Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 050223
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1023 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 1020 PM...THE FIRST LINE OF SHOWERS MOVING ACROSS THE AREA IS
GOING NEARLY AS PREDICTED. SHOWERS BREAKING UP OVER THE NC
MOUNTAINS...WITH SOME ACTIVITY MAKING IT INTO THE FOOTHILLS...WHILE
LINE HOLDING TOGETHER AS IT MOVES INTO THE UPPER SAVANNAH RIVER
VALLEY. EXPECT THESE SHOWERS TO DIMINISH AS THEY MOVE EAST...BUT
STILL BRING SOME RAIN TO THE UPSTATE. THE SECOND LINE OF CONVECTION
IS MOVING ACROSS THE TN BORDER AT THIS TIME. THESE SHOULD ALSO
FOLLOW A SIMILAR TREND AS THE FIRST LINE...BUT WITH LESS COVERAGE
OVER NE GA AND THE UPSTATE. CAM GUIDANCE STILL SHOWING SHOWER
ACTIVITY REDEVELOPING OVER THE NW PIEDMONT AS THE FIRST ROUND OF
COLDER MID LEVEL AIR MOVES IN AFTER MIDNIGHT. HAVE HELD ONTO THIS
FEATURE AS THE CAM GUIDANCE HAS THE CURRENT FORECAST IN HAND.

OTHERWISE...A VIGOROUS COMPACT UPPER LOW WILL DROP SOUTH FROM THE SW
GREAT LAKES REGION TO THE NC MTNS BY MIDDAY THURSDAY. 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 /03Z THURSDAY 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 ON THURSDAY. AN ASSOCIATED COLD FRONT
WILL PUSH THRU OVERNIGHT. THE CU FIELD IS DISSIPATING WITH THE LOSS
OF HEATING...BUT MID CLOUDS ARE INCREASING AS MOISTURE MOVES IN
AHEAD OF THE FRONT. THE LEE TROF OVER THE AREA WILL DISSIPATE AS THE
FRONT MOVES THROUGH AS WELL. THIS WILL TURN THE SOUTHWESTERLY WINDS
TO NORTHWESTERLY OVERNIGHT. THE BAND OF SHOWERS AHEAD OF THE FRONT
WILL DISSIPATE AS IT MOVES ACROSS THE MOUNTAINS...BUT SOME ISOLATED
SHOWERS MAY HOLD TOGETHER. BETTER CHANCE OF SHOWERS...AND POSSIBLY
THUNDERSTORMS DEVELOPS DURING THE DAY THURSDAY AS THE UPPER LOW
MOVES IN. HAVE ADDED A PROB30 TO COVER. NW WINDS INCREASE IN SPEED
THROUGH THE MORNING AND BECOME GUSTY BY AFTERNOON.

AT KAVL...WINDS WILL BE CHANNELED UP THE FRENCH BROAD VALLEY THRU
THE PERIOD...YIELDING NNW WINDS. WINDS HAVE DIMINISHED BRIEFLY AHEAD
OF THE FRONT...BUT WILL INCREASE IN SPEED THROUGH THE PERIOD BEHIND
THE FRONT AND BECOME VERY GUSTY AFTER DAYBREAK THURSDAY. HAVE VCSH
THIS EVENING FOR THE SHOWERS AHEAD OF THE FRONT...AND A PROB30
THURSDAY FOR THE CONVECTION WITH THE UPPER LOW. MVFR CIGS ARE
EXPECTED OVERNIGHT AS LOW LEVEL MOISTURE IS FUNNELED UP THE VALLEY.
LOW VFR RETURNS FOR THURSDAY.

OUTLOOK...THE UPPER LOW MOVES EAST OF THE ARE FRIDAY...BUT MOISTURE
AND INSTABILITY LINGER BRINGING SHRA AND TSRA MAINLY ACROSS THE NC
SITES. DRY HIGH PRES RETURNS SATURDAY...WHILE ANOTHER COLD FRONT
APPROACHES FROM THE NORTH THRU SUNDAY.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  89%     HIGH  81%     HIGH 100%     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/RWH
SHORT TERM...SW
LONG TERM...SBK
AVIATION...RWH


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