Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 080559
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1259 AM EST MON FEB 8 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 TODAY/...
AS OF 1230 AM MON...HAVE UPDATED WINDS/SKY THROUGH THE NEAR TERM. NO
SIGNIFICANT CHANGES AT THIS TIME.

REST OF 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 /TONIGHT 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 /06Z MONDAY THROUGH FRIDAY/...
AT KCLT AND EAST OF THE BLUE RIDGE...INITIALLY VARIABLE WINDS
EARLY THIS MORNING WILL BACK TO SOUTHERLY AFTER DAYBREAK IN
ADVANCE OF APPROACHING COLD FRONT ASSOCIATED WITH A DEEP UPPER
TROUGH. INCREASING MIDLEVEL CLOUDS WILL BE SEEN THRU MIDDAY...WHEN
A VORT LOBE EMBEDDED WITHIN THE TROUGH BEGINS TO PASS OVER THE
REGION. A PERIOD OF LOWER CLOUD BASES ASSOCIATED WITH DEEP CU WILL
DEVELOP OVER THE FIELD IN RESPONSE TO THE UPPER LIFT AND STRONG
MID-UPPER LEVEL LAPSE RATES. THERE IS ALSO A CHANCE OF LOW VFR
SHRA...AND A NONZERO CHANCE OF A TS AND MVFR CIG CHANCE IS AT THE
HIGH END OF THE PROB30 RANGE...BUT AT THIS TIME IT IS DIFFICULT TO
PIN DOWN A SPECIFIC TIME OF PEAK CHANCE...SO WILL KEEP THE PROB30
FOR SEVERAL HOURS /BRIEFLY PREVAILING SHRA ONLY AT KHKY/. CHANCES
TAPER OFF IN THE EVENING IN THE WAKE OF THE VORT LOBE...BUT WITH
FALLING TEMPS IN THE WAKE OF THE FRONT...ANY REMNANT SHOWERS COULD
MIX WITH SN BEFORE ENDING. THAT CHANCE IS LOW ENOUGH TO OMIT AT
THIS POINT.

AT KAVL AND IN THE MOUNTAINS...CONVECTIVE POTENTIAL WITH PASSING
UPPER DISTURBANCE IS A BIT EARLIER IN THE DAY. COOLER TEMPS WILL
SUPPORT ALL SN ON RIDGETOPS AND A RASN MIX IN THE VALLEYS /AND
KAVL/. LATER IN THE AFTERNOON THE BIGGER STORY WILL BE THE ONSET OF
WHAT LOOKS TO BE A PROLONGED NW FLOW SNOW EVENT AS WINDS BACK IN
THE WAKE OF THE DISTURBANCE...AND COLD ADVECTION STRENGTHENS. THE
BETTER CHANCES WILL BE IN THE HIGH ELEVATIONS...BUT A LOW CHANCE
OF -SHSN EXISTS AT KAVL AFTER SUNSET. HANDLING THIS WITH VCSH
FOR NOW. BRISK FLOW ACRS THE MTNS IS PROGGED TO RESULT IN A RARE
CROSSWIND AT KAVL...WITH A FEW GUSTS NOT OUT OF THE QUESTION.

OUTLOOK...SEVERAL ROUNDS OF STRONG UPPER DISTURBANCES WILL CONTINUE
TO SWING ACROSS THE AREA MONDAY NIGHT THRU WEDNESDAY. MOISTURE
AND REINFORCING COLDER AIR ARRIVE FROM THE NORTHWEST DURING
THIS TIME. RESTRICTIONS WILL BE POSSIBLE...ESPECIALLY IN THE
MOUNTAINS...WHERE SNOW SHOWERS ARE MOST LIKELY.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
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 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 THIS MORNING TO 6 PM EST
     THIS EVENING FOR NCZ033-048>053-058-059-062-063.
     WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY MORNING
     FOR NCZ033-048>052-058-059-062.
SC...NONE.

&&

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


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