Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 220552
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1252 AM EST THU JAN 22 2015

.SYNOPSIS...
HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH MOST OF TOMORROW.
LOW PRESSURE IS EXPECTED TO DEVELOP OVER THE NORTHERN GULF OF MEXICO
TOMORROW NIGHT AND BRING WIDESPREAD PRECIPITATION TO THE AREA ON
FRIDAY. DRYING HIGH PRESSURE RETURNS BRIEFLY LATE SATURDAY AND
SUNDAY. A FAST MOVING CLIPPER SYSTEM WILL LIKELY DEVELOP TO OUR
NORTHWEST ON SUNDAY AND MOVE OVER THE REGION ON MONDAY BRINGING
INCREASED CHANCES FOR MORE PRECIPITATION.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 1230 AM...TEMPS CONTINUE TO LAG BEHIND THE FCST COOLING TREND
IN SPITE OF THE HIGH CLOUDINESS MOVING OFF TO THE EAST. NO REASON
YET TO THINK THE FCST WILL CATCH UP TO THE OBSERVATIONS...SO NO
CHANGES WILL BE MADE.

REMAINDER OF PREVIOUS DISCUSSION...

HOWEVER...STILL ANTICIPATE THICKENING HIGH LEVEL CLOUDS OVERNIGHT
EAST OF A 130+ KT UPPER JETLET MOVING FROM THE MS RIVER VALLEY TO
THE SRN APPALACHIANS. AT THE SFC...HIGH PRES NOSING OVER FROM THE NW
WILL KEEP LOWER LEVELS OF THE ATMOSPHERE VERY DRY...AND DRY SUB 700
MB AIR WILL LINGER THROUGH THU UNDER INCREASING MID/UPPER CLOUDS.
DAYTIME TEMPS TOMORROW SHOULD BE ABOUT 8 TO 10 DEGREES COOLER THAN
WED MAXES OWING MAINLY TO THICKENING/LOWERING MID CLOUDS AHEAD OF A
POTENT SOUTHERN STREAM UPPER LEVEL SHORTWAVE APPROACHING FROM THE
WESTERN GULF. NO PRECIPITATION IS ANTICIPATED THROUGH LATE DAY GIVEN
THE HIGH CLOUD BASES AND LACK OF FORCING.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 230 PM WEDNESDAY...LATEST W/V INDICATED A DEEP TROUGH ACROSS
THE SOUTHERN FOUR CORNERS AREA. THE TROUGH IS EXPECTED TO DIG ACROSS
TX ON THURSDAY...WITH A SFC LOW EXPECTED TO DEEPEN ACROSS THE NRN
GULF OF MEXICO. BY LATE THURSDAY...A LARGE AREA OF DEEP MOISTURE IS
FORECAST TO DEVELOP NORTH OF THE LOW CENTER...COVERING MOST OF THE
DEEP SOUTH. SHORT RANGE MODELS ARE IN FAIR AGREEMENT THAT DEEP
MOISTURE AND WEAK 295K ISENTROPIC LIFT WILL ARRIVE ACROSS NE GA AND
THE WESTERN CAROLINAS DURING THE PRE DAWN HOURS ON FRIDAY. I WILL
KEEP POPS LOW THROUGH MOST OF THURSDAY NIGHT...THEN QUICKLY INCREASE
TO CHC AROUND 8Z. SFC TEMPERATURES AT PRECIP ONSET IS FORECAST TO
RANGE BELOW FREEZING ACROSS THE MTNS TO MID TO UPPER 30S EAST OF THE
MTNS. FORECAST SOUNDINGS INDICATE SUB-FREEZING THERMAL PROFILES
ACROSS THE MTNS AND I-40 CORRIDOR...YIELDING SNOW. HOWEVER...AS THE
MILLER A LOW TRACKS TOWARD FL...TEMPERATURES ARE FORECAST TO WARM
AROUND H8 TO 2C TO 3C ACROSS THE SOUTHERN APPALACHIANS. IT APPEARS
THAT P-TYPE WILL VARY CONSIDERABLY WITH ELEVATION AND FROM SOUTH TO
NORTH. BASICALLY...THE SNOW REGION WILL LIFT NORTHWARD AND WILL BE
REPLACED BY AREAS OF SN/PL OR RA/PL...WITH AREAS OF FZRA ALONG THE
EAST FACING SLOPES. BY FRIDAY AFTERNOON...SFC TEMPERATURES ACROSS
THE CWA ARE FORECAST TO RISE INTO THE MID TO UPPER 30S...EXCEPT
ALONG THE EAST SLOPE OF THE NRN MTNS. PRECIP SHOULD GENERALLY FALL
AS A COLD RAIN...BUT MECHANICAL LIFTING MAY PRESERVE AN AREA OF FZRA
ALONG THE NRN MTNS AND ADJACENT FOOTHILLS THROUGH THE AFTERNOON. AT
THIS TIME...IT APPEARS THAT ADVISORY LEVEL ICE IS POSSIBLE ACROSS
THE CENTRAL AND NRN MTNS AND ADJACENT FOOTHILLS.

