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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1214 AM EST THU JAN 29 2015

.SYNOPSIS...
DRY HIGH PRESSURE WILL REMAIN IN PLACE TONIGHT THROUGH THURSDAY. A 
COLD FRONT WILL CROSS THE FORECAST AREA THURSDAY NIGHT WITH ANOTHER 
HIGH PRESSURE SYSTEM BUILDING IN FRIDAY THROUGH SATURDAY. A MOIST 
LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT THE REGION ON SUNDAY INTO 
MONDAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 930 PM...EARLY THIS EVENING...THE FCST STILL LOOKS ON TRACK. 
AS USUAL WITH GOOD RADIATIONAL COOLING NIGHTS...TEMPS HAVE FALLEN 
OFF FASTER THAN THE HOURLY GRID TRENDS...SO THOSE WERE UPDATED. AN 
AREA OF GENERALLY THIN CIRRUS WAS SEEN ENTERING THE OH/TN 
VALLEYS...ASSOCIATED WITH AN APPROACHING UPPER SHORTWAVE. THESE 
CLOUDS WILL STREAM ACRS THE AREA AROUND DAYBREAK. SO NOT EXPECTING 
MUCH IMPACT ON MIN TEMPS. SKY GRIDS WERE ADJUSTED TO KEEP SKIES 
CLEAR THRU THE REST OF THE EVENING PER SAT TRENDS.

AS OF 630 PM...NO CHANGES NEEDED TO THE PUBLIC FCST WITH THIS 
UPDATE. THE ONLY ADJUSTMENT MADE WERE TO THE AVIATION GRIDS FOR THE 
00Z TAF CYCLE.

AS OF 430 PM...FCST IS ON TRACK. SUNNY SKIES AND LIGHT WINDS WITH 
SEASONABLY COOL TEMPS HEADING INTO THE EVENING. TEMPS AND DEWPTS 
WERE ADJUSTED WITH THE LATEST OBS...BLENDING INTO THE EVENING HOURS.

AS OF 230 PM EST WEDNESDAY...RISING HEIGHTS ALOFT AND BUILDING HIGH 
PRESSURE AT THE SURFACE CONTINUE TO YIELD A FAIRLY NICE...YET COOL 
DAY ACROSS NORTHEAST GA AND THE WESTERN CAROLINAS.  LIGHT AND 
NORTHERLY SURFACE WINDS WILL CONTINUE TO SLOWLY VEER SOUTHERLY AS 
ABOVE MENTIONED SFC RIDGE SLIDES OVERHEAD EVENTUALLY TAKING UP ROOT 
JUST OFF THE CAROLINA COAST OVERNIGHT.  COLD/DRY ADVECTION OVER THE 
LAST 12-24 HOURS COMBINED WITH LOW LEVEL MIXING THIS AFTERNOON HAS 
ALLOWED DEWPOINTS TO FALL INTO THE LOW TEENS TO SINGLE DIGITS AT 
SOME LOCATIONS.  WARMING TEMPERATURES AMONGST ABUNDANT INCOMING 
SOLAR RADIATION HAVE LED TO RH LEVELS FALLING INTO THE LOW 20S TO 
UPPER TEENS ACROSS MUCH OF THE NC/SC PIEDMONT REGIONS AND ALSO 
PORTIONS OF NORTHEAST GA.  ALTHOUGH THESE ARE CRITICAL RH LEVELS AS 
IT PERTAINS TO FIRE WX CONCERNS...AS MENTIONED ABOVE WINDS ACROSS 
THE REGION REMAIN LIGHT WITH SOME SITES EVEN REPORTING CALM WINDS.  
THUS...CAUTION IS URGED IF PLANNING TO BURN TODAY...HOWEVER NO FIRE 
WX PRODUCTS ARE PLANNED AT THIS TIME.

