677
FXUS63 KGRR 021123
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
723 AM EDT Sat Aug 2 2025

.KEY MESSAGES...

- Wildfire smoke likely to impact the area this weekend

- Mainly dry and seasonable weather to continue through next week

&&

.DISCUSSION...
Issued at 314 AM EDT Sat Aug 2 2025

- Wildfire smoke likely to impact the area this weekend

Guidance from Michigan EGLE and run to run consistency from smoke
models like with the HRRR indicate that smoke will return to most of
the area through today. Some of it will float down from Northern
Lower where visibilities indicate that it is in place at the sfc
already, and quite a bit will mix down in place this afternoon. The
product AQAGRR has more specifics directly passed on from EGLE.

- Mainly dry and seasonable weather to continue through next week

Aside from the smoke, high confidence remains with regards to a
mainly dry pattern through much of next week, with seasonable
temperatures, and comfortable dew points into early next week before
increasing.

Sfc ridging will be directly overhead through Sunday as we will
remain downstream of a lower amplitude upper ridge. A lack of any
significant flow will keep dew points low in the 40s and 50s. That
dry air combined with the subsidence will keep us dry through Sunday.

The sfc ridge reorients itself, and shifts to Ontario by early next
week. We will still be under the ridge axis, but the subsidence
weakens some as a result. A quite dry atmosphere will continue to
limit rain chances combined with still subsidence in place.

Small rain chances will appear mid-late week, but will be spotty at
best in coverage. This means that a majority of the area will remain
dry through next Friday. The upper ridge weakens a bit as weak short
wave energy tries to flatten it a bit. At the same time, the low
level flow is trying to increase moisture a little bit as it comes
from the Atlantic, vs. from the continental portions of Eastern
Canada. The result will be probably about 20% coverage along lake
breezes that form in the afternoon and coincide with max
heating/diurnal instability.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 723 AM EDT Sat Aug 2 2025

A little bit of ground fog has formed at a few sites this morning,
mainly KJXN and KGRR for the forecast terminals. This fog will
remain shallow and short lived with the sun coming up and mixing
it out quickly. Some high clouds are floating through this
morning, and a few high based cumulus clouds are expected this
afternoon.

Wildfire smoke coming in from Canada is still expected to impact
visibilities a bit this afternoon, and likely through tonight.
Right now we are thinking that MVFR is likely as it drops south
through the state, and mixes down from aloft mid-afternoon.

&&

.MARINE...
Issued at 314 AM EDT Sat Aug 2 2025

After a couple of days of winds and waves increasing late in the
afternoon, we are looking at a few days of relatively light winds
and small waves.

The last couple of days has featured high pressure at the sfc
building in, and working with lower pressures inland to produce
mesoscale wind and wave cores over the lakeshore. Today, and the
next few days will be different with a weak pressure gradient now
established over the area. This will result in winds mainly under 15
knots and waves under 2 ft.

Some smoke will be possible over the lake, reducing visibilities
some. This may be limited as compared to land areas as it appears
much of the smoke will mix down. Less mixing over the relatively
cooler waters leads us to believe this will occur in this scenario.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT tonight for MIZ037>040-
     043>046-050>052-056>059-064>067-071>074.
MARINE...None.

&&

$$

DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ/Thomas