373  
FXUS62 KGSP 270855  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
455 AM EDT MON MAR 27 2017  
   
SYNOPSIS
 
 
MOIST SOUTHERLY FLOW WILL LINGER OVER THE SOUTHEAST THROUGH TUESDAY,  
WITH SEVERAL ROUNDS OF SHOWERS AND THUNDERSTORMS POSSIBLE. DRIER AIR  
WILL BRIEFLY RETURN BY THE MIDDLE OF THE WEEK AS A COLD FRONT  
SETTLES SOUTH OF THE AREA. ANOTHER LOW PRESSURE SYSTEM WILL BRING  
MOISTURE BACK TO THE SOUTHEAST THURSDAY, INCREASING RAIN CHANCES  
THROUGH LATE FRIDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 445 AM EDT: FORECAST POPS WERE CLEANED UP A BIT - FOCUSING  
MAINLY ON MUCH HIGHER SHOWER CHANCES EAST OF I-77 EARLY THIS  
MORNING, AND THEN FANNING ISOLATED TO SCATTERED CONVECTIVE CHANCES  
BACK SOUTHWEST TO NORTHEAST GEROGIA IN THE MOIST SOUTHWESTERLY FLOW.  
 
OTHERWISE, WATER VAPOR IMAGERY REVEALS A CYCLONIC MID/UPPER LEVEL  
CIRCULATION MOVING OVER MISSOURI EARLY THIS MORNING. LOW LEVEL FLOW  
EAST OF THIS SYSTEM IS GENERALLY SOUTH TO SOUTHWEST AND THIS  
PERSISTENT FETCH OF GULF MOISTURE ACROSS THE SOUTHEASTERN STATES  
WILL YIELD CONTINUED MORNING CLOUDS AND LINGERING ISOLATED TO  
SCATTERED SHOWERS FOR OUR REGION. THIS FLOW REGIME WILL CONTINUE  
ACROSS THE SOUTHEAST THROUGH THE DAY. THE COMBINATION OF  
TEMPERATURES WARMING QUICKLY THROUGH THE 70S, DESPITE THE MOSTLY  
CLOUDY CONDITIONS, AND DEWPOINTS SOLIDLY IN THE 50S WILL LIKELY  
PRODUCE SBCAPE VALUES IN THE 1000 TO 2000 J/KG RANGE THIS AFTERNOON.  
NARROW LOBES OF VORTICITY LIFTING EAST AHEAD OF THE MAIN TROUGH THIS  
AFTERNOON WILL PROVIDE A TRIGGERING MECHANISM FOR DEEP CONVECTION.  
ALTHOUGH THUNDERSTORM COVERAGE WILL BE IN THE SOLID SCATTERED RANGE,  
SEVERAL OF THE STORMS COULD BE STRONG TO SEVERE AS CAPE IMPROVES IN  
THE MINUS 10 TO MINUS 30 C HAIL GROWTH ZONE. RELATIVELY MODEST  
SPRING FREEZING LEVELS SHOULD PERMIT 55 DBZ CORES REACHING THE LOWER  
20KFT RANGE THIS AFTERNOON AND EARLY EVENING TO YIELD SOME  
MARGINALLY LARGE HAIL AND BRIEFLY GUSTY WINDS. FORTUNATELY, 850 MB  
FLOW AND ASSOCIATED DEEP LAYER SHEAR WILL BE LESS THAN OBSERVED ON  
SUNDAY, SO CELLS SHOULD NOT PERSIST AS LONG AND A BIT LESS STORM  
ORGANIZATION IS INDICATED. WILL MENTION THE SEVERE POTENTIAL IN THE  
HWO.  
 
THE DEEPER FORCING WILL OCCUR WITH THE TROUGH AS IT CROSSES THE  
SOUTHERN APPALACHIANS OVERNIGHT WITH BETTER UPPER JET DIVERGENCE AND  
DEEP LAYER Q VECTOR CONVERGENCE INDICATED. HOWEVER, INSTABILITY  
SHOULD BE WANING A BIT OVERNIGHT AND LOW LEVEL FLOW WILL START  
VEERING, SO THIS MAY LIMIT THE STRONG TO SEVERE POTENTIAL SOMEWHAT  
FOR THE EARLY MORNING HOURS. THE REAL QUESTION MARK WILL BE HOW WELL  
THE MORE ROBUST CONVECTION FROM THE UPSTREAM SLIGHT TO ENHANCED  
SEVERE THUNDERSTORM RISK AREAS IS ABLE TO SURVIVE AS IT APPROACHES  
THE MOUNTAINS. ALL IN ALL, EXPECT A MILD AND INCREASINGLY WET NIGHT.  
 

