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KEY MESSAGES

- Chances for showers and storms late Sunday into Monday. Storms are not expected to be severe at this time

- A swath or two of an inch or greater by Monday across northern MI is likely. Training of heavier rain could result in local flooding concerns

- Warmer temperatures and off and on rain chances linger through next week

DISCUSSION

Issued at 244 AM EDT Sat Aug 29 2026

Current water vapor satellite depicts mid to high level moisture streaming in from the eastern Pacific, over the Rockies and into the Great Plains as a positively tilted upper trough digs down the western US coast. As the upper ridging is broken down and shoved east, the moisture being injected aloft is aligning with lee cyclogenesis over SD. An MCS is blossoming this morning, and will continue to travel east, around the upper ridge. The upper troughing will slowly track over the northern Rockies this weekend, however before this the surface low will drift towards the western Great Lakes region. This will gradually lift the warm sector towards MI (starting today). Cloud cover will increase as intermittent light rain begins later this afternoon. Lightly breezy southwest winds will become breezy this afternoon (especailly over NW lower), with occasional gusts up to 15 to 25 mph (strongest over coastal and coastal adjacent areas).

By Sunday morning, the warm surface front will stall somewhere over the CWA. By this time, the deeper moisture will have officially arrived, and with it a moderately unstable airmass (around 1000 j/kg) and healthy shear (25 to 30 kts sfc to 3km). Embedded showers and storms will have a chance to form right along the boundary throughout the day, however will likely struggle to form elsewhere over the CWA. That is not to say established showers and storms couldn't move into northern MI from across the lake. This environment will be capable of training storms, which is apparent in modeled QPF signals where a majority show one main +1" swath somewhere over northern MI by Monday morning. Higher uncertainty lies in the exact location (due to where the warm front stalls) and exact timing (Sunday afternoon or overnight). The potential of training showers and storms results in concerns for flooding. Due to the limited coverage of highest amounts, flooding is expected to remain isolated and mostly local (low spots in hilly terrain and a brief rise in creeks and streams).

With the very moist airmass and healthy lower level shear profiles (especailly true along the boundary itself), there will be a non- zero chance for tornados. Gusty outflow winds are also possible, however it will be hard for large hail to reach the surface without melting on its way down. To summarize, severe threats with storms is not expected at this time.

Early next week, the upper level trough becomes negatively tilted and wraps up over the Dakotas. Warmer temperatuers will continue during this time, as the axis of this weaker upper ridge lands over MI Monday. Moisture will linger, which continues intermittent chances for showers and storms (especially as the warm front transitions into a stationary boundary and could be contaminated by cold pools. Showers and storms could fire off of smaller, more mesoscale boundaries Monday. Due to the overall weaker forcing and environment, coverage is not expected to be widespread and intensity is expected to be more minimal. The upper closed low will continue east, tracking along the international border and reaching northern MI by late Tuesday. Some guidance wants to drag a dry slot along with this (on the southern side of the upper closed low). It is too early to have a good read on the chances for this, however it could pause rain chances for Tuesday.

An active pattern over the northern Rockies will continue into early September, which will continue to transport Pacific mid to high level moisture. This could be supplemented by lower level Gulf moisture a few times, which would continue the on and off chances for precipitation through the end of the work week.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 641 AM EDT Sat Aug 29 2026

Chances for showers will increase this afternoon and especially tonight. Expect CIU to lower to MVFR and then IFR later tonight, and PLN becomes MVFR overnight. Otherwise prevailing VFR conditions, though brief restrictions are certainly possible at the other TAF sites. Breezy sw winds by this afternoon.

APX WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from noon today to 10 PM EDT this evening for LHZ345. Small Craft Advisory from noon today to 10 PM EDT this evening for LMZ323-341-342-344>346.