Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 031809
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
209 PM EDT TUE MAY 3 2016

.SYNOPSIS...
A COLD FRONT WILL MOVE SLOWLY ACROSS THE REGION TODAY. A COOLER AND
DRIER AIR MASS WILL MOVE IN BEHIND THE FRONT ON WEDNESDAY. ANOTHER
COLD FRONT WILL CROSS THE REGION ON WEDNESDAY NIGHT AND WILL USHER
IN A MUCH COOLER AIR MASS FROM CANADA FOR THE END OF THE WORK WEEK.
HIGH PRESSURE SHOULD RETURN WITH A WARMING TREND FOR THE BALANCE OF
THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 200 PM...SCATTERED CONVECTION HAS FIRED ACROSS THE EASTERN
BLUE RIDGE ESCARPMENT...FAVORING AN AREA OF ENHANCED CONVERGENCE
ROUGHLY ALONG THE NC/SC BORDER. THE CAMS ARE IN GENERAL AGREEMENT ON
THIS ACTIVITY AFFECTING THE CHARLOTTE METRO AREA LATER THIS AFTN. SO
HAVE LIKELY POPS THERE. THE REST OF THE CWFA LOOKS TO SEE MAINLY
ISOLATED TO SCATTERED CONVECTION AS FORCING IS WEAK TO MODEST AND
CAPE IS ONLY 1000-1500 J/KG. STILL...BULK SHEAR IS SUPPORTIVE FOR
THE STRONGEST CELLS TO GAIN ROTATING UPDRAFTS. THE POTENTIAL FOR A
COUPLE SEVERE STORMS IS MAINLY ACROSS THE I-77 CORRIDOR THIS AFTN TO
EARLY EVENING.

LATER TONIGHT...A COLD FRONT SHOULD PUSH EAST OF THE AREA...AND 850
MB FLOW WILL PICK UP OUT OF THE NW. DRIER AIR WILL WORK IN AND
SHOULD CUT OFF POPS TO JUST ALONG THE TN BORDER THANKS TO UPSLOPE BY
DAYBREAK WEDNESDAY. THIS WILL BE IN SPITE OF A MORE POTENT SHORTWAVE
TROF APPROACHING FROM THE WEST AS IT ROUNDS THE BASE OF THE LONG
WAVE TROF OVER THE OH/TN VALLEYS. BOTH THE GFS AND NAM SHOW
LINGERING MID LEVEL MOISTURE...SO I EXPECT THIS WAVE WILL AT LEAST
FORCE A FAIR AMOUNT OF MID LEVEL CLOUDINESS OVERNIGHT. TEMPS WILL
RUN A CATEGORY OR TWO ABOVE NORMAL.

