Area Forecast Discussion
Issued by NWS Greer, SC

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628
FXUS62 KGSP 072005
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
305 PM EST SUN FEB 7 2016

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN AND MOVE OFF THE ATLANTIC COAST OVERNIGHT
AHEAD AN APPROACHING COLD FRONT. THIS FRONT WILL CROSS THE REGION
MONDAY...WITH A BROAD AND MOIST AREA OF LOW PRESSURE LINGERING INTO
WEDNESDAY NIGHT. CANADIAN HIGH PRESSURE WILL THEN BUILD IN THURSDAY
AND REMAIN THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 230 PM...SATELLITE IMAGERY CONTINUES TO SHOW WHAT A
DIFFERENCE YOUR LOCATION MAKES IN TERMS OF WHAT YOUR IMPRESSION OF
THE KIND OF DAY IT IS. THE WRN EDGE OF THE CLOUD SHIELD ASSOCIATED
WITH THE OFFSHORE LOW HAD MOVED A BIT FARTHER EAST...BUT STILL WAS
STRUNG OUT ACROSS METRO CHARLOTTE. SO...IT IS A BRIGHT SUNNY DAY
OVER MOST OF THE NC MTNS/FOOTHILLS...UPSTATE SC...AND NE
GEORGIA...WITH TEMPS WARMED UP AS EXPECTED. MEANWHILE...THE
CHARLOTTE METRO AREA AND I-77 CORRIDOR ARE STILL STUCK UNDER THE
MID-LEVEL CLOUD DECK. STILL EXPECT THE CLOUD SHIELD TO THIN AND MOVE
OUT TO THE EAST BY THE END OF THE DAY. TEMPS STILL SEEM TO BE IN
LINE EVEN IN THE CLOUDY EAST.

TONIGHT...AS THE UPPER LOW OFF THE CAROLINA COAST PULLS AWAY...A
SHORT WAVE RIDGE WILL MOVE OVERHEAD SUPPORTING WEAK HIGH PRESSURE.
THUS...EXPECT A QUIET EVENING AS WINDS DIMINISH UNDER CLEAR SKY.
THIS QUIET PERIOD WILL BE SHORT-LIVED AS AN UPPER LOW DROPPING DOWN
OVER THE UPPER GT LAKES WILL SEND A STRONG SHORT WAVE DOWN FROM THE
NW AND TOWARD THE REGION. AT THIS POINT...IT DOES NOT APPEAR THAT
THE FORCING AND MOISTURE WILL ARRIVE UNTIL RIGHT AROUND
DAYBREAK...SO THE BALANCE OF THE OVERNIGHT WILL BE DRY...WITH
INCREASING CLOUDINESS. LOW TEMPS SHOULD BE CLOSE TO NORMAL.

