textproduct: Grand Rapids

KEY MESSAGES

- Rain and Thunderstorms Monday Night into Tuesday Night

- Rain Chances Return Late Week into Weekend

DISCUSSION

Issued at 305 AM EDT Sun Mar 29 2026

- Rain and Thunderstorms Monday Night into Tuesday Night

Monday Night into Tuesday Morning:

There is a Marginal Risk for strong to severe storms Monday night into Tuesday morning. Southwest flow will be advecting moisture, warm air, and with the low level jet convergence paired with divergence from the upper level jet storms are expected to develop Monday night. With the changing airmass instability will be building with MUCAPE values around 1000 to 1500 J/kg and 40 to 50 knots of shear. Mid level lapse rates will be around 8 C/km. Storms will be elevated and with the mentioned ingredients hail will be the primary concern, but can't rule out some stronger winds, especially with 40+ knots just above the surface. Timing would bring storms into the area after 8pm with the best chances after midnight. There are differences on how long storms linger into Tuesday morning. Depending on how fast the first round clears will impact the severe potential Tuesday afternoon and evening.

Tuesday Afternoon into Tuesday Night:

Strong southwest flow continues ahead of the trough axis Tuesday afternoon and evening. Overall the best chance for severe thunderstorms looks to be in southern and southeastern portions of the forecast area. This is due to a better potential for surface based storms along with the orientation of the low level jet and right entrance region of the upper level jet. However some solutions keep a bit of CIN in the profile likely impacted by how the initial round of storms play out. Instability will be about the same with 40 to 50 knots of shear. CSU, NCAR's AI NWP Convective Hazard Forecast, and NSSL have been highlighting this severe potential for days with the highest probabilities across southern lower Michigan. Hail and damaging winds will be the primary concern, but there will be a tornado potential for areas that are able to become surface based.

Looking at the potential for some heavy rain, NBM probabilities have increased for an inch or more in 24 hours. There are some rainfall probability axis of 30 to 40 percent in portions of lower Michigan depending on where storms track over the longest.

- Rain Chances Return Late Week into Weekend

Other than some lingering showers early Wednesday morning, dry conditions are expected until our next shortwave trough moves through the area during the Thursday to Friday timeframe. Taking a look at the cluster analysis almost 50 percent of the GEFS members are in a cluster that brings in the shortwave trough faster resulting in rain chances earlier on Thursday, with the other clusters a little slower trending toward Thursday evening into Friday. This is represented by the NBM PoPs being higher across much of the area (60 percent) Thursday night compared to during the day on Thursday. Rain should be diminishing Friday as the trough is progressive, but any dry break looks to be short lived as a deeper trough moves through over the weekend. Again looking at the cluster analysis, there are timing differences. The cold front looks to move through Sunday bringing colder temperatures and drier conditions, but there is a 20 percent chance showers could linger into Sunday afternoon.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 636 AM EDT Sun Mar 29 2026

VFR conditions are expected today with southwest winds. Low level wind shear will be present initially this morning and then redevelop tonight.

MARINE

Issued at 305 AM EDT Sun Mar 29 2026

Small Craft Advisory conditions continue from Holland and northward with southwest winds gusting to 25 knots and waves 4 to 7 feet. Southwesterly winds then become lighter with a lull in the high waves through Monday. Monday night winds pick back up resulting another chance for Small Craft Advisory conditions Monday night into Wednesday. Southwest winds will shift to the northwest behind the front Tuesday before winds become more offshore Wednesday into Thursday.

Thunderstorms are expected at times Monday night into Tuesday night and could be strong to severe with large hail and damaging winds.

FIRE WEATHER

Issued at 1034 AM EDT Sun Mar 29 2026

Based on latest guidance the dewpoints should remain in the 20s this afternoon. So have adjusted the Dewpoints down to reflect that. This also will drop the RH's into the upper 20s this afternoon. So expecting a drier day today. Winds should remain around 10 mph with gusts of 20 to 25 mph possible. Temps should drop off between 6 PM and 8 PM and RH's should recover through that time to above 30 percent and increase as the evening continues.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for LMZ846>849.