textproduct: Grand Rapids

KEY MESSAGES

- Transition to lake effect near lake shore today

- Accumulating snow possible Monday afternoon/night

- Cold week ahead

DISCUSSION

Issued at 306 AM EST Sun Nov 30 2025

- Transition to lake effect near lake shore today

Surface obs reveal low pressure over central Lake MI early this morning. Regional radar shows snow extending west to eastern IA which means we have several hours of synoptic snow to go before we transition to just lake effect snow showers. Spotter reports indicate 3-6 inches of snow have fallen so far. During the past few hours, radar echos have increased to 30 dbz or greater indicative of heavier snowfall and flake size has increased quite a bit since midnight concurrent with the strongest isentropic lift. Pressure advection is maximized through 09z, after which pressure advection becomes more neutral. At that point, expect the snowfall rates to begin to decrease. That said, several more inches of accumulation is anticipated prior to the synoptic system moving east.

Boundary layer wind progs indicate we'll see NNWly winds develop around noon combined with deep moisture to produce lake effect snow showers. Given the wind direction, the lake shore counties will see the largest impact with several more inches of snow.

We'll keep the winter storm warning going through 10 am and see how the lake effect evolves. We may need to extend the warning for a few lake shore counties.

Winds will increase this afternoon as the low moves by and high pressure builds in behind it. This may result in blowing and drifting snow which could create hazardous travel conditions.

- Accumulating snow possible Monday afternoon/night

Boundary layer winds will become southwesterly Monday ahead of the next upper trough. H8 temperatures combined with deep moisture will result in a southwest lake effect event Monday afternoon and night. Several inches of snow are possible centered on northern Ottawa, Muskegon, southern Oceana counties as this event unfolds and headlines may be needed.

- Cold week ahead

Highs around 30 are expected Monday through Wednesday. An arctic cold front will pass through the state Wednesday with the coldest air of the season behind it. H8 temperatures are progd to fall to around -18c behind it; surface high temperatures in the lower 20s are anticipated Thursday and Friday along with more lake effect snow.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 552 AM EST Sun Nov 30 2025

Snow continues across the region. Radar shows dbz's aoa 30, signaling heavy snowfall with visibilities aob 1 mile. We have a few more hours before visibilities will begin to improve. By mid morning MVFR conditions are expected.

Lake effect snow will affect MKG/AZO today as winds become northwesterly. The eastern terminals will see more improvement as they will largely miss the lake effect snow showers.

MARINE

Issued at 306 AM EST Sun Nov 30 2025

No changes to the marine headlines. Surface low over central Lake MI will move east today and winds will become NNWly. As high pressure builds in behind the departing low, winds will increase to gales late this morning and continue through the afternoon. Once the gales decrease this evening, we'll likely need another small craft advisory.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory until 10 AM EST this morning for MIZ037>040. Winter Storm Warning until 10 AM EST this morning for MIZ043>046- 050>052-056>059-064>067-071>074. MARINE...Small Craft Advisory until 10 AM EST this morning for LMZ844>849. Gale Warning from 10 AM this morning to 8 PM EST this evening for LMZ844>849.