Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 271749
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
149 PM EDT FRI MAR 27 2015

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE WILL CROSS THE REGION FROM THE WEST
TONIGHT. COLD AND DRY HIGH PRESSURE WILL SETTLE IN OVER THE WEEKEND.
A LOW PRESSURE CLIPPER SYSTEM AND ASSOCIATED COLD FRONT WILL PASS
OVER THE AREA ON SUNDAY NIGHT OR MONDAY. MOISTURE WILL RETURN MID TO
LATE WEEK AHEAD OF THE NEXT APPROACHING COLD FRONT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM EDT FRIDAY...SHOWERS ARE PUSHING EAST A LITTLE FASTER
THAN EARLIER ANTICIPATED WITH DOWNSLOPING KICKING IN...BUT WEAK
ISENTROPIC UPGLIDE MAINLY AT 295K CONTINUES TO ALLOW LOW CLOUDS TO
LINGER ESPECIALLY ACROSS EASTERN PORTIONS OF THE AREA. BEGINNING TO
SEE SOME BREAKS IN THE CLOUDS IN RESPONSE TO THE DOWNSLOPING ACROSS
NORTHEAST GEORGIA AND EXPECT THIS TREND TO CONTINUE ESPECIALLY
ACROSS THE PIEDMONT...WHILE AT THE SAME TIME SHOULD SEE CONTINUED
CLOUDINESS ACROSS THE RIDGES DUE TO THE NORTHWEST FLOW. TEMPERATURES
UNDERNEATH THE MORE WIDESPREAD CLOUD COVER ARE HOLDING A LITTLE
LOWER THAN FORECAST AND HAVE ADJUSTED GRIDS TO SLOW DOWN THE WARMING
TREND...AND SUBSEQUENTLY LOWERING MAX TEMPS JUST A TAD. HRRR STILL
WANTS TO DEVELOP ADDITIONAL SHOWERS THIS AFTERNOON ACROSS THE
UPSTATE OF SOUTH CAROLINA BUT LOOKING AT TRENDS IN WATER VAPOR
AND THE JET STREAK ROUNDING THE BASE OF THE SHORTWAVE...CURRENTLY
LOOKS LIKE THE HRRR MAY BE A LITTLE TOO FAR WEST WITH THE SHOWER
REDEVELOPMENT THIS AFTERNOON. DID DECREASE POPS SLIGHTLY BUT HAVE
KEPT SLIGHT TO LOW CHANCE POPS ACROSS PORTIONS OF THE UPSTATE FOR
THIS AFTERNOON.

PREVIOUS DISCUSSION...

AS OF 330 AM EDT FRIDAY...NEARLY PHASED NORTHERN/SOUTHERN STREAM
UPPER TROF PATTERN YIELDING FULL LATITUDE TROF AXIS ADVECTION ACROSS
THE CENTRAL/SOUTHERN CONUS THIS MORNING.  SURFACE WAVE OUT AHEAD
ACROSS THE MIDATLANTIC CONTINUES TO PUSH A COLD FRONT THROUGH THE
SOUTHERN APPS AT THIS TIME.  CURRENTLY...THE COLD FRONT IS SLIDING
INTO/THROUGH THE I85 CORRIDOR WHERE WINDS HAVE VEERED SHARPLY TO THE
NORTH.  THE FRONT ITSELF CAN ACTUALLY BE SEEN ON RADAR VIA THE KGSP
HALF DEGREE TILT AS IT PUSHES THROUGH THE GSP AREA.  PRECIP
ASSOCIATED WITH THIS FROPA HAS BEEN LESS THAN IMPRESSIVE TO SAY THE
LEAST DUE TO LACK OF UPPER SUPPORT AND LITTLE TO NO INSTABILITY.
THEREFORE THE FCST HAS BEEN TAILORED BACK WITH RESPECT TO POPS
ACROSS THE EASTERN TWO THIRDS OF THE FCST AREA WHERE ONLY ISOLATED
POPS ARE FEATURED THROUGH DAYBREAK...FURTHER WEST ACROSS THE HIGH
TERRAIN CATEGORICAL POPS PREVAIL.  LATEST MESO MODELS INDICATE
SHOWER EXPANSION ALONG AND SOUTH OF I85 THIS MORNING AS THE BOUNDARY
SLIDES SOUTH INTO A SLIGHTLY MORE MOIST ENVIRONMENT.  THIS ADDED
MOISTURE AND WEAK SURFACE CONVERGENCE WILL YIELD AT LEAST SOME
SCATTERED SHOWERS AROUND SUNRISE THEREFORE LIKELY POPS PERSIST
THROUGH MID MORNING OVER THESE AREAS BEFORE BEING LOWERED.  FURTHER
NORTH BEHIND THE FRONT OVER THE NC PIEDMONT...POPS REMAIN AT LIKELY
LEVELS FOR THE TIME BEING BEFORE BEING GRADUALLY REDUCED TO CHANCE
LEVELS BY MID MORNING.

