Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 152050
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
450 PM EDT WED APR 15 2015

.SYNOPSIS...
A COLD FRONT WILL SETTLE IN FROM THE NORTH TODAY...BRINGING COOL AND
DAMP CONDITIONS THROUGH THURSDAY...WITH ADDITIONAL ROUNDS OF
RAINFALL. UNSETTLED AND WET WEATHER IS EXPECTED TO CONTINUE INTO
EARLY NEXT WEEK...BUT WITH MORE SEASONABLE TEMPERATURES RETURNING BY
FRIDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 500 PM...NO SIGNIFICANT CHANGES TO THE FORECAST AT THIS TIME.
STILL WIDESPREAD PRECIPITATION ESPECIALLY ACROSS EASTERN ZONES UNDER
THE INFLUENCE OF ISENTROPIC UPGLIDE AND WEAK UPPER DIFFLUENCE.
INCREASED POPS SOMEWHAT ON THE EAST WHERE IT IS CURRENTLY RAINING
BUT IN GENERAL LEFT TRENDS THROUGH THE EVENING THE SAME.
TEMPERATURES RUNNING A BIT COOLER THAN FORECAST SO MADE A FEW
UPDATES TO HOURLY TEMPERATURES AS WELL...BUT OVERALL LITTLE CHANGE.

AS OF 215 PM...AN AREA OF MODERATE TO EVEN HEAVY RAIN CONTINUES TO
MOVE E-NE ACROSS THE EASTERN SC UPSTATE AND NC PIEDMONT. THERE IS
ENOUGH MOVEMENT OF THE AXIS OF HEAVY RAIN THAT SHOULD PRECLUDE ANY
SIGNIFICANT HYDRO CONCERNS. HOWEVER...A RELATIVELY QUICK 1/2 TO 1
INCH RAINFALL TOTALS HAVE OCCURRED WITH IT. AN AREA OF UPPER
DIVERGENCE ASSOCIATED WITH A SPEED MAX IN ASSOCIATION WITH
ISENTROPIC LIFT OVER THE WEDGE SEEMS TO BE THE PRIMARY DRIVER OF THE
HEAVIER PRECIP...WITH THE ENHANCED LIFT TRANSLATING EAST OF THE
FORECAST AREA BY 00Z. HENCE...THE HEAVIER RAIN SHOULD MOVE OUT OF
THE AREA BY LATE AFTERNOON.

IN THE WAKE OF THE HEAVIER RAIN...EXPECT THAT LIGHT RAIN/DRIZZLE
WILL PERSIST OVERNIGHT AS WEAK UPGLIDE CONTINUES OVER THE WEDGE.
HENCE...POPS WILL REMAIN ELEVATED OVERNIGHT. TEMPS ARE HOLDING
STEADY OR SLOWLY FALLING AS WEDGE MATURES THIS AFTERNOON AND WILL
SLOWLY FALL OVERNIGHT AS COLD ADVECTION CONTINUES. OVERNIGHT LOWS
WILL BE WELL INTO THE 40S OVER MOST MOUNTAIN LOCATIONS AND
UPPER 40S TO LOWER 50S OUTSIDE THE MOUNTAINS.