 
   
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
 
 
AS OF 225 AM EDT MONDAY: AN ULVL S/W WILL CONTINUE TO CROSS THE AREA  
TUE AND DRAG A BROAD COLD FRONT EAST THROUGHOUT THE DAY. THE ATMOS  
WILL REMAIN UNSETTLED DURING THIS TIME AND ISOL/SCT TSTMS ARE  
PROBABLE EARLY ON THRU THE AFTERNOON. THE MAIN FOCUSING AREA FOR  
STRONGER STORMS WILL BE EAST OF THE MTNS AS PRE-FRONTAL LIFT  
COINCIDES WITH DESTABILIZING WARM SECTOR BY 21Z. THE OP MODELS HAVE  
VARYING IDEAS WITH THE PLACEMENT OF CONVEC AND THE DEGREE OF  
INSTABILITY...BUT THE ERN ZONES WITH BETTER SFC TD POOLING  
ASSOCIATED WITH INCREASED SFC CONVG SHUD BE THE FAVORED AREA FOR  
DEEP CONVECTION...POSSIBLY PRODUCING A FEW SVR STORMS. THIS ACTIVITY  
WILL WANE RATHER QUICKLY AFT FROPA ARND 00Z WITH LITTLE IF ANY  
SHOWERY ACTIVITY LINGERING THRU THE OVERNIGHT PERIOD.  
 
HEIGHTS ACTUALLY BEGIN TO RISE QUICKLY DURING THE AFTERNOON TUE AND  
BY 12Z WED A DEEP LAYERED RIDGE AXIS WILL BE SITUATED JUST WEST OF  
THE FA. A STRONG SUBS INVERSION WILL ENGULF THE AREA AND PREVENT  
DEEP CONVEC ACTIVITY FROM DEVELOPING THRU THE DAY. THERE MAY BE SOME  
-SHRA LATE AND OVERNIGHT ACROSS THE NRN ZONES AS A MOIST WEDGE  
BEGINS TO BUILD IN. MAX TEMPS WILL REACH 10-12 DEGREES ABOVE NORMAL  
IN GOOD DOWNSLOPE FLOW...HOWEVER TD/S WILL BE ABOUT 10 DEGREES  
COOLER THAN TUE'S VALUES. THUS...NO GOOD CHANCE WILL BE HAD TO BREAK  
THE H7 CAP IN A NON/TRIGGERED ENVIRON. MIN TEMPS WILL REMAIN 8-10  
DEGREES ABOVE NORMAL BOTH TUE AND WED NIGHTS.  
 

 
   
LONG TERM /THURSDAY THROUGH SUNDAY/
 
 
AS OF 305 AM EDT MONDAY: A STRONG ULVL RIDGE WILL CROSS THE ERN  
CONUS EARLY THU THRU FRI MORNING. THIS WILL FORCE A CP SFC HIGH OFF  
THE MID-ATL COAST WHICH WILL RIDGE SOUTH ACROSS THE FA. THIS RIDGE  
WILL BRING SOME GLAKES MOISTURE WHICH WILL COMBINE WITH ADVECTING  
LLVL ATL MOISTURE. ISENT LIFT AND INCREASING PRECIP COVERAGE WILL  
THEREBY STRENGTHEN AND HOLD A WEDGE IN DURING THIS TIME. THIS WILL  
MAKE FOR A TRICKY TEMP FORECAST THU AND ALSO THE AMOUNT OF THUNDER  
ACTIVITY POSSIBLY DEVELOPING ACROSS THE WEDGE BNDRY TO THE SOUTH AND  
WEST. FOR NOW...HAVE TSTMS DEVELOPING ACROSS THE FAR SW/RN ZONES AND  
MAX TEMPS RANGING FROM THE U50S NRN PIEDMONT TO M70S OVER THE FAR  
SRN ZONES. THIS COULD CHANGE OVER THE NEXT FEW FCST PACKAGES.  
 
