Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 160731
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
331 AM EDT THU APR 16 2015

.SYNOPSIS...
COOL AND DAMP CONDITIONS WILL CONTINUE TODAY AS A WEDGE OF COLD AIR
REMAINS DAMMED UP AGAINST THE APPALACHIANS. TEMPERATURES RETURN TO
NEAR NORMAL FRIDAY AND SATURDAY FOLLOWING THE EROSION OF THE WEDGE.
A WARM FRONT WILL MOVE INTO THE REGION FROM THE SOUTHWEST SATURDAY
NIGHT INTO SUNDAY...ACCOMPANIED BY ABUNDANT MOISTURE AND MORE
RAINFALL. A COLD FRONTAL PASSAGE EARLY NEXT WEEK WILL FINALLY
RESTORE DRIER CONDITIONS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM EDT...COLD AIR DAMMING REMAINS FIRMLY ENTRENCHED ACROSS
THE REGION THIS MORNING...AND WILL LIKELY CONTINUE THROUGH THE NEAR
TERM PERIOD. THE LATEST SFC ANALYSIS REVEALS 1031 MB HIGH PRESSURE
CENTERED OVER SRN NY STATE...WITH THE SFC RIDGE AXIS EXTENDING DOWN
THROUGH THE WRN CAROLINAS. THE CAD LAYER IS GETTING WEAKLY
REINFORCED BY A SE COASTAL LOW/TROUGH AND A DEEP LAYER OF LIGHT SRLY
UPGLIDE ABOVE THE CAD...AS INDICATED ON THE KGSP VAD WIND PROFILE.
MEANWHILE...WATER VAPOR IMAGERY SHOWS A DEEP LOW PRESSURE SYSTEM
CONSOLIDATING OVER THE FOUR CORNERS REGION OF THE WRN U.S. ANY
SHORTWAVE RIPPLES IN THE DEEP LAYER SWLY FLOW AHEAD OF THIS SYSTEM
WILL JUST BRUSH OR REMAIN W OF THE SRN APPALACHIANS THROUGH THE
PERIOD. THIS WILL LEAD MAINLY TO JUST VERY LIGHT RAIN AND AREAS OF
DRIZZLE FOR OUR REGION...WITH MAX TEMPS BELOW ALL MOS GUIDANCE THIS
AFTN. THE FAR SW MTNS NEAR THE SMOKIES WILL BE THE ONE AREA WHERE
SOME SFC BASED INSTABILITY CAN BE FOUND...AND ISOLD AFTN TSTMS WILL
BE POSSIBLE THERE.

THE PARENT SFC HIGH WILL MOVE OFFSHORE LATER TODAY THROUGH
TONIGHT...BUT ANY PINCHING OF THE CAD LAYER OVER THE WRN CAROLINAS
AND NE GA WILL BE VERY GRADUAL. WILL ALLOW THE CAD TO PERSIST
THROUGH TONIGHT DESPITE ANY WEAK DOWNSLOPING FLOW OVER THE MTNS AS
850 MB VEERS NW OVERNIGHT. QPF WILL BE LIGHT OVER THE NEXT 24
HOURS...WITH NO HYDRO PROBLEMS EXPECTED DESPITE THE MOIST GROUND.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 200 AM THU...AT DAYBREAK FRIDAY THE WEDGE SHOULD STILL BE
ENTRENCHED ACROSS THE AREA...DESPITE THE PARENT HIGH HAVING MOVED
OFFSHORE. THE AXIS OF A SHALLOW SHORTWAVE WILL LIKELY BE OVER OR
JUST TO OUR EAST AT THAT TIME...WITH A WEAK COLD FRONT FOLLOWING
DURING THE DAY. THE MAJOR MODELS DO NOT FAVOR QPF COMING IN AS A
RESULT OF THE FRONTAL FORCING...BUT IT WILL HAVE THE EFFECT OF
ERODING THE WEDGE AND IMPROVING LAPSE RATES. MAX TEMPS SHOULD
REBOUND TO AROUND NORMAL. ON ACCOUNT OF THE BETTER LAPSE RATES SOME
CONVECTION IS EXPECTED IN THE FRONT/S WAKE...BUT DOWNSLOPE FLOW WILL
HELP KEEP IT ISOLATED TO WIDELY SCATTERED. PROFILES WILL BE DRY
ENOUGH TO SUGGEST DECENT GUSTS WILL RESULT FROM ANY TSTMS...BUT
INSTABILITY AND SHEAR LOOK LOW ENOUGH TO PRECLUDE A REMARKABLE
SEVERE THREAT. THE MORE POSITIVE IMPACT OF THE DRIER AIR ALOFT WILL
BE TO MINIMIZE THE THREAT OF HEAVY RAIN. THIS WILL BE WELCOME AFTER
SUCH A WET WEEK AND THE EXPECTATION THAT SOILS WILL BE NEAR CAPACITY.

