Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291758
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1258 PM EST THU JAN 29 2015

.SYNOPSIS...
IN THE WAKE OF A COLD FRONTAL PASSAGE...HIGH PRESSURE WILL BUILD
INTO THE REGION LATER ON FRIDAY. THE HIGH WILL LINGER OVER THE AREA
INTO SUNDAY BEFORE MOISTURE RETURNS OUT AHEAD OF A DEVELOPING
LOW PRESSURE SYSTEM. DRY CANADIAN HIGH MOVES BACK INTO THE AREA BY
TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1240 PM EST UPDATE...LATEST MESO-SCALE MODELS WERE HANDLING WELL
WITH THE BAND OF PRECIP CROSSING THE NC MTNS ZONES AS OF EARLY THIS
AFTERNOON. HENCE...HAVE BLENDED WITH THE CAMPOP FEATURING LIKELY
POPS OVER THE RIDGE TOPS OF THE BLUE RIDGE. ALSO...HAVE CARRIED A
MIX OF RAIN AND SNOW OVER PORTIONS OF THE NORTHERN NC MTNS/VALLEYS
AS TEMPS STRUGGLE TO WARM UP ABOVE 40S.

1000 EST THURSDAY UPDATE...LATEST SURROUNDING REGIONAL RADARS SHOW A
BAND OF LIGHT RETURNS WAS APPROACHING THE SOUTHERN APPALACHIANS FROM
THE TN VALLEY AS OF THIS MORNING. LATEST HRRR AND OTHER MESOSCALE
MODELS INDICATE THAT THIS BAND OF LIGHT PRECIP ASSOCIATED WITH AN
UPPER WAVE WILL MOVE EAST ACROSS THE NC MTN ZONES BETWEEN 16-18Z AND
ACROSS THE NC FOOTHILLS AND PORTIONS OF THE NORTHERN NC PIEDMONT
18-20Z. THEREFORE...POPS WERE UPDATED TO ACCOUNT FOR THIS THRU THIS
AFTERNOON. HOWEVER...PRECIP AMOUNTS APPEAR TO BE VERY LIGHT GIVEN
RELATIVELY DRY AIRMASS AND SHALLOW MOIST LAYER. NO WINTRY P-TYPE IS
EXPECTED THRU THIS AFTERNOON GIVEN GOOD WARMING TREND.

1115 UTC UPDATE...WINDS WERE UPDATED WITH A TWO TO ONE BLEND OF THE
NAM AND ADJMAV...FAVORING THE FORMER FOR STRINGER WINDS AND GUSTS IN
THE MOUNTAINS...BOTH AHEAD OF AND BEHIND THE APPROACHING COLD FRONT.
GUSTS STILL APPEAR TO REACH ADVISORY CRITERIA ONLY AT THE VERY
HIGHEST MOUNTAIN PEAKS LATE TONIGHT...SO NO ADVISORY IS PLANED AT
THIS TIME. SKY COVER WAS UPDATED FROM INFRARED SATELLITE IMAGERY.

AT 230 AM EST THURSDAY...AN UPPER RIDGE OF MODEST AMPLITUDE WILL
CROSS THE EASTERN SEABOARD THIS MORNING...WHILE AND UPPER TROUGH
MOVES FROM THE MS RIVER VALLEY TO THE OH AND TN RIVER VALLEYS. A
SHORTWAVE MOVING THROUGH THIS TROUGH WILL REACH THE CENTRAL
APPALACHIANS BY MIDDAY. THE RIDGE MOVES TO THE GULF STREAM THIS
AFTERNOON...WHILE THE SHORTWAVE MOVES OFF THE MID ATLANTIC COAST.
ANOTHER AND MORE ROBUST SHORTWAVE MOVING THROUGH THE TROUGH REACHES
THE CENTRAL AND SOUTHERN APPALACHIANS IN THE MIDDLE OF THURSDAY
NIGHT...MOVING EAST OF OUR AREA BY MORNING....WHILE THE TROUGH AXIS
REACHES THE EAST COAST.

A SURFACE RIDGE ALONG THE EAST COAST WILL MOVE OFFSHORE TODAY...
WHILE A COLD FRONT MOVES FROM THE MS RIVER VALLEY TO THE
APPALACHIANS. PRECIPITATION AHEAD OF THE FRONT WILL REACH THE
MOUNTAINS SOMETIME THIS MORNING...PERHAPS EARLY ENOUGH TO START AS
LIGHT SNOW. WITH WARMING...SNOW LEVELS RISE ABOVE THE MOUNTAIN TOPS
TODAY. NO APPRECIABLE SNOW ACCUMULATIONS ARE EXPECTED THIS MORNING.
THE MODELS DO NOT SHOW MUCH DEPTH TO THE MOIST LAYER EAST OF THE
BLUE RIDGE...AND PRECIPITATION CHANCES ARE QUITE LIMITED THERE.

