textproduct: Grand Rapids

KEY MESSAGES

- Lake effect snow and cold tonight into Sunday

- Turning warmer this week with rain in the forecast Thursday

DISCUSSION

Issued at 336 AM EST Sat Dec 13 2025

- Lake effect snow and cold tonight into Sunday

Main forecast focus this morning was on the Arctic air intrusion combined with lake effect snow. Specifically the concern is the threat of impacted travel. We have issued a Winter Weather Advisory from this afternoon through tonight and into Sunday morning. The advisory is not for heavy snow, but instead impacted travel. We will see 1 to 3 inches of snow in the lakeshore counties during the aforementioned time frame with an isolated 4 inch amount not out of the question. The issue however is the fact that temperatures will continue to plummet throughout the day. A strong mid level shortwave will work through the region tonight which will give a boost to the lake effect snow. Again, heavy snow is not expected but the combination of very cold air, small/fine snowflakes and blustery conditions/blowing-drifting snow (NW 15-25 mph) will create impacted travel.

When 850mb air of -20C or colder works into the area it correlates to surface temperatures below 15F. At these temperatures salt becomes less effective. Any light snow production, whether it is heavy or not is pasted into a glaze of ice many times due to a constant refreezing process. Therefore, the main concern is impacted travel from this afternoon through Sunday morning for slick conditions. People will need to slow down and allow extra travel time. We do not see these conditions (very cold temperatures and snowfall) all of the time and folks can be unprepared. The HRRR shows temperatures dipping to +5F tonight in portions of the Winter Weather Advisory. Again, those surface temperatures with a consistent light snow is the concern with regard to travel.

As for some of the meteorological parameters agree with previous discussions that the depth of moisture is shallow, but it does increase this evening and tonight with a healthy mid level shortwave working through. At the lakeshore BUFKIT points, the DGZ is off the deck so there should be consistent light snow production. Lift is fairly strong within the shallow cloud layer. The heaviest snow will certainly be tonight. Delta T's will reach the mid 20s C which is extreme.

- Turning warmer this week with rain in the forecast Thursday

The remainder of the forecast shows the upper pattern becoming more zonal with a system forecast to move through the Great Lakes region on Thursday. Southerly flow ahead of this system will push us back into the 30s and even some 40s mid week. At this point, the precipitation looks to be mainly rain with amounts that do not look too significant on the order of a half inch.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 654 AM EST Sat Dec 13 2025

An Arctic cold front is progressing through the TAF sites this morning. As we approach 12z, the front is just upstream of JXN and will move through there by 13z. A gusty west-northwest wind (290-310) can be expected much of the day with speeds of 10-20 knots with gusts to around 25 knots.

Lake effect snow showers have commenced off of Lake Michigan behind the front. We will see off an on snow showers for the next 24 hours or through 12z on Sunday. MKG, AZO and GRR will see the more impactful conditions with visibilities dipping into IFR at times. Inland conditions will be mainly VFR with regard to visibilities. Ceilings will likely remain MVFR today at all TAF sites as lake stratocumulus clouds continues to pour inland off the lake. Tonight as the winds begin to turn more northerly, the inland TAF sites at LAN and JXN will trend VFR.

GRR WATCHES/WARNINGS/ADVISORIES

MI...Winter Weather Advisory from 4 PM this afternoon to 11 AM EST Sunday for MIZ037-038-043-050-056-064-071-072. MARINE...Small Craft Advisory until 7 PM EST Sunday for LMZ844>849.