Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 020603
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
103 AM EST MON MAR 2 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 TODAY/...
AS OF 1255 AM...OCCL SHOWERS WILL CONTINUE TO MOVE ACROSS MAINLY THE
WESTERN MTNS THROUGH THE NEXT COUPLE OF HOURS...BUT WILL LIKELY
BECOME MORE FOCUSED TOWARD THE NORTH GEORGIA AREA BY DAYBREAK...AS
THE DEPTH OF THE MOIST LAYER DECREASES FROM NORTH TO SOUTH THROUGH
THE NIGHT. OTHERWISE...DENSE FOG REMAINS SPORADIC ENOUGH TO PRECLUDE
HOISTING A DFA ATTM. WITH LIGHT SURFACE WINDS EXPECTED TO PERSIST
ACROSS THE AREA THAT IS MOST AT RISK (I.E. THE PIEDMONT)...IT IS
STILL NOT NECESSARILY INEVITABLE THAT ONE WILL BECOME NECESSARY.

EVENING UPDATE...NOT TOO MANY CHANGES WERE NEEDED TO THE OVERNIGHT
FCST. STILL EXPECTING SHALLOW MOISTURE TO REMAIN TRAPPED WITHIN THE
SFC INVERSION KEEPING LOW CLOUDS IN PLACE. THIS WILL CUT OFF RAD
COOLING...BUT A DENSE FG ADV MAY BE NEEDED ACROSS THE NC FTHILLS AND
PIEDMONT WHERE SFC TDD/S ARE ONLY 1-2 DEGREES F. A FEW SITES ARE
ALREADY AT 1/4 MILE VSBY IN THESE AREAS. STILL COUNTING ON DEEPER
MOISTURE ALIGNED WITHIN AND BEHIND A SFC TROF TO REACH THE SW/RN
ZONES IN A FEW HRS...SO POPS WILL BE MAINTAINED IN THE MID TO HIGH
CHANCE RANGE WITH SW/LY ADJ/S MADE TO THE ALIGNMENT. PRECIP WILL BE
LIGHT WITH MORE AREAS RECEIVING DZ THAN -SHRA THROUGH THE OVERNIGHT.

630 PM EST UPDATE...THE FCST IS IN GOOD SHAPE. TWEAKED POPS DOWN A
LITTLE ACROSS THE MTNS. A WEAKLY SUPPORTED SFC BNDRY IS NOT
PRODUCING ENOUGH -SHRA COVERAGE AS CROSSES EAST...BUT PATCHY DZ WILL
CONTINUE THROUGH THE EVENING. TEMP DIURNAL CURVES ACROSS MOST MTN
VALLEYS HAVE BEEN ADJ TO ACCOUNT FOR LATE HEATING IN SCT CONDS.

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 /TONIGHT 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 /06Z MONDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE (EXCEPT KAVL)...VERY POOR AVIATION WEATHER
WILL PERSIST UNTIL AT LEAST SUNRISE ACROSS THE WESTERN CAROLINAS.
THE WORST CONDITIONS SHOULD BE SEEN AT KHKY/KCLT/KAND...WHERE VLIFR
CONDITIONS ARE POSSIBLE AT KCLT AND ALREADY OCCURRING AT KHKY/KAND.
CONDITIONS ARE SLIGHTLY BETTER AT KGSP/GMU...AND WITH A WESTERLY/
SOMEWHAT DOWNSLOPE FLOW IN PLACE JUST ABOVE THE SURFACE...AM
EXPECTING THIS TREND TO HOLD THROUGH THE NIGHT...ALTHOUGH LIFR
CONDITIONS WILL STILL PERSIST. TIMING OF IMPROVING CIGS AND FOG
CONDITIONS AFTER SUNRISE IS QUITE THE CHALLENGE...AS MOISTURE IS
EXPECTED TO REMAIN QUITE ABUNDANT NEAR THE SURFACE THROUGH THE DAY.
HOWEVER...CIGS SHOULD GRADUALLY LIFT TO AT LEAST MVFR AT MOST
TERMINALS BY AFTERNOON AS LIGHT WINDS TURN TOWARD THE N/NW. IN
FACT...DRIER AIR SLOWLY INFILTRATING FROM THE NORTH MAY EVEN RESULT
IN CLEARING AT KHKY DURING THE AFTERNOON. CIGS SHOULD BEGIN TO LOWER
AGAIN BY THE END OF THE PERIOD...ESP ACROSS WESTERN AREAS...AS
ANOTHER COLD AIR DAMMING EVENT BECOMES ESTABLISHED.

AT KAVL...VFR CONDITIONS PERSIST EARLY THIS MORNING...AND IT IS NOT
ENTIRELY CLEAR IF/WHEN DETERIORATION IN FLT CONDITIONS WILL OCCUR...
OR HOW RESTRICTIVE CONDITIONS WILL BECOME. THE MAIN CULPRIT IN THE
CURRENT LACK OF LOW CLOUDS/POOR VISBY APPEARS TO BE A DECENT
WESTERLY DOWNSLOPE FLOW JUST ABOVE THE SURFACE. IN ANYTHING THIS IS
EXPECTED TO GRADUALLY INCREASE THROUGH THE NIGHT...ALTHOUGH SURFACE
WINDS ARE EXPECTED TO TURN UP-VALLEY. NEVERTHELESS...THIS IS NOT
TYPICALLY A GREAT SETUP FOR IFR (OR WORSE) CONDITIONS AT KAVL...SO
HAVE GONE WITH A TREND TOWARD MVFR CONDITIONS BY 08Z. A TEMPO HAS
BEEN INCLUDED TO SUGGEST THE POTENTIAL FOR IFR CIGS (SCT008). VISBY
RESTRICTIONS ALSO REMAIN POSSIBLE. OTHERWISE...VFR CONDITIONS SHOULD
DEVELOP BY AFTERNOON...WHILE CIGS WILL LIKELY BEGIN TO LOWER AGAIN
AFTER SUNSET.

OUTLOOK...LOW CIGS AND LIGHT PRECIP/DRIZZLE WILL BE LIKELY ACROSS
MUCH OF THE AREA LATE MON NIGHT THROUGH AT LEAST TUE. A COLD FRONT
WILL MOVE SLOWLY THROUGH THE REGION WED THROUGH THURSDAY...BRINGING
CHANCES FOR HEAVIER RAINFALL TO THE AREA.

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/JDL/SBK
SHORT TERM...RWH
LONG TERM...WIMBERLEY
AVIATION...JDL



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