FRIDAY NIGHT INTO SATURDAY...THE SFC LOW IS FORECAST TO RAPIDLY
TRACK NORTHEAST ALONG THE ATLANTIC COAST. VEERING FLOW...WRAP AROUND
MOISTURE...AND CAA SHOULD RESULT IN A PERIOD OF UPSLOPE SNOWFALL
ALONG THE TN BORDER. BASED ON THE GFS...A STRONG AREA OF MID LEVEL Q-
VECTOR DIVERGENCE WILL SLIDE ACROSS THE SOUTHERN APPALACHIANS SAT
MORNING. MODELS INDICATE THAT LLVL MOISTURE WILL RAPIDLY DISSIPATE
BETWEEN 12Z - 18Z SAT...ENDING ACCUMULATING SNOWFALL. IT APPEARS
THAT THE OVERLAP OF SNOW SUPPORTING THERMAL PROFILES AND OPTIMAL NW
WINDS WILL REMAIN SHORT...YIELDING 1 TO 2 INCHES OF SNOWFALL. CLOUDS
AND POPS WILL DECREASE THROUGH THE DAY...ESPECIALLY EAST OF THE
MTNS. TEMPERATURES APPEAR VERY CLOSE TO SEASONABLE VALUES.

WE WILL CONTINUE TO HIGHLIGHT THE LATE WEEK WINTER WEATHER IN THE
HWO.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 200 PM WED...THROUGH MOST OF THE MEDIUM RANGE PERIOD THE ERN
STATES WILL REMAIN UNDER A LONGWAVE TROF THRU WHICH MULTIPLE
SHORTWAVES WILL PROGRESS. FOR OUR CWFA THE MOST NOTABLE FEATURE WILL
BE A PARTICULARLY STRONG CLIPPER WHICH WILL CROSS THE SRN
APPALACHIANS SUNDAY NIGHT FOLLOWED BY A LESS WELL DEFINED WAVE
TRAILING IT AND PASSING MONDAY NIGHT. THE OVERALL PATTERN SUGGESTS
PREVAILING NW FLOW THRU THE PERIOD AND THUS THE AREA SEEING THE
GREATEST POTENTIAL OF PRECIP...PARTICULARLY WINTRY PRECIP...IS THE
MTNS. THE CHANCES WILL DEPEND ON AVAILABLE MOISTURE WITH ENHANCEMENT
LIKELY DURING THE PASSAGE OF THE SHORTWAVES. NEAR TO SLIGHTLY ABOVE
NORMAL TEMPS SUNDAY AND SUNDAY NIGHT WILL DIP BELOW NORMAL IN THE
MTNS MONDAY AND ACRS THE AREA BY TUESDAY...THOUGH READINGS SHOULD
NOT BE TOO SURPRISING FOR LATE JANUARY.

