textproduct: Grand Rapids

KEY MESSAGES

- Afternoon chance of showers, isolated thunderstorm

- Freezing temperatures tonight

- Warming trend midweek, rain and thunderstorm chances around Friday

DISCUSSION

Issued at 359 AM EDT Sun Apr 19 2026

- Afternoon chance of showers, isolated thunderstorm

A weak shortwave trough associated with a 500 mb speed max on the backside of the Rossby wave trough will aid in the development of diurnal showers in the vicinity of a cold front dropping through. Fairly steep lapse rates from surface to 600 mb (approx 13,000 feet) may yield 100-250 J/kg of CAPE over Mid Michigan during the afternoon. Showers will tend to grow as they move east. There is a slight chance of an isolated thunderstorm this afternoon especially near and east of Alma, Lansing, and Jackson. Temperatures in Central Michigan would support some snow mixing in. Any relatively robust convective cell, whether a shower or thunderstorm, could produce graupel / small or soft hail and locally gustier winds closer to 40 mph, again, best chances near and east of US-127.

- Freezing temperatures tonight

For Sunday night to Monday morning, post-cold-front air with 850 mb temperatures around -10 C and high pressure moving over the region will support freezing temperatures. There may be some lingering lake-effect clouds in spots and there is some uncertainty if surface winds go completely calm. However, the cooling overnight will be more due to the advection of a deep cold air mass rather than radiational. Above-freezing air above tree height will not be available to mix down mechanically, as a sharp temperature inversion appears unlikely. In every model, early Monday morning temperatures in the vertical profile above the surface are entirely below freezing. It appears the best case scenario if a local surface temperature inversion does develop would be for mechanical mixing of air to keep temperatures in the upper 20s rather than the lower 20s.

NBM median 2-meter temperatures at 7 AM Mon are in the range of 26- 28 degrees except are slightly warmer immediately near Lake Michigan. The 90th percentile (the warmest 10 percent of solutions) are about 29-31 degrees.

For the period of March 1 through April 17, this year has been within the top 10 warmest in terms of daily average temperature, and record wettest at every ASOS / primary climate site. This may lead to increased susceptibility to temperatures in the 20s for some fruit crops. The frost/freeze advisory/warning season has begun for Muskegon, Kent, Montcalm, Gratiot counties and south.

- Warming trend midweek, rain and thunderstorm chances around Friday

Ensembles are in good agreement of a warming trend Tuesday to Thursday as the upper level trough progresses east. Thursday is likely to be the warmest day of the week with highs well into the 70s. Increasing moisture and instability Thursday into Friday will set the stage for a round of showers or thunderstorms near a cold front extending from a northern Plains low.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 217 AM EDT Sun Apr 19 2026

VFR is likely much of today with daytime cumulus bases favored to be at or above 4,000 feet. West/Northwest winds will gust during the late morning through afternoon up to about 20-28 knots. Around 18-22 Z, scattered towering cumulus (TCU) may be present near LAN and JXN, possibly growing into cumulonimbus (CB), as there is about a 10-30 percent chance of a thunderstorm in that area and toward the east. Under any TCU or CB may come briefly gustier winds over 30 knots and graupel (small or soft hail, GS).

MARINE

Issued at 359 AM EDT Sun Apr 19 2026

West winds become more northwest then north during today. Waves of 2 to 5 feet will linger at least through the morning. Weaker winds are expected tonight through Monday morning. Increasing south winds Monday night into Tuesday may again build hazardous waves for small craft.

HYDROLOGY

Issued at 221 PM EDT Sat Apr 18 2026

Major flooding continues on the Muskegon River. The good news is most locations have crested or are cresting now. 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 flooding. Dry conditions are expected through the next several days.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Frost Advisory until 10 AM EDT this morning for MIZ050>052- 056>059-064>067-071>074. Freeze Warning from 11 PM this evening to 11 AM EDT Monday for MIZ050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for LMZ844>849.