


Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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078 FXUS63 KIWX 111830 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 230 PM EDT Fri Jul 11 2025 .KEY MESSAGES... - A few showers and storms early Saturday morning are possible across NW Indiana and SW Lower Michigan. - Better chances for rain/storms between 2-10 PM EDT Saturday, especially along and east of I-69. Storms may be strong to severe with lightning, heavy rainfall, and gusty to damaging winds. - Hot and humid conditions for the weekend, with highest heat indices expected in the mid to upper 90s for Saturday afternoon. - Brief shot of dry and less humid weather Monday, but heat is expected to return by Tuesday and Wednesday. && .DISCUSSION... Issued at 225 PM EDT Fri Jul 11 2025 A decaying round of showers and a few storms moved through the area this morning as part of an overnight MCS that went through Iowa and northern Illinois. In it`s wake, pockets of clearing have become evident on visible satellite imagery. While widespread redevelopment of showers and storms is not expected today, can`t rule out isolated pop-up storms this afternoon and evening. CAMs still have quite a high spread in outcomes over the next 12-24 hours, but it appears like the highest chances for redevelopment along any remnant outflow boundaries will be tonight across eastern Iowa, northern Illinois, and southern Wisconsin with yet another MCS. Given southwesterly low level flow tonight, it`s possible that this system to our west holds together. If it does, NW Indiana and SW Lower Michigan could get in on some rain/storms during the evening and overnight hours into early Saturday. There will be some shear to work with given that surface flow will be southerly this evening and mid level flow will be southwest. Instability will be modest but ample moisture will allow for heavy, efficent rain rates. Should storms develop, strong wind gusts to 50 mph and heavy rain will be possible across the northwest portion of the forecast area. Hot and humid conditions prevail on Saturday with highs in the low 90s and dewpoints into the low to mid 70s. Peak heat indices in the afternoon will likely be in the mid to upper 90s, although rain/storms may bring some relief by late in the afternoon and evening. Saturday`s chances for rain/storms are dependent on the evolution of the overnight decaying MCS. Some of the CAMs, particularly, the HRRR, depict quite a strong MCS developing to our west tonight, which would likely leave an outflow boundary (or multiple) in it`s wake. On Saturday, scattered clusters of storms are likely to develop ahead of a cold front in the afternoon and evening. The Storm Prediction Center has areas along and east of I-69 in a Slight Risk (level 2 of 5) for severe weather on Saturday. The best environment for severe storms will be east of I-69, however, storms may develop along any remnant outflows leftover from the aforementioned overnight MCS. Destabilization may occur as early as 1-2 PM EDT, but best chances for storms will likely be between 4-10 PM EDT Saturday. With minimal shear once again (less than 20 kts), moderate instability (~2000-2500 J/kg MUCAPE) and steeping low level lapse rates, gusty to damaging winds will be the primary threat. Given tall, skinny CAPE profiles, low level southwest flow parallel to the cold front, and PWATs around 1.5-2", heavy rain and flooding will also be possible Saturday. WPC does have much of our forecast area in a Marginal Risk (level 1 of 4) for isolated instances of flash flooding on Saturday afternoon and evening. By Sunday, the cold front will have mostly cleared the area. A few storms could redevelop south of the US 24 corrdior in the afternoon and evening if the front hasn`t entirely cleared the area by then. It will be a similar setup to Saturday with limited shear and moderate instability. Northwest flow behind the front will usher in a brief reprieve from the heat and humidity late in the day Sunday into Monday. An upper level ridge and surface high pressure build across the Great Lakes region into early next week, bringing mainly dry conditions until midweek. Low chances (around 20%) for diurnally driven showers and storms exist Monday and Tuesday. Heat and humidity return with highs in the upper 80s to low 90s Tuesday and Wednesday. The next area-wide chance for rain/storms arrives Wednesday afternoon/evening along a cold front. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 126 PM EDT Fri Jul 11 2025 Northern Indiana will be between weather systems for a majority of this TAF period resulting in primarily VFR conditions outside of any showers/storms. Low pressure over southern IA and the associated trough is promoting thunderstorm development as of this writing. Additional storms are anticipated across eastern IA and northern IL for the remainder of this afternoon and evening. Activity will drift east but weaken. Time of arrival to KSBN is notably later than the prior forecast and this was adjusted accordingly. Becoming somewhat breezy later in this TAF period ahead of the aformentioned trough, now knocking on our door. Thunderstorms are expected to develop right at the end of this TAF period or soon thereafter. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Johnson AVIATION...Brown