MEANWHILE THE PRIMARY UPPER TROF AXIS WILL BE SLIDING INTO THE
REGION TOWARD DAYS END WITH ABUNDANT COLD ADVECTION PATTERN RIDING
ALONG.  LATEST GUIDANCE FAVORS THE TROF BASE SLIDING ATOP THE TN
VALLEY REGION LATE IN THE DAY TODAY YIELDING INCREASED NW FLOW OVER
THE HIGH TERRAIN AS BROAD CHANNELED VORTICITY BAND MOVES IN.
THUS...KEEPING POPS ELEVATED OVER THE MTNS TO ACCOUNT FOR SNOW
SHOWERS THROUGH THE OVERNIGHT HOURS...WHERE SUB ADVISORY LEVEL
SNOWFALL IS FCST.  THE OTHER CONCERN FOR THE OVERNIGHT PERIOD IS THE
STRENGTH OF THE COLD ADVECTION LEADING TO SUBFREEZING TEMPERATURES
ACROSS THE MTNS...AND NEAR FREEZING LEVELS OUTSIDE OF THE MTNS.  AS
THE FROST/FREEZE PROGRAM HAS BEEN ACTIVATED ACROSS SOUTHWEST
NC...WILL BE ISSUING FREEZE WARNING TO ACCOUNT FOR THREATENING
TEMPERATURES TONIGHT.  REGARDING FROST ACROSS NORTHEAST GA AND THE
NC/SC PIEDMONT...EXPECTING WINDS OVERNIGHT TO INCREASE TO LEVELS
NOT SUPPORTIVE OF FROST DEVELOPMENT THEREFORE NO FROST PRODUCTS WILL
BE ISSUED.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
AS OF 315 AM FRIDAY...THE MAIN STORY FOR THE SHORT RANGE WILL BE THE
HIGH AMPLITUDE UPPER TROF THAT SETTLES BRIEFLY OVER THE EAST...WHICH
WILL MAKE IT FEEL MUCH MORE LIKE WINTER THAN EARLY SPRING. AFTER
SOME LINGERING NW FLOW SNOW SHOWER ACTIVITY ENDS AFTER DAYBREAK
SATURDAY...THE REST OF THE DAY SHOULD BE QUIET AS A TRAILING SHORT
WAVE IS CHANNELED AND HAS LITTLE MOISTURE TO WORK WITH. HIGH
PRESSURE WILL BUILD DOWN FROM THE NORTH AND WILL KEEP HIGH TEMPS
CLOSE TO WHAT IS NORMAL FOR MID JANUARY. THE HIGH WILL SETTLE OVER
TOP OF THE WESTERN CAROLINAS BY SUNDAY MORNING AND SHOULD PROVIDE
FOR EXCELLENT RADIATIONAL COOLING CONDITIONS. EXPECT THAT THE ENTIRE
FCST AREA WILL BE BELOW FREEZING BY DAYBREAK SUNDAY. BEING THAT
SATURDAY NIGHT IS THE FOURTH PERIOD OF THE FCST...PREFER TO WAIT FOR
ONE MORE MODEL CYCLE BEFORE ISSUING A FREEZE WATCH...JUST IN CASE
THE MODEL GUIDANCE CHANGES. THE UPPER RIDGE MOVES OVERHEAD SUNDAY
AND THAT SHOULD PUSH THE SFC HIGH OFF TO THE EAST. TEMPS WILL NOT
MODERATE MUCH...THOUGH...AND WILL REMAIN WELL BELOW NORMAL. THE NEXT
SHORT WAVE WILL DIVE DOWN AND ACROSS THE FCST AREA SUNDAY NIGHT AND
MONDAY MORNING. THERE APPEARS TO BE MORE MODEL CONSENSUS WITH THE
TIMING OF THIS FEATURE AND THE ASSOCIATED SFC COLD FRONT...REACHING
THE MTNS SUNDAY NIGHT AND CROSSING THE REGION THRU MIDDAY MONDAY.
THAT WILL ALLOW FOR ELIMINATING THE PRECIP CHANCES FROM THE N/NW
MONDAY AFTERNOON. PARTIAL THICKNESS/FCST SOUNDINGS SHOW LOW
POTENTIAL FOR ANYTHING OTHER THAN RAIN...SO THE MIN TEMP FCST FOR
SUNDAY NIGHT WILL BE KEPT ABOVE FREEZING. HAVE LOWERED HIGH TEMPS ON
MONDAY BASED ON A CONSENSUS OF THE GUIDANCE SUPPORTED BY AN EARLIER
FRONTAL PASSAGE.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
AS OF 230 AM FRIDAY...THE UPPER AIR PATTERN THRU THE MEDIUM RANGE
STILL LOOKS PROGRESSIVE. AN UPPER TROF AXIS OFF THE EAST COAST
MONDAY NIGHT WILL MOVE OFF TO THE EAST. THAT WILL ALLOW SURFACE HIGH
PRESSURE TO BUILD IN FROM THE WEST THRU TUESDAY AS A DEAMPLIFYING
UPPER RIDGE APPROACHES. THINK MONDAY NIGHT AND MOST OF TUESDAY WILL
BE DRY AS A RESULT. THE PROBLEM WILL BE A WEAK SRN STREAM SHORT WAVE
UNDERCUTTING THE DEAMPLIFYING RIDGE ON TUESDAY AND TUESDAY NIGHT.
THE OPERATIONAL GFS AND ECMWF KEEP THE SHORT WAVE WELL TO THE WEST
THRU TUESDAY EVENING...WHICH SUGGESTS THAT MOISTURE RETURN FROM THE
W/SW WILL BE DELAYED UNTIL PERHAPS TUESDAY NIGHT. PRECIP WAS REMOVED
FOR TUESDAY BASED ON THIS CONSENSUS. THE REST OF THE MEDIUM RANGE
LOOKS UNSETTLED AS FIRST THE SHORT WAVE PASSAGE BRINGS UPPER SUPPORT
FOR PRECIP DEVELOPMENT ON WEDNESDAY AND WEDNESDAY NIGHT...THEN A NRN
STREAM WAVE PUSHES A COLD FRONT DOWN FROM THE NW ON THURSDAY TO BE
THE FOCUS FOR ADDITIONAL PRECIP DEVELOPMENT. NO CHANGES WERE MADE
TO THE MEDIUM RANGE FROM WEDNESDAY ONWARD.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...MVFR CIGS CONTINUE FOR CLT AT TAF TIME BUT WITH LOW VFR
CIGS JUST TO THE WEST. STILL SOME -SHRA ACROSS THE AREA BUT MAINLY
WEST OF CLT SO WILL HOLD OFF ON SHRA/VCSH MENTION IN THE TAF FOR
NOW. EXPECT THAT CLT WILL REMAIN MVFR THROUGH 21-22Z WITH A SLOW
LIFTING TREND TO VFR AT THAT TIME. N WINDS AROUND 10KT WITH GUSTS
BETWEEN 15-20KT WILL LOSE GUSTINESS AND DECREASE LATE THIS EVENING
AND OVERNIGHT...BACKING MORE NW OVERNIGHT. CIGS WILL CONTINUE TO
GRADUALLY LIFT BUT REMAIN GENERALLY BELOW 6KFT UNTIL DOWNSLOPING
KICKS IN MORE SIGNIFICANTLY AFTER MIDNIGHT WITH THE WIND SHIFT TO
NW...WHEN CIGS SHOULD LIFT RAPIDLY AND SCATTER OUT. SOME HINTS AT
LOW LEVEL MOISTURE...BETWEEN 60-70 PERCENT RH...AFTER 15Z SATURDAY
SO HAVE INTRODUCED FEW035 FOR LATE IN THE PERIOD WITH WINDS BACK UP
TO AROUND 10KT.