UPPER HEIGHTS RISE OVER THE AREA FRIDAY NIGHT AS HIGH PRESSURE BUILDS
ACRS THE ERN SEABOARD. RIDGE AXIS SHOULD CROSS THE AREA DURING THE
DAY SATURDAY AS A LOW MOVES FROM THE ROCKIES TO THE PLAINS. THE DAY
SHOULD START OFF MOSTLY CLEAR...BUT CLOUDS WILL START TO RETURN FROM
THE SW AHEAD OF THE PLAINS SYSTEM/S WARM FRONT AS IT LIFTS NEWD OUT
OF THE GULF REGION. LAPSE RATES WILL LARGELY BE UNSUPPORTIVE OF DEEP
CONVECTION OVER THE PIEDMONT...BUT SOME CELLS COULD FIRE OVER THE
MTNS. SEVERE AND HEAVY RAIN CONCERNS ARE LOW AND SIMILAR TO
FRIDAY...AS EVEN THE MORE UNSTABLE NAM SHOWS SBCAPE VALUES MOSTLY
REMAINING UNDER 1000 J/KG...WITH GFS/SREF PROBS SUGGESTING MUCH LESS.
TEMPS WILL RISE A FEW DEGREES FURTHER...TOPPING OUT A CATEGORY OR TWO
ABOVE NORMAL.

SATURDAY NIGHT WARM UPGLIDE WILL RAMP UP OVER THE AREA IN ADVANCE OF
THE FRONT. PRECIP CHANCES SHOULD INCREASE GRADUALLY IN ALL ZONES THRU
12Z SUNDAY. A SMALL AMOUNT OF ELEVATED CONVECTION IS NOT OUT OF THE
QUESTION...BUT STRATIFORM RAIN LOOKS TO PREDOMINATE. MINS WILL AGAIN
BE 10-15 DEGREES ABOVE CLIMO.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 215 AM THU...WARM UPGLIDE WILL BE ONGOING ACRS THE AREA SUNDAY
MRNG A SFC WARM FRONT WILL ARRIVE SOMETIME DURING THE DAY...THE
TIMING A LITTLE UNCERTAIN AS THE 15/12Z EC BRINGS IT IN A BIT FASTER
THAN THE 16/00Z GFS. THE WARM FRONT WILL EXTEND FROM A SFC LOW OVER
IOWA AND VICINITY. THE GFS FEATURES A TIGHTER GRADIENT AROUND THE
LOW AND BRINGS A FAIRLY ROBUST 850MB JET ACROSS THE CWFA NEAR THE
FRONT. INSTABILITY WILL BE LIMITED DUE TO THE VERY DEEP MOISTURE
CHARACTERIZED BY PWAT VALUES NEARING 3 STANDARD DEVIATIONS ABOVE
CLIMO. EC IS MORE UNSTABLE POSSIBLY AS A RESULT OF IT PUTTING US IN
THE WARM SECTOR EARLIER IN THE DAY...AND ITS SHEAR PARAMETERS ONLY
LOOK MARGINAL FOR SEVERE WX. HEAVY RAIN LOOKS LIKELY TO BE AT THE
FOREFRONT ONCE AGAIN AS HIGH IMPACT WEATHER FOR THE AREA...WITH THE
GFS LLJ POTENTIALLY DRIVING SIGNIFICANT PRECIP EVEN LACKING MUCH
CONVECTION. THE SFC LOW WILL LIFT NWD BY EARLY MON AND BEGIN TO
OCCLUDE AS THE ASSOCIATED UPPER TROUGH REACHES MAXIMUM DEPTH. THE
COLD FRONT WILL SWING ACROSS MONDAY. GFS/EC SEEM TO AGREE ON A
DAYTIME PASSAGE AND SIGNIFICANT INSTABILITY AS HIGH AS 1500-2000
J/KG OVER THE PIEDMONT. DEEP LAYER SHEAR MAY BE ENOUGH TO GET SOME
FAIRLY ORGANIZED STORMS...THOUGH PROFILES ARE MOSTLY UNIDIRECTIONAL.
ON THE OTHER HAND PWAT VALUES WILL HAVE COME DOWN TO MORE MODEST
VALUES AND HEAVY RAIN LOOKS TO BE OF LESS CONCERN THAN SEVERE.
SUNDAY AND MONDAY LOOK TO BE A COUPLE OF RATHER ACTIVE DAYS.

