Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 280557
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
157 AM EDT MON JUL 28 2014

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE CAROLINAS LATE TONIGHT AND PUSH EAST
ACROSS THE REGION ON MONDAY. IN ITS WAKE...CANADIAN HIGH PRESSURE
WILL DOMINATE THE SURFACE PATTERN THROUGH MIDWEEK LEADING TO WELL
BELOW NORMAL TEMPERATURES AND PLEASANT CONDITIONS. PRECIPITATION
CHANCES WILL RAMP BACK UP AGAIN ON THURSDAY AND FRIDAY AS ATLANTIC
MOISTURE SPREADS OVER THE REGION AND LOW LEVEL WINDS BECOME MORE
EASTERLY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 150 AM EDT MONDAY...LINE OF PREFRONTAL CONVECTION CONTINUES TO
PUSH THROUGH THE BLUE RIDGE AND INTO THE PIEDMONT REGIONS OF NC.
EXPECTING THIS LINE TO CONTINUE ON ITS CURRENT TRAJECTORY ALL THE
WHILE WEAKENING AS IT MOVES INTO A LESS FAVORABLE ENVIRONMENT.  THUS
EARLY TORNADO WATCH WAS ALLOWED TO EXPIRE.  OTHERWISE...WINDS WILL
BEGIN TO INCREASE ACROSS THE WESTERN MOST ZONES WITH GUSTS PICKING
UP OVER THE NEXT FEW HOURS AS THE FRONT INTRUDES FROM THE WEST.
UPDATED POPS/TEMPS/DEWPOINTS TO REFLECT LATEST RADAR AND
OBSERVATIONAL TRENDS AND LEFT THE REMAINDER OF THE FORECAST AS IS.

PREVIOUS DISCUSSION...

EVENING UPDATE...STRONG/SEVERE CONVECTIVE ACTIVITY CONTINUES ACROSS
THE SRN NC ZONES AND INTO THE ERN UPSTATE. MANY REPORTS HAVE BEEN
RECEIVED OF TREES BLOWN DOWN AND LARGE HAIL. THESE STORMS ARE
ORGANIZING IN A PREFRONTAL AREA OF STEEP MLVL LAPSE RATES AND HAVE
TAPPED INTO DCAPE VALUES OVER 1100 J/KG. THERE EXISTS A HIGH AMOUNT
OF EFFECTIVE SHEAR...BUT THE STORMS HAVE MORPHED OUT SUPERCELL
MODE...WITH LOSS OF MLCAPE AND INCREASING LLVL CIN. THERE IS ANOTHER
LINE OF COLD POOL CONVECTION LOCATED OVER NRN TN AND THIS AREA
SHOULD GRADUALLY MERGE WITH EXISTING ACTIVITY ACROSS ERN TN...THEN
CROSS THE GSP CWFA THROUGH THE OVERNIGHT. HYDRO ISSUES ARE BECOMING
A CONCERN AND WILL MONITOR OVERNIGHT FOR POSSIBLE FFG
EXCEEDANCE...WITH RATIOS CURRENTLY RUNNING AROUND 40-50 PERCENT
ACROSS THE ERN SMOKIES AND THE BALSAMS. POPS HAVE BEEN BUMPED INTO
THE CHANCE RANGE ACROSS THE UPSTATE OVERNIGHT WITH LITTLE CHANGES
NEEDED TO THE MIN TEMP GRID. QPF AMOUNTS ALSO HAVE BEEN BUMPED UP
ACROSS THE CURRENT MCS TRACK.

MULTIPLE SUPERCELLS HAVE DEVELOPED ALONG AND AHEAD OF A PRE-FRONTAL
TROUGH ACROSS EASTERN KENTUCKY THIS AFTERNOON. EXPECT CONVECTION TO
CONTINUE TO DEVELOP TOWARD THE SOUTHWEST THROUGH THE AFTERNOON...
LIKELY CONSOLIDATING INTO AN ORGANIZED MCS THAT WILL APPROACH
WESTERN NC BY EARLY EVENING. WITH THAT IN MIND...STILL EXPECT THE
PRIMARY THREAT OVER OUR AREA TO BE DAMAGING DOWNBURST WINDS...
ALTHOUGH WOULD NOT BE SURPRISED TO SEE AN ISOLATED TORNADO...
ESPECIALLY IF THE PRE-FRONTAL/DISCRETE SUPERCELL CURRENTLY SOUTHEAST
OF JKL MANAGES TO HOLD TOGETHER INTO OUR AREA. SEVENTY POPS WILL BE
CONTINUED ACROSS THE NRN NC MTNS...AND HAVE ALSO ADDED A MENTION OF
DAMAGING WINDS AND LARGE HAIL TO THE FORECAST SUITE IN THESE AREAS.
THE SHORT TERM MODELS CONTINUE TO DISSIPATE ANY CONVECTION EAST OF
THE MTNS THIS EVENING...PROBABLY DUE TO A DEVELOPING STRONG WESTERLY
DOWNSLOPE FLOW. HOWEVER...STRONG/COLD POOL-DRIVEN CONVECTION OFTEN
/DOES NOT CARE/ ABOUT DOWNSLOPE FLOW...AND SOME OF THE MESOSCALE
MODELS ARE BEGINNING TO PICK UP ON THE POTENTIAL FOR AN MCS TO BLAST
THROUGH THE FHILLS/PIEDMONT OF NC THIS EVENING. THEREFORE...HAVE
BEGUN TO STEP INTO HIGHER POPS EAST OF THE BLUE RIDGE IN NC THIS
EVENING. THE SEVERE WEATHER THREAT IS EXPECTED TO WIND DOWN BY LATE
EVENING...OR EARLY IN THE OVERNIGHT...ALTHOUGH THERE WILL BE A
CONTINUED POTENTIAL FOR CONVECTION ACROSS THE WESTERN MTNS THROUGH
THE NIGHT...AS THE ACTUAL COLD FRONT APPROACHES AND W RATHER STOUT
W/NW UPSLOPE FLOW DEVELOPS. WITH COLD ADVECTION HOLDING OFF UNTIL
TOMORROW...AND THE EXPECTATION THAT SURFACE WINDS WILL REMAIN
SOMEWHAT ELEVATED TONIGHT...EXPECT MIN TEMPS TO BE ABOUT 5 DEGREES
ABOVE CLIMO.