MEANWHILE...A STRONG LOW PRESSURE SYSTEM WILL DEVELOP ACROSS THE  
SRN PLAINS EARLY THU AND ADVANCE TOWARD THE OH VALLEY BY FRI  
MORNING. THIS FEATURE WILL BRING YET ANOTHER FRONTAL SYSTEM TO THE  
AREA FRI. THE MODELS AGREE WELL WITH BREAKING DOWN THE SFC WEDGE  
ARND 12Z FRI LEAVING PLENTY OF TIME FOR THE ATMOS TO DESTABILIZE IN  
A HIGHLY DYNAMIC ENVIRON....POSSIBLY PRODUCING STG/SVR STORMS ALONG  
A RETREATING TMB. THIS SCENARIO HAS A GOOD AMOUNT OF UNCERTAINTY  
HOWEVER AS THE SPEED OF THE COLD FRONT OR UPPER S/W COULD CHANGE AND  
THE INHERENT COMPLEXITIES AND UNCERTAINTY INVOLVED WITH  
FRONTAL/WEDGE INTERACTIONS. THE FRONT LOOKS TO CROSS EAST OF THE  
AREA LATE FRI AND A DRY AIRMASS SHUD BUILD IN OVER THE WEEKEND. MAX  
TEMPS FRI COULD BE TRICKY AS WELL...BUT FOR NOW HAVE HIGHS REACHING  
NEAR NORMAL LEVELS. OVER THE WEEKEND...HIGHS WILL LIKELY INCREASE TO  
ABOUT 5 DEGREES ABOVE NORMAL IN GOOD INSOL WITHIN A DRYING COLUMN.  
 

 
   
AVIATION /09Z MONDAY THROUGH FRIDAY/
 
 
AT KCLT: PASSING EARLY MORNING SHOWERS HAVE GENERALLY MOVED EAST OF  
I-77, BUT ADDITIONAL ISOLD TO SCATTERED ACTIVITY DEVELOPING BACK  
OVER THE I-85 CORRIDOR IN SC WILL WARRANT CONTINUED VCSH CHANCES.  
PROFILES ARE FAIRLY MOIST AND THERE IS CONSIDERABLE UNCERTAINTY OVER  
WHERE CEILINGS WILL FORM AS TEMPERATURES COOL THROUGH DAYBREAK, BUT  
THE BEST CONSENSUS INDICATES A FAIRLY EXTENDED PERIOD OF MVFR  
CEILINGS CONTINUING UNTIL EARLY AFTERNOON BEFORE LIFTING AND  
SCATTERING OCCURS. THUNDERSTORM CHANCES WILL IMPROVE ONCE AGAIN  
AFTER 19Z AND CONTINUE INTO THE EARLY EVENING HOURS. EXPECT SW WINDS  
AROUND 10 KT OR LESS THROUGHOUT, WITH A FEW LOW END GUSTS POSSIBLE  
THIS AFTERNOON.  
 
ELSEWHERE: ISOLATED SHOWER CHANCES WILL CONTINUE THROUGH THE MORNING  
HOURS IN PERSISTENT, MOIST SOUTHWEST FLOW. ANTICIPATE MVFR LEVEL  
CLOUDS DEVELOPING ALL ACROSS THE MOUNTAINS AND FOOTHILLS, WITH TEMPO  
DAYBREAK IFR CEILINGS POSSIBLE AT TIMES. MVFR CIGS WILL SLOWLY LIFT  
AND SCATTER LATE MORNING INTO EARLY AFTERNOON, WITH THE THUNDERSTORM  
POTENTIAL INCREASING AGAIN AFTER 18Z. EXPECT SOUTH TO SOUTHWEST  
WINDS THROUGHOUT AT 10 KT OR LESS, WITH A FEW LOW END AFTERNOON  
GUSTS POSSIBLE.  
 
OUTLOOK: ANOTHER ROUND OF THUNDERSTORMS WILL BE POSSIBLE ON TUESDAY,  
ESPECIALLY NEAR KCLT. CONTINUED LOW LEVEL MOISTURE WILL PROVIDE A  
GOOD CHANCES OF RESTRICTIONS THROUGHOUT. DRIER CONDITIONS SHOULD  
BRIEFLY RETURN DURING MID-WEEK BEFORE ANOTHER STORM SYSTEM BEGINS  
AFFECTING THE REGION THURSDAY AND FRIDAY.  
 
CONFIDENCE TABLE...  
 
09-15Z 15-21Z 21-03Z 03-06Z  
KCLT HIGH 83% HIGH 90% HIGH 100% HIGH 80%  
KGSP MED 70% HIGH 89% HIGH 100% HIGH 92%  
KAVL MED 68% HIGH 94% HIGH 100% LOW 53%  
KHKY MED 61% HIGH 83% HIGH 100% MED 74%  
KGMU MED 64% HIGH 96% HIGH 100% HIGH 90%  
KAND MED 66% HIGH 90% HIGH 98% 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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

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

 
 

 
SYNOPSIS...HG  
NEAR TERM...HG  
SHORT TERM...SBK  
LONG TERM...SBK  
AVIATION...HG  
 
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