BROAD UPPER TROUGH WILL SLOWLY PROGRESS EWD THRU THE MIDDLE OF NEXT
WEEK...KEEPING FAST BUT QUASI-ZONAL FLOW ON ITS SOUTHERN FRINGE. DRY
SFC HIGH PRESSURE WILL REMAIN OVER THE SOUTHEAST TUE-THU. THE TROUGH
SHEARS OFF INTO A BLOCKING CUTOFF LOW OVER ONTARIO BY THE END OF THE
PERIOD WED NIGHT. GFS DEPICTS ANOTHER WEAK SFC LOW CROSSING THE OH
VALLEY AT THAT TIME...AND DEEP MOISTURE RETURNING TO OUR AREA AHEAD
OF IT.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...DEEP LAYER MOISTURE HAS GENERALLY MOVED EAST OF THE
AIRFIELD...WITH DEPARTING SHOWERS GIVING WAY TO PERSISTENT LIGHT
RAIN AND DRIZZLE IN THE WEAK UPGLIDE OVER THE CAD LAYER. THIS SETUP
WILL CHARACTERIZE THE WEATHER THROUGH THE TAF PERIOD. ANTICIPATE
VARYING CIGS BETWEEN UPPER END IFR AND LOWER END MVFR...WITH DRIZZLE
AND OCCASIONAL MVFR FOG. STEADY NE SFC WINDS AROUND 10 KT WILL SEE
OCCASIONAL GUSTS INTO THE UPPER TEENS...ESPECIALLY DURING THE LATE
MORNING HOURS.

ELSEWHERE...ABUNDANT LOW LEVEL MOISTURE AND CONTINUED WEAK UPGLIDE
WILL PRODUCE FAIRLY WIDESPREAD LIGHT RAIN AND DRIZZLE ACROSS THE
TERMINAL FORECAST AREA THROUGH THE PERIOD. EXPECT MOSTLY IFR CIGS
AND MVFR VSBY...BUT CONDITIONS WILL IMPROVE A CATEGORY OR SO FROM
TIME TO TIME...ESPECIALLY DURING THE DAYLIGHT HOURS. SFC WINDS WILL
BE STEADY NE IN CONTINUED COLD AIR DAMMING...EXCEPT SE AT KAVL INTO
THE FRENCH BROAD VALLEY. A FEW LOW END GUSTS WILL BE POSSIBLE FROM
TIME TO TIME AT THE FOOTHILL TAF SITES.

OUTLOOK...THE WEDGE WILL SLOWLY BREAK UP ON FRIDAY...WITH BRIEFLY
DRIER WEATHER POSSIBLY LINGERING INTO SATURDAY. DEEPER MOISTURE WILL
RETURN ALONG A WARM FRONT SAT NIGHT THROUGH SUNDAY...WITH HEAVY
RAINFALL AND WIDESPREAD RESTRICTIONS LIKELY ONCE AGAIN.
THUNDERSTORMS WILL THEN BE POSSIBLE THROUGH MONDAY AS A COLD FRONT
REACHES THE AREA FROM THE WEST.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       MED   68%     HIGH  96%     HIGH  98%     HIGH  90%
KGSP       HIGH  80%     HIGH  90%     HIGH 100%     HIGH  90%
KAVL       MED   74%     HIGH  82%     HIGH  94%     HIGH  80%
KHKY       LOW   58%     HIGH  88%     HIGH  93%     HIGH  90%
KGMU       MED   79%     HIGH  90%     HIGH 100%     HIGH  90%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  96%

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...WIMBERLEY
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...HG


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