Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 262014
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
414 PM EDT THU MAR 26 2015

.SYNOPSIS...
A COLD FRONT WILL CROSS THE WESTERN CAROLINAS AND NORTHEAST GEORGIA
TONIGHT. A TRAILING UPPER LEVEL DISTURBANCE WILL THEN CROSS THE AREA
FRIDAY THROUGH FRIDAY NIGHT. DRY AND COOL HIGH PRESSURE WILL SETTLE
IN OVER THE WEEKEND. A LOW PRESSURE CLIPPER SYSTEM AND ASSOCIATED
COLD FRONT WILL PASS OVER THE REGION ON MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
2015 UTC UPDATE...POPS WERE LOWERED THE NEXT FEW HOURS BASED ON
RADAR TRENDS...AND THUNDER CHANCES BASED ON THE LATEST MODEL DATA.
SKY COVER WAS UPDATED FROM VISIBLE SATELLITE IMAGERY.

AS OF 225 PM...CLOUDS HAVE THINNED AND BROKEN UP AROUND THE AREA
WHICH SHOULD ALLOW TEMPS TO RISE INTO THE 70S ACRS MUCH OF THE
PIEDMONT AND UPPER 60S IN MTN VALLEYS. HELD ONTO A LOW POP THRU
EARLY EVENING...WITH LATEST SOUNDINGS HAVING A SMALL AMOUNT OF
INSTABILITY ACRS THE PIEDMONT...ALBEIT CAPPED OFF IN THE MIDLEVELS.
THE CHANCE OF THUNDER IN THESE AREAS LOOKS NEAR ZERO THRU THE REST
OF THE DAYTIME HRS.

LOOKING UPSTREAM...DEEP TROUGH CONTINUES TO DIG INTO THE MID
MISSISSIPPI VALLEY...PRECEDED BY A FAIRLY POTENT COLD FRONT AND AN
WAVE OF LOW PRESSURE OVER THE CENTRAL APPALACHIANS. A BAND OF
CONVECTIVE PRECIP AND EMBEDDED TSTMS IS SEEN OVER WV AND ERN
KY...JUST AHEAD OF THE SFC FRONT. LATEST HRRR AND 4KM SPC WRF TAKE
THIS FEATURE NEWD...WHILE MORE ACTIVITY DEVELOPS ALONG THE FRONT
OVER THE TENN VALLEY. THE FRONT IS EXPECTED TO SLOWLY MOVE ACRS THE
MTNS OVERNIGHT AS THE TROUGH DIGS AND THE SFC WAVE MOVES TO THE MID
ATLANTIC COAST. BOTH THE CONVECTION ALLOWING MODELS AS WELL AS THE
GFS/NAM SHOW QPF IN OUR CWFA INVOF THE FRONT...THOUGH THIS APPEARS
DUE TO REDEVELOPMENT RATHER THAN ADVECTION OF THE CURRENT ACTIVITY.
INDEED MOST GUIDANCE SHOWS MODEST INSTABILITY OF UP TO A FEW HUNDRED
J/KG...MAINLY ELEVATED IN NATURE...PRESENT IN THE CWFA PRIOR TO THE
FRONT. THUNDER CHANCES ARE MAINLY CONFINED TO THE MTNS AND AREAS
SOUTH OF I-85. THOUGH 0-3KM SHEAR WOULD SUGGEST SOME ORGANIZATION OR
DMGG WIND THREAT WITH TSRA...THE EFFECTIVE SHEAR IS SMALL AND SVR WX
IS NOT ANTICIPATED. SPC DOES NOT HAVE THE CWFA IN ANY PROBABILISTIC
THREAT AREAS THRU 12Z. DESPITE THE FRONT ARRIVING LATE...MINS WILL
BE A COUPLE CATEGORIES ABOVE CLIMO.

COLD AIR BEGINS TO SWEEP IN BEHIND THE FRONT...AND NWLY WINDS WILL
STILL HAVE SOME MOISTURE TO WORK WITH. SMALL CHANCES OF NW FLOW SNOW
ARE INCLUDED NEAR DAYBREAK...THOUGH IN REALITY IF THE COLD AIR
ARRIVES EARLY ENOUGH A MIX OF PTYPES COULD OCCUR AS IT CUTS
UNDERNEATH THE VERY WARM MIDLEVEL AIR STILL PRESENT...CREATING A
WARM NOSE. PRECIP CHANCES WILL GENERALLY TREND DOWNWARD IN THE WAKE
OF THE FRONT AS THE DAY PROGRESSES...BUT SOME DEGREE OF UPPER
DYNAMIC FORCING WILL BE PRESENT WITH THE TROUGH STILL JUST TO OUR
WEST. MIDLEVEL LAPSE RATES IMPROVE SUFFICIENTLY TO ALLOW SLIGHT SFC
BASED INSTABILITY BY AFTN. THESE INGREDIENTS COULD PRODUCE SOME
SPOTTY SHOWERS...WITH TEMPS AGAIN BECOMING SUPPORTIVE OF SNOW OR A
RA/SN MIX IN THE HIGH ELEVATIONS BY SUNSET. EARLY AFTN MAX TEMPS
WILL MAINLY BE IN THE 50S IN THE PIEDMONT AND MTN VALLEYS...WITH
UPPER 30S AND LOWER 40S IN THE HIGH ELEVATIONS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 145 PM THURSDAY..A DEEP UPPER TROUGH CENTERED WEST OF THE AREA
FRIDAY EVENING IS FORECAST TO SWING THROUGH THE AREA BY EARLY
SATURDAY AND MOVE INTO THE ATLANTIC EARLY SUNDAY. IN THE WAKE OF THE
TROUGH...WEAK RIDGING WILL OCCUR ACROSS THE SE STATES ON SUNDAY.

