Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010007
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
807 PM EDT THU APR 30 2015

.SYNOPSIS...
AS A LOW PRESSURE SYSTEM GRADUALLY MOVES OFFSHORE TONIGHT AND
TOMORROW...DRIER AIR WILL OVERSPREAD THE REGION AND REMAIN IN PLACE
THROUGH EARLY NEXT WEEK. THIS PATTERN WILL BE SLOW TO CHANGE AND
WILL FAVOR MOSTLY DRY AND MILD CONDITIONS THROUGH MID WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 8 PM...DISORGANIZED AREA OF SHOWERS IS CURRENTLY MOVING OFF
THE HIGH TERRAIN...FOLLOWING THE PREVIOUS BAND/S TREND OF DISPLAYING
A GENERAL WEAKENING/CONTINUED DISORGANIZATION TREND AS IT ENCOUNTERS
THE DOWNSLOPE FLOW OFF THE BLUE RIDGE. POPS WILL THEREFORE BE
MAINTAINED AT LIKELY FOR ANOTHER COUPLE OF HOURS ACROSS THE MTNS...
AND IN THE CHANCE RANGE OUTSIDE THE MTNS...BUT AS LOW LEVEL LAPSE
RATES CONTINUE TO WEAKEN AND WHAT LITTLE BUOYANCY IS AVAILABLE IN
THE ENVIRONMENT WANES...SHOWER CHANCES SHOULD DIMINISH QUITE A BIT
OVER THE NEXT FEW HOURS. GUSTY WINDS WILL REMAIN POSSIBLE WITH SOME
OF THE HEAVIER SHOWER CORES.

AS OF 425 PM...THE FIRST REAL BAND OF SHOWERS ASSOCIATED WITH UPPER
LOW/COLD POOL AND NW FLOW IS PROGRESSING ACROSS THE NC MTNS ATTM.
IT/S NOT ABUNDANTLY CLEAR HOW THIS ACTIVITY WILL RESPOND TO THE
ONGOING DOWNSLOPE FLOW EAST OF THE BLUE RIDGE...SO WHILE POPS HAVE
BEEN INCREASED ACROSS THE NC FOOTHILLS...THEY HAVE BEEN MAINTAINED
IN THE 50-60 PERCENT RANGE. THE PRIMARY ADJUSTMENT TO THE FORECAST
FOR THE REMAINDER OF THE AFTERNOON HAS BEEN TO TEMPER THE THUNDER
MENTION...AS COVERAGE OF DEEPER CONVECTION HAS BEEN ISOLATED AT
BEST THUS FAR...AND IS UNLIKELY TO CHANGE BASED UPON THE RATHER
SHALLOW NATURE OF BUOYANCY PROFILES. WE WILL GENERALLY MENTION
SCATTERED TS ACROSS THE MTNS...AND ISOLATED TO THE EAST. HAVING SAID
THAT...THERE WILL PROBABLY BE QUITE A BIT OF SMALL HAIL THIS
AFTERNOON...AS FREEZING LEVELS ARE BELOW 10 KFT...AND WILL ONLY FALL
MORE AS THE UPPER LOW DRAWS NEARER. SOME GUSTY WINDS WILL ALSO
LIKELY BE SEEN IN LIGHT OF LOW LEVEL LAPSE RATES GREATER THEN 9 C/KM
AND SURFACE DEWPOINT DEPRESSIONS OF AROUND 30 DEGREES.

AS OF 225 PM EDT THU...A CLOSED 500 MB LOW SPINNING OVER THE OHIO
VALLEY WILL MOVE SE ACROSS THE APPALACHIANS TONIGHT. AHEAD OF THIS
SYSTEM...REGIONAL RADAR COVERAGE HAS INCREASED FROM SE KY TO THE SRN
APPALACHIANS. THE LATEST HRRR MODEL RUNS INDICATE SEVERAL ROUNDS OF
SCATTERED CONVECTION CROSSING THE REGION THROUGH THE EVENING
HOURS...IMPACTING LOCATIONS FARTHER S WITH TIME AS A COLD FRONT
PUSHES THROUGH THE AREA. STEEP MID LEVEL LAPSE RATES AROUND 7 DEG
C/KM OR BETTER WILL TRAVERSE THE AREA WITH THE UPPER COLD
POCKET...ESPECIALLY THE INTERSTATE 40 CORRIDOR. IN ADDITION...
FREEZING LEVELS AT OR BELOW 8 KFT WILL CONTRIBUTE TO SMALL HAIL
POTENTIAL WITH ANY BETTER CONVECTIVE ELEMENTS. SHEAR COULD BE A BIT
BETTER IN SRN SECTIONS THIS EVENING...BUT THE WIND DOES NOT APPEAR
TO POSE MUCH THREAT GIVEN THE LIMITED DCAPE AND SHALLOW TOPS. THE
HWO MENTION ADVERTISING SMALL HAIL WITH ANY THUNDER WILL BE
MAINTAINED.