ON THURSDAY...IT LOOKS LIKE THE WEDGE WILL HOLD FAST OVER THE
REGION. UPGLIDE WILL REMAIN WEAK SO THAT PRECIP SHOULD BE PATCHY AND
LIGHT. HOWEVER...WILL BUMP POPS UP TO LIKELY OVER THE NC FOOTHILLS
AND AREAS OF NORTH OF CHARLOTTE FRIDAY AFTERNOON AS A VORT MAX
ARRIVES AND PRODUCES BETTER LIFT IN THAT AREA. MAX TEMPS THU WILL BE
WELL BELOW CLIMO WITH HIGHS MOSTLY IN THE MID 50S...EXCEPT 60S IN THE
SW MOUNTAIN VALLEYS AWAY FROM THE WEDGE.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 235 PM EDT WEDNESDAY...THE SHORT TERM FCST PERIOD INITIALIZES
THURSDAY EVENING AMIDST RISING HEIGHTS ALOFT DUE TO INTRUSION OF
SOUTHERN STREAM SHORT WAVE RIDGING OVER THE SOUTHEAST.  FURTHER
WEST...A CLOSED UPPER LOW WILL BE ROTATING ATOP THE FOUR CORNERS
LEADING TO SOUTHWEST FLOW ALOFT OVER THE DEEP SOUTH.  MEANWHILE AT
THE SURFACE...A WAVE OFF THE CAROLINA COAST WILL PROVIDE
REINFORCEMENT OF THE ONGOING CAD EVENT.  WEAK UPGLIDE REGIME
CONTINUES TO LOOK PROBABLE DURING THIS TIMEFRAME...AT LEAST
INITIALLY.  GUIDANCE DOES FAVOR CAD EROSION SOMETIME EARLY ON FRIDAY
WITH SOME DISCONTINUITY ON THE TIMING.  NEVERTHELESS...IT LOOKS AS
IF THE BEST FORCING FOR UPGLIDE WILL ERODE NLT FRIDAY AFTERNOON
ALLOWING PRECIP CHANCES TO FALL OVER THE SOUTHERN TIER OF THE FCST
AREA.  FURTHER NORTH ACROSS WESTERN NC...MODELS LEND THEMSELVES
TOWARD WEAK COLD FRONTAL INTRUSION WITH SHOWERS AND PERHAPS A FEW
THUNDERSTORMS POSSIBLE.  HIGH PRESSURE WILL BUILD IN OVERNIGHT INTO
SATURDAY ALLOWING FOR DEEP LAYER RIDGING ACROSS THE SOUTHEAST BEFORE
SAID SURFACE HIGH MIGRATES EAST DURING THE DAY ALLOWING FOR
GRADUALLY DEVELOPMENT OF SOUTHERN ATLANTIC WAA REGIME.  MEANWHILE
FURTHER WEST...SURFACE CYCLOGENESIS IS PROGGED OVER THE LOWER
MISSISSIPPI RIVER VALLEY PER NEARLY ALL OPERATIONAL GUID.  A WARM
FRONT WILL EXTENDED EASTWARD INTO THE DEEP SOUTH WITH A MARCH
NORTHWARD INEVITABLE THROUGH THE DAY ON SATURDAY.  MODELS TEND TO
DISAGREE WITH REGARDS TO TIMING OF THE WARM FRONTAL PRECIP ARRIVAL
ON SATURDAY WITH THE NAM BEING MUCH SLOWER THAN THE
ECMWF/GFS/SREF/CMC.  THAT SAID...ALL SOURCES TREND TOWARDS SOME
CONVECTIVE ACTIVITY DURING THE AFTERNOON HOURS AS HEATING AND
IMPROVING DEWPOINTS YIELD SOME MARGINAL INSTABILITY.

ALL SAID...THE FCST FEATURES DECREASING POPS ACROSS THE NC/SC
PIEDMONT ON FRIDAY AFTERNOON...WITH POPS LINGERING AT CHANCE LEVELS
ACROSS THE MTNS.  A DRY FORECAST PREVAILS BY SUNRISE SATURDAY AHEAD
OF INCREASING POPS INTO THE AFTERNOON AS MOISTURE IMPROVES LEADING
TO POSSIBLE DIURNAL CONVECTION.  FINALLY POPS WILL INCREASE FURTHER
TO LOW END LIKELY RANGES ACROSS THE WESTERN TIER OF THE FCST AREA
LATE IN THE PERIOD AS ABOVE MENTIONED WARM FRONTAL ACTIVATION
NEARS.  TEMPERATURES THROUGH THE PERIOD WILL REMAIN AT OR ABOVE
CLIMO.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 230 PM WED...THE LATEST RUNS OF THE GFS AND ECMWF AGREED WELL
WITH THE PLACEMENT AND TIMING OF MAIN FEATURES ON SUNDAY. BOTH
SOLUTIONS INDICATE THAT A CLOSED MID LEVEL LOW OVER THE SOUTHERN AND
CENTRAL PLAINS WILL PHASE WITH A TROF ASSOCIATED WITH ANOTHER CLOSED
LOW OVER CENTRAL CANADA. A SFC LOW IS FORECAST TO DEVELOP OVER THE
CENTRAL CONUS...WITH A WARM FRONT STRETCHING EAST ACROSS THE
SOUTHEAST U.S. THE CENTER OF SFC HIGH PRESSURE IS EXPECTED TO PUSH
OFF SHORE OF NY...WITH WEAK RIDGING RUNNING SW TO THE CAROLINAS. THE
GFS INDICATES THAT LLVL FLOW WILL STRENGTHEN DURING THE EARLY
MORNING HOURS...FOLLOWING THE PASSAGE OF A WARM FRONT. GFS SHOWS
THAT THE STRENGTHENING FLOW WILL PROVIDE A WIDE AREA OF ISENTROPIC
LIFT...PRIMARILY BETWEEN 6Z-18Z SUN. IN ADDITION...H5 RIDGE AXIS
WILL LIFT NORTHEAST DURING THE DAYLIGHT HOURS SUNDAY...AS THE TROF
AXIS SWEEPS ACROSS THE SOUTHERN PLAINS. GFS INDICATES THAT H5 Q-
VECTOR CONVERGENCE WILL INCREASE ACROSS THE FORECAST AREA SUN
AFTERNOON. SIGNIFICANT QPF IS INDICATED ON BOTH SOLUTIONS...WITH THE
GFS INDICATING GREATER THAN 1.5 INCHES/6 HRS POSSIBLE ALONG THE
UPSLOPE AREAS. I WILL INCREASE POPS TO CATE SUNDAY AFTERNOON...WITH
A COMPROMISE OF GFS AND ECMWF QPF. TEMPERATURES WILL START OUT THE
DAY MILD...WITH MOST AREAS IN THE LOW 60S. WAVES OF MODERATE RAIN
AND THICK CLOUDS SHOULD KEEP DAYTIME WARMUP LIMITED TO 5 TO 10
DEGREES.