THE 21/12Z GFS AND 21/00Z EC SHOWED GOOD AGREEMENT ON THE SUNDAY
NIGHT CLIPPER IN TERMS OF TIMING...PLACEMENT AND STRENGTH. THESE
MODELS BASICALLY SHOWED A CLOSED 500MB CONTOUR CROSSING WEST VA AND
THE SHORTWAVE AXIS BEING EAST OF THE CWFA BY 12Z MON. THE 21/12Z GEM
WAS WEAKER WITH THE WAVE AND A FEW HOURS SLOWER...AND THE 21/12Z EC
TRENDED TOWARD THE CANADIAN SOLUTION. THOUGH THE SETUP IS NOT VERY
FAVORABLE FOR SIGNIFICANT ACCUMULATING SNOW IN THE PIEDMONT...GIVEN
DOWNSLOPE FLOW AND LIMITED MOISTURE...A SLOWER SOLUTION BRINGING THE
WAVE THRU DURING THE DAYLIGHT HRS IMPLIES FROZEN PRECIP IS EVEN LESS
OF A CONCERN. MODEL QPF RESPONSE FROM THE GFS AND OLD EC WAS
PRACTICALLY NIL OVER THE PIEDMONT...BUT BOTH THE GEM AND NEW EC HAVE
SLIGHT AMOUNTS OF SBCAPE OVER OUR AREA DURING MONDAY WHICH MAY HELP
EXPLAIN THEIR HIGHER QPF. FOR NOW I KEPT THE PIEDMONT POPS IN SCHC
RANGE SUNDAY NIGHT BUT DID LET THESE LINGER THRU MUCH OF THE DAY
MONDAY. WITH THE SECONDARY CLIPPER-LIKE WAVE DROPPING DOWN MONDAY
NIGHT A SCHC REMAINS OVER THE NW PIEDMONT AT THAT TIME ALSO.

EARLY TUE MRNG THE REMAINING POPS ARE JUST FORCED BY NW FLOW WHICH
WEAKENS SUFFICIENTLY TO LET THE POPS DROP OFF...AND WITH THE TROUGH
LIFTING AWAY THRU THE REMAINDER OF THE PERIOD THE FCST IS DRY.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
ZCZC GSPWRKTAF 000 TTAA00 KCAE 220236

AT KCLT AND ELSEWHERE...VFR CONDITIONS SHOULD PREVAIL THRU THE TAF
PERIOD. CLEAR SKY WILL GIVE WAY TO HIGH CLOUDINESS THAT WILL ARRIVE
WITH AN UPPER JET STREAK DURING THE PRE-DAWN HOURS. FROM THAT POINT
ONWARD...IT WILL BE A MATTER OF THICKENING CIRRUS...FOLLOWED
STEADILY BY THE ARRIVAL OF A MID LEVEL DECK BY AFTERNOON...AND THEN
LOWERING CEILINGS THIS EVENING. RESTRICTIONS ARE NOT EXPECTED...EVEN
AT THE WESTERN TAF SITES...BEFORE 06Z FRIDAY. WIND WILL BE VERY
LIGHT THROUGH SUNRISE...WITH A NE WIND AT MOST SITES OUTSIDE THE
MTNS DEVELOPING AFTER SUNRISE AND CONTINUING THRU THE END OF THE
PERIOD. THE WIND SHOULD BE CHANNELED NW AT KAVL...BUT LIGHT.

OUTLOOK...CONDITIONS WILL STEADILY DETERIORATE FROM THE SW EARLY
FRIDAY MORNING AS MOISTURE SPREADS NE FROM A DEVELOPING AREA OF LOW
PRESSURE OVER THE NW GULF. THE LOW WILL MOVE FROM THE NRN GULF OF
MEXICO TO THE SE COAST AND WILL BRING PRECIPITATION AND RESTRICTIONS
TO OUR AREA FRIDAY AND FRIDAY NIGHT. THERE COULD BE WINTRY PRECIP
FROM KAVL TO KHKY FOR SEVERAL HOURS ON FRIDAY. KCLT COULD ALSO HAVE
A BRIEF PERIOD OF WINTRY MIXED PRECIP AT ONSET FRI MORNING IF THE
PRECIP STARTS TO FALL EARLY ENOUGH...HOWEVER...THE MOST RECENT
GUIDANCE SUGGESTS THE TEMPERATURE AT ONSET AT KCLT WILL BE TOO WARM
FOR SNOW. ANOTHER SYSTEM ON MONDAY COULD BRING MORE RESTRICTIONS
FROM THE NW.

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 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...NONE.
SC...NONE.

&&

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


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