Area Forecast Discussion
Issued by NWS Greer, SC

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306
FXUS62 KGSP 131426
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
926 AM EST SAT FEB 13 2016

.SYNOPSIS...
THE LEADING EDGE OF AN ARCTIC AIRMASS WILL PUSH INTO THE REGION
TODAY AND SETTLE SOLIDLY OVER THE AREA ON SUNDAY. A LOW PRESSURE
SYSTEM WILL APPROACH FROM THE WEST ON MONDAY...CROSS THE REGION
MONDAY NIGHT...AND DEPART TO THE EAST ON TUESDAY. A WINTRY MIX OF
PRECIPITATION IS LIKELY WITH THIS SYSTEM. ANOTHER FAST MOVING SYSTEM
WILL CROSS THE SOUTHERN APPALACHIANS MID WEEK...WITH DRYING AND
WARMING EXPECTED LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
1430 UTC UPDATE...ONLY MINOR ADJUSTMENTS WERE MADE TO WINDS AND
TEMPERATURES. SKY COVER WAS REDUCED PER SATELLITE IMAGERY. AREAS OF
SNOW WERE TRIMMED BACK NEAR THE NC BORER PER RADAR AND SATELLITE
TRENDS.

AS OF 630 AM...SNOW SHOWER ACTIVITY IS ON A DOWNWARD TRENDS ACROSS
EASTERN KY/TN AND SOUTHERN APPALACHIANS EARLY THIS MORNING. WHILE
MINOR ADDITIONAL ACCUMS WILL BE POSSIBLE THRU LATE MORNING...FOR THE
MOST PART THINGS ARE WINDING DOWN. ROADS ARE LIKELY SNOW COVERED AND
SLICK IN THE USUAL NW FLOW AREAS THIS MORNING. PLUS HIGH ELEVATIONS
ARE SEEING WIND CHILLS DIPPING BELOW -5 DEGREES. SO WE HAVE ALLOWED
THE WINTER WEATHER ADVISORY TO EXPIRE...BUT KEEPING THE WIND CHILL
ADVISORIES GOING. OVERALL...TEMPS ARE STILL RUNNING WARMER THAN
FCST...AND LOOKING CURRENT MAX TEMPS...I OPTED TO BUMP THEM UP A DEG
OR TWO EAST OF THE MTNS WHERE DOWNSLOPE SHOULD NEGATE THE CAA.

AS OF 200 AM...A DEEP TROF CONTINUES TO DOMINATE THE EASTERN
CONUS...WITH THE AXIS NOW SHIFTING JUST EAST OF THE CWFA TODAY.
CONFLUENT NWLY FLOW ON THE BACK SIDE OF THE TROUGH WILL USHER IN A
LARGE ARCTIC HIGH PRESSURE SYSTEM INTO THE REGION TODAY THRU
TONIGHT. STRONG LLVL WINDS AND CAA IS RESULTING IN WIND ADVISORY
CRITERIA WINDS ACROSS THE NORTHERN NC MTNS. ALSO...REGIONAL RADAR
MOSAIC STILL SHOWING HEALTHY SNOW SHOWERS ACROSS EASTERN KY/TN. SO
EXPECT CONTINUED LIKELY TO CATEGORICAL COVERAGE OF SNOW ALONG THE TN
BORDER FOR THE NEXT FEW HOURS. THEN SNOW SHOULD TAPER OFF FAIRLY
QUICKLY STARTING RIGHT BEFORE DAYBREAK THRU THE REST OF THE MORNING.
TEMPS ARE NOT FALLING AS QUICKLY AS EXPECTED. PROBABLY DUE TO
TURBULENT MIXING AND CLOUDS/SNOW ADDING A LITTLE HEAT. STILL...THE
COMBINATION OF WIND AND FALLING TEMPS SHOULD RESULT IN SUB-ZERO WIND
CHILLS FOR MUCH OF THE ELEVATIONS ABOVE 3500 FT THIS MORNING.

BY MIDDAY...SNOW SHOWERS SHOULD BE WINDING DOWN TO JUST A FEW
FLURRIES AND LINGERING STRATUS ALONG THE TN BORDER...WHILE WINDS
SLOWLY WEAKEN...BUT REMAIN BREEZY. TEMPS WILL ONLY HOLD STEADY OR
RISE SLIGHTLY IN THE NORTHERN MTNS...SO WIND CHILLS WILL HOVER IN
THE 0 TO -5 RANGE THRU THE DAY. ELSEWHERE...IT WILL BE COLD WITH
TEMPS RANGING FROM 15 TO 30 DEGREES BELOW NORMAL...DESPITE FULL SUN
OUTSIDE THE NW FLOW STRATUS.

