Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261957
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
257 PM EST MON JAN 26 2015

.SYNOPSIS...
IN THE WAKE OF A STRONG DEPARTING LOW...DRY HIGH PRESSURE WILL
SPREAD BACK OVER THE REGION FROM THE NORTHWEST TONIGHT AND TOMORROW.
ANOTHER COLD FRONT IS EXPECTED TO CROSS THE REGION LATE THURSDAY
INTO EARLY FRIDAY WITH ANOTHER ROUND OF HIGH PRESSURE IN ITS WAKE.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 245 PM EST MONDAY...BROAD FULL LATITUDE LONGWAVE UPPER TROF
REMAINS ACROSS THE EASTERN CONUS WITH SHARP RIDGING ACROSS THE WEST.
CLOSER TO HOME...BRISK NORTHWEST FLOW AMONGST THE AMPLIFIED UPPER
PATTERN AND POOLED LOW LEVEL MOISTURE CONTINUES TO YIELD LIGHT
UPSLOPE SNOW SHOWERS ALONG THE TN BORDER.  FURTHER EAST...FCST
FEATURES DECREASING POPS ACROSS NC PIEDMONT AS EARLIER SHOWER
ACTIVITY HAS DIMINISHED WITH ONLY A FEW LIGHT ECHOES EVIDENT ON
RADAR.  MODELS CONTINUE TO TREND TOWARDS A BRIEF LULL IN NORTHWEST
FLOW SNOW SHOWER ACTIVITY ALONG THE TN BORDER COUNTIES BEFORE A
SECOND ROUND OF CHANNELED VORTICITY SLIDES THROUGH THE REGION
TONIGHT.  LOW LEVEL MOISTURE ASSOCIATED WITH THIS ENERGY IMPULSE
WILL POOL ALONG THE MOUNTAINS ONCE AGAIN LEADING TO RE INITIATION OF
SNOW SHOWERS.  THUS...LIKELY/CATEGORICAL POPS ARE FEATURED IN THE
FCST.   MODEL QPF CONTINUES TO YIELD SUB WARNING CRITERIA SNOW
TOTALS THUS OPTED TO EXTENDED CURRENT ADVISORY THROUGH NOON TUESDAY
TO ALSO INCLUDE EXPANSION NORTHWARD INTO THE NORTHERN MOUNTAINS OF
WESTERN NC.  FORECAST ACCUMULATIONS WILL GENERALLY REMAIN AROUND 2
TO 3 INCHES WITH SOME 4 INCH TOTALS POSSIBLE ALONG THE HIGHER PEAKS
AND RIDGETOPS OF THE SMOKIES BY MORNING.  IN ADDITION TO THE
SNOWFALL...GUSTY NORTHWEST WINDS WILL PREVAIL THROUGH MUCH OF THE
NIGHT WITH SOME OF THE HIGHER ELEVATIONS SITES EXPERIENCING GUSTS
NEAR 40MPH...WHILE THE LOWER ELEVATIONS TOP OUT WITH GUSTS NEARING
25-30MPH.

OUTSIDE OF THE MOUNTAINS...CONDITIONS WILL GRADUALLY IMPROVE THROUGH
THE OVERNIGHT WITH SKIES BEGINNING TO SCT NEAR MIDDAY TUESDAY.
DOWNSLOPING FLOW WILL YIELD TEMPERATURES JUST BELOW NORMAL DESPITE
COLD ADVECTION PATTERN.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 230 PM MONDAY...THE FIRST PART OF THE SHORT RANGE LOOKS LIKE
THE QUIETEST PART OF THE ENTIRE FCST. ANY REMAINING NW FLOW SNOW
SHOWERS OVER THE NRN MOUNTAINS OF NC SHOULD TAPER OFF RIGHT AWAY
TUESDAY EVE. THE AXIS OF THE UPPER TROF SHOULD MOVE SLOWLY OFF THE E
COAST TUESDAY NIGHT...WHICH WILL KEEP A DRY NW FLOW OVERHEAD. AN
UPPER RIDGE WILL SLOWLY BUILD IN FROM THE WEST ON WEDNESDAY WITH THE
AXIS OF THE UPPER RIDGE MOVING OVERHEAD WEDNESDAY NIGHT. THIS WILL
SUPPORT DRY AND COOL HIGH PRESSURE THAT WILL KEEP TEMPS GENERALLY A
CATEGORY OR SO BELOW NORMAL.

