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Local forecast by
"City, St"
  
000
FXUS62 KGSP 211449
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
949 AM EST SUN DEC 21 2014

.SYNOPSIS...
LOW LEVEL MOISTURE WILL LINGER ACROSS THE REGION TODAY THROUGH 
MONDAY. DEEPER MOISTURE WILL ARRIVE FROM THE WEST ON TUESDAY AHEAD 
OF A STRONG COLD FRONT. THE COLD FRONT WILL CROSS THE REGION ON 
WEDNESDAY. COLD AND WINDY CONDITIONS WILL SET UP IN THE MOUNTAINS 
THROUGH THURSDAY...WITH DRIER CONDITIONS EXPECTED EAST OF THE 
MOUNTAINS THROUGH LATE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 930 AM...UPPER FLOW WILL CONTINUE TO AMPLIFY TODAY...WITH A 
DIGGING TROF ACRS THE GREAT PLAINS...AND UPPER RIDGE ALONG THE EAST 
COAST. A STRONG SUBTROPICAL JET CAN BE SEEN ON WATER VAPOR IMAGERY 
FROM CENTRAL MEXICO TO THE CAROLINAS. AS THE FLOW BECOMES MORE SWLY 
ALOFT...MOISTURE AND UPGLIDE SHUD BEGIN TO INCREASE FROM THE SOUTH 
THIS AFTN. BEFORE THEN...A WEAK WEDGE CONTINUES TO LINGER...WITH A 
1028MB HIGH ACRS THE CENTRAL APPALACHIANS. PLENTY OF STRATUS STILL 
SEEN ON VISIBLE IMAGERY AND IN THE METARS...WITH A FEW BREAKS IN THE 
MTNS AND ACRS THE MIDLANDS. OVERALL...I THINK GIVEN INCREASING SWLY 
850 MB WAA FLOW...AND A DECENT INVERSION STILL IN THE FCST SNDGS 
ABOVE 900 MB...I THINK THE BREAKS WILL REMAIN SPOTTY AND 
INTERMITTENT. SO WITH ALL THAT SAID...NO SIGNIFICANT CHANGES TO THE 
FCST WITH THIS UPDATE. COOL WEDGE-LIKE TEMPS...CLOUDY...AND A RETURN 
OF SOME SLGT CHC TO LOW-END CHC POP LATE AFTN INTO THIS EVENING ACRS 
THE SOUTHERN HALF OF THE CWFA LOOKS GOOD.

AT 230 AM EST SUNDAY...A MEAN UPPER TROUGH AXIS WAS LOCATED OVER THE 
CENTER OF THE NATION EARLY THIS MORNING...WITH LOW AMPLITUDE RIDGING 
DOWNSTREAM OVER THE SOUTHEAST AND LOWER GREAT LAKES. WEAK SHORTWAVE 
ENERGY WAS MOVING OUT OF THE BASE OF THE TROUGH OVER THE GULF 
STATES. AT THE SURFACE...A HIGH PRESSURE RIDGE EXTENDED FORM QUEBEC 
TO THE GULF STATES. A STATIONARY FRONT WAS LOCATED FROM OFF THE 
CAROLINA AND GA COASTS...ACROSS N FL...TO THE CENTRAL GULF OF MEXICO.

LIGHT MOIST UPSLOPE FLOW INTO THE BLUE RIDGE THIS MORNING MAY RESULT 
IN SOME VERY LIGHT PRECIPITATION...SOME OF WHICH MAY FALL AS 
FREEZING RAIN OF FREEZING DRIZZLE...BUT ACCUMULATIONS ARE EXPECTED 
TO BE VERY LIGHT AND RATHER SPOTTY.
  
