753  
FXUS61 KILN 200527  
AFDILN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON OH  
127 AM EDT WED OCT 20 2021  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL PROVIDE MOSTLY SUNNY AND WARM CONDITIONS  
THROUGH WEDNESDAY. DEVELOPING LOW PRESSURE AND AN ASSOCIATED  
COLD FRONT WILL INCREASE PRECIPITATION CHANCES FROM WEDNESDAY  
NIGHT THROUGH THURSDAY BEFORE COOLER CONDITIONS RETURN FOR LATE  
WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
SURFACE HIGH PRESSURE CENTERED OVER THE SOUTHEAST UNITED STATES  
WILL CONTINUE TO PROVIDE FAIR CONDITIONS THIS EVENING THROUGH  
TONIGHT. OUTSIDE OF A FEW THIN CIRRUS CLOUDS THROUGH LATE  
EVENING, CLEAR SKIES WILL ONCE AGAIN ALLOW EFFICIENT RADIATIONAL  
COOLING. WITH THIS IN MIND, LOW TEMPERATURES SHOULD ONCE AGAIN  
DIP INTO THE MID-40S.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/
 
 
HIGH PRESSURE SHIFTS OFF THE CAROLINA COAST WEDNESDAY AS  
DEVELOPING LOW PRESSURE MOVES EAST INTO IOWA. OUTSIDE OF A FEW  
MID AND HIGH CLOUDS, MOST OF THE SIGNS OF APPROACHING LOW  
PRESSURE WILL HOLD OFF UNTIL AFTER SUNSET WEDNESDAY. WITH STEADY  
SOUTHWESTERLY FLOW, TEMPERATURES WILL PEAK IN THE LOW 70S.  
 
MOISTURE INCREASES OVER THE OHIO VALLEY WEDNESDAY NIGHT AS THE  
SURFACE LOW SLIDES INTO THE GREAT LAKES. LATEST GUIDANCE BRINGS  
BEST CHANCE OF SHOWERS LATE IN THE PERIOD TO THE NORTHERN HALF  
OF THE CWA CLOSEST TO THE MID-LEVEL SHORTWAVE. UNDER INCREASING  
CLOUD COVER AND SOUTHWEST FLOW AHEAD OF THE COLD FRONT, LOW  
TEMPERATURES WILL STAY UP IN THE MID TO UPPER 50S.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
 
 
THE PERIOD BEGINS WITH A HIGH CONFIDENCE FRONTAL PASSAGE ON THURSDAY  
MORNING INTO EARLY AFTERNOON ACROSS THE ILN FORECAST AREA,  
ACCOMPANIED BY A THREAT OF SHOWERS AND A FEW STORMS PERHAPS IN THE  
SCIOTO VALLEY WITH AUTUMNAL COOLING TO FOLLOW, AND ENDS IN AN  
EXTREMELY LOW CONFIDENCE PATTERN WHICH MAY SPELL CONSIDERABLE  
WARMING.  
 
IN THE DETAILS, AT 12Z ON THURSDAY, A STRONG SHORTWAVE TROUGH WILL  
BE LOCATED OVER LAKE MICHIGAN WITH A COLD FRONT ARCING SOUTH THROUGH  
INDIANA. OUT AHEAD OF THE FRONT, AN ELEVATED BAND OF SHOWERS MAY BE  
MOVING THROUGH THE WESTERN ILN CWA ON THURSDAY MORNING IN STRONG  
THETA-E ADVECTION ABOVE THE BOUNDARY LAYER. AS THE DAY PROGRESSES,  
THERE IS SOME POTENTIAL FOR THESE SHOWERS TO BECOME SURFACE BASED TO  
SOME DEGREE BY EARLY-MID AFTERNOON OVER THE SCIOTO VALLEY, OR  
PERHAPS SURFACE-BASED SHOWER DEVELOPMENT TO OCCUR ALONG THE FRONT  
ITSELF BEFORE EXITING THE FORECAST AREA. THERE IS A NARROW WINDOW  
AMONG THE VARIOUS DETERMINISTIC RUNS OF ENOUGH SURFACE BASED  
INSTABILITY TO DEVELOP IN PORTIONS OF THE LOWER SCIOTO VALLEY TO  
ALLOW DEEP ENOUGH UPDRAFTS FOR THUNDER MENTION. THIS MAY NEED TO BE  
EXPANDED NORTHWARD A LITTLE IN FUTURE FORECASTS. GIVEN STRONG FLOW  
FIELDS WHICH WILL BE UNIDIRECTIONAL /SOUTHWESTERLY/ IN NATURE, IT IS  
NOT OUT OF THE REALM OF POSSIBILITY THAT SOME STRONG/GUSTY STORMS  
COULD OCCUR IN OUR SOUTHEAST/EASTERN COUNTIES BEFORE THE FRONT  
EXITS, ESPECIALLY IF THE BOUNDARY ENDS UP PASSING THROUGH AN HOUR OR  
TWO SLOWER THAN EXPECTED.  
 
