Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 021823
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
223 PM EDT MON MAY 2 2016

.SYNOPSIS...
A WARM AND HUMID AIRMASS WILL PERSIST AHEAD OF A COLD FRONT
APPROACHING FROM THE NORTHWEST THROUGH TONIGHT. THIS FRONT WILL
SLOWLY CROSS THE AREA ON TUESDAY. ANOTHER COLD FRONT WILL CROSS THE
REGION ON THURSDAY AND BRING A COOLER AND DRIER AIR MASS FROM CANADA
THAT SHOULD PERSIST INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 150 PM...AS EXPECTED...THE REGION IS SEEING CONVECTION
POPPING UP ON RADAR IMAGERY...AS SBCAPE HAS INCREASED TO 1500-2500
J/KG AND CONVECTIVE TEMPS HAVE BEEN MADE. FORCING IS STILL SUBTLE
OVERALL...BUT WILL INCREASE AS THE AFTN AND EVENING PROGRESSES.
THE RAP SHOWS 0-6 KM BULK SHEAR AROUND 20-30 KTS...WITH 30-40 KTS
ALONG THE I-40 CORRIDOR. IN THAT AREA...THE SHEAR AND INSTBY WILL
COMBINE FOR A BETTER SEVERE STORM THREAT...WITH SUPERCELL-LIKE
STORMS POSSIBLE. SO A SEVERE THUNDERSTORM WATCH WILL BE ISSUED
FROM BUNCOMBE COUNTY NORTH AND EAST UNTIL 10 PM THIS EVENING. TO
THE SOUTH...GIVEN THE STRONG INSTBY...EXPECT AT LEAST A FEW SEVERE
STORMS WILL BE POSSIBLE THIS AS WELL.

THIS EVENING...GUIDANCE IN GOOD AGREEMENT THAT A COLD FRONT WILL
PUSH INTO THE NC MTNS FROM THE WEST...WHILE AN AREA OF DECENT UPPER
DIVERGENCE WILL SET UP WITHIN A RIGHT ENTRANCE REGION OF A JET
STREAK. FORECAST SOUNDINGS SHOW LINGERING ELCAPE OF 800-1500 J/KG
WITH IMPROVING SHEAR. CAMS AREA ALSO IN GOOD AGREEMENT ON A MAXIMUM
OF CONVECTIVE COVERAGE THIS EVENING. SO POPS ARE MAXIMIZED IN THE
LIKELY TO CATEGORICAL RANGE FROM 0-6Z...THEN START TO TAPER OFF FROM
WEST TO EAST THRU DAYBREAK. LOW TEMPS WILL BE ABOUT 10 DEGREES ABOVE
NORMAL.

