Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261946
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
246 PM EST WED NOV 26 2014

.SYNOPSIS...
AN UPPER LEVEL SYSTEM WILL CROSS WESTERN NORTH CAROLINA EARLY
THURSDAY. DRY HIGH PRESSURE WILL RETURN FRIDAY AND LINGER INTO THE
WEEKEND. EXPECT A COLD FRONT TO SLOWLY CROSS OUR REGION FROM THE
NORTH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 215 PM EST...A SCATTERED TO BROKEN LOWER LEVEL STRATOCUMULUS
FIELD PERSISTS IN THE LINGERING BOUNDARY LAYER MOISTURE BEHIND THE
DEPARTED UPPER WAVE AND JET STREAK. ATTENTION NOW TURNS TO THE NEXT
UPSTREAM TROUGH AXIS DIGGING THROUGH THE CENTRAL MS RIVER VALLEY
THIS AFTN. THE FORECAST MODELS AGREE FAIRLY WELL IN BRINGING A
STRONG BUT CHANNELED VORTICITY MAXIMUM WITH THIS WAVE THROUGH THE
REGION OVERNIGHT...WITH MOIST NW FLOW DEVELOPING IN IT/S WAKE. THE
DEEP LAYER QG FORCING SHOULD BE MAXIMIZED MAINLY AROUND 06Z TO
09Z...AND HAVE THE GREATEST IMPACT ACROSS WRN NC. THERE IS ALSO
FAIRLY GOOD CONSENSUS THAT THE THERMAL PROFILES WILL WET BULB DOWN
TO SUPPORT SNOW ACROSS THE MTNS...AND EVEN INTO THE LOWER
VALLEYS...DURING THE EARLY MORNING HOURS. MOISTURE SHOULD BE JUST
DEEP ENOUGH TO SUPPORT SNOW CRYSTAL GROWTH...BUT THAT MAY NOT EVEN
BE AN ISSUE IF CONVECTIVE SHOWERS FORM AS A POOL OF 7 TO 8 DEG C/KM
LAPSE RATES CROSSES THE REGION OVERNIGHT. THIS INSTABILITY...ALONG
WITH A +2 PV UNIT SATURATED GEOSTROPHIC EPV MAX...MAY WELL PERMIT
SOME SNOW SHOWERS TO BREAK CONTAINMENT EAST OF THE BLUE RIDGE EARLY
THU MORNING. BRIEF SNOW SHOWER ACTIVITY WILL THUS BE POSSIBLE ACROSS
THE INTERSTATE 40 CORRIDOR INTO THE PIEDMONT. HOWEVER...THE DURATION
OF THIS ACTIVITY SHOULD BE BRIEF ENOUGH FOR LITTLE TO NO
ACCUMULATIONS TO DEVELOP WITH MINS GENERALLY IN THE MID 30S.

THE PRECIPITATION FOCUS WILL THEN STEADILY SHIFT BACK TO THE WRN NC
MTN COUNTIES NEAR THE TN BORDER THU MORNING AS A MORE TRADITIONAL NW
UPSLOPE FLOW SNOW SITUATION SETS UP. ANTICIPATE THE DEEPEST SFC TO
850 MB MOISTURE THROUGH 18Z...WITH UPSLOPE MOISTURE GRADUALLY WANING
THROUGH THU AFTN. THE CURRENT WINTER WEATHER ADVISORY LOOKS WELL
PLACED. BREEZY TO WINDY CONDITIONS WILL DEVELOP IN THE HIGHER
ELEVATIONS DURING THE PEAK COLD ADVECTION THU...AS THE PRES GRADIENT
TIGHTENS BEHIND THE DEPARTING WAVE. EXPECT CHILLY 30S TO LOWER 40S
MAXES IN THE MTNS...BUT LOWER 50S ARE MORE LIKELY IN THE EVENTUAL
DOWNSLOPE ACROSS THE FOOTHILLS/PIEDMONT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AT 230 PM EST WEDNESDAY...ON THURSDAY EVENING...A DEAMPLIFYING UPPER
TROUGH AXIS WILL BE NEAR THE EAST COAST...WHILE A RIDGE WILL BE
UPSTREAM NEAR THE WEST COAST. A CHANNELED UPPER VORT LOBE ROUNDING
THE BASE OF THE TROUGH WILL BE OVER CENTRAL NC...MOVING AWAY FROM
OUR AREA. THE UPPER TROUGH WILL CONTINUE TO DEAMPLIFY ON FRIDAY AS
THE TROUGH AXIS MOVES OFF THE EAST COAST...WHILE WEAK SHORTWAVE
ENERGY MOVES ACROSS OUR AREA FROM THE NW. BY SATURDAY A NEARLY ZONAL
FLOW WILL EXIST OVER THE SOUTHERN TIER OF STATE BY SATURDAY.

