Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 272103
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
503 PM EDT SAT JUN 27 2015

.SYNOPSIS...
A COLD FRONT WILL BE MOVING THROUGH THE AREA TONIGHT AND WILL BE
WELL EAST OF THE REGION BY SUNDAY. ANOTHER FRONT WILL APPROACH THE
REGION BY MID-WEEK AND WEAKEN ACROSS THE MOUNTAINS. THEREAFTER THE
REGION WILL STAY IN A WARM AND MOIST ENVIRONMENT WHICH WILL
SUPPORT ISOLATED TO SCATTERED SHOWER AND THUNDERSTORM COVERAGE
TYPICAL OF EARLY JULY.

&&

.NEAR TERM /THROUGH SUNDAY/...
445 PM UPDATE...PREFRONTAL ACTIVITY HAS MATURED INTO LINEAR SEGMENTS
NEAR THE NC/SC BORDER ON ACCOUNT OF THE APPRECIABLE SHEAR. AWAY FROM
THESE SEGMENTS COVERAGE HAS REMAINED FAIRLY STEADY. THERE STILL
APPEARS TO BE A WINDOW DURING WHICH NEW STORMS MAY BE ABLE TO
FORM...PROBABLY LASTING UNTIL SUNSET. IT DOES SEEM LIKELY THAT THE
COVERAGE WILL BE ENOUGH TO USE UP A LOT OF THE DIURNAL
INSTABILITY...SUCH THAT THE FRONT WILL NOT HAVE MUCH TO WORK WITH BY
THE TIME IT ARRIVES. MESO MODELS DEPICT THE FRONT COMING THROUGH
EARLIER THAN ITS CURRENT MOTION WOULD SUGGEST...AND GIVEN THE
PRESENT SHEAR WE CAN/T REALLY RULE OUT THE CLOSING OF THE CONVECTIVE
WINDOW...SO TO SPEAK...UNTIL THE FRONT COMES THRU. SO SLIGHT UPWARD
ADJUSTMENTS HAVE BEEN MADE TO THE EVENING POPS. TEMPS WERE ALSO
ADJUSTED GOING INTO THE EVENING...WITH OUTFLOW HAVING BROUGHT TEMPS
DOWN SUBSTANTIALLY OVER MUCH OF THE AREA. EVEN THE BEST VERIFYING
GUIDANCE HAS DONE A POOR JOB OF REFLECTING THIS...SO CONFIDENCE IS
LOW ON THE HRLY TEMP TRENDS.

PREVIOUS DISCUSSION...CONVECTION CONTINUES TO GRADUALLY INCREASE IN
COVERAGE AND INTENSITY THIS AFTERNOON...MAINLY ACROSS THE WESTERN
HALF OF THE FORECAST AREA...AND PARTICULARLY ACROSS NORTH GEORGIA
AND THE TENN VALLEY. THE COLD FRONT IS CURRENTLY DRAPED ACROSS
(ROUGHLY) THE CUMBERLAND PLATEAU...ACCOMPANIED BY A FINAL NARROW
LINE OF CONVECTION. STILL THINK THE /MAIN SHOW/ FOR OUR AREA WILL BE
WITH THE PRE-FRONTAL ACTIVITY AS IT CONTINUES TO MARCH EAST INTO A
MORE UNSTABLE AIRMASS...CHARACTERIZED BY SBCAPE VALUES IN THE
1500-2500 J/KG RANGE...WITH THE MOST BUOYANT AIR BEING ACROSS OUR
SOUTHERN AND EASTERN PIEDMONT AREAS. 0-6KM BULK SHEAR EXCEEDING 30
KTS WILL CONTINUE TO OVERSPREAD THE REGION THROUGHOUT THE
AFTERNOON...THUS THERE REMAINS A VERY GOOD CHANCE THAT ACTIVITY WILL
BEGIN TO ORGANIZE INTO CLUSTERS AND/OR LINES AS IT ENCOUNTERS THE
MORE ROBUST INSTABILITY. A COUPLE OF SUPERCELLS WILL ALSO BE
POSSIBLE...ESP IN THE HIGHER SHEARED ENVIRONS ACROSS OUR NC ZONES.
WITH FREEZING LEVELS HOVERING AROUND 15 KFT...DAMAGING DOWNBURSTS
STILL APPEAR TO BE THE PRIMARY THREAT...MAINLY WITH ORGANIZED
CLUSTERS...ALTHOUGH LARGE HAIL AND PERHAPS A BRIEF/WEAK TORNADO WILL
BE POSSIBLE WITH ISOLATED ROTATING STORMS.

