textproduct: Grand Rapids

KEY MESSAGES

- Line of Storms Crosses Area Tonight, Strong to Severe Possible

- Cooler Sunday, Drier Pattern Ahead

DISCUSSION

Issued at 253 PM EDT Fri Apr 17 2026

- Line of Storms Crosses Area Tonight, Strong to Severe Possible

Storms out west across the upper Mississippi Valley will traverse east through the evening reaching the lakeshore near 9am. HREF/RAP guidance is less bullish on CAPE than yesterday with MUCAPE on the order of 500-1000 J/kg by the time storms arrive thanks to a wam nose just off the surface. 30-45 knots of deep layer, and 0-3 km shear will be sufficient for the potential of storms remaining organized as they approach. Damaging winds in any bowing segments are the main concern, with a non-zero, but low, risk of tornadoes. The greatest risk will be near and west of US131 where the earlier arrival will support better instability lessening with eastward extent. Showers and garden variety storms will follow the primary line continuing through daybreak. Widespread rainfall of 0.25-0.75" is expected with isolated totals to around 1.5 inches. The progressive nature of the storms should limit areal flooding concerns but any training or heavier swaths will bring that potential given saturated soils.

- Cooler Sunday, Warmer and Drier Pattern Next Week

Colder air filters in behind the cold front with 850mb temps falling into the negatives. This will also support breezy conditions later Saturday with gusts to 30-35 mph. Highs in the 40s and lows in the 20s to low 30s between Sunday Morning and Monday will be a notable change from recent patterns. The bright side is the incoming ridging and northwest flow will be much drier than we have been of late. Dry weather is likely until late next week when the approach of our next system brings precipitation back into the forecast. Temperatures then rebound into the 60s and 70s.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 121 PM EDT Fri Apr 17 2026

Fog and low clouds have dissipated and all sites are VFR as of present. A line of weakening thunderstorms will move in from the west after 01z with showers behind it, with conditions falling to MVFR at all terminals, with periods of IFR and lower conditions possible. LLWS is also expected out of convection given the strong low-level jet in play. Gusts to 25 knots, higher possible in any thunderstorms, are expected near and behind the line of storms/cold front with souhterly winds becoming westerly.

MARINE

Issued at 253 PM EDT Fri Apr 17 2026

Webcams show that fog has dissiapted across the nearshore waters so will be ending the Marine Dense Fog advisory with this package. Winds and waves increase to levels hazardous to small craft tonight and continue through the weekend. A Small Craft Advisory goes into effect this evening continuing into Sunday. A line of thunderstorms is expected to cross the lake this evening. Wind gusts to 34 knots are possible as this line moves through.

HYDROLOGY

Issued at 253 PM EDT Fri Apr 17 2026

Major flooding continues on the Muskegon River. The good news is that the river at most locations will be cresting within the next 24 hours (Upstream areas of the river including Evart crested earlier today). It will likely take until late next week for all locations to come under flood stage, so the recovery process will be slow. Meanwhile, water levels continue to rise on the Grand River, and confidence is increasing that this will end up being another minor flood event, slightly higher and worse than the one that happened earlier this month, but not a record flood at any locations. However, some of the lowest and easily flooded locations on the river like Comstock Park and Robinson Township will have moderate to possibly major flooding.

A final round of rain moves back into Lower Michigan tonight, and is expected to drop around one-half inch of rain over a large area, with locally higher streaks of 1"+ possible at some locations. Given the saturated soils everywhere, this could result in some renewed minor flooding, primarily impacting roadways. Thankfully, this expected rainfall is not anticipated to make the river flooding significantly worse at any locations. Beyond this next round of rain, we dry out for at least the better part of a week going forward, which will be a very welcome chance for the rivers to begin the slow process of recovering to more normal levels.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT Sunday for LMZ844>849.