Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261753
AFDGSP

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

.SYNOPSIS...
WARM SOUTHERLY FLOW WILL GRADUALLY INCREASE AHEAD OF AN APPROACHING
COLD FRONT TODAY. THE 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 TONIGHT/...
AS OF 145 PM...THE MORNING WAS A BIT COOLER THAN
ANTICIPATED...BUT CLOUDS HAVE THINNED AND BROKEN UP AROUND THE AREA
WHICH SHOULD ALLOW TEMPS TO RISE INTO THE MID 70S BY THE TIME OF
PEAK HEATING. HELD ONTO A LOW POP THRU THE AFTN...WITH LATEST
SOUNDINGS HAVING A SMALL AMOUNT OF INSTABILITY. HOWEVER THIS IS
CAPPED OFF IN THE MIDLEVELS AND TSRA ARE NO LONGER LOOKING MUCH OF A
THREAT DURING THE DAY TODAY. HOWEVER...AHEAD OF THE FRONT TONIGHT IT
STILL APPEARS AS IF SOME THUNDER IS POSSIBLE IN THE I-85 CORRIDOR
AND POINTS SOUTH/EAST.

AS OF 345 AM...WEAK ISENTROPIC LIFT AT 295 K WILL SUPPORT WIDESPREAD
LOW CEILINGS AND PATCHY FOG EARLY THIS MORNING. THE THICK LOW CLOUDS
WILL LIKELY LINGER A FEW HOURS AFTER SUNRISE. IN ADDITION...SCT TI
WIDELY SCT -SHRA WILL CONTINUE ACROSS THE REGION THROUGH SUNRISE.
THE 0Z NAM INDICATES THAT LLVL WINDS WILL VEER FROM THE SOUTHWEST
SHORTLY AFTER SUNRISE...RESULTING LITTLE TO NO ISENTROPIC LIFT AND
ENDING UPSLOPE FLOW. CLOUD COVER MAY BEGIN TO THIN ONCE LLVL LIFT
HAS CEASED...ESPECIALLY FROM MID DAY THROUGH THE AFTERNOON.
INCREASING SUN AND MARGINALLY GUSTY SOUTHWEST WINDS SHOULD
RESULT IN MILD AFTERNOON TEMPERATURES ACROSS THE CWA. A BLEND OF
PREFERRED TEMPERATURE GUIDANCE YIELD HIGHS FROM AROUND 70 WITHIN THE
MTN VALLEYS TO THE MID TO UPPER 70S EAST OF I-85. DEWPOINTS WILL
RISE INTO THE 50S THIS AFTERNOON.

NEAR TERM MODELS INDICATE THAT A COLD FRONT WILL SLIDE ACROSS
EASTERN KY/TN THIS AFTERNOON...CROSSING THE SOUTHERN APPALACHIANS
BETWEEN 0Z-3Z...THEN PUSHING EAST OF THE PIEDMONT BY 9Z. POOLING
DEWPOINTS AND MILD TEMPERATURES SHOULD YIELD CAPE VALUES BETWEEN 500-
1000 J/KG ALONG AND AHEAD OF THE COLD FRONT. A BAND OF SHRA/TSRA IS
FORECAST TO REACH THE TN/NC LINE BETWEEN 0Z TO 3Z. I WILL INCREASE
POPS THROUGH THIS EVENING...PEAKING POPS AT 6Z IN THE HIGH LIKELY TO
CATEGORICAL RANGES. I WILL MENTION SHOWERS WITH CHC/SCHC OF TSRA. IN
THE WAKE OF THE FRONT...BRISK CAA WILL BUILD ACROSS THE WESTERN
CAROLINAS AND NORTHEAST GEORGIA. BY 12Z FRI...TN BORDER COUNTIES MAY
COOL H850 TEMPS TO 0 TO -2C. MIN TEMPERATURES ARE FORECAST TO RANGE
IN THE U30S WITHIN MTN VALLEYS TO MID TO UPPER 40S EAST. THE CAA
COULD SUPPORT A FEW TN BORDER -SHSN.

&&

.SHORT TERM /FRIDAY 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 /18Z 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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  88%     HIGH 100%     HIGH  82%     HIGH  91%
KGSP       HIGH  86%     HIGH 100%     HIGH  85%     MED   62%
KAVL       HIGH  98%     HIGH  86%     HIGH  83%     HIGH  88%
KHKY       HIGH  90%     HIGH  94%     MED   64%     HIGH  90%
KGMU       HIGH  89%     HIGH 100%     MED   76%     MED   62%
KAND       HIGH  86%     HIGH  91%     LOW   58%     MED   68%

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...ARK
NEAR TERM...NED/WIMBERLEY
SHORT TERM...LG
LONG TERM...JDL
AVIATION...WIMBERLEY
CLIMATE...ARK


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