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Area Forecast Discussion

633
FXUS62 KGSP 261807
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
107 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 1255 PM EST...THE PRECIPITATION SHIELD AND DEEPER MOISTURE
LAYER HAS EXITED NE OF THE AREA WITH THE DEPARTING JET STREAK AND
PHASING UPPER WAVE. WATER VAPOR IMAGERY SHOWS THE NEXT UPSTREAM
TROUGH AXIS DIGGING INTO THE CENTRAL MS RIVER VALLEY EARLY THIS
AFTN. THE FORECAST MODELS AGREE FAIRLY WELL WITH 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 TYPE SHOWERS FORM AS A POOL OF 7 TO 8 DEG C/KM LAPSE
RATES CROSSES THE REGION OVERNIGHT. THIS INSTABILITY...ALONG WITH A
+2 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.

THE PRECIPITATION FOCUS WILL THEN STEADILY SHIFT BACK TO THE WRN NC
MTN COUNTIES NEAR THE TN BORDER AS A MORE TRADITIONAL UPSLOPE 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 40 MAXES IN THE
MTNS...BUT LOWER 50S ARE MORE LIKELY IN THE EVENTUAL DOWNSLOPE
ACROSS THE FOOTHILLS/PIEDMONT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 300 AM WED...DRY HIGH PRESSURE WILL FILTER IN THU NIGHT INTO
FRI. MIN TEMPS FRI MRNG WILL BE IN THE L20S MTNS AND U20S TO AROUND
30 IN THE PIEDMONT. SKIES WILL BE MOSTLY CLEAR BY THIS TIME...BUT
CONTINUED NLY WINDS WILL KEEP TEMPS FROM RISING OUT OF THE 40S OVER
MOST OF THE AREA FRI AFTN. SLIGHT RETURN FLOW SETS UP FRI NIGHT
WHICH WILL KEEP TEMPS FROM PLUNGING AS MUCH...ALSO INTRODUCING A
LITTLE CLOUD COVER INTO THE AREA.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 220 AM WEDNESDAY...THE MEDIUM RANGE FCST PICKS UP AT 12Z ON
SATURDAY WITH A RELATIVELY ZONAL UPPER PATTERN OVER MOST OF THE
CONUS. AS WE MOVE INTO SUN...ANOTHER BROAD H5 TROF DIGS DOWN OVER
THE FAR NORTHERN STATES AND THEN OVER THE GREAT LAKES. AT THE SAME
TIME...FLAT UPPER RIDGING WILL PERSIST SPREAD OVER THE GULF OF MEX
AND PERSIST OVER THE REGION THRU MOST OF THE PERIOD. THE LONG RANGE
GUIDANCE ACTUALLY HAS THE RIDGE AMPLIFYING TOWARDS THE VERY END OF
THE MEDIUM RANGE.

AT THE SFC...HIGH PRESSURE WILL BE CENTERED OVER THE FCST AREA AT
THE START OF THE PERIOD WITH WARMER SLY FLOW INCREASING THICKNESSES
AND TEMPS OVER THE WEEKEND. THE NEXT FRONTAL SYSTEM WILL APPROACH
THE AREA BY EARLY MON AND LAY DOWN ACROSS OUR NORTHERN FRINGE.
STRONG HIGH PRESSURE BEHIND THE FRONT WILL SLIDE EASTWARD AND
APPEARS TO SET UP A POTENTIALLY STRONG CAD PATTERN TO OUR NE BY DAY
7. THE ECMWF AND CANADIAN OPERATIONAL MODELS REMAIN MORE MOIST WITH
THIS FRONT AND SUBSEQUENT WEDGE PATTERN...YET AS WE HAVE SEEN MANY
TIMES BEFORE...MODELS TEND TO OVERESTIMATE THE EXTENT OF THE DEEPER
LYR MOISTURE IN THESE SCENARIOS. WITH THAT SAID...THE ONLY POPS I
HAVE ARE SLIGHT TO LOW END SOLID CHANCE FROM LATE SUN ONWARD. THE
BEST CHANCES ARE STILL OVER THE HIGHER TERRAIN AND ALONG THE NC/TENN
BORDER REGION. TEMPS WILL WARM THRU MON WITH VALUES EXCEEDING
CLIMATOLOGY. VALUES SHOULD COOL AGAIN AS WE GO INTO MID WEEK AND THE
FLOW BECOMES MORE NELY.

&&

.AVIATION /18Z 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...TEMPO TO OCCASIONAL MVFR CIGS WILL PERSIST THROUGH LATE
DAY AS HEATING INTERACTS WITH LINGERING BOUNDARY LAYER MOISTURE.
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 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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  87%     HIGH  93%     HIGH  92%     HIGH  87%
KGSP       HIGH  80%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  94%     HIGH 100%     HIGH  88%     HIGH  80%
KHKY       HIGH  93%     HIGH 100%     HIGH  81%     HIGH  93%
KGMU       MED   76%     HIGH 100%     HIGH 100%     HIGH  93%
KAND       HIGH  95%     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...JDL
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...HG



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