THE COLD CORE LOW WILL PASS OVERHEAD TONIGHT...WITH SOME MEASURE OF
NW FLOW MOISTURE PERSISTING ALONG THE SPINE OF THE SRN APPALACHIANS
INTO FRI MORNING. CONTINUED MTN SHOWERS FROM STEEP LAPSE RATES WILL
BE THE MAIN CONCERN. ALTHOUGH 850 MB TEMPS SHOULD STAY JUST ABOVE
FREEZING...ANY BETTER SHOWER RATES COULD BRING SNOW LEVELS DOWN INTO
THE HIGHER TERRAIN. ANY SNOW ACCUMS SHOULD BE LIGHT AND CONFINED TO
THE RIDGE TOPS...BUT FLURRIES/RIME/GRAUPEL UNDER ANY HEAVIER SHOWERS
CANNOT BE RULED OUT DOWN INTO THE MTN VALLEYS. ALSO CANNOT RULE OUT
ISOLD ADVECTIVE FREEZE ACROSS THE HIGHEST PEAKS OVERNIGHT...BUT NO
WARNING PRODUCT SHOULD BE NEEDED.

THE CLOSED H5 LOW SHOULD MOVE OFF TO THE EAST FRI MORNING...WITH
DEEP LAYER NRLY FLOW IN PLACE ACROSS THE FORECAST AREA. MOISTURE IN
THE NRLY FLOW WILL AFFECT MAINLY THE FOOTHILLS AND PIEDMONT OF WRN
NC FRI. FAIRLY STEEP LAPSE RATES WILL KEEP THE SHOWER POTENTIAL
GOING THROUGH FRI. WILL FEATURE MAXES A BIT BELOW GUIDANCE CONSENSUS
GIVEN THE COLD AIR STRATOCUMULUS SKY COVER.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 200 PM THU...CLOSED UPPER LOW WILL MOVE FURTHER OUT OVER THE
ATLANTIC FRI NIGHT INTO SAT...AND AS HEIGHTS RISE IN ITS WAKE DRY
HIGH PRESSURE WILL FILL IN OVER OUR AREA. DIURNAL ACTIVITY FRI AFTN
DOES NOT APPEAR TO STAND MUCH CHANCE OF LASTING PAST 00Z SAT...SO A
DRY FCST FOR THE FRI NIGHT PERIOD LOOKS FINE. MIN/MAX TEMPS SATURDAY
WILL BE A COUPLE DEGREES BELOW CLIMO. SUBSIDENCE BENEATH THE HIGH
APPEARS TO BE ENOUGH TO STIFLE ANY DIURNAL CONVECTION SATURDAY EVEN
WITH A WEAK UPPER WAVE PASSING OVERHEAD. HOWEVER...BY SUNDAY THE HIGH
WILL HAVE SHIFTED TO THE SOUTHEAST COAST. THE SUBSIDENCE INVERSION IS
A BIT WEAKER AND LAPSE RATES BENEATH IT A BIT BETTER. WE ALSO LOOK TO
WARM A LITTLE MORE...MAXES RETURNING TO ABOUT CLIMO. LOW POPS ARE
SUGGESTED BY THE NAM/GFS INVOF THE BLUE RIDGE WHERE RELATIVELY
SHALLOW CONVECTION COULD FIRE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 100 PM THU...HIGH PRESSURE INITIALLY OVER THE EAST COAST SUNDAY
NIGHT WILL SHIFT EWD INTO A BERMUDA HIGH CONFIGURATION OVER THE
SUBSEQUENT FEW DAYS. UPPER HEIGHTS AND THICKNESSES GRADUALLY INCREASE
OVER THE SOUTHEAST AS A RESULT...SO WE CAN EXPECT TEMPS TO RISE A BIT
ABOVE NORMAL BY MIDWEEK. GULF FLOW WILL ALLOW AN UPWARD TREND IN
AFTERNOON INSTABILITY THRU THE PERIOD...SUGGESTING INCREASING POPS
EACH DAY. HOWEVER THEY REMAIN LOW ENOUGH TO MITIGATE SEVERE THREAT.