WEDNESDAY...ANOTHER POTENT SHORTWAVE WILL DIVE THRU THE LONGWAVE
TROF AXIS...SHARPENING THE TROF AND CLOSING OFF AN UPPER LOW BY END
OF THE DAY OVER THE OHIO VALLEY. A SECONDARY COLD FRONT ASSOCIATED
WITH THIS ENERGY WILL BE KNOCKING ON THE DOOR OF THE NC MTNS BY 00Z
THU. THE FRONT WILL HAVE SOME MOISTURE WITH IT...AND POPS WILL START
TO RAMP UP ALONG THE TN/NC BORDER DURING THE DAY. EAST OF THE
MTNS...MID CLOUDS ARE EXPECTED TO THIN OUT RESULTING IN A PARTLY TO
MOSTLY SUNNY DAY. HOWEVER...THICKNESSES FALL SHARPLY FROM PREVIOUS
DAY...SO TEMPS WILL BE NOTICEABLY COOLER WITH LESS HUMIDITY. HIGHS
WILL BE AT OR SLIGHTLY BELOW NORMAL.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 130 AM EDT TUESDAY...THE BIG STORY FOR THE LATTER HALF OF THE
WEEK WILL BE THE BIG COOL DOWN COURTESY OF A DEEP UPPER LOW THAT
ROLLS DOWN FROM THE GT LAKES AND ACROSS THE WESTERN CAROLINAS ON
THURSDAY. NOT EXACTLY BLACKBERRY WINTER...AS IT DOES NOT APPEAR THAT
LOW TEMPS WILL GET ANYWHERE NEAR RECORDS...BUT UNSEASONABLY COOL
NONETHELESS. WE BEGIN ON WEDNESDAY MORNING IN A RELATIVE LULL AS A
DRY SLOT CROSSES THE FCST AREA IN THE WAKE OF AN INITIAL VORT LOBE.
THE LACK OF FORCING AND MOISTURE SHOULD MAKE IT DIFFICULT FOR PRECIP
TO DEVELOP...SO PRECIP CHANCES WERE BROUGHT DOWN BELOW 15 PCT THRU
MOST OF THE MORNING HOURS. THE MODELS ARE IN DECENT AGREEMENT OF
BRINGING THE MAIN VORT CENTER DOWN FROM THE NW AS THE UPPER LOW
APPROACHES ON WEDNESDAY AFTERNOON. EXCELLENT FORCING AND DEEP
MOISTURE SHOULD REACH THE MTNS AROUND MIDDAY SO PRECIP CHANCES GO UP
FROM THERE. THE PASSAGE OF THE VORT CENTER ACROSS THE FCST AREA
SHOULD FORCE SHOWERS TO BREACH THE MTNS AND MOVE OUT E OF THE BLUE
RIDGE MAINLY WEDNESDAY EVENING. AFTER THE VORT PASSES...PRECIP
PRODUCTION SHOULD SCALE BACK TO THE UPSLOPE AREAS ON THE TN BORDER
FOR THE REST OF THE NIGHT AND EARLY THURSDAY MORNING. THE UPPER LOW
CENTER IS EXPECTED TO CROSS THE FCST AREA DURING THE DAY ON
THURSDAY. AS THIS HAPPENS...THE COLD POOL ALOFT WILL MOVE OVERHEAD
AND RESULT IN VERY STEEP LOW LEVEL LAPSE RATES. CONVECTION SHOULD
BREAK OUT DURING THE AFTERNOON ACROSS THE ENTIRE FCST AREA. FCST
SOUNDINGS SHOW A WET BULB ZERO AROUND 5K FEET...SO SMALL HAIL WILL
PROBABLY REACH THE GROUND IN THE STRONGER CONVECTION. HIGH TEMPS
WILL BE ON THE ORDER OF 10 TO 15 DEG BELOW NORMAL. THE CONVECTIVE
ACTIVITY SHOULD TAPER OFF WITH LOSS OF HEATING...AND PRECIP CHANCES
WILL ONCE AGAIN TAPER BACK TO THE NW FLOW UPSLOPE AREAS ON THE TN
BORDER THROUGH EARLY FRIDAY MORNING. THE COLDEST TEMPS WILL BE
THURSDAY NIGHT...WITH LOW TEMPS ON THE ORDER OF 5 TO 10 DEG BELOW
NORMAL...REACHING THE MID/UPPER 30S IN PARTS OF THE NC MTNS.
HOWEVER...LINGERING CLOUD COVER AND STRONG NW WINDS WILL PROBABLY
PRECLUDE ANY FROST...AND TEMPS WILL NOT BE COLD ENUF FOR AN
ADVECTIVE FREEZE. THE PRECIP CHANCES SHOULD DIMINISH ON FRIDAY AND
TEMPS WILL REBOUND A BIT AS THE UPPER LOW SPINS SLOWLY AWAY ALONG
THE MID-ATLANTIC COAST. SOME LINGERING PRECIP CHANCE IS WARRANTED
OVER THE NRN MTNS...AND PERHAPS E OF I-77 CLOSER TO THE DEPARTING
COLD AIR ALOFT.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 245 AM EDT TUESDAY...THE LATEST OPERATIONAL MODEL GUIDANCE
SUGGESTS THAT THE NEXT CLOSED LOW DROPPING DOWN ACROSS THE GT LAKES
AND ERN CANADA LATE IN THE WEEKEND MIGHT BE A BIT DEEPER THAN
PREVIOUSLY INDICATED...AND IN RESPONSE THE MODEL GUIDANCE PUSHES A
SFC BOUNDARY FARTHER S INTO THE WESTERN CAROLINAS. THE CONSENSUS OF
THE GUIDANCE STILL ONLY SHOWS A SLIGHT CHANCE OF PRECIP OVER THE NRN
ZONES ON SUNDAY INTO MONDAY...WHICH IS HARDLY COMPELLING ENOUGH TO
CHANGE AN ONGOING DRY FCST. HOWEVER...IT NOW APPEARS THAT OUR
WEATHER MIGHT NOT BE QUITE AS FAIR LATE IN THE PERIOD THAN
PREVIOUSLY THOUGHT. NO SIGNIFICANT CHANGES WERE MADE OVERALL...JUST
SOME TWEAKS TO PRECIP CHANCES OVER THE NRN PART OF THE FCST AREA.
TEMPS STILL LOOK LIKE THEY WILL CONTINUE TO RECOVER TOWARD NORMAL
OVER THE WEEKEND...BUT IF THE FRONT CONTINUES ITS SWD TREND IN THE
GUIDANCE...WE MIGHT NOT BE SEEING THE ABOVE NORMAL TEMPS CURRENTLY
CARRIED EARLY NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...CONVECTION IS FIRING ACROSS THE NC ESCARPMENT AND TRACKING
EAST...WITH THE MAIN TSTM MAKING A BEELINE FOR KCLT. TIMING THE
STORM...EXPECT IT TO BE IN THE VICINITY IN THE 19-21Z TIME FRAME.
OTHER THAN VARIABLE WIND GUSTS ASSOCIATED WITH THE
CONVECTION...WINDS SHOULD FAVOR A SW DIRECTION THRU ABOUT 02Z...WITH
A COLD FRONT SHOULD PASS TO THE EAST. THEN WINDS SWITCH TO NW FOR THE
REST OF THE PERIOD...INCREASING TO 6 KT OR MORE BY MIDDAY WEDNESDAY.
CONDITIONS ARE EXPECTED TO BE VFR OTHER THAN WITH THE TSRA...WITH
LINGERING LOW VFR CIGS OVERNIGHT...SCATTERING OUT AFTER DAYBREAK
WEDNESDAY.

