%

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
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG



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