FRONTAL PASSAGE TAKES PLACE OVERNIGHT...WITH DOWNSLOPE DRYING IN THE
LEE OF THE MOUNTAINS...AND MOIST NW FLOW INTO THE NC MOUNTAINS
BORDERING TN. SNOW LEVEL ARE EXPECTED TO FALL TO THE VALLEY FLOORS
THIS EVENING...WHILE COVERAGE RETREATS CLOSER TO THE TN BORDER.
RIGHT NOW IT APPEARS THAT SNOWFALL ACCUMULATIONS WILL RUN JUST UNDER
TWO INCHES OVERNIGHT...BUT ADVISORY CRITERIA WILL ONLY BE APPROACHED
ON THE VERY HIGHEST PEAKS...SO NO SNOW ADVISORY IS PLANNED. WINDS
WILL INCREASE IN THE TIGHT PRESSURE GRADIENT BEHIND THE FRONT...BUT
WIND ADVISORY CRITERIA WILL ONLY BE REACHED LATE TONIGHT ON PEAKS
OVER 5000 FT...SO NO WIND ADVISORY IS PLANNED AT THIS TIME.

HIGH TEMPERATURES WILL RUN NEAR NORMAL TODAY AS WARM ADVECTION UNDER
THE UPPER RIDGE IS OFFSET BY INCREASING CLOUD COVER...AND LOW
TEMPERATURES TONIGHT WILL RUN SLIGHTLY ABOVE NORMAL AS WINDS KEEP
THE ATMOSPHERE MIXED.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 115 AM THURSDAY...THE SHORT TERM BEGINS WITH AN INCREASING
SUBSIDENCE ZONE AND A WANING NWFS EVENT. DRY CP AIR WILL BEGIN
FILTERING INTO THE MTNS AND LIMIT THE ADDITIONAL SNOWFALL POTENTIAL.
LIKELY AROUND ANOTHER HALF TO ONE INCH THROUGH 21Z ACROSS WRN MTN
SPINE. GOOD H85 CAA ALONG WITH DEEP SUBSIDENCE WILL CONTINUE THE
STRONG WINDS/GUSTS ACROSS THE NC MTNS...WITH ADVISORY OR EVEN
WARNING CRITERIA BEING MET ABOVE 4000 FEET AS MODEL SOUNDINGS
INDICATE AN UPWARD TREND IN VELOCITIES ATOP THE MIXED LAYER THROUGH
MID AFTERNOON. WILL KEEP THE HWO MENTION FOR NOW AND THE DAY SHIFT
WILL LIKELY ISSUE THE NPW AS THE EVENT MOVES INTO THE 2ND PERIOD.
WINDS WILL RELAX SLOWLY THROUGH THE EVENING WITH A GOOD H85 TGRAD
EVENTUALLY LOOSENING AFT 00Z. MAX TEMPS WILL ABOUT 15 DEGREES BELOW
NORMAL MTN VALLEYS AND 3-5 DEGREES BELOW NORMAL NON/MTNS. HEIGHTS
BEGIN TO RISE FRI NIGHT AND FLAT RIDGING WILL BE IN PLACE BY SAT
AFTERNOON. THIS WILL ENABLE THE CP SFC HIGH TO CROSS THE FA
THROUGH THE PERIOD BECOMING SITUATED OFF THE CAROLINA COAST BY 12Z
SUN. THUS...SKIES WILL CLEAR AND TEMPS WILL REMAIN A FEW DEGREES
BELOW NORMAL AS A LLVL THETA/E TROF MIXES IN.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 255 AM THURSDAY MORNING...THE MEDIUM RANGE FCST PICKS UP AT
12Z ON SUNDAY WITH RELATIVELY ZONAL UPPER FLOW OVER THE CAROLINAS
AND A DEEPENING UPPER TROF TO OUR WEST. OVER THE NEXT 24 TO 36
HRS...THE TROF AXIS IS EXPECTED TO PASS OVERHEAD WITH MORE ZONAL
FLOW IN ITS WAKE. DURING THIS PERIOD...A SOUTHERN STREAM H5 LOW
SPINS UP OVER THE BAJA PENINSULA AND GRADUALLY DRIFTS NE TOWARDS OUR
AREA. BY THE END OF THE MEDIUM RANGE...THIS LOW WILL LIKELY GET
ABSORBED BY ANOTHER DEEPENING UPPER TROF.