ON FRIDAY NIGHT...THERE MAY BE SOME LINGERING SHOWERS ACROSS THE
PIEDMONT ALONG THE AXIS OF A DEPARTING VORT MAX...SO HAVE MAINTAINED
A MENTION OF CHANCE POPS THERE BEFORE MIDNIGHT. ALSO...SOME NW FLOW
SNOW WILL LIKELY BE ON GOING AS ANOTHER VORT MAX CROSSES THE
MOUNTAINS AHEAD OF THE APPROACHING BASE OF THE UPPER TROF.
MEANWHILE...850 MB TEMPS WILL FALL TO THE  -8C TO -12C RANGE BY 12Z
SATURDAY. HENCE...A PERIOD OF DECENT NW FLOW SNOW SHOULD OCCUR
FRIDAY NIGHT. IN REGARD TO SNOW ACCUMS...THE LATEST MODEL CONSENSUS
OF QPF HAS TICKED UPWARD SOMEWHAT SO THAT ADVISORY TYPE SNOWFALL MAY
OCCUR IN THE SMOKIES. SNOW ACCUMULATIONS WILL BE ON THE ORDER OF 2-3
INCHES IN SMOKIES WITH GENERALLY 1-2 INCHES ELSEWHERE IN THE TN
BORDER COUNTIES.

IN ADDITION...IT IS LOOKING LIKE THE MOUNTAINS WILL EXPERIENCE AN
ADVECTIVE FREEZE FRIDAY NIGHT...WITH LOW TEMPS IN THE 20S. THE
PIEDMONT WILL SEE TEMPS IN THE 30S...WITH ISOLD FREEZING TEMPS AND
POSSIBLY SOME PATCHY FROST WHERE WINDS CAN DECOUPLE IN SHELTERED
AREAS.

NW FLOW AND COLD AIR ADVENTION WILL CONTINUE ON SATURDAY AS THE CP
HIGH REMAINS WEST OF THE AREA. HOWEVER...ENOUGH DRY AIR ARRIVES TO
CUT OFF THE SNOW SHOWER ACTIVITY IN THE MOUNTAINS EARLY SAT. HIGHS
SATURDAY WILL REMAIN CHILLY WITH HIGHS 15-20 DEGREES BELOW CLIMO.

THE CP HIGH WILL SETTLE OVER THE AREA FRIDAY NIGHT PRODUCING IDEAL
RADIATIVE COOLING CONDITIONS. A HARD FREEZE IS EXPECTED ACROSS ALL
OF THE MOUNTAINS...WITH FREEZING TEMPS ALSO EXPECTED OUTSIDE THE
MOUNTAINS. MIN TEMPS SUNDAY MORNING LOOK TO BE IN THE TEENS TO MID
20S IN THE MTNS AND MID 20S TO LWR 30S ACRS THE PIEDMONT. THESE MIN
TEMPS WILL APPROACH RECORD LOWS ACRS THE PIEDMONT (SEE CLIMATE
SECTION BELOW).

EVEN WITH PLENTY OF SUNSHINE AND WEAK WARM ADVECTION RETURING ON
SUNDAY...MAX TEMPS ARE STILL EXPECTED TO BE A COUPLE CATEGORIES
BELOW CLIMO.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 140 PM THURSDAY...THE MEDIUM RANGE BEGINS WITH A PROGRESSIVE
TROUGH AND ATTENDANT FRONTAL BOUNDARY MOVING ACROSS THE EASTERN
STATES IN THE SUNDAY NIGHT/MONDAY TIME FRAME. THIS WILL SUPPORT
CHANCE POPS ACROSS THE MTNS BY 12Z MONDAY. UPPER FORCING IS EXPECTED
TO PASS NORTH OF THE REGION...AS FRONTAL ZONE BEGINS TO SLOW DOWN
ACROSS THE SOUTHERN APPALACHIANS. THE RESULT IN VEERING LOW LEVEL
FLOW IN THE VICINITY OF THE FRONT...WITH RESULTANT WEAKLY
CONVERGENT/DOWNSLOPE FLOW LIMITING THE PRECIP POTENTIAL OUTSIDE THE
MTNS...AND POPS WILL GENERALLY BE MAINTAINED IN THE SLIGHT CHANCE
RANGE THERE.

