Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 262051
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
451 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/...
430 PM UPDATE...THE NORTH END OF THE CONVECTIVE LINE OVER GEORGIA
HAS BEGUN TO WEAKEN LIKELY AS IT ENCOUNTERS MORE STABLE AIR OVER
THE NE GA PIEDMONT. HOWEVER THE SOUTH END OF THAT LINE IS
REORGANIZING ALONG A GUST FRONT OR POSSIBLY SEA BREEZE FRONT.
WHILE THE VORT MAXES ASSOC WITH THE SYNOPTIC SCALE SHORTWAVE
APPEAR TO BE ON TRACK TO PASS WEST OF THE MTNS THIS EVENING...MCVS
FROM THESE LINES WILL SWING OVER OUR CWFA. LATEST PROGS STILL
FEATURE INCREASING CAPE VALUES THRU THE EVENING WITH WEAK
ISENTROPIC LIFT AS WELL AS THE DYNAMIC LIFT HIGHER ALOFT. REVISED
POPS TO BRING THE NRN LINE IN OVER THE NEXT COUPLE HRS...AS WELL
AS TO REFLECT BETTER CHANCES OVER THE WRN UPSTATE WITH THIS NEW
SEGMENT ORGANIZING. SOME DISCRETE ACTIVITY WILL ALSO CONTINUE
PRIOR TO THE ARRIVAL OF THE LINES...BUT FROM THE LOOK OF THE CU
FIELD ON VIS SAT...WHICH DOES NOT LOOK CONGESTED OVER MUCH OF THE
AREA...THIS WILL MAINLY AFFECT JUST THE UPSTATE AS CELLS DEVELOP
OVER THE CSRA AND MIDLANDS AND MOVE N.

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 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 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 /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 /21Z TUESDAY THROUGH SUNDAY/...
AT KCLT...ANTICIPATE MAINLY VFR CIGS THROUGH LATE DAY AS CONVECTIVE
CUMULUS ABOUNDS. THE HRRR SHOWS LINEAR CONVECTION OVER GA THIS AFTN
MAKING A RUN ACROSS THE SC UPSTATE AND THREATENING THE KCLT AIRFIELD
BY 02Z. SHRA ARE MORE LIKELY THAN TSRA WITH DIMINISHING
INSTABILITY...BUT THERE APPEARS ENOUGH UPPER FORCING AND LINGERING
MUCAPE TO EXPECT A COUPLE OF EMBEDDED TSRA WITHIN A RAIN SHIELD AS
THE FEATURES MOVE IN. 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 WEAKENING
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 KAND...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...

            21-03Z        03-09Z        09-15Z        15-18Z
KCLT       HIGH 100%     HIGH  98%     MED   73%     HIGH  82%
KGSP       HIGH 100%     HIGH  98%     HIGH  88%     HIGH  92%
KAVL       HIGH  85%     HIGH  89%     HIGH  86%     HIGH  90%
KHKY       HIGH 100%     HIGH 100%     MED   78%     HIGH  80%
KGMU       HIGH 100%     HIGH 100%     HIGH  88%     HIGH  87%
KAND       HIGH 100%     HIGH 100%     HIGH  84%     HIGH  87%

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/WIMBERLEY
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG/WIMBERLEY


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