textproduct: Grand Rapids

KEY MESSAGES

- Travel impacts ongoing with current lake effect event

- A period of quiet weather Monday through Wednesday

- Quick rain event on Thursday

DISCUSSION

Issued at 344 AM EST Sun Dec 14 2025

- Travel impacts ongoing with current lake effect event

The lake effect event and ongoing Winter Weather Advisory are going down as planned. As we thought, fairly widespread travel impacts have occurred as seen by the midrive website the past 12 hrs. Accidents in the lakeshore counties and even more notable the slowed (sometimes significantly) travel speeds indicate conditions are poor. Temperatures towards the Lake Michigan shoreline are in the upper single digits and lower teens and with a consistent snowfall icy road conditions developed and are occurring. At this point feel we are looking at the possibility of another 1-2 inches of new snow this morning before it tapers off considerably this afternoon. Bottom line, we are not making any headline changes this morning and will let things play out. We will continue to highlight the icy roads/slowed travel in the WSWGRR. The upper cyclonic shear axis will move east of the lake this afternoon and that will mark the end of the stronger snow shower activity due to large scale subsidence.

- A period of quiet weather Monday through Wednesday

A period of quieter weather is expected from Monday through Wednesday as the pattern shifts from one of deep upper troughing (currently over the Great Lakes) to that of a zonal flow. The quick west to east upper flow that develops this week will bring shortwave troughs through our area about every other day. The first will zip through the northern Great Lakes and may bring Central Lower Michigan some light snow Monday morning. Any accumulations up there will be on the order of a trace to possible around an inch near U.S. 10. The next wave moves through Tuesday night into Wednesday and we look to stay dry with that system.

We will see a fairly significant change in temperatures in the next handful of days with -20C air at 850mb overhead now rising to +8C in in the Euro by Tuesday evening. Highs around 20 today will rise into the 30s on Tuesday and to around 40 on Wednesday.

- Quick rain event on Thursday

The next wave in line swings through the region Wednesday night into Thursday with a good surge of air out of the south. The low that moves through the region is deep (980s mb) with strong 850mb winds in excess of 50 knots. Surface dew points are forecast to rise into the lower 40s F and PWAT values increase to around 0.90 inches ahead of the front. Both of these values are high for this time of year. Rainfall amounts look to be between 0.30 and 0.70 inches based on the current operational GFS and ECWMF. We will certainly see a ripening of the snowpack with the increase in temp/dew point as well as raining directly onto it. Given the quick hitting nature of the warm air, it sweeps east fairly quick, we are not anticipating significant hydro issues at this time. Our hydro ensemble forecast system is showing within bank rises at this point for Thur/Fri. We will continue to monitor trends of both the rainfall/warmth and river level forecasts. What can be expect is some local ponding of water given many drains are currently covered in snow and ice and at least some of this will remain.

Another surge of cold air and lake effect snow sets up for Friday behind the Thursday low.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1202 PM EST Sun Dec 14 2025

Ceilings will be chaotic this afternoon and evening with cigs bouncing on either side of 3kft thanks to lake effect stratocu moving inland. Leaning on the NAMNEST, a few hours of intermittent MVFR snow showers are likely at MKG before diminishing mid to late afternoon. Light snow showers are possible mainly at MKG and flurries at the other terminals. MKG and GRR have the best chance of falling back into a few hours of MVFR overnight before climbing to VFR by Monday morning. Other terminals do have a 20-30 percent chance of falling back to MVFR tonight which will be monitored. Monday morning then sees wind gusts increase to 20-25 knots, after 09z at MKG and after 14z inland.

MARINE

Issued at 256 AM EST Sun Dec 14 2025

We are in a period of stronger winds on Lake Michigan with northwest winds of 20 to 30 knots currently. These winds are being aided by a tight pressure gradient aided by strong polar high pressure in the plains states of near 1042mb. There will be a brief lull in the wind this afternoon and evening as the mean ridge positions sinks southeast through the Great Lakes. Quickly on the backside of the high however winds ramp up once again, likely to gale force.

So, we have a long duration Small Craft Advisory in place now which we have extended to 400am in the morning (Monday). We will also be issuing a Gale Warning for a period of stronger winds late tonight and on Monday. It appears we will tap into gales to 35-40 knots for a time centered Monday morning into midday.

Waves will likely peak this morning around 10 feet towards South Haven and even at this hour the South Haven webcam looks rough. In the gales on Monday morning the WaveWatch3 has waves peaking around Muskegon near 12 feet (10am).

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory until 4 AM EST Monday for LMZ844>849. Gale Warning from 4 AM to 3 PM EST Monday for LMZ844>849.