FOR THE REMAINDER OF THE PERIOD...WESTERN HEIGHT FALLS AND EASTERN
RISES IN THE WAKE OF THE DEPARTING TROUGH WILL RESULT IN
ESTABLISHMENT OF FAST/QUASI-ZONAL FLOW ACROSS MUCH OF THE CONUS
THROUGH THE MIDDLE PART OF NEXT WEEK. MEANWHILE...THE AFOREMENTIONED
BAROCLINIC ZONE WILL BECOME QUASI-STATIONARY WITHIN THIS FLOW
PATTERN. IT IS THEREFORE NOT SURPRISING THAT GLOBAL MODEL DETAILS
DIVERGE DURING THIS TIME FRAME...AS THEY STRUGGLE TO RESOLVE WEAK
SHORT WAVES RIPPLING THROUGH THIS LOW AMPLITUDE PATTERN. THE GFS
OFFERS THE WETTER SOLUTION...WITH AT LEAST A COUPLE OF WEAK WAVES
SPREADING LIGHT PRECIP INTO THE REGION PRIOR TO THE ARRIVAL OF
ANOTHER FRONTAL SYSTEM LATE IN THE WEEK. THE ECMWF IS QUITE A BIT
DRIER. CONSIDERING THE PATTERN...IT PROBABLY BEHOOVES US TO MAINTAIN
AT LEAST A SLIGHT CHANCE POP DURING MOST PERIODS OF THE MEDIUM
RANGE...WITH THE HIGHEST POPS RESERVED FOR DAY 7 FOR THE POTENTIAL
APPROACH OF THE NEXT FRONTAL SYSTEM.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
AT KCLT...A SMALL CHANCE OF PRECIP EXISTS THIS AFTN...THOUGH TOO
SMALL TO MENTION. ANY PRECIP WOULD BE CONVECTIVE IN NATURE BUT
LATEST NAM/RAP SOUNDINGS ARE CAPPED IN THE MIDLEVELS...SO
PARTICULARLY DEEP CONVECTION OR THUNDER NOT EXPECTED. SWLY WINDS
WILL OCCASIONALLY GUST TO NEAR 20 KT. COLD FRONT WILL APPROACH FROM
THE NW TONIGHT...WITH WSHFT TO NW LIKELY 08-09Z. LLVL FORCING IN THE
PRESENCE OF ABUNDANT MOISTURE IS LIKELY TO BRING POPS AFTER MIDNIGHT
IF NOT SOONER. SOME ELEVATED INSTABILITY WILL STILL BE
PRESENT...HENCE PROB30 TSRA. IFR CANNOT BE RULED OUT IF A TSRA DOES
PASS OVER THE FIELD. CIGS ARE EXPECTED TO BOTTOM OUT AT LOW MVFR
INVOF THE FRONT...WITH POPS DIMINISHING AND CIGS GRADUALLY LIFTING
AFTER DAYBREAK.

ELSEWHERE...MAINLY VFR LEVEL CLOUDS WILL BE SEEN THIS AFTN WITH
SPOTTY CU AT MVFR LEVELS...THOUGH CIGS SHOULD REMAIN VFR. SMALL POPS
WILL CONTINUE THRU THE AFTN THOUGH TOO LOW TO MENTION. IN GENERAL
TRENDS OVERNIGHT WITH THE FROPA WILL BE SIMILAR TO KCLT...THOUGH THE
NWLY SHIFT WILL OCCUR AS EARLY AS 02-03Z AT KAVL AND OCCURRING AT
ALL SITES BEFORE DAWN. THUNDER CHANCES AHEAD OF THE FRONT EXIST
MAINLY AT THE UPSTATE SC SITES. GUIDANCE SPLIT ON FLT CATEGORY
OVERNIGHT BUT MVFR SEEMS MOST LIKELY GIVEN RELATIVELY LIGHT PRECIP
AND WINDS KEEPING THE BDY LAYER MIXED. KAND IS AN EXCEPTION WHERE
THE SIGNAL IS STRONGER FOR IFR. TSRA MIGHT PRODUCE BRIEF IFR
WHEREVER THEY OCCUR. IMPROVING CONDITIONS INTO MIDDAY FRI WITH
CONTINUED NWLY WINDS AND OCNL LOW END GUSTS.

OUTLOOK...SCATTERED SHOWERS MAY PRODUCE SOME RESTRICTIONS FRI AFTN.
HIGH PRESSURE WILL BUILD OVER THE REGION BEGINNING FRIDAY NIGHT
PRODUCING VFR CONDITIONS. A WEAK FRONT PASSING THRU SUNDAY NIGHT MAY
PRODUCE A FEW RESTRICTIONS BUT VFR SHOULD RETURN IN ITS WAKE.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  82%     HIGH  95%
KGSP       HIGH 100%     HIGH 100%     HIGH  86%     MED   62%
KAVL       HIGH 100%     HIGH  87%     HIGH  96%     HIGH  82%
KHKY       HIGH  96%     HIGH 100%     MED   73%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH  82%     MED   62%
KAND       HIGH  98%     HIGH 100%     MED   64%     MED   72%

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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...RWH
NEAR TERM...JAT/WIMBERLEY
SHORT TERM...LG
LONG TERM...JDL
AVIATION...WIMBERLEY
CLIMATE...


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