THE MODELS SHOW A WEAK SURFACE WAVE DEVELOPING ALONG THE COASTAL 
FRONT TODAY...WHICH WILL BRING MOIST ISENTROPIC UPGLIDE NW OVER THE 
SURFACE RIDGE AND ACROSS OUR AREA. THIS WILL KEEP CLOUD COVER IN 
PLACE OVER THE AREA...AND SUPPORT LIGHT RAIN BY THIS EVENING... 
ESPECIALLY OVER THE PIEDMONT. HIGH TEMPERATURES WILL RUN SLIGHTLY 
BELOW NORMAL DUE TO CLOUDS...DESPITE ABOVE NORMAL HEIGHTS ALOFT. 
MINIMUM TEMPERATURES TONIGHT WILL RUN AROUND SEVEN DEGREES ABOVE 
NORMAL. THERE MAY BE A FEW AREAS AT HIGH ELEVATIONS OF THE MOUNTAINS 
THAT SEE SOME FREEZING RAIN TOWARD DAWN MONDAY...BUT THE DURATION 
WILL BE TOO SHORT FOR MUCH ICE ACCUMULATIONS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 220 AM EST SUNDAY...WEAK SFC CAD WILL BE ESTABLISHED ACROSS 
THE REGION ON MON...WITH 1026 MB HIGH PRES NOSING SWD EAST OF THE 
APPALACHIANS...AND SRLY 850 MB FLOW DEVELOPING AHEAD OF FALLING 
HEIGHTS BACK ACROSS THE PLAINS STATES. THE PRECIPITATION WILL LIKELY 
BE VERY LIGHT...WITH DRIZZLE EXPECTED AT TIMES. WILL FEATURE BELOW 
GUIDANCE MAX TEMPS FOR MONDAY AFTERNOON.

VERY LITTLE MOVEMENT IN THE SFC CAD LAYER IS EXPECTED THROUGH MONDAY 
NIGHT. UPGLIDE AND SRN TIER MTN UPSLOPE FLOW WILL STEADILY IMPROVE 
TUE THROUGH TUE NIGHT...WITH WIDESPREAD RAIN/SHOWERS GRADUALLY 
DEVELOPING. CONSIDERABLE GULF COAST AND SE COASTAL PLAIN CONVECTION 
IS STILL FEATURED IN THE MODELS TUE TO TUE NIGHT...WHICH MAY SERVE 
TO INHIBIT THE TRANSPORT OF DEEPER MOISTURE AND ASSOCIATED HIGHER 
QPF INTO THE SRN APPALACHIANS AND SURROUNDING AREAS. MODERATE TO 
OCCASIONALLY HEAVY RAINFALL COULD STILL RESULT...BUT LITTLE OR NO 
HYDRO PROBLEMS ARE EXPECTED. THIS PERIOD SHOULD ALSO SEE STEADY 
EROSION/PINCHING OF THE SFC CAD LAYER BACK TOWARD THE NRN NC BLUE 
RIDGE THROUGH LATE TUE NIGHT...WITH NON DIURNAL WARMING OF PIEDMONT 
TEMPERATURES.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 230 AM EST SUNDAY...THE POTENTIAL FOR HIGH SHEAR LOW CAPE 
CONVECTION ALONG THE IMMEDIATE COLD FROPA WED WILL DEPEND ON SEVERAL 
FACTORS. A SLOW STEADY EROSION OF THE SFC CAD IS EXPECTED...BUT SFC 
BASED INSTABILITY MAY ONLY BUBBLE UP TO A COUPLE HUNDRED J/KG OF 
CAPE BY MIDDAY WED IN THE UNCOVERED PIEDMONT. THERE ARE TIMING 
DIFFERENCES...WITH THE BEST DEEP LAYER FORCING ON THE GFS TOWARD WED 
EVENING...WHILE THE ECMWF IS FASTER TOWARD MIDDAY. FINALLY THE GULF 
COASTAL CONVECTION MAY DISRUPT ANY DEVELOPING SHALLOW CONVECTIVE 
LINE SEGMENTS FARTHER INLAND. THE POTENTIAL FOR ISOLD SEVERE 
CONVECTION WILL HAVE TO BE MONITORED...BUT CONFIDENCE IS TOO LOW FOR 
ANY HWO MENTION AT THIS POINT.

THE SLOWEST OPERATIONAL GFS HAS SFC WAVES DEVELOPING ALONG THE FRONT 
AND DELAYING FROPA INTO WED EVENING...WHILE OTHER SOLUTIONS ARE A 
BIT FASTER WITH EARLIER COOLING ACROSS THE MTNS WED NIGHT. A BRIEF 
PERIOD OF UPSLOPE SNOW SHOWERS SHOULD DEVELOP POST FROPA IN THE WRN 
MTNS THROUGH THU MORNING...BUT A LESS THAN FAVORABLE WESTERLY 
DIRECTION TO THE LOW LEVEL FLOW SHOULD CURTAIL THE FORCING A BIT. 
SNOW ACCUMS CHRISTMAS MORNING ARE EXPECTED TO BE SUB ADVISORY GIVEN 
THE LIMITED DURATION OF THE DEEPER MOISTURE AND THE LESS THAN 
FAVORABLE WIND COMPONENT. 