TUESDAY...THE ENTRANCE REGION OF THE UPPER JET WILL SHIFT EAST...BUT
PERIODS OF MID-UPPER LEVEL DPVA WILL CONTINUE AS A POSITIVELY TILTED
TROUGH MAKES LITTLE PROGRESS EAST ACROSS THE MID MS VALLEY. A SFC
COLD FRONT WILL STALL ALONG THE BLUE RIDGE IN THE MORNING...AND
LIKELY BE A FOCUS FOR ANOTHER ROUND OF AFTN SHOWERS AND
THUNDERSTORMS...MAINLY ALONG AND EAST OF I-85. BULK SHEAR LOOKS
BETTER THAN MONDAY...BUT THE BETTER CAPE WILL BE TO THE EAST AS DRY
AIR STARTS TO WORK IN FROM THE WEST. A DAY 2 MARGINAL SEVERE RISK IS
JUST TO OUR EAST. TEMPS WILL BE ABOUT 5-10 DEG ABOVE NORMAL UNDER
PARTLY CLOUDY SKIES.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 330 AM EDT MONDAY...IT LOOKS LIKE THE SHORT RANGE PART OF THE
FORECAST HOLDS A CHANGE IN THE PATTERN WHICH WILL PUT AN END TO OUR
RECENT ACTIVE WEATHER REGIME. ON TUESDAY...A SURFACE WAVE SHOULD
MOVE AWAY TO THE NORTHEAST ALONG THE COLD FRONT...WHICH COMBINED
WITH A DIGGING UPPER TROF SHOULD HELP TO SLOWLY PUSH THE BOUNDARY
ACROSS THE FORECAST AREA DURING THE DAY. UPPER FORCING WILL BE WEAK
AND LOW LEVEL FLOW GRADUALLY COMES AROUND TO SOMETHING MORE
WESTERLY...WHICH DOES NOT SUGGEST MUCH IN THE WAY OF PRECIP
COVERAGE. WE MAY BEGIN THE PERIOD WITH SCATTERED PRECIP COVERAGE BUT
WITH THE BOUNDARY MOVING IN FROM THE WEST DURING THE DAY...PRECIP
PROB DIMINISHES AND MOVES EASTWARD WITH TIME. THE FCST REFLECTS THIS
DOWNWARD TREND...ESPECIALLY TUESDAY NIGHT WHEN THE BOUNDARY SHOULD
BE TO OUR EAST. IN SPITE OF THE BETTER FORCING ASSOCIATED WITH THE
INITIAL SHORT WAVE MOVING THROUGH...THIS MID/UPPER SYSTEM HAS LITTLE
IN THE WAY OF MOISTURE...THUS PRECIP CHANCES WERE CUT BACK IN MOST
PLACES. WILL HOLD ONTO SOME LINGERING CHANCE OVER THE EASTERN ZONES
IN THE EVENING...BUT THIS WILL TRANSITION TO A SMALL CHANCE ONLY
NEAR THE TN BORDER EARLY WEDNESDAY MORNING. ON WEDNESDAY...THE
MODELS SUGGEST A RELATIVE LULL BEFORE THE ARRIVAL OF THE NEXT WAVE
AND THE ACCOMPANYING MOISTURE DROPPING DOWN AROUND THE UPPER LOW
FROM THE NW. THIS SYSTEM SHOULD ARRIVE LATE IN THE DAY...ACCOUNTING
FOR AN INCREASE IN PRECIP CHANCES NEAR THE TN BORDER. SOME SHOWER
ACTIVITY COULD BREAK CONTAINMENT AND MOVE OUT OVER THE PIEDMONT IN
THE EVENING WITH THE PASSAGE OF THE MAIN VORT CENTER. IN ITS
WAKE...PRECIP CHANCES TAPER BACK TO THE NW FLOW UPSLOPE AREAS EARLY
THURSDAY MORNING. TEMPS WILL BE NEAR NORMAL TUESDAY AS THE FRONT
PASSES...WITH A COOL-DOWN BEGINNING ON WEDNESDAY WITH THE INITIAL
WAVE.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 410 AM MONDAY...THE MAIN STORY FOR THE LATE PART OF THE WEEK
WILL BE THE BIG COOL-DOWN EXPECTED FOR THURSDAY AS A DEEP UPPER LOW
ROLLS DOWN FROM THE GT LAKES AND ACROSS THE MID-ATLANTIC REGION. THE
MODELS HAVE A COOLER TREND FOR HIGH TEMPS ON THURSDAY SO ABOUT A
CATEGORY WAS CUT OFF...WHICH WILL BRING TEMPS DOWN TO SOMETHING ON
THE ORDER OF TEN DEGREES BELOW NORMAL. PRECIP CHANCES SHOULD EXPAND
OUTWARD FROM THE TN BORDER DURING THE DAY WITH STEEP LOW LEVEL LAPSE
RATES SUPPORTING SHALLOW CONVECTIVE SHOWERS MAINLY OVER THE NC
FOOTHILLS AND PIEDMONT...PERHAPS LASTING INTO THE EARLY EVENING
BEFORE DIMINISHING WITH THE LOSS OF HEATING. A CHANCE OF SHOWERS
WILL PERSIST ALONG THE TN BORDER RIGHT THROUGH FRIDAY MORNING. WITH
THE COLDEST AIR AT MID LEVELS DRIFTING OVERHEAD EARLY THURSDAY...
CANNOT RULE OUT A FEW WET SNOWFLAKES AT ELEVATIONS ABOVE 6K FEET.
ISOLATED SHOWERS COULD DEVELOP ONCE AGAIN OVER THE NC FOOTHILLS AND
PIEDMONT ON FRIDAY AFTERNOON. TEMPS WILL BEGIN TO MODERATE FROM
FRIDAY INTO THE WEEKEND. FOR THE WEEKEND...THE UPPER PATTERN REMAINS
SLOWLY PROGRESSIVE WITH THE EASTERN UPPER LOW MOVING OFF THE EAST
COAST AND AN UPPER RIDGE BUILDING IN FROM THE WEST. THIS WILL
SUPPORT HIGH PRESSURE AT THE SURFACE THAT SHOULD SPELL DRY WEATHER
WITH TEMPS GRADUALLY RETURNING TOWARD NORMAL.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
AT KCLT...THUNDERSTORM ACTIVITY IS BEGINNING TO PICK UP RAPIDLY THIS
AFTN...WITH NUMEROUS SHOWERS AND STORMS EXPECTED BY LATE AFTN. GIVEN
THE SHOTGUN APPEARANCE ON RADAR...TIMING WHEN CELLS WILL IMPACT
STILL TOO UNCERTAIN...SO WILL GO WITH FOUR HOUR TEMPO FROM 18-22Z.
THE INSTBY IS FAIRLY ROBUST...SO GUSTY WINDS AND/OR HAIL THREAT WILL
EXIST WITH THE AFTN ACTIVITY. LATER THIS EVENING...STORMS FROM THE
WEST ARE EXPECT TO CROSS THE AREA...AS MOISTURE AND FORCING SHOULD
SUPPORT CONVECTION WELL PASSED SUNSET. WILL CONTINUE THE PREVAILING
TSRA WITH LOWERING CIGS TO MVFR. CONVECTION SHOULD BEGIN TO TAPER
OFF IN THE 6-9Z TIME FRAME. LOW CLOUDS WILL BEGIN TO LIFT LATE
TUESDAY MORNING. WINDS WILL FAVOR A SW DIRECTION THRU THE
PERIOD...WITH A FEW LOW-END GUSTS POSSIBLE THIS AFTN...BUT MAINLY
GUSTS WILL BE WITH CONVECTION.

