Area Forecast Discussion

KEY MESSAGES

- Hot and humid today and Wednesday. Shower and thunderstorm chances return this afternoon through Wednesday (40 to 70%). Chances may linger into Thursday as well.

- There is a marginal risk for isolated strong to severe storms Today between 6 pm and midnight. Main threat is damaging winds if storms become severe. Confidence remains low at this time.

- There is a moderate swim risk for Lake Michigan beaches along the Berrien Co, MI shoreline today. Breaking waves and currents expected.

DISCUSSION

Issued at 147 PM EDT Mon Sep 14 2026

Very pleasant temperatures in the 70s and dewpoints in the 40s will shift away as the sfc ridge moves east and an increasing low level flow starts ushering much higher dewpoints to the area. This will take a bit of time, with values into the low to mid 50s by 12Z Tue. Off to our NW, an axis of much higher dewpoints will be pooled along a slow moving frontal boundary that is expected to approach later tomorrow and linger across the region (in a weaker state) through Thursday. Dewpoints and low level temps will climb through the day with a much more muggy feel returning by afternoon. High temps before any convection occurs will reach well into the 80s for most locations and if cloud cover stay away long enough, a few 90s are possible in SW areas.

Models have generally backed off on upstream convection making it into NW parts of the area as it encounters the drier air mass and outruns the better forcing. As we move into Tuesday afternoon and beyond, this changes with at least chance pops warranted as leftover outflow boundaries that may drift in during peak heating interact with increasing CAPE. There seems to be a continued lean towards better development in the 20 to 22Z time frame, mainly NW but honestly could end up just about anywhere. These then progress southeast through about 2Z to 3Z Wed before shifting out of the area or weakening. Shear profiles are on the lower side (25 to maybe 35 kts) for some organization of convection, and decent low level lapse rates will help with the initial lift, but mid level lapse rates are quite unfavorable for more robust convection. SPC has maintained the Marginal Risk for severe storms with some gusty wind potential for those storms that can interact with boundaries and maybe sustain some briefly better updrafts and cores.

Beyond 6Z Wed forecast becomes even more challenging as frontal boundary slowly weakens and stalls over the general area with models struggling (as to be expected) with the handling of subtle waves and possible new development or propagation of upstream convection. Given the amount of lingering moisture in the area and at least some instability, it won't take much to pop additional showers and storms, thus warranting the chc to likely pops through Thursday. By no means does it look like a washout with periods of little/no precip likely in between waves, but no way to time those out at this point in the forecast. Severe threat should be very minimal, if non existent, but heavy rain/localized flooding could become an issue with high PWATs and any repeated training of multiple rounds of convection. Marginal risk for Excessive Rainfall remains in place Tue and Wed and is reasonable.

No changes beyond Thursday as models seem to want to push the ridging north into MI for the weekend. However, history over the past several weeks in this setup has pointed towards low confidence on how much of this comes to fruition. As a result, blend is left alone with some slgt chc to chc pops, especially Sat.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 146 AM EDT Tue Sep 15 2026

Predominantly VFR to MVFR conditions at the terminals this period, with a warm front lifting northward through the afternoon/evening, followed by a cold front into the overnight. There is still considerable uncertainty as to the timing of things (mostly impacting KSBN this period). Have prob 30s for the 12-15z period to account for any showers/storms that make it into KSBN. Most of the models have the storms far to our west dying out before they reach the terminal, but with increasing WAA we could start to see some light rain showers ahead of the line. Then we may see a quick break until the afternoon, when guidance generates showers/isolated storms based on a potential outflow boundary that arrives in the 18-23z time frame (dies out before going eastward). The cold front and more likely MVFR conditions will move through with any showers or storms along the cold front--likely 3z-6z. Kept prob 30 in the 18-23z time, and then have predominant showers between 1z-6z (with prob 30 for more MVFR/TSRA chances). KFWA will likely have showers and isolated storms later in the night, towards the 3-12z time frame. Have a prob30 at KFWA to cover MVFR conditions that are likely within heavier showers/storms. Otherwise, LLWS this morning at KSBN as the warm front lifts northeastward.

IWX WATCHES / WARNINGS / ADVISORIES

IN...None. OH...None. MI...None. MARINE...Small Craft Advisory until 11 AM EDT this morning for LMZ043- 046.