BASED UPON THE ANOMALOUSLY STRONG DEEP LAYER FLOW...AND THE
POTENTIAL FOR OUTFLOW-DOMINATED CONVECTION...ACTIVITY SHOULD SWEEP
ACROSS THE AREA THROUGH THE AFTERNOON AND EARLY EVENING IN RATHER
QUICK FASHION. IN FACT...POPS DROP TO LESS THAN SLIGHT CHANCE ACROSS
ALL BUT THE SOUTHERN ZONES BY MIDNIGHT (SUSPECT THE NARROW
CONVECTIVE LINE ALONG THE FRONT WILL TEND TO PETER OUT...ESP AS THE
ATMOSPHERE OVER OUR AREA GETS INCR OVERTURNED BY THE PRE-FRONTAL
ACTIVITY). AS COOLER AND MUCH DRIER AIR FILTERS INTO THE REGION
BEHIND THE FRONT LATE TONIGHT...TEMPS SHOULD COOL TO NEAR-NORMAL
LEVELS.

SUNDAY WILL BE ABOUT AS FINE A LATE-JUNE DAY AS ONE SEES IN THE
SOUTHEAST...MAINLY OWING TO THE MUCH DRIER AIR. IN FACT...DEWPOINTS
WILL LIKELY MIX OUT TO THE LOWER/MID 50S IN MANY AREAS OUTSIDE THE
MTNS...AND POSSIBLY THE 40S ACROSS THE HIGHER TERRAIN. ALTHOUGH
TEMPS ARE EXPECTED TO ONLY BE A CATEGORY OR SO BELOW CLIMO...
CONSIDERING HOW HOT IT/S BEEN OVER THE PAST TWO WEEKS...IT WILL
PROBABLY FEEL LIKE AUTUMN TO MOST FOLKS.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AT 230 PM EDT SATURDAY... OVERALL BIG PICTURE CONTINUES TO INDICATE
AN ANOMALOUS UPPER AIR PATTERN...WITH HIGH AMPLITUDE RIDGING ACROSS
THE WESTERN CONUS AND TROFFING IN THE EAST.

DURING THIS PART OF THE FORECAST CYCLE WE SHOULD MAINTAIN A NWLY TO
WESTERLY FLOW ALOFT. A WEAK BUBBLE OF SURFACE HIGH PRESSURE WILL
MIGRATE THROUGH OUR FORECAST AREA SUNDAY NIGHT AND MONDAY WITH QUIET
WEATHER CONDITIONS ON TAP.

ENERGY DROPPING SEWD MONDAY NIGHT...FROM THE UPPER MIDWEST AND
WESTERN GREAT LAKES...WILL REACH THE NC MOUNTAINS. DPVA COUPLED WITH
BACKING SURFACE-H85 FLOW (AN INCREASE IN MOISTURE)...WILL LEAD TO A
SMALL CHANCE OF SHOWERS OR THUNDERSTORMS. THIS SHOULD BE NOTED IN
THE WEE HOURS LATE MONDAY NIGHT/TUESDAY BEFORE DAYBREAK.

A TEMPORARY BACKING FLOW WILL THEN SET-UP THROUGHOUT OUR FA TUESDAY.
A SECONDARY COLD FRONT...ASSOCIATED WITH THE UPPER LEVEL ENERGY...
WILL EITHER WASH OUT OR BECOME ABSORBED IN A LEE TROUGH TYPE
CONFIGURATION. NEVERTHELESS...MOISTURE RAMPING UP...A SHOT OF ENERGY
SWIFTLY MOVING THROUGH THE REGION AND A WARM AIR ADVECTION PATTERN
SETTLING IN...WILL LEAD TO CHANCE POPS OVER OUR REGION.

RUNNING VARIOUS TOOLS FOR STABILITY INDICES SUGGEST THUNDER MENTION
OVER ALL OF OUR REGION DURING THIS EPISODE.

IN THE TEMPERATURE DEPARTMENT...H85 THERMAL PROFILE AND THICKNESS
LEVELS...ALL INDICATE A SLOW UPWARD TREND IN THE MAXIMUM AND MINIMUM
TEMPERATURES...AS WE MOVE OUT IN TIME EARLY IN THE NEW WORK WEEK.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AT 300 PM EDT SATURDAY...THE MEDIUM-RANGE PERIOD BEGINS ON TUESDAY
NIGHT WITH A DEEP MID-LEVEL RIDGE CENTERED OVER THE INTERMOUNTAIN
WEST AND CORRESPONDING MID-LEVEL TROUGH EXTENDING FROM THE HUDSON
BAY TO THE GULF COAST.  HOWEVER...DURING THE WEEK THE PATTERN SLOWLY
EVOLVES AS THE RIDGE CENTER RETROGRADES TOWARDS CA/NV WHILE THE
TROUGH AXIS SHIFTS WEST TOWARDS THE MS RIVER VALLEY.  MEANWHILE THE
ATLANTIC SUBTROPICAL RIDGE DEEPENS AND EXPANDS WEST TOWARDS THE EAST
COAST...PLACING THE LOCAL AREA IN WSW FLOW ALOFT BY THE END OF THE
PERIOD ON SUNDAY MORNING.

