textproduct: Grand Rapids

KEY MESSAGES

- Scattered showers and storms today with a warm front

- Threat for severe storms on Monday

- Additional severe storms possible Tuesday

- Quieter weather mid to late week

DISCUSSION

Issued at 409 AM EDT Sun May 17 2026

- Scattered showers and storms today with a warm front

A warm front will lift northward through Southwest Lower Michigan tonight bring in higher dew point air and associated instability. By evening mid 60s dew points should be in place over much of the area. MUCAPE values should surge into the 1500 to 2500 j/kg range. Plenty of instability for storms with the trigger being the warm front. CAMs are not overly bullish though on coverage which makes sense given today's convection will be located within an upper ridge position overhead. Feel a few storms are possible this morning with a slight increase in coverage this afternoon given daytime heating. Severe weather is not out of the question today and SPC rightly has us in a marginal threat. Deep layer shear is actually quite strong due to a convectively induced mid level jet that move in from the west today from strong storms in the Central Plains this past evening. The stronger shear, moderate instability and a warm front nearby make all severe weather hazards possible today. Showers and storms should lift to the north/end this evening as the warm front lifts northward and we lose daytime heating.

- Threat for severe storms on Monday

The active weather pattern that begins today will continue into Monday. Another round of showers and strong to severe storms are possible on Monday. The SPC has Southwest Lower Michigan in a slight risk for severe weather. A strong southwesterly low level jet of 35-40 knots will be in place with another convectively induced mid level jet moving through as well. The threat on monday looks to be centered in the midday through afternoon hours as this is when a MCV will likely be working through the areas from overnight convection in the plains. MUCAPE values should increase to around 2000 j/kg with deep layer shear on the order of 30 to 40 knots. Wind and hail look to be the main threats on Monday in the open warm sector of the system.

- Additional severe storms possible Tuesday

Another round of storms and possible severe weather will occur as a strong cold front sweeps from west to east through the area on Tuesday. 30 to 40 knots of deep layer shear looks to be in place once again with in excess of 2000 j/kg of MUCAPE ahead of the cold front. Wind and hail will once again be threats during the afternoon.

- Quieter weather mid to late week

Cooler and drier weather is expected overall mid to late week with high pressure building in from the north. 850mb temperatures actually dive towards zero C Wednesday from a peak around +18C Monday night. Wednesday and Thursday certainly look dry, but there is some model disparity out on Friday with the GFS and the ECMWF at odds in regard to the pattern. The GFS has a low in the area while the ECWMF has ridging.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 202 AM EDT Sun May 17 2026

A warm front will lift north through Southwest Lower Michigan tonight, including through all of the TAF sites. The front may touch off a few showers and storms this morning between 11z and 16z at KMKG and KGRR and then for all the TAF sites this afternoon between 17z and 22z. For the most part VFR weather is expected to prevail outside of some scattered showers and storms. The time frame that this activity would impact any one of the TAF sites will be limited. There is a chance for some MVFR ceilings at KMKG for a couple of hours around 18z, but left this small chance out of the TAF at this point. The front should be north of the TAF sites this evening and expect quieter/VFR conditions after 01z.

Winds will generally be out of the south today with sustained speeds of 08-12 knots with some gusts to around 20 knots.

MARINE

Issued at 409 AM EDT Sun May 17 2026

Strong southerly flow will develop tonight and continue into the early portion of the work week. For now we will cover the first 24 hours of the wind and issue a Small Craft Advisory from this evening through Monday for areas north of Holland. The wind will continue into Monday night and Tuesday and expand to the south of Holland as well with time. So, as we move forward the SCA will need to be expanded in time and also in area (to the south). Waves will reach the 3 to 6 foot range north of Holland on Monday.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from 11 PM this evening to 8 PM EDT Monday for LMZ846>849.