432  
FXUS61 KILN 211434  
AFDILN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON OH  
1034 AM EDT MON AUG 21 2017  
   
SYNOPSIS
 
 
WEAK DISTURBANCES IN THE UPPER FLOW WILL BRING A CHANCE OF  
THUNDERSTORMS TO NORTHERN OHIO TODAY. A COLD FRONT WILL BRING  
MORE ORGANIZED SHOWERS AND THUNDERSTORMS ON TUESDAY, THEN DRIER  
AND COOLER AIR MOVES IN FOR THE REST OF THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
LATEST RUNS OF THE MODELS CONTINUE TO SUGGEST THAT VORT MAXS IN  
THE ZONAL H5 FLOW WILL ACT AS THE CATALYST FOR CONVECTION  
ACROSS NRN IN/OH THIS AFTERNOON. TWEAKED THE ONSET OF THE TIMING  
BY AN HOUR HERE OR THERE, BUT STILL LEFT THE BEST POP CHANCES  
ACROSS WEST CENTRAL OHIO WITH LESSER CHANCES AS YOU HEAD SOUTH.  
 
CLOUD DEVELOP TODAY COULD HINDER THE ECLIPSE VIEWING, BUT RIGHT  
NOW DON'T EXPECT A THICK OVERCAST DECK.  
 
ADJUSTED THE TEMPERATURES DOWN A DEGREE OR TWO DUE TO THE  
ECLIPSE AND ADJUSTED THE HOURLY TEMPERATURE TRACE.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/
 
 
THIS EVENING, CONVECTION OR DECAYING SHOWERS FROM THE AFTERNOON  
WILL START TO COME TO AN END AS DAYTIME HEATING IS LOST. TONIGHT  
A POTENT UPPER LEVEL SYSTEM OVER THE HUDSON BAY WILL BEGIN TO  
WRAP UP INTO AN UPPER LEVEL LOW AND HEAD SOUTH. MID AND UPPER  
LEVEL FLOW WILL QUICKLY START TO AMPLIFY AS THE NEWLY FORMED LOW  
PUSHES SOUTHEAST.  
 
AHEAD OF THE MAIN UPPER LEVEL SYSTEM A WEDGE OF PV WILL SWING  
EAST HELPING TO GET SHOWERS AND THUNDERSTORMS GOING TUESDAY  
AFTERNOON. SFC TO 6 KM BULK SHEAR VALUES AT THIS TIME ARE AROUND  
40 KTS (SLIGHTLY HIGHER ON THE NAM AND SLIGHTLY LOWER ON THE  
GFS). ML CAPE VALUES ON THE GFS ARE ONLY AROUND 700 J/KG WHILE  
THE NAM HAS VALUES APPROACHING 2000 J/KG. LOOKING MORE IN DEPTH  
AT FORECAST SOUNDINGS REVEALS WHY. THE GFS CLEARLY SHOWS A  
CIRRUS SHIELD INHIBITING THE AREA FROM FULLY DESTABILIZING. ALSO  
AT THIS TIME THE COLD FRONT HAS YET TO ENTER OUR CWA. THEREFORE  
CONVECTION WILL BE DEPENDENT ON DESTABILIZATION AS SURFACE  
CONVERGENCE FROM THE FRONT WILL COME LATER. NOT SURPRISINGLY SPC  
HAS THEREFORE KEPT THE AREA IN A SLIGHT RISK GIVEN SUPPORTIVE  
BULK SHEAR VECTORS AND QUESTIONABLE INSTABILITY. THE PRIMARY  
THREAT STILL LOOKS TO BE DAMAGING WINDS (POSSIBLY SOME TYPE OF  
BROKEN LINE FORMING).  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
 
 
SHOWERS AND THUNDERSTORMS WILL LINGER INTO TUESDAY EVENING,  
ESPECIALLY ACROSS SOUTHEAST PORTIONS OF OUR FORECAST AREA. HOWEVER,  
AS THE COLD FRONT PUSHES OFF TO OUR SOUTHEAST AND DRIER AIR BEGINS  
TO FILTER IN BEHIND THE FRONT, EXPECT PCPN TO TAPER OFF FROM THE  
NORTHWEST AS WE HEAD INTO TUESDAY NIGHT.  
 
SURFACE HIGH PRESSURE WILL BUILD DOWN ACROSS THE GREAT LAKES THROUGH  
THE REST OF THE WEEK. THIS WILL LEAD TO MAINLY DRY AND COOLER  
CONDITIONS. HOWEVER, SOME MID AND UPPER LEVEL SHORT WAVE ENERGY  
DROPPING DOWN ACROSS THE GREAT LAKES ON THURSDAY COULD LEAD TO A FEW  
SHOWERS, ESPECIALLY ACROSS NORTHEAST PORTIONS OF OUR AREA.  
TEMPERATURES THROUGH THE END OF THE WEEK WILL BE SEVERAL DEGREES  
BELOW NORMAL WITH HIGHS IN THE 70S AND OVERNIGHT LOWS IN THE 50S. WE  
WILL START TO GET INTO SOME RETURN FLOW THROUGH THE WEEKEND, LEADING  
TO A SLIGHT WARMUP BY THE END OF THE LONG TERM PERIOD.  
 

 
   
AVIATION /15Z MONDAY THROUGH FRIDAY/
 
 
CONVECTION HAS FALLEN APART AS IT HAS MOVED INTO THE AREA THIS  
MORNING WITH ONLY SOME LINGERING LOW CIGS AT KLUK. THIS  
AFTERNOON HIGH RES MODELS THEN INDICATE SHOWERS AND  
THUNDERSTORMS POSSIBLY FORMING ACROSS OUR NORTHWESTERN ZONES  
ALONG THE NOSE OF A WEAK LLJ. THE RAP, HRRR, WRF DART, AND NMM  
SHOW CONVECTION IN SOME FORM OR FASHION WHILE THE NSSL WRF AND  
NAM 3 KM ARE DRY. FOR NOW HAVE JUST ADDED A VCSH FOR KDAY DUE TO  
UNCERTAINTY IN FORMATION.  
 
TUESDAY MORNING INTO AFTERNOON MORE SHOWERS AND THUNDERSTORMS  
WILL BE POSSIBLE AHEAD OF AN APPROACHING COLD FRONT.  
 
OUTLOOK...THUNDERSTORMS ARE LIKELY TUESDAY INTO TUESDAY  
EVENING.  
 

 
   
ILN WATCHES/WARNINGS/ADVISORIES
 
 
OH...NONE.  
KY...NONE.  
IN...NONE.  
 

 
 

 
SYNOPSIS...HAINES  
NEAR TERM...  
SHORT TERM...HAINES  
LONG TERM...JGL  
AVIATION...HAINES  
 
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