OTHERWISE...ANTICIPATE ZONAL FLOW IN THE WAKE OF THE PASSING TROUGH 
THU THROUGH THU NIGHT. A GRADUAL RETURN TO DEEPER LAYER SW FLOW IS 
EXPECTED FRI/FRI NIGHT AS ANOTHER TROUGH DEEPENS OVER THE PLAINS AND 
MOVES EAST THROUGH MS RIVER VALLEY. THE ASSOCIATED FRONTAL SYSTEM 
SHOULD REACH THE FORECAST AREA ON SAT...BUT WITH MORE LIMITED 
MOISTURE THAN THE MID WEEK SYSTEM.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT KCLT...THE DEW POINT DEPRESSION DOES NOT FAVOR FOG THIS 
MORNING. THE MVFR CIG IS EXPECTED TO LIFT TO LOW VFR SOMETIME THIS 
MORNING...FALLING BACK TO MVFR AND THEN IFR THIS EVENING. LIGHT RAIN 
IS EXPECTED TONIGHT AS A SURFACE LOW MOVES UP THE COAST. ALTHOUGH 
SOME GUIDANCE SUPPORTS DAYBREAK FOG MONDAY MORNING...THE CONSENSUS 
DOES NOT. WINDS ARE EXPECTED TO FAVOR THE NE TODAY..DESPITE 
STUBBORNLY REAMING ESE OVERNIGHT.

AT KAVL...RESTRICTIONS HAVE IMPROVED JUST RECENTLY...BUT MAY 
DETERIORATE AGAIN EARLY THIS MORNING...WITH VFR BY MIDDAY. MVFR 
RETURNS THIS EVENING...FOLLOWED LIFR BEFORE DAYBREAK MONDAY. LIGHT 
RAIN IS EXPECTED TONIGHT AS A LOW MOVES UP THE COAST. WINDS WILL 
FAVOR THE SE...CHANNELING DOWN VALLEY. 
 
ELSEWHERE...CIGS MAY FLUCTUATE BETWEEN IFR AND MVFR FOR A FEW HOURS 
THIS MORNING...WITH MVFR EXPECTED LATER IN THE MORNING. KGSP AN KGMU 
ARE EXPECTED TO GO VFR THIS AFTERNOON...BEFORE FALLING BACK TO MVFR 
THIS EVENING...AND LIFR LATE TONIGHT. KAND AND KHKY ARE EXPECTED TO 
REMAIN MVFR. DAYBREAK VSBY RESTRICTIONS HAVE NOT BEEN AS BAD AS 
EXPECTED THIS MORNING. A GUIDANCE BLEND ONLY SUPPORTS LOW VFR VSBY 
MONDAY MORNING....DESPITE SOME MEMBERS SUPPORTING LOWER 
RESTRICTIONS...AND LIGHT RAIN MOVING IN TONIGHT AS A LOW MOVES UP 
THE COAST. WINDS WILL FAVOR THE NE.

OUTLOOK...LINGERING LOW LEVEL MOISTURE IS LIKELY TO KEEP LOW STRATUS 
AROUND THRU MONDAY. A COLD FRONT WILL APPROACH ON TUESDAY FROM THE 
WEST AND MOVE THROUGH ON WED. WIDESPREAD SHOWERS WITH RESTRICTIONS 
SHOULD ARRIVE TUESDAY AFTERNOON AND WILL CONTINUE UNTIL THE FRONT 
CLEARS THE AREA LATE WEDNESDAY.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z 
KCLT       HIGH 100%     HIGH 100%     HIGH  97%     HIGH 100%     
KGSP       MED   77%     HIGH 100%     HIGH  90%     LOW   54%     
KAVL       MED   62%     HIGH  85%     HIGH  83%     HIGH  96%     
KHKY       MED   75%     MED   70%     MED   70%     HIGH  83%     
KGMU       MED   77%     HIGH 100%     HIGH  90%     LOW   55%     
KAND       HIGH  81%     MED   72%     HIGH  90%     MED   66%     

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


National Weather Service
Weather Forecast Office Greenville-Spartanburg
GSP International Airport
1549 GSP Drive
Greer, SC 29651
(864) 848-3859
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Page last modified: January 20, 2010

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