WHICH BRING US TO MONDAY. A STRONG SHORT WAVE WILL COME BARRELING
ACROSS THE MTNS IN THE MORNING HOURS WITH GOOD MID/UPPER FORCING AND
A SWATH OF DEEP MOISTURE. WHILE THE DIRECTION OF THE LOW LEVEL FLOW
IS MORE WESTERLY THRU THE DAY...THE LOW LEVEL FORCING WILL STILL BE
DECENT AS A COLD FRONT PASSES...MAINLY DURING THE 15Z TO 18Z TIME
FRAME. COLD AIR RUSHES IN AS THE WAVE PASSES. FCST SOUNDINGS SUGGEST
AN ELEVATION-DEPENDENT RAIN/SNOW SCENARIO WITH THE SNOW LEVEL AT
LEAST AS LOW AS 3K FEET. THE MODELS ALSO SUGGEST A CONVECTIVE
COMPONENT AS VERY STEEP LAPSE RATES MOVE ACROSS THE AREA WITH THE
CORE OF THE COLDEST AIR AT MID-LEVELS. GOING WITH QPF FROM BLEND OF
WPC AND OPERATIONAL MODELS...WE SHOULD HAVE SOMETHING ON THE ORDER
OF TWO TO FOUR TENTHS ON THE TN BORDER AND ABOUT 1/4 INCH LIQUID
EQUIVALENT ACROSS THE MTNS OUTSIDE THE UPPER FR. BROAD VALLEY...MOST
OF WHICH WOULD BE SNOW AT ELEVATIONS ABOVE 2500 FEET. THUS...WE HAVE
THE POTENTIAL FOR 2-4 INCHES OF SNOW DURING DAYLIGHT HOURS ACROSS
MOST OF THE MTNS AWAY FROM THE VALLEY FLOORS. AT THIS POINT...THINK
IT WISE TO LEAD INTO THIS EVENT WITH AT LEAST A WINTER WX ADVY FOR
ALL BUT TRANSYLVANIA/HENDERSON AND LET THE EVE/MID SHIFT DECIDE
ABOUT BEGINNING A WARNING DURING THE DAY. OUTSIDE THE MTNS...EXPECT
PRECIP TO BREAK CONTAINMENT WITH THE POTENTIAL FOR SHALLOW
CONVECTION IN A FAVORABLE ENVIRONMENT AS THE SHORT WAVE PASSES. WILL
FAN A CHANCE OF PRECIP OUT ACROSS THE AREA E OF THE BLUE RIDGE
THROUGH THE AFTERNOON. AT THIS POINT...WET BULB TEMP PROFILES
SUGGEST THE BOUNDARY LAYER WILL JUST BE TOO WARM FOR ANYTHING BUT
LIQUID. WILL NOT RULE OUT SOME SNOW REACHING THE TOP OF PARIS MTN IN
SC OR THE S MTNS IN NC...BUT THE COLD AIR WILL HAVE TO ARRIVE MUCH
EARLIER THAN EXPECTED FOR ANY WET SNOW TO REACH THE GROUND ACROSS
THE MAJORITY OF THE AREA E OF THE MTNS. TEMPS WILL BE RELATIVELY
COOL BECAUSE OF THE PRECIP AND CLOUD COVER.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 PM SUNDAY...SHORT RANGE MODELS INDICATES THAT H85 CAA WILL
CONTINUE ACROSS THE FORECAST AREA MONDAY NIGHT. GFS INDICATES THAT
H85 TEMPS OVER KAVL FALL FROM -5 C AT 0Z TUES TO -10 C BY 12Z TUES.
THE PASSAGE OF THE MID LEVEL TROF AND H85 FLOW FROM THE NW AT 20 TO
25 KTS SHOULD CONTINUE UPSLOPE SHOWERS ALONG THE TN BORDER. THE CAA
WILL COOL THERMAL PROFILES ACROSS THE MTNS TO RESULT IN ONLY -SHSN
AS THE P-TYPE AFTER SUNSET MON. NW FLOW AND DEEP MOISTURE WILL
SUPPORT ACCUMULATING SN SHOWERS ON TUESDAY...INTO WEDNESDAY MORNING.
SNOWFALL RATES ARE EXPECTED TO RANGE FROM THREE QUARTERS TO ONE AND
HALF INCHES PER SIX HOURS ALONG THE TN LINE. IN ADDITION...LOW
TEMPERATURES TUESDAY MORNING IS FORECAST TO RANGE FROM THE TEENS TO
LOW 20S ACROSS THE MTNS TO UPPER 20S EAST. THIS WILL FREEZE ANY
LINGERING MOISTURE ON ROADS AND BRIDGES...LEADING TO SLICK SPOTS.

ON WEDNESDAY...MOISTURE WILL GRADUALLY ERODE ACROSS EASTERN TN AND
THE SW NC MTNS. ANOTHER SURGE IN CAA WILL LIKELY OCCUR DURING THE
DAY...LOWERING H85 TEMPS TO -18C BY 0Z THURSDAY AS H85 WINDS
INCREASE TO 30 TO 35 KTS. THURSDAY WILL SEE HIGHS REMAINING WELL
BELOW FREEZING ACROSS THE MTNS TO UPPER 30S EAST. ACCUMULATING SN
WILL CONTINUE...BUT RATES LIGHTER THAN TUESDAY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM EST SUNDAY...THE AXIS OF THE BROAD LONGWAVE EASTERN
TROUGH WILL MOVE EAST OF THE FORECAST AREA WEDNESDAY NIGHT. DEEP
LAYER NORTHWEST FLOW ON THE BACK SIDE OF TROUGH AXIS WILL THEN SET
UP THROUGH THE DAY ON THURSDAY...WITH THE BULK OF THE MOISTURE
PULLING AWAY TO THE NORTHEAST. LOW LEVEL NW UPSLOPE FLOW MOISTURE
INTO THE SOUTHERN APPALACHIANS WILL DIMINISH AS WELL. THE COLD WILL
BE THE MAIN STORY BY DAYBREAK THURSDAY...WITH MINIMUM TEMPERATURES
SOME 10 TO 20 DEGREES BELOW CLIMO...AND WIND CHILL VALUES LIKELY
REACHING 15 TO 20 DEGREES BELOW ZERO ALONG THE HIGHER TERRAIN.