EMBEDDED WITHIN THE UPPER-LEVEL FLOW TUESDAY NIGHT IS A SHORTWAVE
WHICH WILL PIVOT AROUND THE LOWER GREAT LAKES AND THROUGH NEW
ENGLAND BY WEDNESDAY MORNING. AN ASSOCIATED WEAK COLD FRONT
APPROACHES FROM THE TN RIVER VALLEY INCREASING COVERAGE OF SHOWERS
AND THUNDERSTORMS THROUGH WEDNESDAY MORNING. THE FRONT DISSIPATES
OVER THE CAROLINAS ON WEDNESDAY.  THEREAFTER...AT LEAST A HALF DOZEN
NOTABLE SHORTWAVES PIVOT AROUND THE MEAN FLOW THROUGH THE PERIOD. AS
HAS BEEN THE STORY FOR THE PAST SEVERAL DAYS...MODEL GUIDANCE
DISAGREES ON THE TIMING AND POTENCY OF EACH SHORTWAVE...BUT THE
OVERALL IMPACT OF EACH SYSTEM ON OUR AREA WILL BE TO MAINTAIN CHANCE
POPS ACROSS THE AREA AND PERHAPS SUPPORT OVERNIGHT CONVECTION.

THROUGHOUT THE WORK WEEK...HIGH TEMPERATURES WILL REMAIN NEAR NORMAL.
WHILE THERE IS STILL PLENTY OF TIME FOR THE FORECAST TO CHANGE...THE
CURRENT OUTLOOK FOR THE INDEPENDENCE DAY WEEKEND CALLS FOR ISOLATED
TO SCATTERED DIURNAL CONVECTION WITH TEMPERATURES SLIGHTLY ABOVE
NORMAL.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
AT KCLT...LINEAR SEGMENTS OF STRONG CONVECTION WILL PROGRESS ACRS
THE PIEDMONT THRU SUNSET...WITH AN OUTSIDE CHANCE OF SHRA/TSRA UNTIL
COLD FROPA LATE IN THE EVENING. TEMPOS FOR TSRA WILL BE CARRIED FROM
21-00Z...WITH VCSH EITHER SIDE OF THIS PERIOD. TEMPO COULD EVEN BE
EXTENDED LATER IF CONVECTIVE COVERAGE IS SUFFICIENT UPSTREAM AT
SUNSET. GUSTY WINDS TO 30-35 KT AND IFR CONDITIONS WILL BE POSSIBLE
WITH STRONGER CELLS. THESE TRENDS WILL BE MONITORED FOR POTENTIAL
UPDATES. OTHERWISE...SW WINDS AT AROUND 10 KTS WILL CONTINUE INTO
THE EVENING...BECMG LIGHT BY MIDNIGHT. IN THE WAKE OF A COLD
FRONT...WINDS WILL THEN INCREASE OUT OF THE NW AT 5-10 KTS SUNDAY
MORNING.

ELSEWHERE...CONVECTIVE ACTIVITY WILL BE MOST INTENSE THRU SUNSET BUT
CHANCES DO NOT DIMINISH UNTIL AFTER FROPA THIS EVENING. TEMPOS FOR
TSRA...WITH MVFR CONDITIONS AND GUSTY WINDS...ARE CARRIED AT ALL
TERMINALS THIS AFTERNOON INTO EARLY EVENING. CONVECTION SHOULD BEGIN
TO WIND DOWN BY MID-EVENING...IF NOT SOONER. AS A COLD FRONT SWEEPS
ACROSS THE AREA TONIGHT...DEVELOPING W/NW LOW LEVEL FLOW IS EXPECTED
TO ADVECT DRIER AIR INTO THE REGION...THUS CHANCES FOR OVERNIGHT
VISBY/CIG RESTRICTIONS APPEAR LOW...EXCEPT PERHAPS IN THE VALLEYS SW
OF KAVL.

OUTLOOK...A DRIER AND COOLER AIRMASS WILL PERSIST OVER THE REGION
THROUGH EARLY WEEK...BRINGING MOSTLY VFR CONDITIONS. AN ACTIVE
PATTERN WILL RETURN BY MID-WEEK...WITH PERIODIC SHRA/TSRA POSSIBLY
BRINGING RESTRICTIONS.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-18Z
KCLT       HIGH  83%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  83%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  83%     HIGH  87%     LOW   54%     HIGH 100%
KHKY       HIGH  83%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  83%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  83%     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...JMP
NEAR TERM...JDL/WIMBERLEY
SHORT TERM...TS
LONG TERM...JMP
AVIATION...JDL/WIMBERLEY


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