MEANWHILE FURTHER WEST...AN SERIES OF UPPER SHORT WAVE IMPULSES ARE 
SLIDING THROUGH THE CENTRAL/NORTHERN PLAINS WITH THE FIRST OF WHICH 
YIELDING WEAK SFC CYCLOGENESIS.  A COLD FRONT ASSOCIATED WITH THIS 
FEATURE WILL APPROACH THE SOUTHERN/CENTRAL APPALACHIANS THROUGH THE 
DAY ON THURSDAY WITH PREFRONTAL PRECIP SPREADING INTO THE WESTERN NC 
MOUNTAINS AROUND NOON.  AT THAT TIME...TEMPERATURES WILL HAVE 
RECOVERED ENOUGH SUCH THAT ANY PTYPE CONCERNS ARE NOT EXPECTED.  AS 
THE FRONT SLIDES THROUGH THE HIGH TERRAIN LATE IN THE DAY TOWARDS 
EVENING...SNOW LEVELS WILL FALL ACROSS THE HIGH TERRAIN WITH A BRIEF 
PERIOD OF RAIN/SNOW MIX POSSIBLE ACROSS THE NORTHERN MOUNTAINS 
BEFORE PERIODS END.  THUS THE FCST FEATURES INCREASING CHANCE LEVEL 
POPS THROUGH MIDDAY ACROSS MUCH OF THE WESTERN NC HIGH TERRAIN WITH 
A DRY FCST PREVAILING OVER THE PIEDMONT REGIONS.  TEMPERATURES ON 
THURSDAY WILL APPROACH NORMAL LEVELS AS SOUTHERLY FLOW PREVAILS 
AMIDST MOSTLY SUNNY...ALTHOUGH INCREASINGLY CLOUDY SKIES.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 230 PM WEDNESDAY...THE MAIN FOCUS FOR THE SHORT RANGE WILL BE 
THE PASSAGE OF A SHORT WAVE AND COLD FRONT THURSDAY NIGHT. PRECIP 
CHANCES WILL ALREADY EXIST OVER THE MTNS AT 00Z FRIDAY AND SEE 
LITTLE REASON IN THE NEW GUIDANCE TO CHANGE THAT. FORCING AND THE 
DEEPEST MOISTURE STILL MAXIMIZE AROUND 06Z FRIDAY...SO A LIKELY POP 
LOOKS GOOD ON THE TN BORDER. THE FORCING AND MOISTURE SLOWLY WANE 
FROM THAT POINT ONWARD. WILL GRADUALLY TAPER OFF THE POP THRU 
FRIDAY...AND WILL END IT BY THE END OF THE DAYTIME. THERE IS SOME 
QUESTION ABOUT THE DEGREE OF COLD AIR AS THE FRONT IS MOVING ACROSS 
THE MTNS. SOME OF THE INITIAL PRECIP COULD BE MORE IN THE FORM OF 
RAIN...ALTHO THE FCST FAVORS A LARGER COVERAGE OF SNOW THAN MIGHT BE 
SUPPORTED DIRECTLY FROM THE MODEL DATA. THIS WILL BE A LIMITING 
FACTOR IN KEEPING SNOW AMOUNTS ON THE TN BORDER WELL WITHIN THE 
ADVISORY RANGE. THIS WILL BE INCLUDED IN THE HWO AS A POSSIBILITY OF 
LIGHT SNOW.  THE MAIN ACCUM POTENTIAL WILL BE THE SECOND HALF OF THE 
THIRD FCST PERIOD...THUS IT IS STILL TOO FAR IN THE FUTURE TO ISSUE 
AND ADVISORY. THE MODEL GUIDANCE ALSO CONTINUES TO SUPPORT STRONG 
WINDS ACROSS THE RIDGETOPS BEHIND THE FRONT LATE THURSDAY NIGHT AND 
FRIDAY MORNING...ALTHO THE TREND IS FOR SLIGHTLY LESS WIND AT THE 
TOP OF THE MIXED LAYER. THE TREND SUGGESTS MORE OF AN ADVISORY-LEVEL 
EVENT APART FROM ELEVATIONS ABOVE 5K FEET...AND THE HWO WILL BE 
WORDED ACCORDINGLY.

