528  
FXUS62 KCAE 172359  
AFDCAE  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE COLUMBIA SC  
759 PM EDT THU AUG 17 2017  
   
SYNOPSIS
 
 
A SURFACE PRESSURE TROUGH WILL LINGER IN THE FORECAST AREA  
THROUGH EARLY NEXT WEEK. UPPER RIDGING OVER THE REGION WILL  
WEAKEN SOMEWHAT FRIDAY AND SATURDAY, AND THEN BECOME A LITTLE  
STRONGER EARLY NEXT WEEK. THE PATTERN SUPPORTS PARTLY CLOUDY  
SKIES WITH SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS.  
IT WILL BE HOT WITH HEAT INDEX VALUES PEAKING 100 TO 108.  
 

 
   
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
 
 
THIS EVENING, WIDELY SCATTERED TO ISOLATED CONVECTION WILL  
LIKELY DIMINISH BY 11 PM. WARM TEMPERATURES ALOFT WILL LIMIT  
UPDRAFT STRENGTH AND MAKE ANY SEVERE WEATHER UNLIKELY. 850 TO  
300 MB MEAN WIND SPEEDS OF AROUND 10 KTS WILL ALSO LIMIT  
LOCALIZED HEAVY RAIN POTENTIAL, PROVIDING DECENT STORM MOTION.  
 
TONIGHT...A FEW LEFTOVER CONVECTIVE DEBRIS CLOUDS AND A WEAK  
LOW LEVEL JET WILL INHIBIT EARLY MORNING STRATUS/FOG  
DEVELOPMENT. MODEL GUIDANCE ALSO SUGGESTS A LACK OF EARLY  
MORNING FOG AND STRATUS. OVERNIGHT LOWS WILL AGAIN BE VERY MILD  
WITH TEMPERATURES IN THE MID TO UPPER 70S.  
 

 
   
SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/
 
 
A WEAK COLD FRONT WILL APPROACH THE AREA BY FRIDAY EVENING.  
EXPECT SCATTERED AFTERNOON AND EVENING THUNDERSTORMS DUE TO THE  
USUAL DAYTIME HEATING SURFACE INSTABILITY. PRECIPITABLE WATER  
AROUND 2 INCHES SUPPORTS HEAVY DOWNPOURS WITH THE THUNDERSTORMS.  
HOWEVER, SHEAR WILL BE WEAK AND INSTABILITY SHOULD REMAIN  
LIMITED WITH RELATIVELY WARM MID-LEVEL AIR, SO THERE IS A LOW  
THREAT OF SEVERE THUNDERSTORMS. IT WILL REMAIN HOT WITH MAXIMUM  
HEAT INDEX VALUES 105 TO 108, JUST A LITTLE BELOW THE HEAT  
ADVISORY CRITERIA OF 110.  
 
THE FRONT WILL STALL BETWEEN COLUMBIA AND THE COAST ON SATURDAY.  
THIS WILL BE A FOCUS FOR MORE SHOWERS AND THUNDERSTORMS, MAINLY  
IN THE AFTERNOON. MODEL GUIDANCE HAS SHOWN A DRYING TREND FOR  
SATURDAY AND SUNDAY, PUSHING THE DRIER AIR FURTHER SOUTH OVER  
THE PAST FEW RUNS. 90 PERCENT OF THE EUROPEAN ENSEMBLE MEMBERS  
AND ALL OF THE GEFS MEMBERS SUGGEST POPS NO HIGHER THAN 40  
PERCENT ACROSS THE EASTERN FORECAST AREA (FA) AND NO HIGHER THAN  
25 PERCENT ACROSS THE WESTERN FA. REDUCED POPS BASED ON THE  
MODEL TRENDS AND ENSEMBLE SPREAD BUT KEPT THEM ON THE HIGHER END  
FOR CONSISTENCY. TEMPERATURES ON SATURDAY AND SUNDAY MAY NOT BE  
QUITE AS HOT AS FRIDAY, BUT HEAT INDICES WILL STILL BE 100 TO  
105 DEGREES.  
 

 
   
LONG TERM /MONDAY THROUGH THURSDAY/
 
 
UPPER RIDGING WILL CONTINUE TO BUILD OVER THE AREA ON MONDAY AS  
SURFACE HIGH PRESSURE STRENGTHENS OVER THE WESTERN ATLANTIC. LOW-  
LEVEL MOISTURE SHOULD REMAIN HIGH DUE TO A SOUTHEAST FLOW OFF  
THE OCEAN. THE PATTERN SUPPORTS PARTLY CLOUDY SKIES WITH A  
CHANCE OF MAINLY DIURNAL AFTERNOON THUNDERSTORMS. SIMILAR  
CONDITIONS ARE EXPECTED ON TUESDAY. ANOTHER WEAK FRONT WILL  
APPROACH ON WEDNESDAY, AND THUNDERSTORMS WILL REMAIN POSSIBLE.  
UPPER LEVEL TROUGHING SHOULD REMAIN IN PLACE OVER THE EASTERN  
U.S. ON THURSDAY, THEREFORE SHOWERS AND THUNDERSTORMS WILL  
CONTINUE. IT WILL REMAIN WARM THROUGH THE PERIOD WITH HIGH  
TEMPERATURES IN THE LOW 90S AND HEAT INDEX VALUES IN THE LOW  
100S.  
 

 
   
AVIATION /00Z FRIDAY THROUGH TUESDAY/
 
 
GENERALLY VFR CONDITIONS THROUGH THE PERIOD EXCEPT POSSIBLE  
RESTRICTIONS IN THUNDERSTORMS.  
 
ISOLATED CONVECTION WINDING DOWN THIS EVENING...THEREFORE NOT  
MENTIONED IN TAFS. LIGHT WINDS FORECAST OVERNIGHT. FOG/STRATUS  
NOT EXPECTED OVERNIGHT WITH A LOW LEVEL JET AROUND 15 KNOTS AND  
SOME LINGERING CONVECTIVE DEBRIS CLOUDS. DIURNAL CUMULUS CLOUDS  
SHOULD BEGIN DEVELOP AROUND 15Z WITH STRONG HEATING AND WINDS  
BECOMING WEST TO SOUTHWEST 5 TO 10 KNOTS. CONDITIONS FAVOR  
ISOLATED TO SCATTERED CONVECTION DEVELOPING DURING THE  
AFTERNOON. HAVE INCLUDED VCSH AT ALL AFTER 17Z.  
 
EXTENDED AVIATION OUTLOOK...SCATTERED MAINLY AFTERNOON AND EVENING  
SHOWERS AND THUNDERSTORMS POSSIBLE EACH DAY. ALSO, LOW-LEVEL  
MOISTURE COULD RESULT IN EARLY MORNING FOG AND/OR STRATUS.  
 

 
   
CAE WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
SC...NONE.  
 

 
 

 
 
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