Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 042031
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
431 PM EDT WED MAY 4 2016

.SYNOPSIS...
A COLD FRONT WILL CROSS THE REGION TONIGHT AND USHER IN A COOL AIR
MASS FROM CANADA THROUGH THE END OF THE WORK WEEK. HIGH PRESSURE
RETURNS WITH A WARMING TREND FOR THE BALANCE OF THE WEEKEND...BEFORE
A COLD FRONT SLOWLY APPROACHES FROM THE NORTH ON SUNDAY. THIS FRONT
WILL MOVE NORTH AS A WARM FRONT EARLY MONDAY WITH ATLANTIC HIGH
PRESSURE DOMINATING THE REGION THROUGH TUESDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 430 PM...SHOWERS ALONG THE COLD FRONT MOVING TOWARD THE AREA
HAVE BEEN SLOWER TO MOVE EAST THAN EXPECTED. THEREFORE...HAVE SLOWED
PRECIP ONSET ACROSS THE MOUNTAINS THIS AFTERNOON...BUT ALLOW THEM TO
QUICKLY RAMP UP DURING THE EARLY EVENING. OTHER UPDATES WERE MAINLY
FOR CURRENT CONDITIONS.

OTHERWISE...A VIGOROUS COMPACT UPPER LOW WILL DROP SOUTH FROM THE SW
GREAT LAKES REGION TO THE NC MTNS BY MIDDAY THURSDAY. A LEADING SFC
COLD FRONT WILL PUSH THRU THE AREA TONIGHT...AND WILL BE ACCOMPANIED
BY A LINE OF SHOWERS AND PERHAPS A FEW EMBEDDED TSTMS...ENTERING THE
NC MTNS IN THE 21Z TO 00Z TIME FRAME EARLY THIS EVENING. STRONG 850
MB CAA WITHIN 30-40 KT OF FLOW WILL BRING 850 TEMPS DOWN TO AROUND
0C. THIS TRANSLATES TO SNOW LEVELS FALLING TO AROUND 5000 FT OR SO
OVERNIGHT. SO A FEW FLAKES OF SNOW WILL BE POSSIBLE...BUT NOT
EXPECTING ANYTHING MORE THAN AN INCH OR TWO ON THE HIGHEST PEAKS.
THE LINE OF SHOWERS WILL FIZZLE AT IT CROSSES THE MTNS...BUT A FEW
LINGERING SHOWERS OR SPRINKLES WILL BE POSSIBLE OUT ACRS THE NC
FOOTHILLS AND PIEDMONT. TEMPS WILL A COUPLE CATEGORIES BELOW
NORMAL...AND UP TO 10 DEG BELOW NORMAL ON THE HIGHEST PEAKS.

THURSDAY...AS THE UPPER LOW SWINGS IN FROM THE NW...STRONG UPPER
LEVEL FORCING COMBINED WITH STEEP LAPSE RATES WILL RESULT IN POPCORN
CONVECTION DEVELOPING DURING PEAK HEATING. THIS IS IN SPITE OF TEMPS
REMAINING ABOUT 5-10 DEG BELOW NORMAL (MAINLY 40-50 MTNS AND MID-UPR
60S PIEDMONT). FCST SNDGS SHOW CAPE INTO THE HAIL GROWTH ZONE. SO
ISOLATED THUNDER WITH SMALL HAIL WILL BE POSSIBLE...ESP IN THE MTNS.
SOME OF THE ACTIVITY WILL "BREAK CONTAINMENT" INTO THE
PIEDMONT...PER THE CAMS AND THE NAM.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 300 PM WEDNESDAY...THE UPPER LEVEL LOW WILL MOVE TOWARD THE
MID-ATLANTIC COAST FRIDAY NIGHT AND THEN PINWHEEL AROUND UNTIL
SATURDAY AFTERNOON...BEFORE EXITING OFFSHORE SATURDAY NIGHT.

THE NORTHWESTERLY FLOW AROUND THE BACKSIDE OF THE LOW WILL BRING
SHOWERS MAINLY TO THE MOUNTAINS AND NC FOOTHILLS AND PIEDMONT. THERE
WILL BE A SLIGHT CHANCE OF THUNDERSTORMS IN A FEW SPOTS FRIDAY
AFTERNOON...THE SPINE OF THE SOUTHERN APPALACHIANS AND EAST OF
INTERSTATE 77. OTHERWISE...EXPECT MAINLY DRY CONDITIONS WITH
TEMPERATURES BELOW CLIMATOLOGY.

HEIGHTS WILL BUILD ACROSS THE REGION BY SATURDAY ALLOWING
TEMPERATURES TO RETURN TO NEAR CLIMATOLOGY AND CONDITIONS TO DRY
OUT.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 155 PM EDT WEDNESDAY...NO NEED FOR ANY MAJOR CHANGES TO THE
GOING FCST. THE MODELS CONTINUE TO SHOW GOOD CONSISTENCY RUN TO RUN
AND WITH EACH OTHER WITH THE SYNOPTIC PATTERN AND EXPECTED SENSIBLE
WX THROUGH MOST OF THE PERIOD.