AT THE SURFACE...SOME LINGERING NW FLOW SNOW SHOWERS WILL PERSIST
ALONG THE TN BORDER THURSDAY NIGHT IN THE PRESSURE GRADIENT BETWEEN
A DEPARTING COASTAL LOW AND HIGH PRESSURE IN THE MS RIVER VALLEY.
ACCUMULATIONS WITH THIS DIMINISHING ACTIVITY WILL BE MINIMAL. THE
HIGH PRESSURE ARRIVES ON FRIDAY...WHEN THE MODELS SUGGEST SOME UPPER
LEVEL CLOUD COVER SPREADING OVER THE MOUNTAINS FORM THE WEST. THIS
CLOUD COVER WILL EXTEND EAST ACROSS MOST OF THE AREA BY FRIDAY
EVENING...GRADUALLY MOVING NORTH OF THE AREA BY LATE SATURDAY.

TEMPERATURES WILL RUN AROUND 12 DEGREES TO SO BELOW NORMAL ON
THURSDAY NIGHT THROUGH FRIDAY NIGHT AS THE COOL HIGH PRESSURE
ARRIVES...DESPITE RISING HEIGHTS ALOFT. BY SATURDAY...HIGH
TEMPERATURES WILL RISE TO WITHIN 3 DEGREES OR SO OF NORMAL AS WARM
ADVECTION SETS UP ON THE BACK SIDE OF THE SURFACE HIGH AND HEIGHTS
ALOFT CONTINUE TO RISE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM EST WEDNESDAY...A WEAK UPPER RIDGE AXIS WILL CROSS THE
REGION SAT NIGHT THROUGH SUN...WITH A WEAK POSITIVELY TILTED UPPER
TROUGH PASSING OVERHEAD ON TUE. ANOTHER WEAK UPPER TROUGH IS
FORECAST TO CROSS THE REGION BY WED.