TONIGHT...THE CENTER OF ARCTIC HIGH PRESSURE WILL SETTLE OVER THE
CENTRAL APPALACHIANS...WHILE A WEAK ALBERTA CLIPPER DIVES INTO THE
PLAINS STATES. THE UPPER FLOW WILL FLATTEN OUT SOMEWHAT AS THE
CLIPPER SYSTEM APPROACHES...ALLOWING SOME MID AND HIGH CLOUDS TO
START STREAMING ATOP THE AREA LATE. STILL...IT LOOKS LIKE A DECENT
RADIATIONAL COOLING NIGHT...WITH SOME OF THE COLDEST TEMPS OF THE
WINTER EXPECTED BY DAYBREAK SUNDAY. LOWS WILL BE GENERALLY 20-25
DEGREES BELOW NORMAL. EVEN THOUGH WINDS WILL BE SUBSTANTIALLY WEAKER
IN THE NORTHERN MTNS...THE COLDER TEMPS WILL RESULT IN DANGEROUS
WIND CHILLS CONTINUING THRU THE NIGHT.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 245 AM EST SATURDAY...CONSIDERABLE UNCERTAINTY PERSISTS WITH
THE WINTRY WEATHER FORECAST FOR SUNDAY NIGHT THROUGH TUE. ONE
QUESTION CENTERS AROUND HOW QUICKLY THE COLD AND DRY ARCTIC AIRMASS
PRESENT AT ONSET SUNDAY NIGHT WILL RETREAT/MODIFY THROUGH THE
PERIOD. UNCERTAINTY ALSO ARISES OVER THE SURFACE LOW TRACK
FORECASTS...WITH THE GFS/ECMWF CAMP STARTING OFF THE SURFACE LOW
WEST OF THE MOUNTAINS AND TRACKING IT THROUGH THE CENTRAL/SOUTHERN
APPALACHIANS...WHILE THE NAM/GEM CAMP DEPICT MORE OF A REDEVELOPING
PIEDMONT LOW TO THE SOUTHEAST. THESE DIFFERENCES WILL NEED TO BE
RESOLVED BEFORE ENOUGH CONFIDENCE EXISTS TO POST A WINTER STORM
WATCH.

FOR THE SPECIFICS...A NORTHERN STREAM SYSTEM MOVING ACROSS THE UPPER
MIDWEST ON SUNDAY WILL EXTEND A WARM FRONTAL FEATURE ACROSS THE
SOUTHERN APPALACHIANS THROUGH THE DAY...WITH ASSOCIATED UPGLIDE
MOISTURE ARRIVING AT MID LEVELS. LOWER LEVELS...HOWEVER...REMAIN
MOSTLY DRY THROUGH LATE DAY. MEANWHILE...1034 MB SURFACE HIGH
PRESSURE WILL MOVE EAST THROUGH THE MID ATLANTIC REGION SUNDAY AND
OFFSHORE SUNDAY NIGHT. THE LOW LEVEL THICKNESS TROUGH REMAINING
ACROSS THE WESTERN CAROLINAS WILL BE COLD AND DRY AND FAVORABLE FOR
HYBRID COLD AIR DAMMING AS THE PRECIPITATION STARTS AHEAD OF AN
APPROACHING SOUTHERN STREAM WAVE. THE MODELS HAVE TRENDED LESS
AMPLIFIED AND MORE PROGRESSIVE WITH THIS SOUTHERN WAVE WHICH
SHARPENS UP OVER THE MS RIVER VALLEY ON MONDAY. A CONSENSUS OF THE
VARYING MODEL PROFILES PROMOTES A SLOW WARMUP WITH GRADUAL CAD
EROSION LATE MONDAY INTO MONDAY NIGHT. THE FASTER SOLUTIONS NOW
BRING A MID DRY SLOT IN QUICKLY BEHIND THE WAVE LATE MONDAY NIGHT
THROUGH TUESDAY MORNING...WITH HEAVIEST PRECIPITATION SHUTTING OFF
MORE QUICKLY.