AN ERN UPPER LOW WILL CONTINUE TO DIG SOUTH SUN AND PUSH A BACKDOOR
COLD FRONT INTO THE NRN ZONES EARLY SUN. WITH A SFC HIGH CENTER
SITUATED OFFSHORE...THIS FRONT WILL BE SUPPLIED WITH A GOOD AMOUNT
OF GOM MOISTURE AND HIGH THETA/E AIR. AS THE FRONT SETTLES IN
SUN...SCT AFTERNOON -SHRA/TSTMS SHUD DEVELOP ACROSS THE I-40
CORRIDOR. SOUNDINGS AREN/T TOO IMPRESSIVE WITH THE AVAILABLE
CAPE...BUT A COUPLE OF THESE STORMS COULD BECOME QUITE STRONG GIVEN
THE EXPECTED ABOVE NORMAL SFC TEMPS AND HIGH TD/S. THIS ACTIVITY
WILL WANE QUICKLY SUN NIGHT AS THE FRONTAL ZONE MOVES NORTH AND A
LOW AMPLITUDE ULVL RIDGE BUILDS IN. THIS PATTERN WILL KEEP THE AREA
MOSTLY DRY THRU TUE...EXCEPT FOR THE NC MTNS WHERE POCKETS OF ULVL
ENERGY HELP INSTIGATE DIURNAL CONVECTION.

THE RIDGE AXIS SHIFTS EAST TUE AND THE CWFA WILL COME UNDER THE
INFLUENCE OF INCREASINGLY UPPER DIFLUENT FLOW AHEAD OF AN H5 LOW
TRACKING ACROSS THE LOWER MIDWEST. THE HIGHER UNSTABLE AIR WILL
REMAIN TO THE WEST OF THE AREA WED/THU...BUT GOOD MOISTURE FLUX WILL
KEEP POPS JUSTIFIED IN THE LOW/MID CHANCE RANGE ACROSS THE THE WRN
ZONES....WITH MAINLY ISOL CONVEC ACTIVITY ANTICIPATED EAST. TEMPS
WILL REMAIN FAIRLY PERSISTENT WITH HIGHS BEGINNING A COUPLE CATS
ABOVE NORMAL SUN THEN A SUBTLE DECREASE OF ABOUT 2-3 DEGREES BY WED.
MINS WILL LINGER A LITTLE BELOW OR NEAR NORMAL.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE EAST OF THE MTNS...VFR CONDITIONS THRU THE
PERIOD. A VIGOROUS UPPER DISTURBANCE WILL DROP SE FROM THE OH VLY
INTO THE WESTERN CAROLINAS BY THE END OF THE 18Z TAF PERIOD. AN
ASSOCIATED COLD FRONT WILL PUSH THRU OVERNIGHT. AHEAD OF THE
FRONT...A STOUT CU FIELD HAS DEVELOPED...WITH BASES IN THE 5-7 KFT
RANGE. A LEE TROF IS ALSO SETTING UP THANKS TO NWLY LLVL FLOW. SO
WINDS SHOULD FAVOR A SW TO WSW DIRECTION FROM LATE AFTN THRU THE
EVENING. THEN THE FRONT WILL PASS THRU AND SHIFT WINDS BACK TO NW
OVERNIGHT. A BAND OF SHOWERS IS EXPECTED TO ACCOMPANY THE FRONT AND
PUSH INTO THE MTNS EARLY THIS EVENING...BUT FIZZLE OUT BEFORE
REACHING THE PIEDMONT.

AT KAVL...WINDS WILL BE CHANNELED UP THE FRENCH BROAD VALLEY THRU
THE PERIOD...YIELDING NNW WINDS. WINDS ARE FORECAST TO FREQUENTLY
GUST INTO THE MID 20S DURING THE AFTERNOON...THEN AGAIN LATE TONIGHT
BEHIND THE PASSING COLD FRONT. A BAND OF SHOWERS WILL APPROACH KAVL
FROM THE NW EARLY THIS EVENING...AND MAY REACH THE TERMINAL...SO
WILL HIGHLIGHT WITH VCSH. LATER TONIGHT...GUIDANCE IS FORECASTING
SOME MVFR CIGS WITHIN THE NW FLOW...THEN LIFTING TO VFR AGAIN AFTER
DAYBREAK. AN UPPER LOW WILL BE NEARLY DIRECTLY OVER THE NC MTNS BY
18Z...AND ADDITIONAL SHRA ARE EXPECTED TO DEVELOP UNDERNEATH.

OUTLOOK...A STRONG UPPER LOW WILL SWING THRU THE AREA THRU
FRIDAY...AND WILL BRING SHRA AND TSRA MAINLY ACROSS THE NC SITES
BOTH THU AND FRI AFTN. DRY HIGH PRES RETURNS SATURDAY...WHILE
ANOTHER COLD FRONT APPROACHES FROM THE NORTH THRU SUNDAY.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  98%     HIGH  91%     HIGH 100%
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 SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...ARK
SHORT TERM...SW
LONG TERM...SBK
AVIATION...ARK


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