ON THURSDAY...THE MODELS SHOW A PAIR OF SHORT WAVES MOVING THRU THE
MIDWEST AND AROUND A MEAN TROF OVER THE EAST. THE FIRST WAVE SHOULD
STAY OVER THE OH VALLEY ON THURSDAY AFTERNOON. WARM ADVECTION AHEAD
OF THE WAVE MAY HELP TO DEVELOP SOME LIGHT PRECIP ACROSS THE FCST
AREA...WITH THE BEST CHANCE OVER THE MTNS. FCST SOUNDINGS SUGGEST
THIS WILL BE AN ELEVATION-DEPENDENT RAIN OR SNOW SITUATION. THERE
SHOULD BE A SMALL CHANCE FOR PRECIP OUTSIDE THE MTNS THAT SHOULD
FALL AS RAIN. TEMPS WERE UNDERCUT FROM THE GUIDANCE...WITH THE
EXPECTATION THAT INCREASING CLOUDS AND SOME LIGHT PRECIP WILL
CONTINUE TO KEEP TEMPS BELOW NORMAL. THE SECOND WAVE SHOULD HELP TO
DRIVE A COLD FRONT ACROSS THE WESTERN CAROLINAS THURSDAY NIGHT. MOST
OF THE PRECIP WITH THIS FEATURE WILL BE CONFINED TO THE MTNS.
IMPROVING MOIST UPSLOPE FLOW BEHIND THE FRONT SHOULD MAINTAIN A
CHANCE OF PRECIP ON THE TN BORDER THROUGH AT LEAST DAYBREAK ON
FRIDAY. THIS SHOULD BE IN THE FORM OF SNOW SHOWERS OWING TO THE COLD
ADVECTION BEHIND THE FRONT. MIN TEMPS E OF THE MTNS SHOULD BE ABOVE
NORMAL BECAUSE OF LINGERING CLOUDS.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 215 PM MONDAY...A PROMINENT TROUGH AXIS WILL MOVE QUICKLY EAST
OF THE FORECAST AREA FRI MORNING AND THEN OFF THE ERN SEABOARD
THROUGH THE DAY. SHALLOW MOISTURE IN THE NW FLOW COLD ADVECTION
BEHIND THE TROUGH COULD LINGER THROUGH LATE FRI MORNING...BUT WITH
LITTLE TO NO ADDITIONAL SNOW ACCUMULATIONS IN ANY UPSLOPE SHOWERS IN
THE WRN MTNS. MAXES WILL FALL BELOW CLIMO...PERHAPS 10 DEGREES OR
MORE BELOW CLIMO IN THE NC MOUNTAINS.

THE UPPER LEVEL FLOW PATTERN WILL BECOME ZONAL THROUGH SAT WITH SFC
HIGH PRESSURE LIKELY BUILDING OVER TO THE N OF THE REGION. A STEADY
INCREASE IN MID AND HIGH CLOUDS IS EXPECTED. MODEL DIFFERENCES THEN
APPEAR THROUGH THE LATTER HALF OF THE WEEKEND...WITH THE GFS
GENERALLY FASTER THAN RECENT ECMWF RUNS IN FEATURING A NRN STREAM
WAVE DIGGING INTO THE MIDWEST ON SUNDAY. THE 00Z OPERATIONAL ECMWF
WAS A BIT SLOWER...BUT THE 12Z RUN IS NOW CLOSER TO THE GFS TIMING
ON THE WAVE. THE MAIN SENSIBLE WEATHER DIFFERENCE FOR SUNDAY IS THAT
THE FASTER GFS TIMING ALLOWS PRECIPITATION TO ARRIVE BY
DAYBREAK...WITH A SRN TIER FREEZING RAIN/NRN TIER SNOW AND SLEET
THREAT...WITH RELATIVELY PROMINENT CAD SETTING UP FROM THE NE.
PROFILES WOULD THEN WARM FOR THE PEAK OF THE WARM ADVECTION...WITH
MAINLY A RAIN PTYPE EXCEPT FOR LINGERING FZRA IN ANY COLD POCKETS
JUST E OF THE BLUE RIDGE. THE ECMWF HAS A SLOWER ONSET OF
PRECIPITATION...WITH LESS MORNING FREEZING RAIN THREAT...MUCH WEAKER
CAD...BUT THEN MORE OF A RAIN VERSUS SNOW PTYPE ISSUE THROUGHOUT THE
WHOLE EVENT. SUNDAY TEMPS HAVE BEEN LOWERED SLIGHTLY...AND PTYPES
REMAIN RAIN/SNOW.