AT THE SFC...HIGH PRESSURE WILL BE MOVING OFF THE SE COAST EARLY
SUNDAY AS ANOTHER LOW SPINS UP TO OUR WSW OVER THE LOWER MISS RIVER
VALLEY. THE ASSOCIATED BROAD AREA OF DEEP LYR MOISTURE WILL SPREAD
OVER THE REGION THRU THE DAY WITH OVERCAST CONDITIONS AND LIKELY
POPS BY LATE SUN/EARLY MON FOR PRETTY MUCH ALL ZONES. THE GFS
REMAINS ABOUT 12 HRS FASTER WITH THE DEVELOPMENT OF THIS SYSTEM
COMPARED TO THE ECMWF AND CMC. IN THE LOWS WAKE...ANOTHER CANADIAN
HIGH PUSHES BACK INTO THE REGION FROM THE NW ON MON AND DRIES THINGS
OUT. THE CENTER OF THE HIGH WILL PASS OVER THE AREA ON TUES AND MOVE
OFFSHORE BY EARLY WED. BEYOND THIS POINT THE MODEL GUIDANCE REMAINS
FAIRLY AMBIGUOUS WITH THE SYNOPTIC PATTERN. THE GFS BRINGS ANOTHER
REINFORCING CANADIAN HIGH DOWN OVER THE REGION ON THURS AND KEEPS
THINGS DRY. THE ECMWF TRIES TO SPIN UP ANOTHER MILLER A TYPE LOW
OVER THE NORTHERN GULF OF MEX ON WED AND MOVE THE SYSTEM ACROSS THE
CAROLINA COAST LATE WED/EARLY THURS AND AFTER THAT...IT DRIES THINGS
OUT LIKE THE GFS. THE PREVIOUS RUNS OF THE GFS HINTED MORE TOWARDS
THE MILLER A TYPE LOW DEVELOPING...SO THE CURRENT DRY SCENARIO LOOKS
QUESTIONABLE. AS FOR THE SENSIBLE FCST...I TRENDED A BIT COOLER FOR
THE MON/TUES PERIOD WITH LOWS EARLY TUES IN THE LOW TO MID 20S
ACROSS THE THE LOWER ELEVATIONS AND TEENS ACROSS THE HIGHER TERRAIN.
POP TRENDS WERE NOT CHANGED MUCH FOR THE FIRST HALF OF THE PERIOD
WITH BEST CHANCES LATE SUN THRU EARLY MON. FOR TUES/WED...I KEPT
POPS AT SLIGHT TO SOLID CHANCE DUE TO THE CONTINUING UNCERTAINTY
WITH THE GULF LOW.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...EXPECT VFR CONDITIONS TO PERSIST THROUGH 18Z FRIDAY. A
LIGHT BAND OF PRECIP ASSOCIATED WITH A WEAK UPPER WAVE WILL CROSS
THE NC MTNS THROUGH THIS AFTERNOON. HOWEVER...LATEST MESO-MODELS
INDICATE THAT THIS FEATURE WILL WEAKEN CONSIDERABLY AS IT ENTERS THE
NC FOOTHILLS/PIEDMONT BY EARLY THIS AFTERNOON. SO NO PRECIP WAS
MENTIONED IN THE TAF. SW WINDS SHOULD PERSIST WITH OCCASIONAL GUSTS
TO AROUND 15-20KTS POSSIBLE THRU THIS AFTERNOON. TONIGHT...SW WINDS
SHOULD TO VEER TO THE NW AS A SURFACE COLD FRONT PUSHES THROUGH THE
REGION. AS SURFACE PRESSURE TIGHTENS UP BEHIND THE FRONT...GUSTY NW
WINDS OF 15-20KTS WILL DEVELOP BY AROUND 15Z. CLOUD CIGS WILL BOTTOM
OUT AROUND 8K FT DURING THE FROPA TONIGHT.

ELSEWHERE...VFR THROUGH THE PERIOD EXCEPT KAVL WHERE MVFR CLOUDS
WILL SPREAD IN FROM THE NORTH TONIGHT DUE TO THE FROPA. A LIGHT BAND
OF PRECIP WILL MOVE ACROSS THE NC MTN ZONES THROUGH THIS AFTERNOON.
HOWEVER...THE PRECIP APPEARS TO BE VERY LIGHT AND IT WILL BE MAINLY
CONFINED TO THE RIDGE TOPS OF THE MTNS. HENCE...NO PRECIP WAS
MENTIONED IN KAVL. OTHERWISE...EXPECT MOSTLY CLOUDY SKIES WITH SW
WINDS PERSISTING THROUGH LATE THIS EVENING ACROSS MUCH OF THE
REGION. WINDS WILL VEER THE NW TONIGHT AS A SURFACE COLD FRONT
PUSHES THROUGH THE AREA. AGAIN...PRECIP CHANCES ARE TOO LOW TO
MENTION IN THE TAF. TIGHT PRESSURE GRADIENT BEHIND THE FRONT WILL
RESULT IN GUSTY NW WINDS ACROSS MUCH OF THE REGION BY FRI MORNING.

OUTLOOK...A PAIR OF CLIPPER SYSTEMS WILL BRING CHANCES FOR RAIN OR
SNOW SHOWERS TO THE NC MTNS FRI. MOST OF THESE SHOWERS WILL REMAIN
WEST AND NORTH OF KAVL...BUT BRIEF PERIODS OF RESTRICTIONS CANNOT BE
RULED OUT. OTHERWISE...MAINLY VFR CONDITIONS ARE EXPECTED ACROSS THE
AREA UNTIL MOISTURE BEGINS TO RETURN SUNDAY. DRYING IS EXPECTED ON
MONDAY.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  96%     HIGH  81%     MED   60%
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 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...JAT/JOH
SHORT TERM...SBK
LONG TERM...JPT
AVIATION...JOH


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