Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 101744
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1244 PM EST WED FEB 10 2016

.SYNOPSIS...
A BROAD AND MOIST AREA OF LOW PRESSURE WILL PERSIST OVER THE
AREA THROUGH TONIGHT. CANADIAN HIGH PRESSURE WILL THEN BUILD IN
THURSDAY AND REMAIN THROUGH THE WEEKEND. HOWEVER...DEVELOPING
COASTAL SYSTEMS BRING CHANCES OF PRECIPITATION FRIDAY AND THEN
AGAIN EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1240 PM EST WEDNESDAY...OPTED TO GO AHEAD AND CANCEL THE
WWY ACROSS ALL ZONES NOT ADJACENT TO THE TN LINE WHERE WEAK NWFS
CONTINUE.  ALSO ALLOWED WIND CHILL ADVISORY TO EXPIRE AS THE LOWEST
WIND CHILLS ARE NOW ONLY BEING OBSERVED AT ELEVATIONS ABOVE 5KFT.
OTHERWISE...TWEAKED TEMPS/DEWS AND SKY TO ACCOUNT FOR RECENT OBS/SAT
TRENDS AND LEFT THE REMAINDER OF THE FCST UNCHANGED FOR THIS UPDATE.

PREVIOUS DISCUSSION...THE AXIS OF THE TROUGH WILL FINALLY SWING EAST
OF THE REGION TODAY...WITH SLOW HEIGHT RISES THRU THU MORNING. A
BROAD AREA OF CHANNELED VORT WILL PROGRESS ACRS THE CWFA TODAY
ACCORDINGLY. THIS IS EXPECTED TO BRING SOME PARTIAL CLOUD COVER
BACK TO THE PIEDMONT. MOISTURE IS MORE SHALLOW THERE THAN THE
PAST COUPLE OF DAYS...AND AS SUBSIDENCE DEVELOPS IN THE WAKE OF
THE WAVE ANY SHALLOW CONVECTION WILL BE CAPPED OFF QUICKLY. THAT
SAID A FEW FLURRIES MIGHT BE SEEN BENEATH THE PIEDMONT CLOUDS...BUT
NOT AS COMMONLY AS WE SAW ON MON-TUE.

AS THE CHANNELED VORT MAX PASSES OVER THE MTNS...A COUPLE CAMS
INCLUDING THE NSSL WRF DEVELOP SOME LIGHT PRECIP OVER UPPER
EAST TN. INCLUDED A SLIGHT UPTICK IN POPS AGAIN EARLY THIS
AFTN. SOME INSTABILITY DOES REDEVELOP THERE AS WELL DESPITE THE
SUBSIDENCE. THOUGH ADDITIONAL SNOW IS EXPECTED TO BE LESS THAN
AN INCH...SOME VISIBILITY ISSUES AND SLICK SPOTS WILL PERSIST ON
HIGH-ELEVATION ROADS...SO THE WINTER WX ADVISORY WILL BE EXTENDED
THRU THE DAY TODAY. STRENGTHENING LOW LEVEL COLD ADVECTION WILL
OCCUR AS HIGH PRESSURE BEGINS TO BUILD IN TONIGHT...KEEPING THE
BOUNDARY LAYER MIXED AND RESULTING IN BLUSTERY CONDITIONS IN THE
MOUNTAINS. PREVIOUSLY ISSUED WIND CHILL ADVISORIES FOR TONIGHT
LOOK GOOD IN LIGHT OF REVISED TEMPS AND WINDS.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 330 AM WEDNESDAY...ANY LINGERING NW FLOW SNOW SHOWERS WILL
QUICKLY END THU MORNING AS MOISTURE DRIES UP. LOW WIND CHILL VALUES
AT THE START OF THE DAY ACROSS THE MTNS WILL WARM ABOVE ADVISORY
LEVEL BY MID MORNING. TEMPS WARM THU AHEAD OF THE NEXT CLIPPER
SYSTEM DIVING TOWARD THE AREA. THERE WILL BE SOME INCREASING CLOUDS
DURING THE AFTERNOON...BUT NO PRECIP. HIGHS WILL BE 10 TO 15 DEGREES
BELOW NORMAL. LOWS THU NITE WILL BE 5 TO 10 DEGREES BELOW NORMAL.

