Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 012130
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
430 PM EST SUN MAR 1 2015

.SYNOPSIS...
MOISTURE WILL INCREASE THROUGH THE EVENING AHEAD OF AN APPROACHING
COLD FRONT. THE FRONT WILL CROSS THE FORECAST AREA ON MONDAY WITH
ANOTHER ROUND OF CANADIAN HIGH PRESSURE BUILDING IN ITS WAKE. YET
ANOTHER MOIST COLD FRONT IS EXPECTED TO APPROACH THE REGION LATE
WEDNESDAY WITH DRIER AIR BEHIND IT.

&&

.NEAR TERM /THROUGH MONDAY/...
430 PM EST UPDATE...OVC/BKN LLVL CLOUDS WILL PERSIST THROUGH THE
AFTERNOON AND EVENING AS THE BL REMAINS SATURATED AND THE CENTER OF
THE SMALL SCALE SFC HIGH KEEPS SOME MEASURE OF ISENT LIFT WHILE THE
SFC FLOW REMAINS WEAK. THERE ARE SOME NOTABLE CLOUD BREAKS ACROSS
THE NC MTNS WHICH WILL BE ADDED TO THE GRIDS. THE CURRENT POP TRENDS
HAVE THE PRECIP IN CHECK WITH DIMINISHING -RA/DZ OVER THE SE/RN
ZONES AND INCREASING -SHRA POPS OVER THE NC MTN AND NE GA WITH WEAK
BNDRY MOVING IN. TEMPS/TDS ARE HOLDING NEARLY STEADY STATE IN THIS
ENVIRONMENT AND ONLY MINOR TWEAKS WERE NEEDED THROUGH THE NEXT
UPDATE.

AS OF 220 PM EST SUNDAY...SPLIT FLOW REGIME ALOFT PREVAILS ACROSS
THE CONUS WITH ZONAL FLOW DOMINATING THE PATTERN ATOP THE
SOUTHEAST.  AT THE SURFACE...HIGH PRESSURE WEDGE CONTINUES TO HOLD
OVER NORTHEAST GA AND THE WESTERN CAROLINAS WHILE WEAK MOIST UPGLIDE
ATOP SAID WEDGE YIELDS SCATTERED LIGHT SHOWERS OVER PORTIONS OF THE
NC/SC PIEDMONT.  SATURATED BOUNDARY LAYER AMONGST WEAK SFC FLOW
SETTING UP GOOD CONDITIONS FOR REDUCED VISB DUE TO PATCHY FOG/MIST
WHILE CEILINGS REMAIN GENERALLY LESS THAN 1KFT.  EXPECTING THESE
CONDITIONS TO PERSIST INTO THE AFTERNOON BEFORE CAD WEDGE WEAKENS
SOMEWHAT AS PARENT HIGH MIGRATES OFFSHORE.  NEVERTHELESS...MOSTLY
CLOUDY SKIES WILL PREVAIL THROUGH THE OVERNIGHT WITH INITIALIZED
LIKELY/CHANCE LEVEL POPS DECREASING AS UPGLIDE REGIME WEAKENS.