ELSEWHERE...CONVECTION IS FAVORING A SUBTLE BOUNDARY ROUGHLY ALONG
THE NC/SC BORDER...WITH ONLY ISOLATED TO SCATTERED SHRA/TSRA
EXPECTED ELSEWHERE THE REST OF THE AFTN. A COLD FRONT WILL EXIT TO
THE EAST EARLY THIS EVENING...WITH DRYING NWLY FLOW TAKING OVER THE
AREA FOR THE REST OF THE PERIOD. MOISTURE WILL LINGER FOR VFR CIGS
MAINLY IN THE NC FOOTHILLS/PIEDMONT...AND MVFR CIGS WORKING UP THE
VALLEY TO KAVL. THERE MAY BE SOME PATCHY FOG AROUND ANY SITES THAT
RECEIVE SOME RAIN THIS AFTN/EVE THEN SEE WINDS GO LIGHT WITH
CLEARING SKIES. BUT OVERALL...NOT EXPECTING MUCH FOG TONIGHT. CLOUDS
SHOULD SCATTER OUT AFTER DAYBREAK WEDNESDAY...AS DRIER AIR FILTERS
IN FROM THE NW.

OUTLOOK...A STRONG UPPER LOW WILL SWING THRU THE AREA WED NIGHT THRU
FRIDAY...AND WILL BRING SHRA AND TSRA MAINLY ACROSS THE NC SITES
BOTH THU AND FRI AFTN.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  94%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  83%     MED   76%     HIGH  95%
KHKY       HIGH  80%     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 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/WJM



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