Portage, Michigan Weather Forecast Discussion

087
FXUS63 KGRR 300535
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
135 AM EDT Tue Sep 30 2025
.KEY MESSAGES...
- Warm and dry conditions will continue this week
&&
.DISCUSSION...
Issued at 219 PM EDT Mon Sep 29 2025
- Warm and dry conditions will continue this week
Only impactful weather expected in the short term is patchy morning
fog Tuesday chiefly affecting our eastern forecast area. Please
refer to the AVIATION section of this discussion for additional
details. Fog coverage in general the past few mornings has
diminished as we see progressively reduced evapotranspiration
several days removed from our last significant rain. However, this
will be compensated for as we experience more pronounced
northeasterly flow that will source boundary layer moisture from
Saginaw Bay and Lake Huron. As previously noted, any fog will be
quick to dissipate after sunrise.
A sharpening upper ridge over the Manitoba region Tuesday will
reinforce the associated downstream surface high and drive a back
door cold front into the forecast area. Maximum temperatures
Wednesday consequently will be close to 10 degrees cooler, but
still above normal. Maximum temperatures could be back in the
lower 80s by this weekend which is significantly above the typical
mid/upper 60s associated with early October.
Precipitation chances this weekend remain limited but some guidance
does suggest the upper ridge will break down. Predictability will
probably remain limited until mid week at best.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 135 AM EDT Tue Sep 30 2025
More of the same general conditions for these aviation forecasts
as we have seen over the past few days. Skies will remain mostly
clear. We are thinking some patchy fog will once again be
possible. We have gone with ground fog at KGRR, with more dense
fog at the other inland sites aside from KMKG. Any fog will burn
off by 13-14z. This will leave mostly sunny skies once the fog
dissipates. The winds will pick up from the ENE around 8-10 knots
at all sites. These winds will stay up enough to likely hold the
lake breeze at bay right along the shore.
&&
.MARINE...
Issued at 145 PM EDT Mon Sep 29 2025
Light winds and low waves are expected through much of Tuesday.
Wind direction will tend to get tugged northwest this afternoon
and Tue afternoon with the contribution of the daytime lake
breeze, otherwise winds will mostly be from the northeast/east
tonight through Wednesday. Tuesday night, breezier east-northeast
winds 10-20 knots are possible, which will build up larger waves
toward midlake.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...TJT
AVIATION...NJJ
MARINE...CAS

NWS GRR Office Area Forecast Discussion