THE REST OF THE FCST WILL BE RELATIVELY BENIGN. WE SHOULD SEE THE 
UPPER FLOW FLATTEN AND BECOME MORE ZONAL THRU FRIDAY NIGHT AND 
SATURDAY...WHICH WILL SUPPORT SURFACE HIGH PRESSURE MOVING ACROSS 
THE MTNS AND MID-ATLC/CAROLINAS. THAT SHOULD KEEP TEMPS ABOUT A 
CATEGORY OR SO BELOW NORMAL...WITH CLEAR SKY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 250 PM...UNCERTAINTY REIGNS DURING THE MEDIUM RANGE PERIOD 
WITH LITTLE RUN TO RUN MODEL CONSISTENCY. THAT SAID...THEY DO AGREE 
ON AN UNSETTLED PERIOD WITH 2 WX SYSTEMS AFFECTING THE AREA...ONE 
EARLY IN THE PERIOD AND ONE LATE. ALOFT...THE ECMWF AND THE GFS SHOW 
A NORTHERN STREAM SHORT WAVE CROSSING THE AREA DURING THE SUN NITE- 
MONDAY TIME FRAME AS A CLOSED LOW MOVES SOUTH IN THE BAJA CALIFORNIA 
AREA. AT THE SFC HOWEVER...THE ECMWF MOVES A DRY COLD FRONT INTO THE 
AREA SUNDAY...WITH A LOW PRESSURE FORMING TO OUR WEST AND MOVING 
ACROSS THE AREA SUN NITE. THIS SYSTEM THEN MOVES EAST OF THE DURING 
THE DAY MONDAY. THE GFS ALSO BRINGS A COLD FRONT IN BUT IT IS SLOWER 
WITH THE FRONT COMING IN SUN NITE AND THE MAIN LOW PRESSURE CENTER 
REMAINING TO OUR NORTH. THE GFS ALSO DEVELOPS A PRE-FRONTAL TROF 
ACROSS THE AREA SUNDAY...DEVELOPING PRECIP EARLIER THAN THE ECMWF. 
THE GFS IS ALSO WARMER INDICATING A MAINLY LIQUID PRECIP EVENT UNTIL 
NW FLOW SNOW DEVELOPS SUN NITE AND MON AS THE MAIN AREA OF PRECIP 
MOVES EAST. THE ECMWF IS COLDER SHOWING SNOW AS FAR SOUTH AS THE I-
85 CORRIDOR. THE GFS ENSEMBLE MEAN IS NOT ESPECIALLY COLD...KEEPING 
THE COLDEST TEMPS ACROSS THE MTNS UNTIL AFTER THE PRECIP EXITS. 
GIVEN ALL THE UNCERTAINTY...HAVE USED A MDL BLEND WHICH BRINGS THE 
BEST PRECIP CHC ACROSS THE AREA SUN AND SUN NITE...THEN TAPERING OFF 
TO A NW FLOW SNOW FOR MON AFTERNOON. USED A CONSERVATIVE RAIN/SNOW 
TEMP FOR THE WEATHER WHICH KEEPS SNOW LIMITED MAINLY TO THE MTNS... 
WITH SOME SNOW ACROSS THE I-40 CORRIDOR AT ONSET. SHOULD THE ECMWF 
PROVE RIGHT...THEN SNOW WOULD FALL MUCH FARTHER SOUTH.

GOOD MODEL AGREEMENT THAT DRY AND COLD WX EXPECTED MON NITE AND 
TUESDAY AS VERY COLD HIGH PRESSURE MOVES IN. IN FACT...THE GFS 
ENSEMBLE MEAN H85 TEMP IS AS COLD AS 2 STANDARD DEVIATIONS BELOW 
NORMAL AT ITS COLDEST TUE MORN. 