MONDAY WILL SEE THE ONSET OF COLD ADVECTION OVER THE MTNS...WHERE
MAXES ARE EXPECTED TO TOP OUT A LITTLE BELOW CLIMO. MEANWHILE...
DESPITE FALLING THICKNESSES...DOWNSLOPE WARMING SHOULD YIELD HIGHS
VERY CLOSE TO CLIMATOLOGICAL NORMS EAST OF THE MTNS. CANNOT RULE OUT
SOME NW UPSLOPE FLOW SHOWERS ACROSS THE WESTERN MTNS DURING THE
AFTERNOON...BUT WILL CONTINUE WITH A POP FORECAST JUST A SHADE BELOW
SLIGHT CHANCE.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
AS OF 130 PM SUNDAY...NWLY FLOW WILL PREVAIL IN THE LOW- TO
MID-LEVELS MONDAY NIGHT WITH THE AXIS OF A DEEP ERN CONUS TROUGH
EXTENDING FROM ERN ONTARIO SWD INTO SC/GA. COOL AIR WILL CONTINUE TO
FILTER INTO THE REGION AT THIS TIME AS CONTINENTAL HIGH PRESSURE
SETTLES IN ACRS THE INLAND SOUTH. HIGH LLVL RH IS NOTED ON GFS/NAM IN
THE COLD-ADVECTIVE FLOW INTO THE MTNS...REMINISCENT OF THE COOL
SEASON. THE MOIST LAYER IS SO SHALLOW ONLY THE MOST FAVORED UPSLOPE
AREAS LOOK TO HAVE ANY MENTIONABLE CHANCE OF PRECIP.

H7 HEIGHTS BOTTOM OUT AROUND DAYBREAK TUE AND INCREASE SLIGHTLY
THEREAFTER. THIS CREATES A CAPPING INVERSION THAT WILL RESTRICT DEEP
CONVECTION TUE AFTN...BUT THE MAJOR MODELS VARIOUSLY STILL DEVELOP
SMALL AMOUNTS OF QPF IN THE FA. BY WED THERE IS LITTLE REAL CHANGE IN
THE PATTERN...BUT THE FLOW REGIME BECOMES VERY WEAK IN THE LOWER
TROPOSPHERE AND MODEL PROFILES SHOW THE INVERSION WEAKENING AS WELL.
A GREATER PROPORTION OF GUIDANCE PRODUCES QPF IN THE HIGHER
TERRAIN...BUT THIS MAY BE OVERDONE GIVEN RECENT POST-FRONTAL
PERFORMANCE. ALSO...GIVEN THE CONTINUED SLIGHT HEIGHT RISES I WILL
CURRENTLY FAVOR THE INVERSION HOLDING FAST. THUS NO QPF IS IN THE
FCST FOR WED. MAX TEMPS WILL BE NEAR 10 DEGREES BELOW CLIMO...
TRENDING UPWARD SLIGHTLY FROM TUE TO WED. MIN TEMPS HOWEVER WILL BE
SLIGHTLY COOLER WED MRNG WITH WINDS BEING LIGHTER OVERNIGHT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 140 PM EDT SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH BROAD AND DEEP UPPER TROFFING IN PLACE OVER THE
EASTERN CONUS WHILE AN EQUALLY IMPRESSIVE UPPER RIDGE IS IN PLACE
OVER THE WEST. THE LONG RANGE GUIDANCE CONTINUES TO SUGGEST THAT WE
WILL REMAIN IN THIS AMPLIFIED PATTERN INTO THE WEEKEND WITH SOME
AMOUNT OF DEAMPLIFICATION LIKELY OVER THE WEEKEND. COMPARED TO
PREVIOUS FCSTS...ITS LOOKING LESS CERTAIN THAT THE NORTHERN STREAM
UPPER FLOW WILL COMPLETELY CUTOFF THE TROF AND ALLOW A CLOSED LOW TO
DEVELOP OVER THE WEEKEND. THE LATEST GFS ENSEMBLE RUN HAS ABOUT HALF
OF THE MEMBERS COMPLETELY CUTTING THE TROF OFF AND HALF MAINTAINING
SOME DEGREE OF TROFFING.