UPGLIDE MOISTURE SHOULD GET STARTED IN EARNEST ACROSS THE FORECAST
AREA BEFORE DAYBREAK MONDAY. STILL ANTICIPATE NEARLY ALL SNOW AT
ONSET WITH THE 850 MB ZERO DEGREE ISOTHERM ALONG THE SOUTHERN
PERIPHERY OF THE FORECAST AREA. HOWEVER...THE WARM NOSE ALOFT SHOULD
STEADILY EXPAND AND MOVE NORTHWARD THROUGH THE DAY TO PERMIT A
TRANSITION TO SLEET AND THEN FREEZING RAIN THROUGHOUT MOST AREAS BY
MONDAY EVENING. THE MID LEVEL DRYING AND ASSOCIATED REMOVAL OF ICE
NUCLEI MAY KEEP ANY OVERNIGHT PRECIPITATION RAIN OR FREEZING
RAIN/FREEZING DRIZZLE IN ANY LINGERING COLDER MOUNTAINS POCKETS.
THEN...NORTHWEST UPSLOPE MOISTURE ON TUESDAY MORNING WILL DIMINISH
THROUGH TUESDAY AFTERNOON...WITH A BRIEF LULL IN PRECIPITATION
LIKELY. ALL TOLD...AT LEAST ADVISORY SNOW OR ICE ACCUMS LOOK QUITE
POSSIBLE FOR A SIGNIFICANT CHUNK OF THE FORECAST AREA...WITH MAINLY
THE NORTHERN MOUNTAINS AT RISK OF WINTER STORM SNOW/ICE AT THIS
POINT. WINTER STORM WATCHES COULD BE NEEDED FOR MONDAY AS EARLY AS
THIS AFTERNOON.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 245 AM EST SATURDAY...THE NEXT UPSTREAM SHORTWAVE ROUNDING THE
BROAD EASTERN TROUGH WILL CROSS THE SOUTHERN APPALACHIANS TUESDAY
NIGHT. A RESURGENCE OF UPSLOPE MOISTURE WILL ACCOMPANY THE WAVE AS
COLDER TEMPERATURES BRIEFLY RETURN...AND SOME SCATTERED SNOW SHOWER
ACTIVITY COULD BREAK CONTAINMENT EAST OF THE MOUNTAINS IN THE EARLY
MORNING HOURS WED. BEHIND THE DEPARTING THE WAVE...HEIGHTS WILL
BUILD IN FROM THE WEST LATER WEDNESDAY THROUGH THURSDAY. TIMING
DIFFERENCES EXIST ON THE NEXT UPSTREAM WAVE LATE WEEK IN THE
PROGRESSIVE FLOW PATTEN...AND NO PRECIPITATION WILL BE ADVERTISED
THROUGH FRIDAY. THE MAIN FEATURE OF THE FORECAST WED THROUGH FRI
WILL BE DRYING AND WARMING CONDITIONS WITH MAX TEMPERATURES FINALLY
CLIMBING ABOVE CLIMATOLOGY BY FRIDAY.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT AND ELSEWHERE EAST OF THE MTNS...VFR...WITH GENERALLY SKC OR
FEW250 THE DAY...THEN INCREASING HIGH CLOUDS THAT WILL THICKEN AND
LOWER TO A MID CLOUD DECK FROM WEST TO EAST OVERNIGHT. WINDS WILL
REMAIN OUT OF THE NW...WITH SOME LOW-END GUSTS EXPECTED AS MIXING
DEEPENS MID-LATE MORNING THRU EARLY AFTERNOON...ESPECIALLY ACROSS
THE NC SITES. WINDS VEER TO NE TONIGHT...GENERALLY 4-6 KTS.

AT KAVL...GUSTY NNW WINDS AND MVFR STRATUS WILL CONTINUE DUE TO
MOIST NW FLOW CHANNELED UP THE FRENCH BROAD VALLEY THIS MORNING.
SHOULD SEE GRADUALLY CLEARING LATE MORNING WITH VFR EXPECTED REST OF
THE 12Z TAF PERIOD...BUT WINDS WILL BE SLOW TO SUBSIDE THRU THE
DAY...FINALLY LOSING GUSTS LATE EVENING.

OUTLOOK...A LARGE AREA OF ARCTIC HIGH PRESSURE WILL SETTLE OVER THE
REGION ON SUNDAY. THEN A STRONG LOW PRESSURE SYSTEM WILL DEVELOP AND
CROSS THE AREA LATE SUNDAY NIGHT THRU TUESDAY...BRINGING WIDESPREAD
CLOUDS/PRECIP. THIS SYSTEM MAY PRODUCE SIGNIFICANT WINTER
IMPACTS...ESPECIALLY IN THE NC MTNS.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   77%     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...WIND CHILL ADVISORY UNTIL 10 AM EST SUNDAY FOR NCZ033-049-050.
     WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR NCZ048-051-052-
     058-059.
SC...NONE.

&&

$$
SYNOPSIS...HG
NEAR TERM...ARK/JAT
SHORT TERM...HG
LONG TERM...HG
AVIATION...ARK



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