THE GUIDANCE THEN DIFFERS AGAIN ON THE HANDLING OF THE AFORE 
MENTIONED CLOSED LOW OVER BAJA CALIFORNIA. THEY BOTH OPEN THE LOW 
AND MOVE IT EAST INTO THE SERN CONUS. HOWEVER...THE ECMWF IS FASTER 
AND FARTHER SOUTH THAN THE GFS. AT THE SFC...BOTH MODELS AGREE ON A 
MILLER-A TYPE SCENARIO. HOWEVER...THE ECMWF KEEPS THE LOW CLOSER TO 
THE GULF COAST AND FASTER WHILE THE GFS IS FARTHER NORTH AND SLOWER. 
DESPITE THE COLD HIGH PRESSURE MOVING IN AHEAD OF THIS SYSTEM...IT 
IS NOT A CLASSICAL TYPE CAD. THE PARENT HIGH IS OVER THE MID-
ATLANTIC AND TRANSIENT. STILL...IF PRECIP WERE TO START EARLY 
ENUF...THEN A WINTRY MIX WOULD DEVELOP EVEN ACROSS THE SRN CWFA 
BEFORE WARMING TO ALL RAIN FOR THE AFTERNOON...EXCEPT ACROSS THE NC 
MTNS. GIVEN THE UNCERTAINTY...HAVE LIMITED POP TO CHC...AND USED A 
CONSERVATIVE RAIN/SNOW TEMP FOR WEATHER.

&&

.AVIATION /05Z THURSDAY THROUGH MONDAY/...
AT KCLT...VFR. A HIGH LEVEL CIG IS EXPECTED TO SPREAD EAST OVER THE 
FIELD THIS AFTERNOON IN ADVANCE OF A COLD FRONT. BY THIS EVENING A 
LOW VFR CIG WILL MOVE IN. EVENING PRECIPITATION CHANCES REMAIN TOO 
LOW TO MENTION AT THIS TIME. LIGHT SE WINDS WILL VEER TO S THIS 
MORNING THEN SW THIS AFTERNOON...WITH GUSTS INCREASE DURING THE DAY. 
FRONTAL PASSAGE AND NW WINDS WILL WAIT UNTIL AFTER THIS FORECAST.

ELSEWHERE...VFR. CIRRUS WILL SPREAD HIGH LEVEL CIGS ACROSS THE AREA 
THIS MORNING IN ADVANCE OF A COLD FRONT. CIGS FALL TO LOW VFR THIS 
EVENING. PRECIPITATION CHANCES THIS EVENING ARE BEST IN THE 
MOUNTAINS...BUT ONLY MARGINALLY WORTHY OF A MENTION AT KAVL. IF SOME 
SNOW CAN FALL AT KAVL...VSBY MIGHT BE REDUCED...BUT CONFIDENCE IN 
THIS SCENARIO IS TOO LIMITED TO MENTION AT THIS TIME. LIGHT AND 
VARIABLE WINDS WILL GO S BY DAWN THEN SW BY MIDDAY...WITH GUSTS 
INCREASING. KAVL WINDS VEER NW THIS EVENING AS THE FRONT MOVES 
THROUGH...WHILE FOOTHILLS WINDS REMAIN SW JUST AHEAD OF THE FRONT.

OUTLOOK...A PAIR OF CLIPPER SYSTEMS WILL BRING CHANCES FOR RAIN OR 
SNOW SHOWERS TO THE NC MTNS FRI. MOST OF THESE SHOWERS WILL REMAIN 
WEST AND NORTH OF KAVL...BUT BRIEF PERIODS OF RESTRICTIONS CANNOT BE 
RULED OUT. OTHERWISE...MAINLY VFR CONDITIONS ARE EXPECTED ACROSS THE 
AREA UNTIL MOISTURE BEGINS TO RETURN SUNDAY. DRYING IS EXPECTED ON 
MONDAY.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z 
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...JOH
NEAR TERM...ARK/CDG/JAT
SHORT TERM...PM
LONG TERM...RWH
AVIATION...JAT

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