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Area Forecast Discussion

001
FXUS62 KGSP 270823
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
423 AM EDT FRI MAR 27 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE EAST OF THE AREA THIS MORNING. A TRAILING
UPPER LEVEL DISTURBANCE WILL THEN CROSS THE AREA THROUGH TONIGHT.
DRY AND SEASONALLY COLD HIGH PRESSURE WILL SETTLE IN OVER THE
WEEKEND. A LOW PRESSURE CLIPPER SYSTEM AND ASSOCIATED COLD FRONT
WILL PASS OVER THE REGION ON SUNDAY NIGHT OR MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
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 /09Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VFR/MVFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.
INITIALIZED TAF AT LOW VFR WITH SW WINDS AT 09KTS BEFORE INTRODUCING
-SHRA AT 08Z AS LEADING EDGE OF PRECIP BAND SHOULD BE ENTERING THE
NC PIEDMONT REGION ALONG WITH THE FRONT.  CIGS WILL LOWER AT THAT
POINT TO MVFR LEVELS WITH SOME BRIEF MVFR VISB POSSIBLE ASSOCIATED
WITH THE SHRA...THUS ADDED TEMPO FOR SUCH.  WINDS WILL ALSO VEER
SHARPLY NW WITH SOME 15-20KT GUSTS POSSIBLE THROUGH MID MORNING.
CARRIED WX MENTION THROUGH 16Z WHERE N WINDS PREVAIL AMIDST MVFR
CIGS.   CIGS WILL LIFT THROUGH MIDDAY WITH LOW VFR ROUNDING OUT THE
PERIOD AFTER THE 21Z TIMEFRAME.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE AS FRONTAL PRECIP CONTINUES
TO SLIDE THROUGH THE REGION LEADING TO MVFR CONDITIONS OVERNIGHT.
INITIALIZED ALL TAFS VFR ASIDE FOR KAVL WHERE MVFR CIGS ARE ALREADY
IN PLACE.  LOWERED ALL SITES TO MVFR AFTER A FEW HORUS WITH A BRIEF
TEMPO TO IFR AT KAVL INCLUDED.  KEPT VISB RESTRICITIONS AT MVFR
LEVELS AS VEERING/GUSTY WINDS SHOULD HELP INHIBIT ANY SIGNIFICANT
BR/FG.  ALL SITES REMAIN RESTRICTED TO MVFR THROUGH MORNING BEFORE
GRADUAL IMPROVEMENT AS DRIER AIR ADVECTS IN BEHIND THE FRONT LATE
DAY.  LASTLY...EXPECTING LIGHT SHSN ALONG THE TN LINE ASSOCIATED
WITH CAA PATTERN...THUS WOULD NOT BE SURPRISED TO SEE A FEW FLURRIES
AT KAVL NEAR PERIODS END HOWEVER LEFT ANY MENTION OUT OF TAF FOR
THIS ISSUANCE.

OUTLOOK...DRY HIGH PRESSURE PREVAILS THROUGH SUNDAY...THEN ANOTHER
FRONT MOVES IN WITH PRECIPITATION ON MONDAY.  RESTRICTIONS LOOK
MOST LIKELY IN AND AROUND THE MOUNTAIN VALLEYS THUS AFFECTING
KAVL.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       MED   75%     HIGH  95%     HIGH  95%     HIGH 100%
KGSP       MED   68%     HIGH  89%     HIGH  98%     HIGH 100%
KAVL       LOW   58%     HIGH  89%     HIGH 100%     HIGH 100%
KHKY       MED   77%     MED   73%     HIGH 100%     HIGH 100%
KGMU       MED   72%     HIGH  89%     HIGH  98%     HIGH 100%
KAND       MED   73%     HIGH  89%     HIGH  95%     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 WARNING FROM MIDNIGHT TONIGHT TO NOON EDT SATURDAY FOR
     GAZ010.
NC...FREEZE WARNING FROM MIDNIGHT TONIGHT TO NOON EDT SATURDAY FOR
     NCZ048-051>053-058-059-062>065-507-509.
SC...NONE.

&&

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



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