ON MONDAY...A COLD FRONT WILL APPROACH THE FORECAST AREA SUNDAY
NIGHT...EXPECTED TO SWEEP ACROSS THE REGION MONDAY AFTERNOON AND
EVENING. POPS WILL REMAIN IN THE LIKELY TO CHANCE RANGE AS THE FRONT
APPROACHES. SOUTHWEST WINDS AHEAD OF THE FRONT WILL LIKELY SUPPORT
MILD DEWPOINTS...WITH MOST AREAS AROUND 60 DEGREES. A BLEND OF
TEMPERATURE GUIDANCE INDICATES HIGHS SHOULD RANGE FROM THE LOW 70S
WITHIN THE FRENCH BROAD VALLEYS TO UPPER 70S EAST. FORECAST
SOUNDINGS INDICATE THAT CAPES SHOULD SURGE ABOVE 1000 J/KG WITH WBZ
BELOW 8 KFT. I WILL FORECAST AT LEAST CHC POPS TO TSRA MONDAY
AFTERNOON.

TUESDAY AND WEDNESDAY...I WILL FAVOR THE ECMWF TIMING AND PLACEMENT
OF HIGH PRESSURE ACROSS THE SOUTHERN APPALACHIANS. THE FORECAST WILL
REMAIN DRY WITH SEASONABLE TEMPERATURES.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT /21Z UPDATE/...LIGHT TO MODERATE RAIN CONTINUES ACROSS THE
AIRPORT WITH CIGS REMAINING HIGH IFR TO LOW MVFR...WITH GUSTY WINDS
CONTINUING FROM THE NE. EXPECT WINDS TO BEGIN TO DROP OFF THROUGH
THE EVENING HOURS...WITH SOLID IFR CIGS RETURNING BY 00Z ALONG WITH
PERIODS OF LIGHT RAIN AND DRIZZLE OVERNIGHT. THE CONSENSUS OF THE
GUIDANCE LOCKS IFR CONDITIONS IN FOR THE NIGHT. SOMEWHAT DRIER AIR
WORKING IN FRIDAY MORNING SHOULD ALLOW CIGS TO IMPROVE TO MVFR.

ELSEWHERE...WIDESPREAD MODERATE RAIN FROM NEAR KHKY SW TO KAND WILL
CONTINUE TO MOVE EAST AND ALLOW VSBYS TO IMPROVE TO VFR. IN THE WAKE
OF THE RAIN...CIGS MAY SEE A BUMP UP TO MVFR FOR A COUPLE HOURS.
HOWEVER...ALL GUIDANCE THEN LOCKS IFR CONDITIONS IN THROUGH ABOUT
MID MORNING FRIDAY. ALSO...VSBYS MAY BE REDUCED AT TIMES IN LIGHT
RAIN/DRIZZLE/FOG.

OUTLOOK...COLD AIR DAMMING WILL PERSIST THROUGH THU NIGHT LEADING TO
CONTINUED CIG/VSBY RESTRICTIONS AND AREAS OF PRECIPITATION. THE
WEDGE WILL SLOWLY BREAK UP ON FRIDAY ALONG WITH IMPROVING CONDITIONS
WITH THE BREAK IN THE WEATHER PERHAPS EXTENDING THROUGH SATURDAY.
HOWEVER...A FEW THUNDERSTORMS MAY DEVELOP FRIDAY AND SATURDAY
AFTERNOONS ESPECIALLY OVER THE NC MOUNTAINS. MORE RAIN WITH
RESTRICTIONS IS EXPECTED TO RETURN ON SUNDAY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-18Z
KCLT       MED   60%     HIGH  80%     HIGH  85%     HIGH 100%
KGSP       LOW   50%     HIGH  85%     MED   78%     HIGH  91%
KAVL       LOW   50%     MED   71%     MED   69%     MED   76%
KHKY       MED   77%     HIGH  80%     MED   64%     HIGH  91%
KGMU       LOW   44%     HIGH  85%     HIGH  80%     HIGH  91%
KAND       LOW   44%     HIGH  85%     HIGH  80%     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...LG/TDP
SHORT TERM...CDG
LONG TERM...NED
AVIATION...LG/TDP


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