THE EASTERN TROUGH WILL FLATTEN OUT SOMEWHAT THURSDAY NIGHT INTO
FRIDAY...BUT ADDITIONAL CHANNELED VORTICITY MAY STREAM INTO THE
SOUTHERN APPALACHIANS ON THE LINGERING WNW FLOW. DEEPER MOISTURE
SHOULD BE RESURGENT AS WELL...AND SOME MEASURE OF LIGHT UPGLIDE
COULD ACCOMPANY THE WAVE EVEN EAST OF THE MOUNTAINS ON FRIDAY.
OVERALL...PRECIPITATION CHANCES WILL EXPERIENCE AN UPTICK THROUGHOUT
ON FRIDAY. THICKNESSES WILL SUPPORT MAINLY A SNOW/RAIN FORECAST FROM
NORTHWEST TO SOUTHEAST SECTIONS...BUT WITH MIXED PTYPES POSSIBLE
THROUGHOUT INTO FRIDAY EVENING. NW FLOW MOISTURE WILL GRADUALLY
DIMINISH FRIDAY NIGHT INTO EARLY SATURDAY.

HEIGHTS WILL BEGIN RISING FROM THE WEST OVER THE WEEKEND...WITH
PROFILES DRYING THROUGHOUT. HOWEVER...TEMPERATURES WILL REMAIN WELL
BELOW CLIMATOLOGY. THE LATEST ECMWF IS COMING AROUND TO THE GFS
SOLUTION OF UPSTREAM HEIGHT FALLS ACROSS THE NORTHERN PLAINS SUNDAY
THAT REACH THE MID MS VALLEY AT THE END OF THE PERIOD.
HOWEVER...THIS ACTIVITY WILL REMAIN WELL UPSTREAM OF THE SOUTHEAST
UNITED STATES THROUGH THE END OF THE PERIOD ON SUNDAY.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AT KCLT....THE MID-LEVEL CLOUD DECK REMAINS OVERHEAD AT ISSUANCE
TIME...BUT THIS IS EXPECTED TO FINALLY MOVE OFF TO THE EAST BY MID-
AFTERNOON. THIS SHOULD ALLOW GUSTY NNE WIND TO CONTINUE UNTIL LATE
AFTERNOON WHEN THE PRESSURE GRADIENT RELAXES AND THE BOUNDARY LAYER
STARTS TO DECOUPLE. EXPECT CLEAR SKY OVERNIGHT WITH LIGHT MOSTLY NW
WIND EVENTUALLY SHIFTING AROUND TO LIGHT SW OR S BEFORE DAYBREAK AS
THE NEXT UPPER SYSTEM APPROACHES. AT THIS TIME...IT DOES NOT APPEAR
THIS SYSTEM WILL REACH CHARLOTTE BEFORE THE VERY END OF THE TAF
PERIOD.

ELSEWHERE OUTSIDE THE MTNS...VFR CONDITIONS WILL CONTINUE THROUGH
THE PERIOD. EXPECT INCREASING HIGH CLOUDS TOWARD DAYBREAK. THINK ANY
LOW CLOUDS THAT MOVE IN AS THE NEXT SYSTEM CROSSES THE MTNS WILL
REMAIN VFR. RELATIVELY LOW CHANCE THAT ANY PRECIP WILL BREAK OUT
PAST THE MTNS BY THE END OF THE TAF PERIOD...EXCEPT FOR MAYBE KHKY.

AT KAVL...WITH LOW VFR MAY DEVELOP AROUND DAYBREAK. MOST OF THE
PRECIP ASSOCIATED WITH THE PASSAGE OF THE UPPER SYSTEM WILL STAY
CLOSER TO THE TN BORDER...BUT LIGHT PRECIP CANNOT BE RULED OUT IN
THE MORNING. EVENTUALLY...THE IMPROVING NW FLOW WILL BLOW LOW CLOUDS
AND SNOW SHOWERS UP THE FR. BROAD VALLEY...THUS THE MVFR CEILING
TOWARD THE END OF THE PERIOD.

OUTLOOK...SEVERAL ROUNDS OF STRONG UPPER LEVEL DISTURBANCES...
MOISTURE...AND REINFORCING COLDER AIR ARRIVE FROM THE NORTHWEST
MONDAY NIGHT THROUGH WEDNESDAY. RESTRICTIONS WILL BE POSSIBLE...
ESPECIALLY IN THE MOUNTAINS...WHERE SNOW SHOWERS ARE MOST LIKELY.

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  89%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   79%

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 FROM 6 AM TO 6 PM EST MONDAY FOR
     NCZ033-048>053-058-059-062-063.
     WINTER STORM WATCH FROM MONDAY EVENING THROUGH THURSDAY
     MORNING FOR NCZ033-048>052-058-059-062.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...PM
SHORT TERM...NED
LONG TERM...HG
AVIATION...PM



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