FRIDAY...GUIDANCE DIGS ANOTHER SHORT WAVE INTO THE BASE OF THE MEAN
TROUGH ACROSS THE EASTERN CONUS. WHILE ALL THE MODELS REFLECT SOME
WEAK SURFACE DEVELOPMENT IN RESPONSE TO THIS FEATURE...WHERE THIS
OCCURS IS THE MATTER OF SOME CONTENTION. THE NAM CONTINUES TO SHOW
ITS SURFACE WAVE...AND RESULTING LIFT AND MOISTURE...FOR PRECIP TO
MOVE ACROSS MUCH OF THE AREA. HOWEVER...THE BULK OF THE OTHER
GUIDANCE HAS THE LOW FARTHER TO THE SOUTH WITH BETTER DEVELOPMENT
OCCURRING CLOSER TO THE COAST AS THE LOW MOVES NE. THERE IS DECENT
AGREEMENT ON SOME MOUNTAIN SNOW DEVELOPING...SO HAVE GONE WITH
CHANCE POP THERE...AND A BRIEF SLIGHT CHANCE POP ELSEWHERE. COULD
SEE SOME LOW END ACCUMS ACROSS THE MTNS...WITH MAINLY RAIN
ELSEWHERE. SOME NW FLOW SNOW WILL LINGER FRI NITE. HIGHS FRI AND
LOWS FRI NITE SHUD AGAIN BE 10 TO 15 DEGREES BELOW NORMAL AND 5 TO
10 DEGREES BELOW NORMAL RESPECTIVELY. WINDS WILL BE STRONGER FRI
NITE BEHIND THE CLIPPER...POTENTIALLY TAKING HIGH ELEVATION WIND
CHILL VALUES BACK DOWN AROUND 5 BELOW.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 350 AM WEDNESDAY...FORECAST CONFIDENCE REMAINS RELATIVELY HIGH
FOR THE EARLY PART OF THE EXTENDED...THE WEEKEND...BUT RATHER LOW
FOR EARLY NEXT WEEK. A WESTERN RIDGE/EASTERN TROUGH PATTERN WILL BE
IN PLACE AT THE START OF THE PERIOD SAT. NW FLOW MOISTURE DIMINISHES
QUICKLY SAT MORNING...BRINGING AN END TO ANY NW FLOW SNOW SHOWERS.
COLD AND DRY ARCTIC HIGH PRESSURE WILL BUILD INTO THE AREA THRU THE
WEEKEND. TEMPS WILL BE QUITE COLD WITH HIGHS DROPPING TO READINGS
NEAR THE NORMAL LOWS ON SUNDAY. LOWS WILL BE 15 TO 20 DEGREES BELOW
NORMAL SAT NITE. ALTHOUGH THE WINDS WILL HAVE DIMINISHED SAT NITE...
WITH THE COLD TEMPS IN PLACE...HIGH ELEVATION WIND CHILL VALUES WILL
AGAIN DROP DOWN TO AS LOW 15 BELOW.