AT THE SURFACE...HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC
WILL CONTINUE TO RIDGE WESTWARD INTO THE FORECAST AREA SAT NIGHT
THROUGH AT LEAST MONDAY BRINGING MOSTLY DRY CONDITIONS WITH GOOD WAA
SWLY FLOW TO OUR CWA. MEANWHILE...A SURFACE COLD FRONT EXTENDING
FROM THE GREAT LAKES REGION TO THE WESTERN GULF SAT NIGHT WILL
SLOWLY PUSH SOUTHEASTWARD INTO THE SOUTHERN APPALACHIANS THROUGH MON
NIGHT. HENCE...HAVE INHERITED DRY WEATHER SAT NIGHT AND SUN FOR MOST
LOCATIONS. POPS THEN RAMP UP INTO THE 20/30S OVER THE MTNS ZONES ON
MONDAY AS THE FRONT REACHES THE TN BORDERLINE. THE FRONT WILL THEN
SLIP TROUGH THE FORECAST AREA MON NIGHT WITH A COLD AIR DAMMING
SETTING UP BY TUE AS A CANADIAN HIGH PRESSURE OVER THE GREAT LAKES
REGION SLIDES EAST INTO THE NORTHEAST STATES. POPS REMAIN ON THE LOW
SIDE GIVEN THE LACK OF DEEP MOISTURE/UPPER FORCING. WED...THE NEW
12Z ECMWF INDICATES THAT ANOTHER COLD FRONT WILL APPROACH FROM THE
NW AND CROSSES THE AREA WED NIGHT INTO THU MORNING WHILE THE GFS
KEEPS THE CAD THRU THE PERIOD. GIVE THE UNCERTAINTY...HAVE KEPT THE
POPS IN THE SLIGHT CHANCE RANGE. TEMPERATURES WILL BE AROUND 2-5
DEGREES ABOVE NORMAL SUN/MON AND NEAR NORMAL TUE/WED.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...AS THE DEEPER LAYER CLOUD SHIELD HAS CLEARED THE AREA THIS
AFTN...HEATING HAS ALLOWED FAIRLY WIDESPREAD MVFR LEVEL CIGS TO
REDEVELOP...AND THIS SHOULD BE THE CASE MORE OFTEN THAN NOT AT KCLT
THROUGH AT LEAST 21Z. IMPROVEMENT TO VFR IS LIKELY THIS
EVENING...BUT THE APPROACHING STRONG UPPER SHORTWAVE COULD ALLOW
MVFR CIGS TO FORM AGAIN AT TIMES OVERNIGHT. THERE IS ALSO A
POSSIBILITY OF SHOWERS IN THE VICINITY LATE TONIGHT WITH THE PASSING
WAVE...POSSIBLY EVEN MIXING WITH SNOW AT TIMES JUST NORTH OF
KCLT...BUT ALL OF THIS IS TOO LOW CONFIDENCE TO MENTION IN THE TAF.
EXPECT WINDS TO TOGGLE WSW OR SW THIS EVENING AND THEN RETURN
SHARPLY NW AND BECOME GUSTY BEHIND THE PASSING UPPER WAVE CIRCA 16Z
THU...WITH DRYING ENSUING.

ELSEWHERE...HEATING INTERACTING WITH LINGERING BOUNDARY LAYER
MOISTURE THIS AFTN IS PRODUCING MAINLY SCT025 BKN035 ON
AVERAGE...THOUGH TEMPO MVFR CANNOT BE RULED OUT. CLOUDS ASSOCIATED
WITH THE UPSTREAM SHORTWAVE MOVING RAPIDLY E THROUGH THE MS RIVER
VALLEY WILL START SPREADING BACK IN QUICKLY THIS EVENING. ANTICIPATE
A RETURN TO MVFR CIGS FROM KAVL TO KHKY 06Z TO 09Z...WITH TEMPO MVFR
POSSIBLE BUT NOT LIKELY FARTHER SOUTH. WILL ALSO FEATURE A VCSH
MENTION AT KAVL AND KHKY...WHICH SHOULD BE SNOW AT KAVL AND COULD BE
SNOW UNDER ANY HEAVIER RATES AT KHKY. THE UPSTATE SITES SHOULD
REMAIN DRY THROUGH THU MORNING...BUT ISOLD SHOWERS CANNOT BE RULED
OUT. WINDS WILL TOGGLE FROM NW TO SW THROUGH THE EVENING BUT RETURN
SHARPLY NW AND GUSTY BEHIND THE WAVE LATE IN THE PERIOD.

OUTLOOK...DRY HIGH PRESSURE WILL SET UP OVER THE AREA FRI THROUGH
THE WEEKEND. A COLD FRONT WILL APPROACH FROM THE NORTHWEST EARLY
NEXT WEEK.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       HIGH  88%     HIGH  96%     HIGH  92%     HIGH  85%
KGSP       HIGH  80%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  87%     MED   79%
KHKY       HIGH  93%     HIGH 100%     MED   74%     HIGH  96%
KGMU       MED   76%     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 FROM MIDNIGHT TONIGHT TO NOON EST
     THURSDAY FOR NCZ033-048>052-058-059.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...HG
SHORT TERM...JAT
LONG TERM...JOH
AVIATION...HG



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