624   
FXUS63 KIWX 221009  
AFDIWX  
  
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
609 AM EDT FRI AUG 22 2025  
   
KEY MESSAGES  
  
- PATCHY FOG EARLY THIS MORNING.  
  
- THERE ARE LOW CHANCES (10-30%) FOR SHOWERS SATURDAY AFTERNOON.  
  SCATTERED LAKE EFFECT SHOWERS LIKELY ON MONDAY.  
  
- SIGNIFICANTLY COOLER THAN NORMAL TEMPERATURES SUNDAY THROUGH  
  TUESDAY.   
  
- DANGEROUS SWIMMING CONDITIONS FOR SOUTHEAST LAKE MICHIGAN BEACHES   
POSSIBLE SUNDAY INTO MONDAY.  
  
  
   
DISCUSSION  
  
ISSUED AT 252 AM EDT FRI AUG 22 2025  
  
GIVEN THE DRY AND COMFORTABLE AIRMASS OVER THE REGION THIS MORNING   
COMBINED WITH RESIDUAL GROUND MOISTURE FROM RECENT RAINFALL, AREAS   
OF PATCHY FOG ARE POSSIBLE THIS MORNING. PATCHY FOG WILL LIKELY   
DEVELOP BETWEEN 5 AM TO 9 AM ET THIS MORNING BEFORE DISSIPATING.   
TODAY, ANOTHER PLEASANT AUGUST DAY IS AHEAD WITH HIGHS NEAR 80   
DEGREES, INTERMITTENT SUNSHINE, AND COMFORTABLE HUMIDITY   
LEVELS. WINDS WILL STILL BE FROM THE NORTHEAST, WHICH WILL HELP   
KEEP SOME LAKE EFFECT CLOUD COVER OFF OF LAKE ERIE OVER THE   
AREA, ESPECIALLY OVER NORTHWEST OHIO AND NORTHEAST INDIANA.   
  
THE NEXT CHANCE FOR RAIN/STORMS ARRIVES DURING THE DAY ON SATURDAY.   
A LARGE AREA OF LOW PRESSURE WILL SPIN AND DEVELOP OVER ONTARIO,   
WITH THE SYSTEM'S ATTENDANT COLD FRONT EXPECTED TO MOVE THROUGH MUCH   
OF THE EASTERN CONUS. THIS FRONT LOOKS TO COME THROUGH OUR FORECAST   
AREA DURING THE AFTERNOON AND EVENING HOURS ON SATURDAY, BRINGING   
LOW CHANCES (10-30%) FOR SHOWERS AND STORMS. WITH UNCERTAINTIES   
STILL ON HOW MUCH MOISTURE AND FORCING WILL ACCOMPANY THIS FRONT,   
HAVE KEPT POPS LOW.  
  
BEHIND THIS FRONT, STRONG CAA WILL PUSH A REFRESHING,   
SUBSTANTIALLY COOLER AIRMASS ACROSS MUCH OF THE MIDWEST AND   
GREAT LAKES. WITH COLD AIR MOVING OVER THE RELATIVELY WARM   
WATERS OF LAKE MICHIGAN, EXPECT LAKE EFFECT CLOUDS AND SHOWERS   
LATE SUNDAY INTO THE DAY ON MONDAY AND AGAIN POTENTIALLY ON   
TUESDAY. SUNDAY'S CHANCES MAY BE LIMITED DEPENDING ON HOW MUCH   
DRY AIR IS ALOFT. SOUNDINGS NEAR LAKE MICHIGAN DEPICT A   
FAVORABLE ENVIRONMENT FOR DIURNALLY-DRIVEN LAKE EFFECT SHOWERS   
ON MONDAY WITH LOW LEVEL CONVERGENCE ALONG A TROUGH THAT PIVOTS   
THROUGH, CYCLONIC FLOW, AND TALL INVERSION HEIGHTS OF 7-8 KM.   
CAN'T RULE OUT POTENTIAL FOR WATERSPOUTS OVER SOUTHERN LAKE   
MICHIGAN AS WELL, ESPECIALLY IF THE LOW LEVEL CONVERGENCE SETS   
UP OVER THE LAKE. TEMPERATURES ON MONDAY AND TUESDAY WILL   
STRUGGLE TO REACH THE LOW 70S FOR HIGHS, ESPECIALLY IN AREAS   
CLOSER TO LAKE MICHIGAN WHERE LAKE EFFECT CLOUD COVER REMAINS.   
MEANWHILE, PARTICULARLY AWAY FROM THE LAKE, NIGHTS WILL BE CRISP  
WITH NEAR- RECORD LOWS IN THE MID TO UPPER 40S!   
  
AS A LARGE AREA OF SURFACE HIGH PRESSURE BUILDS ACROSS THE CENTRAL   
CONUS MIDWEEK, EXPECT DRY CONDITIONS TO PERSIST THROUGH MUCH OF THE   
WEEK. TEMPERATURES WILL SLOWLY REBOUND TOWARDS MORE SEASONABLE   
LEVELS BY THE WEEKEND (WITH HIGHS NEAR 80 DEGREES).  
  
  
   
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/  
  
ISSUED AT 607 AM EDT FRI AUG 22 2025  
  
PATCHY FOG, DENSE AT TIMES, WILL COME AND GO OVER THE NEXT  
COUPLE HOURS. COVERAGE HAS BEEN VARIABLE WHICH SQUASHES FORECAST  
CONFIDENCE WITH RESPECT TO TIMING OF FM GROUPS. INCREASING CLOUD  
COVER LATE IN THE TAF PERIOD, ESPECIALLY AT KSBN, SHOULD LIMIT  
THE OVERALL FOG CONCERN FOR THE COMING NIGHT. LIGHT WIND  
OTHERWISE TODAY BENEATH HIGH PRESSURE.   
  
  
   
IWX WATCHES/WARNINGS/ADVISORIES  
  
IN...NONE.  
OH...NONE.  
MI...NONE.  
MARINE...NONE.  
  
  
  
  
  
DISCUSSION...JOHNSON  
AVIATION...BROWN  
 
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