UNCERTAINTY INCREASES IN THE FORECAST SUNDAY NIGHT INTO MONDAY AS AN
UPSTREAM TROUGH AMPLIFIES ACROSS THE MIDWEST...BUT WITH MODEL
DIFFERENCES SHOWING UP AS THE BASE OF TROUGH REACHES THE SOUTHEAST.
WARM FRONTAL MOISTURE MAY BRUSH THE SOUTHERN APPALACHIANS AHEAD OF
THIS SYSTEM LATE SUNDAY...BUT THE BEST MOISTURE AND FORCING AHEAD OF
A REINFORCING COLD FRONT WILL BE LATER SUNDAY NITE THROUGH MONDAY
NITE. THE GFS/GEFS CONTINUE TO FEATURE A MORE PROGRESSIVE TROUGH
PASSAGE INTO TUESDAY WHILE THE ECMWF REAMPLIFIES THE WAVE WEST OF THE
APPALACHIANS. THAT SAID..THE GFS HAS MORE SLY INFLOW WITH THIS
SYSTEM THAN PREVIOUS RUNS...BUT STILL NOT AS STRONG MORE MOIST AS
THE ECMWF. THIS PERMITS ANOTHER ROUND OF SOUTHEAST MOISTURE TO
DEVELOP. THERMAL PROFILES SUGGEST AN ONSET AS SNOW WITH THE COLD AND
DRY ANTECEDENT AIR SUNDAY NIGHT. SOME CHANGEOVER TO RAIN ACROSS SE
SECTIONS WILL BE POSSIBLE MONDAY AFTERNOON. THE GUIDANCE DIFFERS ON
THE STRENGTH OF ANY DEVELOPING CAD AND RESULTING SURFACE TEMPS.
THERE COULD BE ENUF WARMING THAT PRECIP OUTSIDE OF THE MTNS REMAINS
RAIN UNTIL THE FRONT PASSES...WHILE TEMPS COULD COOL ENUF FOR A
CHANGEOVER BACK TO SNOW BEFORE ENDING. THEREFORE...HAVE GONE WITH A
GUIDANCE BLEND AND A NORMAL DIURNAL TEMP PATTERN...SHOWING A MIX OR
CHANGEOVER MONDAY NITE. THERE IS GOOD AGREEMENT ON A RETURN TO NW
FLOW SNOW OVER THE MTNS INTO TUE. GIVEN THE LOW CONFIDENCE AND
UNCERTAINTY...WILL CONTINUE TO HOLD OFF ON A MENTION IN THE HWO FOR
NOW.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE EAST OF THE MTNS...VFR THROUGH THE PERIOD
AT ALL SITES.  MOISTURE IN THE LLVS STARTING TO MATERIALIZE
INTO FEW/SCT LOW VFR CU ACROSS THE NC/SC PIEDMONT.  THUS ALL
TAFS FEATURES SUCH THROUGH THE AFTERNOON ALONG WITH GUSTY WNW
WINDS...HOWEVER WITH THE EXCEPTION OF A TEMPO PERIOD WHERE WINDS
WILL BE A BIT BACKED WSW AT KCLT.  BEYOND THAT...LOW VFR CU LIFTS
TOWARDS SUNSET WITH MID CLOUDS PREVAILING THROUGH MID MORNING
AMIDST MODERATE WNW FLOW AT THE SURFACE.  GUIDANCE TENDS TO BACK
FLOW WSW YET AGAIN TOMORROW MORNING ACROSS THE PIEDMONT HOWEVER
OPTED TO HOLD ONTO WNW FOR NOW.

AT KAVL...SIMILAR TO THAT OF THE SITES ABOVE HOWEVER WITH SUSTAINED
GUSTY NW WINDS THROUGH THE VAST MAJORITY OF THE PERIOD BEFORE GUSTS
SUBSIDE AROUND DAYBREAK TOMORROW.  SKIES WILL REMAIN BKN/SCT IN
THE LOW VFR RANGE THROUGH THE TAF CYCLE DESPITE WEAKENED MOIST
UPSLOPING ALONG THE TN LINE.

OUTLOOK...A DEEP UPPER TROF WILL BEGIN TO LIFT NE OUT OF THE
AREA...TAPERING OFF THE NW FLOW SNOW SHOWERS TODAY AND CLEARING
SKIES ON THURSDAY.  ANOTHER DISTURBANCE WILL QUICKLY CROSS THE
AREA ON FRIDAY...WHICH MAY PRODUCE A BRIEF PERIOD OF WINTRY PRECIP
ACROSS THE AREA.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     LOW   57%
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...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NCZ033-
     048>052-058.
     WIND CHILL ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST
     THURSDAY FOR NCZ033-048>052-058-059-062>064.
SC...NONE.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...CDG/WIMBERLEY
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG


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