218
FXUS63 KGRR 122322
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
722 PM EDT Sun Oct 12 2025

.KEY MESSAGES...

- Areas of fog forming again tonight

- Warmer and drier than normal through late this week

- More active weather pattern arrives for next weekend and beyond

&&

.DISCUSSION...
Issued at 300 PM EDT Sun Oct 12 2025

- Areas of fog forming again tonight

Overnight radiational cooling led to extensive fog formation
overnight that lingered late into the morning hours today. The same
basic weather pattern of high pressure/subsidence and generally
light winds remains in place for tonight. Thus, persistence alone
would suggest we`ll probably see some more fog forming. One
difference may be some midlevel clouds impinging on our lakeshore
areas after midnight, which may lessen fog formation. More info is
available in the aviation section of this discussion below.

- Warmer and drier than normal through late this week

Overall, yet another warmer than normal and mostly dry week is on
track for West Michigan. Average highs this time of year are in the
low 60s - which means our temperatures near 70 for much of the week
will be about 5 to 10 degrees above average. This relatively
tranquil weather is thanks to persistent high pressure that keeps
regenerating to our west, putting us in the sinking air (subsidence)
portion of the overall weather pattern. As this ridge of high
pressure amplifies again early in the week, there is a hint in the
models of a shortwave clipping us in northwest flow, which could
produce some showers on Tuesday night. However, with dry air
entrenched at the low levels and fairly weak forcing, this could
easily end up being nothing more than some sprinkles. Regardless,
ridging strengthens again with more sunshine and slightly cooler
(but still above-average) temperatures for the 2nd half of the week.
Overnight temperatures will probably drop down toward the freezing
mark Wednesday night, so another widespread frost is very possible
under clear skies.

- More active weather pattern arrives for next weekend and beyond

Confidence continues to grow that the general weather pattern
changes starting Friday night into next weekend and beyond. This new
pattern will feature a much higher zonal index of the upper level
flow, allowing numerous shortwaves and lows to pass through the
Great Lakes bringing periodic rain chances. We currently don`t see
any specifically heavy rain events on the horizon, but definitely a
more typical fall-like pattern in terms of both temperatures and
rain chances as we head into the 2nd half of October.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 722 PM EDT Sun Oct 12 2025

VFR diurnal Cu will diminish over the next 1-2 hours. Then, the
potential exists for fog and low stratus overnight across West
Michigan, however uncertainty as to the impact of upstream
mid/high clouds has confidence lower in how far conditions will
deteriorate tonight. Have continued MVFR at AZO, GRR, and BTL, and
introduced a mention of IFR at AZO where crossover temperatures
best support worse conditions. IFR and lower conditions are most
likely at LAN and JXN where the least impact of mid/high level
clouds will be felt. Have introduced IFR at LAN given this and
LIFR at JXN given lighter winds and local effects. However, this
forecast does have bust potential in both directions. If clouds
largely limit their impact to the lakeshore region, more
widespread IFR and lower conditions are possible similar to last
night. If cloud cover is more robust, visibilities will be higher
at the terminals. Fog will burn off after sunrise, with southeast
winds becoming west to northerly.

&&

.MARINE...
Issued at 300 PM EDT Sun Oct 12 2025

Southeast winds of 10-20 knots are expected through the day, with
offshore flow keeping waves below small craft levels today. Winds
slowly veer to northerly by Monday Night as a system moves into the
region. Increasing northerly flow to around 20 knots Tuesday into
Tuesday Night may be sufficient to bring Small Craft Advisory level
waves into our waters, particularly south of Holland. A second
system will bring another chance for hazardous winds and waves to
Lake Michigan, along with rain, Friday into the weekend.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...AMD
AVIATION...Thomas
MARINE...Thomas