THERE WILL ALSO BE GUSTY WINDS IN THE WAKE OF THE FRONT ON THURSDAY  
AFTERNOON PARTICULARLY OVER WESTERN OHIO AND EASTERN INDIANA. HAVE  
MOVED WINDS AND ESPECIALLY WIND GUSTS HIGHER FOR THURSDAY AFTERNOON,  
BUT POTENTIALLY NOT HIGH ENOUGH AS WE MAY SEE SOME 30KT GUSTS AT  
PEAK HEATING OVER THE HIGHER TERRAIN AREAS /E.G., BELLEFONTAINE  
RIDGE./  
 
STRONG COLD ADVECTION IN THE WAKE OF THE FRONT ON THURSDAY NIGHT,  
AND A REINFORCING SECONDARY COLD FRONT ON FRIDAY, GUARANTEE THE  
EVENTUAL DEVELOPMENT OF PLENTY OF STRATOCUMULUS AND LIGHT SHOWER  
THREAT ESPECIALLY FOR FRIDAY, WHERE HIGHS WILL ONLY MAKE THE 50S TO  
AROUND 60.  
 
UNCERTAINLY BEGINS TO RAPIDLY INCREASE OVER THE WEEKEND AND INTO  
EARLY NEXT WEEK AS THERE IS NOT GOOD AGREEMENT ON THE PATH/STRENGTH  
OF ENERGY ATTEMPTING TO UNDERCUT HIGH LATITUDE BLOCKING / LONGWAVE  
RIDGE MOVING EAST TOWARD THE GREAT LAKES. FOR RIGHT NOW AM RUNNING  
A DRY/COOL SATURDAY WITH SOME MODEST INCREASES IN RAIN CHANCES ON  
SUNDAY AS A WARM FRONTAL ZONE BEGINS TO SET UP OVER THE OHIO VALLEY  
AND ATTEMPT TO PUSH NORTH. HOWEVER, IF ENERGY RUNS ALONG THIS  
BOUNDARY PRECIPITATION CHANCES WILL NEED TO GREATLY INCREASE AND  
TEMPS MAY BE TOO OPTIMISTIC. ALSO AM EXTENDING RAIN CHANCES INTO  
MONDAY TO ACCOUNT FOR THE VARIED SPEED/LATITUDE OF THE POTENTIAL  
ENERGY PASSING THROUGH THE GREAT LAKES. THIS BEGINS A PERIOD OF  
HIGH VARIABILITY IN THE DETERMINISTIC AND ENSEMBLE MEMBERS, WITH  
NOTABLE SPREAD ON 2M TEMP PLUMES SUNDAY->TUESDAY. THIS COMES TO A  
HEAD ON MONDAY/TUESDAY, WITH NBM TEMPERATURE STANDARD DEVIATIONS  
MAXIMIZED OVER THE OHIO VALLEY INDICATING A GREAT AMOUNT OF  
UNCERTAINTY ON WARM FRONTAL LOCATION AS THE LONGWAVE UPPER RIDGE  
MOVES IN AND WEAKENING/UNDERCUTTING ENERGY MOVING OUT. WHILE THE  
NBM 50%ILE AND MEAN TEMPS HAVE RISEN CONSIDERABLY FOR MON/TUE, IT  
SHOULD BE NOTED THERE ARE STILL A NUMBER OF DATA WHICH SUGGESTS  
ROBUST WARMING WILL NOT OCCUR TO THE LEVEL DETERMINISTIC RUNS (E.G.,  
THE 10.19.12Z GFS FOR EXAMPLE), THUS CONSIDERABLE ATTENTION  
NEEDS TO BE PAID TO THIS PORTION OF THE FORECAST FOR FUTURE  
ADJUSTMENTS.  
 

 
   
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
 
 
VFR WILL CONTINUE UNDER HIGH PRESSURE, EXCEPT AT LUK WHERE BR  
AND FG ARE REDUCING VISIBILITY THIS MORNING. SKIES ARE SKC FOR  
THE FIRST PART OF THE FORECAST, WITH CIRRUS MOVING IN LATER WELL  
AHEAD OF LOW PRESSURE. WINDS FROM THE SOUTH TO SOUTHWEST WILL  
RISE TO AROUND 10 KNOTS THIS AFTERNOON.  
 
OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE THURSDAY. MVFR  
CEILINGS POSSIBLE FRIDAY AND FRIDAY NIGHT.  
 

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

 
 

 
SYNOPSIS...HOGUE  
NEAR TERM...HOGUE  
SHORT TERM...HOGUE  
LONG TERM...BINAU  
AVIATION...CONIGLIO  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab OH Page
The Nexlab IN Page
The Nexlab KY Page Main Text Page