DIFFERENCES ARE MORE STARK SUN NIGHT INTO MONDAY. THE GFS DRIVES A
COLD FRONT THROUGH THE REGION AND DRIES THINGS OUT...OTHER THAN ANY
LINGERING NW FLOW MOISTURE IN THE WRN MTNS. THE ECMWF...ON THE OTHER
HAND...DEVELOPS A SFC WAVE OVER THE SE AND KEEPS HEAVY PRECIPITATION
IN THE REGION SUNDAY NIGHT INTO MONDAY. ASSOCIATED PTYPE ISSUES
WOULD CONTINUE DEPENDING ON THE SFC LOW TRACK. WILL CONTINUE TO KEEP
ALL PTYPES RAIN VERSUS SNOW THROUGHOUT GIVEN ALL THE UNCERTAINTY IN
THERMAL PROFILES.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD.  NORTHWEST
WINDS WILL INCREASE THIS AFTERNOON WITH GUSTS SUBSIDING INTO THE
EARLY EVENING AS THE PRESSURE GRADIENT AND MIXING RELAX.  LOW VFR
CIGS WILL PERSIST THROUGH MIDDAY BEFORE INCREASING SLIGHTLY INTO THE
6-8KFT RANGE AROUND 21Z.  MID LEVEL SCT DECK IS FCST THROUGH MUCH OF
THE OVERNIGHT AHEAD OF AN APPROACHING SHORTWAVE IMPULSE AND ITS
ASSOCIATED MOISTURE.  THUS...THE MID LEVEL SCT DECK IS PROGGED TO
THICKEN WITH CIGS IN THE 10KFT RANGE POSSIBLE AROUND DAYBREAK
TUESDAY LASTING THROUGH MID MORNING BEFORE SCT OUT ONCE AGAIN.
WINDS WILL REMAIN NORTHERLY THROUGH THE REMAINDER OF THE PERIOD WITH
SPEEDS GENERALLY LESS THAN 5-7KTS.

ELSEWHERE...VFR CIGS AND GUSTY WINDS WILL HIGHLIGHT THIS TAF
CYCLE...ESPECIALLY AT KAVL WHERE VALLEY CHANNELING COULD YIELD GUSTS
IN EXCESS OF 25KTS.  ALSO AT KAVL...LOW VFR...AND POSSIBLE HIGH
LEVEL MVFR CIGS WILL PREVAIL THROUGH MUCH OF THE TAF CYCLE DUE TO
UPSTREAM NORTHWEST FLOW SNOW SHOWERS ALONG THE TN LINE.  THUS...TAF
FEATURES LOW VFR DETERIORATING TO MVFR JUST AFTER MIDNIGHT.  WOULD
NOTE THAT CONFIDENCE IN THE MVFR CIGS REMAINS RATHER LOW.
OTHERWISE...GUSTY WEST TO NORTHWEST WINDS WILL PREVAIL THROUGH
SUNSET AT ALL OTHER TAF SITES BENEATH SCT MID LEVEL CIGS.  A SECOND
ROUND OF MID LEVEL CIG FORMATION IS PROGGED AS UPSTREAM SHORTWAVE
IMPULSE AND ASSOCIATED CHANNELED VORTICITY SLIDE INTO THE REGION
JUST BEFORE DAYBREAK.  THUS TAFS FEATURE BKN CIGS AROUND 8-10KFT
BEFORE SCT AFTER SUNRISE.

OUTLOOK...A SERIES OF CLIPPER SYSTEMS WILL BRING PERIODIC CHANCES
FOR SNOW SHOWERS...MAINLY TO THE MOUNTAINS THROUGH THE WEEK. MOST OF
THESE SNOW SHOWERS WILL REMAIN WEST AND NORTH OF KAVL...BUT BRIEF
PERIODS OF RESTRICTIONS AND SNOW SHOWERS CANNOT BE RULED OUT THERE.
OTHERWISE...MAINLY VFR CONDITIONS ARE EXPECTED.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
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%     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 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...WINTER WEATHER ADVISORY UNTIL NOON EST TUESDAY FOR NCZ033-
     048>052-058-059.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...CDG
SHORT TERM...PM
LONG TERM...HG
AVIATION...CDG



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