ELSEWHERE...VERY SIMILAR TREND TO CLT BUT INITIALIZING MAINLY LOW
VFR WITH ONLY SPOTTY MVFR. CANNOT RULE OUT BRIEF -SHRA THROUGH THE
AFTERNOON BUT WITH LIFTING TREND IN CIGS CHANCES WILL CONTINUE TO
DIMINISH. CIGS SHOULD REMAIN VFR THROUGH THE PERIOD WITH N WINDS
BACKING TO NW ALLOWING SKIES TO CLEAR FOR THE MOST PART OVERNIGHT
FOR ALL BUT KAVL...WHERE SOME LOW VFR CIGS MAY REMAIN THROUGH AROUND
SUNRISE. CAA AND NORTHWEST FLOW BEHIND THE FRONT WILL LEAD TO -SHSN
ALONG THE TN LINE AND CANNOT RULE OUT ISOLATED FLURRIES AT KAVL BUT
CONFIDENCE NOT HIGH ENOUGH TO INCLUDE IN TAF AT THIS TIME.

OUTLOOK...DRY HIGH PRESSURE WILL PREVAIL THROUGH THE WEEKEND WITH
ANOTHER FRONT APPROACHING FOR MONDAY. RAIN CHANCES INCREASE THROUGH
MIDDAY MONDAY WITH BEST CHANCES FOR WESTERN TAFS...WITH CIG/VSBY
RESTRICTIONS FOLLOWING A SIMILAR TREND BUT CANNOT BE RULED OUT AT
ANY SITE ON MONDAY BEFORE THE FRONT CLEARS THE AREA.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       HIGH  90%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  80%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH  90%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  80%     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

&&

.CLIMATE...
RECORD MINIMUM TEMPERATURES FOR MARCH 28TH...

GSP  26  1982
CLT  25  1982
AVL  11  1887

RECORD MINIMUM TEMPERATURES FOR MARCH 29TH...

GSP  26  1899
CLT  26  2013
AVL  19  1982

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR GAZ010-017-018-026-028-029.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO NOON EDT SATURDAY FOR
     GAZ010.
NC...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR NCZ048-051>053-058-059-062>065-068>072-082-507>510.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO NOON EDT SATURDAY FOR
     NCZ048-051>053-058-059-062>065-507-509.
SC...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
     FOR SCZ001>014-019.

&&

$$
SYNOPSIS...PM
NEAR TERM...CDG/TDP
SHORT TERM...PM
LONG TERM...PM
AVIATION...TDP
CLIMATE...PM



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