ELSEWHERE...SIMILAR TO KCLT ABOVE. HAVE VCTS AND/OR TEMPO FOR TSRA
THIS AFTN...AS RADAR ECHOES ARE BLOSSOMING QUICKLY. MORE STORMS WILL
ENTER THE AREA FROM THE WEST THIS EVENING...WITH MOISTURE AND
FORCING SUPPORTING CONVECTION WELL PAST SUNSET. PREVAILING TSRA AND
PROB30 FOR TS THRU MOST OF THE NIGHT. CONVECTION SHOULD TAPER OFF
FROM WEST TO EAST DURING THE PRE-DAWN HOURS. WINDS WILL FAVOR A S TO
SW DIRECTION THRU THE PERIOD...EXCEPT SWITCHING TO NW AROUND 6Z AT
KAVL AS A FRONT PUSHES IN FROM THE WEST. THE FRONT IS EXPECTED TO
GET HUNG UP ALONG THE BLUE RIDGE THRU 18Z TUESDAY. AS FOR FOG AND/OR
STRATUS...GUIDANCE IS MIXED...BUT I EXPECT THAT IF WE GET WIDESPREAD
RAIN OVERNIGHT AND SOME CLEARING OF MID CLOUDS AND PRECIP ENDS
BEFORE DAYBREAK...MAY SEE MORE IFR OR LOWER RESTRICTIONS. WILL GO
WITH MVFR FOR NOW. CIGS WILL BEGIN TO LIFT LATE TUESDAY MORNING.

OUTLOOK...AFTN SHRA/TSRA EXPECT AGAIN TUESDAY...BUT MOSTLY EAST OF
THE MTNS. DRY AIR WILL WORK IN FROM THE WEST TUESDAY NIGHT THRU
WEDNESDAY. A STRONG UPPER LOW WILL SWING THRU THE AREA WED NIGHT
THRU THU...AND WILL BRING SHRA AND TSRA MAINLY TO THE MTNS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  98%     HIGH  86%     HIGH  80%
KGSP       HIGH 100%     HIGH  91%     MED   71%     HIGH  83%
KAVL       HIGH 100%     HIGH  80%     MED   75%     HIGH  81%
KHKY       HIGH 100%     HIGH  91%     HIGH  85%     HIGH  80%
KGMU       HIGH 100%     HIGH  89%     MED   70%     HIGH  84%
KAND       HIGH 100%     HIGH  87%     MED   62%     HIGH  86%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

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

&&

$$
SYNOPSIS...HG
NEAR TERM...ARK
SHORT TERM...PM
LONG TERM...PM
AVIATION...ARK



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