MEANWHILE FURTHER NORTHWEST...NORTHERN STREAM UPPER SHORTWAVE IS
EJECTING OUT OF CENTRAL CANADA INTO THE UPPER MIDWEST ALL THE WHILE
AIDING SURFACE CYCLOGENESIS OVER THE OHIO VALLEY.  IN
RESPONSE...WEAK LOW PRESSURE CONTINUES TO FORM WITH A SLOW MOVING
COLD FRONT DRAPED SOUTHWEST INTO THE MID/LOWER MISSISSIPPI RIVER
VALLEY.  THIS FRONT WILL MAKE A RUN AT THE SOUTHERN APPS MID MORNING
MONDAY WITH BROAD HIGH PRESSURE SPILLING IN SHARPLY BEHIND.  MODEL
PROGS INDICATE THAT THE FRONT IS LIKELY TO GET HUNG UP ALONG THE
TERRAIN AS THE ABOVE MENTIONED RIDGE SLIDES BY TO THE NORTH.  THIS
WILL LIKELY INITIATE A TRANSITION TO MORE OF A BACK DOOR FROPA.  AS
FOR THE REMAINDER OF THE FCST...POPS WILL REMAIN ELEVATED ALONG THE
HIGH TERRAIN THROUGH SUNDAY EVENING AHEAD OF THE FRONT...WITH POPS
SLOWLY INCREASING TO SLIGHT CHANCE LEVELS ACROSS THE NC/SC PIEDMONT
MONDAY MORNING/AFTERNOON AS THE BACK DOOR FRONT INTRUDES.  WINDS
THROUGH THE PERIOD WILL GENERALLY REMAIN LIGHT WITH FLOW POSSIBLY
SHIFTING SOUTHERLY THIS AFTERNOON...BEFORE BACKING NORTHERLY ON
MONDAY.  TEMPERATURES WILL REMAIN BELOW CLIMO DUE TO ABUNDANT SKY
COVER AND ROUNDS OF PRECIP.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 235 PM SUNDAY...HYBRID COLD AIR DAMMING SETS UP ONCE AGAIN MON
NITE AND TUE AS HIGH PRESSURE BUILDS IN FROM THE NE. EXPECT PRECIP
TO RETURN ACROSS THE AREA AS LOW LEVEL MOISTURE AND ISENTROPIC LIFT
MOVE BACK NORTH ACROSS THE AREA. ALTHOUGH LOWS WILL BE AROUND 5
DEGREES ABOVE NORMAL MON NITE...TEMPS WILL BE COLD ENUF FOR SOME
LIGHT FREEZING RAIN TO DEVELOP ACROSS THE NRN MTNS AND BLUE RIDGE
AREAS OF NC. RIGHT NOW...QPF LOOKS TO BE VERY LIGHT...SO WOULD ONLY
EXPECT MINOR ICE ACCRETIONS...MAINLY ON ELEVATED SURFACES. OF
COURSE...WILL HAVE TO KEEP AN EYE ON THIS FOR POTENTIAL ADVISORY.
HIGHS TUESDAY WILL RISE ACROSS THE MTNS...OUTSIDE OF THE CAD...BUT
WILL ONLY SEE A SMALL RISE OR REMAIN NEARLY STEADY ELSEWHERE WITH
CLOUDS AND LIGHT RAIN/DRIZZLE REMAINING OVER THE AREA. HIGHS END UP
10 TO 20 DEGREES BELOW NORMAL.

THE CAD SLOWLY ERODES FROM THE TOP DOWN LATE TUE NITE INTO WED AS A
COLD FRONT APPROACHES FROM THE WEST. THERE IS STILL QUITE A BIT OF
DIFFERENCE IN TIMING OF THE FRONT. HOWEVER...THERE IS GOOD AGREEMENT
THAT PRECIP TAPERS OFF OUTSIDE OF THE MTNS TUE NITE...WITH BEST CHC
RETREATING TO THE MTNS...BEFORE DIFFERENCES EMERGE ON SPEED OF
PRECIP SPREADING BACK IN FROM THE WEST. THEREFORE...HAVE GONE WITH A
MDL BLEND FOR POP. PRECIP SHOULD REMAIN RAIN AND DRIZZLE TUE NITE
AND WED MORNING AS THE CAD ERODES...THEN CHANGE TO SHOWERS FOR THE
AFTERNOON. THERE COULD BE A FEW TSRA DURING THE AFTERNOON. AGAIN...
THIS IS UNCERTAIN DUE TO THE TIMING DIFFERENCES. SHOULD SEE EARLY
LOWS TUE NITE 5 TO 10 DEGREES ABOVE NORMAL...THEN SLOWLY RISING
TEMPS. HIGHS WED COULD BE AS MUCH AS 5 TO 10 DEGREES ABOVE NORMAL AS
WELL. HOWEVER...FRONTAL MOVEMENT AND RESULTING PRECIP WILL PLAY A
BIG PART IN THE ACTUAL NUMBERS.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 215 PM SUNDAY...FRONTAL ZONE AT LEADING EDGE OF CANADIAN HIGH
PRESSURE WILL SLOWLY CROSS THE CWFA WED NIGHT AND THU. SOME SPREAD
CONTINUES TO BE SEEN BETWEEN THE LATEST AVBL OPNL GFS/EC/GEM RUNS IN
TERMS OF THE SPEED OF THE FROPA...BUT THE GFS NOW APPEARS TO BE AN
OUTLIER IN ITS DEPICTION OF THE FRONT MOVING IN QUICKLY BUT STALLING
DUE TO THE DEVELOPMENT OF A SFC WAVE OVER THE COASTAL PLAIN. EC/GEM
AND EVEN MOST MEMBERS OF THE GFS ENSEMBLE SUGGEST THE FRONT WILL LOSE
STEAM AS IT PROGRESSES THRU THE SOUTHEAST. GFS ACCORDINGLY REMAINS
THE WETTEST MODEL. WILL ADVERTISE HIGH-END POPS BUT KEEP QPF ON THE
LOW END. A CONCERN WITH THE FROPA IS THE POSSIBILITY OF A PTYPE
TRANSITION ON ITS BACK SIDE. GFS PROFILES SUGGEST RAIN GRADUALLY
CHANGING TO SNOW WITH FZRA AND SLEET IN BETWEEN...AND PARTIAL
THICKNESS TECHNIQUES FROM EC/GEM WOULD BASICALLY SUGGEST THE SAME.
FOLLOWING PARTIAL THICKNESSES AND SFC TEMPS...THE MTNS COULD SEE SOME
ACCUMULATING SNOW...POSSIBLY MIXED WITH SLEET...LATE WED NIGHT AND
THU MRNG. THE PIEDMONT MAY SEE A LITTLE WINTRY MIX THU MRNG AND THEN
AGAIN THU NIGHT IF PCPN LASTS THAT LONG. TEMPS THU WILL TOP OUT
AROUND 15 DEGREES BELOW NORMAL.

