Area Forecast Discussion

KEY MESSAGES

- Dry and mild through mid-week, with slow improvement to areas experiencing localized flooding near rivers, lakes, and poor drainage areas.

- Mild to warm late week with rain and thunder chances Friday and Friday night.

- Drier and closer to seasonable this weekend.

DISCUSSION

Issued at 127 AM EDT Tue Apr 21 2026

Pattern Synopsis and Forecast:

Broad northwest flow aloft over northern MI today with ridging building across the central portions of the CONUS. Weak short wave within the northwest flow will move across the region later today. The combination of the main lift from this shortwave likely being too far south and the lack of sufficient moisture/instabilty across northern Michigan should keep the precipitation to our south. Nevertheless, always worth keeping half an eye on locations south of M-55 in this type of regime.

Heights really begin to rise on Wednesday as ridging moves eastward closer to the Great Lakes. High and dry as sfc high pressure settles in. In response to deep troughing crashing into the West Coast and moving east into the Intermountain West and Plains states, ridging settles right over top of the Great Lakes on Thursday. Temperatures respond accordingly, with 70s likely across the interior, 60s closer to the Lake Huron coast and north of the bridge. A few pieces of guidance want to spit out a shower or two Thursday afternoon but the progged upper pattern and thermal structure should really mitigate that potential. Waters will continue to recede during this dry stretch through mid week, resulting in continued improvement to the localized flooding across some rivers, lakes, and poor drainage areas (some lakes will take longer to respond).

Deep troughing will continue to jog north or northeastward Thursday night into Friday, with an additional piece of energy moving into the Mid MS Valley and eventually the Upper Midwest to some degree. Consequently, dominant sfc low pressure system across the northern Plains will move northward with associated frontal boundary poised to move eastward into northern MI through the day on Friday. The band of precip associated with this feature (potentially enhanced by short wave energy) will be moisture rich, with PW ~200% of normal or greater. Steadiest precip falls Friday and Friday night with the potential for 0.50" of rain or more for some. Ensemble guidance have a low to medium-ish (~20 to 50%) chance for >0.50" of rain during this time, which has been consistent with NBM probs the last few days. Any convectively enhanced rainfall would certainly lead to higher rain totals despite at least some questions in regard to instability quality (although the EPS, GEPS, and their parent models suggest at least modest amounts to work with). Thus, locally heavy rain will be possible with this system given enough instability manifests, with plenty of time to refine the forecast.

Precipitation wanes by the early part of the weekend, with a convoluted upper level pattern left in its wake. Large, omnipotent upper low to our west will likely be spinning away across the Northern Plains and largely in adjacent southern Canada, with another troughing complex way to our east. Persistent upper high south of Greenland and off the Canadian coast lock this upper low in place (plus or minus) blocking up the pattern and leaving northern MI in limbo to some extent. As of now, expect more seasonable temps and a bit of a break in the precipitation but we'll keep an eye on this moving forward.

HYDROLOGY

Issued at 127 AM EDT Tue Apr 21 2026

River levels across the board continue to decrease, albeit some lakes are still elevated and causing issues. Mullet lake leveled out around 596.1 ft, a full 2 ft above the record heights, and there have been reports and footage of homes still flooded along Black Lake. Thus, localized flooding near some rivers, lakes, and poor drainages continue. That being said, the current flow (analyzed by the National Water Model) across portions of the Pigeon, Sturgeon, Thunder Bay, portions of the Au Sable, and Boardman Rivers are at an annual exceedance of between 20-50% (in other words, an ARI flow rate of 2-5 years, which is minor). This is true for rivers across the Tittabawassee/Tobacco River Basin as well. Conversely, flows across the Manistee River, Cheboygan River, Black River, and portions of the Muskegon River remain at a ~2% annual exceedance (flow rate ARI of 50 years, much more significant). This is evident in the hydrographs across our area as well, with a steady decrease for most. Our flood warnings remain across the locations with the higher flows, more or less. Localized flooding does continue near some of these rivers, lakes, and poor drainage areas.

Improvement should continue through much of the rest of this week with dry conditions through Thursday. The next rain maker will move in during the day on Friday for most, with moderate rain possible across northern MI. Current guidance suggests a low to medium-ish (~20 to 50%) chance for >0.50" through Friday night. Convectively enhanced precipitation would lead to locally heavy rainfall given enough instability manifests. HEFS guidance does show subtle river rises/responses due to this rainfall, but nothing alarming at this time. That being said, the sensitive, poor drainage areas with lingering water/flooding will need to be watched, especially with soil moisture still ~45-60% across portions of northern lower Michigan.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 1146 PM EDT Mon Apr 20 2026

VFR. Mid and high clouds at times, especially tonight. Dry air in low levels though, so no chances for precip. Southerly winds increase tonight, LLWS is forecast at all sites tonight and/or Tuesday morning.

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APX WATCHES / WARNINGS / ADVISORIES

MI...None. MARINE...Small Craft Advisory until 11 AM EDT this morning for LHZ345. Small Craft Advisory until 2 PM EDT this afternoon for LHZ348- 349. Small Craft Advisory until 11 AM EDT this morning for LMZ323- 341-342-344>346. Small Craft Advisory until 11 AM EDT this morning for LSZ321.