textproduct: Grand Rapids

KEY MESSAGES

- Showers today; afternoon/evening thunder possible

- Frost possible north Wednesday night

- Warmer with showers/storms possible late weekend and next week

DISCUSSION

Issued at 312 AM EDT Tue May 12 2026

- Showers today; afternoon/evening thunder possible

An approaching clipper will push isolated showers through the cwa this morning. However, during the afternoon, coverage of the showers will increase as the low gets closer. Although instability isn't overwhelming, mid level lapse rages increase to 6.5-7c/km this afternoon that may result in a few storms 21z-03z. Lift will also be aided by the arrival of the accompanying upper level short wave. Expect the strongest storms to remain west and southwest of the cwa.

- Frost possible north Wednesday night

Colder air will flow into the region once again behind the clipper. Highs Wednesday will be in the upper 40s north to mid 50s south and lows Wednesday night will fall into the mid 30s along the northern row of counties. Thus, another frost advisory may be needed Wednesday night.

- Warmer with showers/storms possible late weekend and next week

Late in the weekend, we develop a broad southwest flow as ridging takes hold over the northeast US. This will send a plethora of short waves moving up the ridge toward the Great Lakes. As moisture and temperatures increase, the result will be an increase in convective development. NCAR medium range AI ensembles point toward Sunday and Monday as timeframes when convection could be stronger. It's during this time that a developing low over the Plains begins to lift north and a warm front moves into the cwa followed by the trailing cold front.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 618 AM EDT Tue May 12 2026

No significant changes to the forecast. Radar shows a decaying area of light showers moving across the lake. These showers should weaken as they move closer to MKG. More precipitation was noted over Wisconsin, closer to the low. As this precipitation moves over the terminals late this afternoon and evening, we're likely to see some thunder develop as instability increases with the arrival of an upper short wave. Additionally, a LLJ moving across the Lower Peninsula will create some LLWS after 00z.

MARINE

Issued at 312 AM EDT Tue May 12 2026

No changes to the small craft advisory. Winds and waves will pick up in speed and height as the pressure gradient tightens in response to a clipper moving across the state. Highest waves will be north of Holland this afternoon. After a brief lull, the winds will shift to the northwest tomorrow and waves will build southward during the afternoon. The small craft advisory may have to be extended in time Wednesday.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Freeze Warning until 8 AM EDT this morning for MIZ037>040-045- 046. Frost Advisory until 8 AM EDT this morning for MIZ043-044- 050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.