WHILE THE OPNL GFS AND GEM CONTINUE TO PUSH THE FRONT OUT OF THE AREA
AND ALLOW DRY HIGH PRESSURE TO DOMINATE FRI AND INTO THE WEEKEND...
A NUMBER OF GEM ENSEMBLE MEMBERS INSTEAD STALL IT JUST TO OUR
SOUTH...THIS ALSO BEING SHOWN BY THE 01/00Z EC. 12Z EC HAS COME IN
WITH THE FRONT STALLING FURTHER SOUTH WHICH LENDS MORE CONFIDENCE TO
A DRY FCST. THIS WILL CONTINUE TO BE ADVERTISED THRU THE WEEKEND.
THOUGH TEMPS WILL GRADUALLY MODERATE...UNDER COOL HIGH PRESSURE THEY
WILL REMAIN BELOW NORMAL THRU THE END OF THE PERIOD.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
AT KCLT...AS WITH PREVIOUS FCST...GUIDANCE DISCREPANCIES CONTINUE TO
YIELD LOW CONFIDENCE ON TIMING AND VALUES OF VISB.  THAT SAID
MOSTLY IFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE PERIOD
DOMINATED BY LOW CIGS AND ABOVE MENTIONED VARIABLE VISB. INITIALIZED
TAFS AT IFR CIGS AND 4SM VISB AMIDST LIGHT NE FLOW WITH A TEMPO FOR
RA AS A BAND OF PRECIP SLIDES UP THE I85 CORRIDOR TOWARDS THE
AIRFIELD.  BEYOND THAT...CARRY SOLID IFR THROUGH THE OVERNIGHT WITH
VARIABLE VISB WITH SOME GUIDANCE FAVORING PATCHY DENSE FOG BY
EARLY/MID MORNING.  OPTED NOT TO INCLUDE IN TAF AT THIS TIME.  WINDS
WILL VEER SOUTHERLY LATE THIS AFTERNOON BEFORE CALMING FOR THE
OVERNIGHT.  WINDS WILL SHIFT BACK TO THE NORTH AS WEAK BACK DOOR
FRONT SLIDES IN BY MORNING.  VISB SHOULD BE IMPROVED BY THEN AS ALL
PRECIP HAS EXITED THE REGION...HOWEVER VERY MOIST PBL WILL WARRANT
CONTINUATION OF IFR/MVFR CIGS THROUGH PERIODS END.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE AS VISB FCST CONFIDENCE
REMAINS LOW.  FEEL BETTER ABOUT IFR CIGS AS WEDGE REMAINS LOCKED IN.
THUS...INITIALIZED TAFS ALL SITES ASIDE FOR KAVL WITH SOME MENTION
OF WX FOR CURRENT PRECIP...BE IT PREVAILING...OR TEMPO.
RESTRICTIONS CONTINUE THROUGH THE NIGHT DUE TO PERSISTENT WEDGE AND
MOIST/DECOUPLING PBL.  WOULD NOT BE SURPRISED TO SEE PATCHY DENSE
FOG BY MORNING...BUT LEFT OUT OF TAF AT THIS TIME DUE TO LOW
CONFIDENCE.  OTHERWISE...WINDS WILL VEER SOUTHERLY AT ALL SITES THIS
AFTERNOON BEFORE BACKING NORTHERLY LATE IN THE PERIOD AS ABOVE
MENTIONED BACK DOOR FRONT INTRUDES.  CIGS WILL RECOVER SOMEWHAT LATE
IN THE PERIOD...ALTHOUGH LIKELY REMAINING AT MVFR LEVELS.

OUTLOOK...ANOTHER CANADIAN HIGH SLIDES NORTH OF THE CAROLINAS EARLY
IN THE WEEK. AS THE HIGH MOVES NE OF THE REGION...ANOTHER BRIEF CAD
PATTERN IS POSSIBLE. PERIODS OF PRECIP AND FLIGHT RESTRICTIONS ARE
LIKELY TUE-WED. A COLD FRONT WILL MOVE THROUGH THE REGION BY THU
BRINGING WET WEATHER AND POSSIBLE RESTRICTIONS.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     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 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...CDG/SBK
SHORT TERM...RWH
LONG TERM...WIMBERLEY
AVIATION...CDG



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