AT THE SFC...CANADIAN HIGH PRESSURE WILL CONTINUE TO SLIDE
SOUTHEASTWARD AND WEAKEN ON THURS AS BNDRY LYR FLOW REMAINS NLY TO
WEAK AND VRB. BY EARLY FRI...THE MODELS CONTINUE TO VEER THE FLOW
MORE FROM THE EAST TO NE AND MOVE A LARGE PLUME OF DEEPER LYR
MOISTURE OVER THE CWFA FROM THE SOUTHWEST. THIS UPSLOPE POTENTIAL
COUPLED WITH UPPER LVL DIVERGENCE COURTESY OF THE UPPER TROF AND
POSSIBLY THE CLOSED UPPER LOW IF IT ACTUALLY DEVELOPS...WILL IMPROVE
OUR CHANCES FOR WIDESPREAD SHOWERS AND TS FOR THE REST OF THE MEDIUM
RANGE. OTHERWISE...NO SIGNIFICANT CHANGES WERE MADE TO THE
TEMPERATURE FCST WITH VALUES EXPECTED TO REMAIN WELL BELOW NORMAL
FOR LATE JULY/EARLY AUGUST.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.  LINE
OF CONVECTION PUSHING THROUGH THE BLUE RIDGE AND INTO THE PIEDMONT
WILL LIKELY HOLD TOGETHER...IMPACTING THE AIRFIELD WITHIN NEXT
HOUR.  THUS WILL CARRY ONE HOUR TEMPO TO ACCOUNT FOR TSRA AND LOW
VFR CIGS.  CONDITIONS WILL IMPROVE BEHIND THE PASSING LINE WITH
WINDS/CLOUDS DECREASING FOR THE MORNING.  EXPECTING GUSTY NW WINDS
THIS AFTERNOON AS THE FRONT ITSELF PUSHES THROUGH AND HIGH PRESSURE
BUILDS IN FROM THE WEST.  THEREFORE INCLUDED G20KT MENTION THROUGH
THE AFTERNOON HOURS AMIDST FEW LOW VFR CLOUDS AND SCT HIGH LEVEL
CIRRUS.  GUSTING SHOULD SUBSIDE BY AROUND 00Z LEADING TO PREVAILING
NORTHERLY FLOW AROUND THE 7KTS RANGE THROUGH THE PERIOD.

ELSEWHERE...VFR CONDITIONS ARE EXPECTED TO PREVAIL AT ALL SITES WITH
THE EXCEPTION OF KAVL WHERE BRIEF MENTION OF MVFR LEVEL CIGS IS
INCLUDED AROUND DAYBREAK.  OTHERWISE...LINE OF CONVECTION CURRENTLY
MOVING THROUGH THE REGION WILL LIKELY CONTINUE TO IMPACT ALL NC
SITES OVER THE NEXT FEW HOURS.  CONFIDENCE REMAINS LOWER AS TO
SOUTHERN EXTENT OF THE HEAVIER TSRA...HOWEVER DECIDED TO INCLUDE
TEMPOS FOR TSRA AT THE SC SITES TO BE SAFE...WITH SLIGHT TIMING
DIFFERENCES AT EACH LOCATION.  BEYOND THAT...EXPECTING SKIES TO
CLEAR OUT BY MID/LATE MORNING AT ALL SITES WITH WINDS INCREASING
INTO THE AFTERNOON AS HIGH PRESSURE BUILDS IN FROM THE WEST.  THUS
INCLUDED GUST MENTION AMIDST NW FLOW AT THE SURFACE AT ALL LOCATIONS
DURING THE AFTERNOON BEFORE SUBSIDING AS TIGHTER PRESSURE GRADIENT
ALONG FRONT PUSHES SOUTHEAST BY EARLY EVENING.

OUTLOOK...HIGH PRESSURE WILL PREVAIL THROUGH THE FIRST HALF OF THE
WEEK WITH ONLY POSSIBLE RESTRICITONS BEING MOUNTAIN VALLEY
FOG/STRATUS.  MOISTURE WILL INCREASE BY LATE WEEK AS EASTERLY FLOW
RETURNS LEADING TO IMPROVING PRECIPITATION/FOG/STRATUS CHANCES.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     HIGH  94%     HIGH 100%     HIGH 100%
KHKY       HIGH  91%     HIGH  95%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  95%     HIGH  95%     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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...CDG/JDL/SBK
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...CDG






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