OPERATIONAL GFS/EC AS WELL AS MOST GEFS MEMBERS INDICATE AN INVERTED
TROUGH DEVELOPING ON THE SRN BOUNDARY OF THE BERMUDA HIGH BY LATE
TUE...WHICH DRIFTS NWD AND CLOSES OFF BY EARLY THU. THERE IS SOME
SPREAD ON HOW FAR WEST THIS FEATURE TRACKS...THE EC KEEPING IT NEAR
THE ATLANTIC COAST VICE THE GFS AND GEFS CONSENSUS TAKING IT E OF THE
BAHAMAS. IT APPEARS UNLIKELY TO BRING ANY PRECIP TO OUR AREA BASED ON
THE CURRENT PROGS.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT...ONE AREA OF SHOWERS IS MOVING EAST OF THE TERMINAL EARLY
THIS EVENING...WHILE ANOTHER IS BEGINNING TO PUSH OFF THE HIGH
TERRAIN TO THE WEST. THIS SECOND AREA OF SHOWERS HAS BEEN APPEARING
INCREASINGLY DISORGANIZED AS IT PUSHES QUICKLY EAST...SO WHILE SHOWER
CHANCES WILL REMAIN THROUGH ABOUT 03Z OR SO...FEEL THE PROBABILITY
IS LOW ENOUGH TO STICK WITH VCSH THROUGH THAT TIME. ANY SHOWERS THAT
DO PASS NEAR THE TERMINAL WILL POSE A CONTINUED RISK FOR BRIEF GUSTY
WINDS...PRIMARILY OUT OF THE N OR NW. OTHERWISE...NW WINDS ARE
EXPECTED TO GRADUALLY DIMINISH THIS EVENING...WHILE MID-LEVEL CLOUDS
AND/OR STRATOCUMULUS SHOULD LINGER IN THE 050-100 RANGE THROUGH MUCH
OF THE OVERNIGHT...IF NOT THROUGH MUCH OF THE PERIOD. SHOWERS MAY
DEVELOP ONCE AGAIN FRI AFTERNOON...BUT COVERAGE IS EXPECTED TO BE
CONSIDERABLY MORE LIMITED THAN TODAY.

ELSEWHERE...SHOWERS WILL REMAIN MOST LIKELY NEAR KAVL THIS
EVENING...WHERE A TEMPO FOR RA/GUSTY WINDS HAS BEEN INTRODUCED
THROUGH 02Z. VCSH SHOULD SUFFICE TO COVER THE SHOWER THREAT AT THE
REMAINING TERMINALS THIS EVENING. GUSTY WINDS WILL BE POSSIBLE WITH
ANY SHOWERS PASSING NEAR THE TERMINALS. OTHERWISE...NW WINDS WILL
PERSIST THROUGH THE OVERNIGHT...GRADUALLY DIMINISHING AT ALL
LOCATIONS EXCEPT KAVL...WHERE 10-15 KT WINDS SHOULD PERSIST. THIS
MOIST UP-VALLEY FLOW COULD RESULT IN BRIEF PERIODS OF MVFR CIGS
AFTER MIDNIGHT. ALL OTHER TERMINALS SHOULD EXPERIENCE VFR CONDITIONS
THROUGH THE PERIOD...WITH PERIODS OF STRATOCU AND/OR MID-LEVEL
CLOUDS IN THE 050-100 RANGE EXPECTED. SHOWERS MAY DEVELOP ONCE AGAIN
FRI AFTERNOON...BUT COVERAGE IS EXPECTED TO BE CONSIDERABLY MORE
LIMITED THAN TODAY.

OUTLOOK...DRY HIGH PRESSURE WILL GRADUALLY BUILD INTO THE AREA LATE
FRIDAY THROUGH THE WEEKEND. RETURN FLOW MOISTURE WILL ONLY SLOWLY
REDEVELOP EARLY NEXT WEEK.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  94%     HIGH  94%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     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...HG/JDL
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...JDL



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