234
FXUS63 KGRR 041111
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
711 AM EDT Mon Aug 4 2025

.KEY MESSAGES...

- Some possible improvement with the wildfire smoke today

- Small rain chances inland areas Wednesday afternoon

- Becoming very warm and increasingly humid later this week

&&

.DISCUSSION...
Issued at 328 AM EDT Mon Aug 4 2025

- Some possible improvement with the wildfire smoke today

We are under another Air Quality Alert for today from Michigan EGLE.
The plume of smoke that has been stuck under the light wind regime
of the ridge over the area has the chance to move back north a
little bit today and allow for some improvement later. This is due
to the center of sfc ridge moving NE of the area. This will allow a
little bit of a southerly component to move in and potentially push
the southern edge of the smoke a little bit north. It will not
completely go away with no significant wind to move it out.

- Small rain chances inland areas Wednesday afternoon

Aside from the wildfire smoke from Canada, we continue to remain
under a seasonably warm and less humid air mass. Even though the
center of the sfc ridge moves away from the area, we will still see
an extension of the ridge axis remain overhead. Limited sfc moisture
return and mild mid-levels and subsidence will continue to allow for
dry conditions to continue through Tuesday.

We have added a small pop to the forecast for inland locations for
Wednesday afternoon. There are some subtle changes going on to make
this happen. Dew points at the sfc inching up, along with a weak
upper trough as a weakness between two upper ridges dominating the
U.S. weather will allow for about a 20 pop or so. MU CAPEs are
forecast to increase to as much as 1,000+ J/kg, and the mid level
warm layer weakens a bit to allow for some vertical development. The
main impetus at the sfc will be areas of lake breeze convergence and
any other mesoscale convergence features. Anything that forms will
likely not be too organized with a light flow aloft significantly
limited deep layer shear.

- Becoming very warm and increasingly humid later this week

The weak trough inbetween the upper ridging that will be over the
area on Wednesday, will shift east of the area by Thursday. This is
the result of the heat ridge that has been over the Southern Plains
expanding/building over our area.

Mid levels warming considerably will cap any convection that tries
to fire for Thursday and through the weekend. Instability will
increase with better dew points/moisture moving in. The cap will
prevent it from doing much with the instability. This ridge is
looking more and more likely that it will bring very warm
temperatures as the heights build, and increasingly humid conditions
as the flow from the south slowly brings in.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 710 AM EDT Mon Aug 4 2025

As expected, some patchy fog has developed at some of the
terminals. For the most part it has been MVFR with some spotty IFR
at times. The fog will diminish, but some smoke may hang on,
keeping visibilities from completely recovering initially. We do
believe that the smoke will not cause as much of an impact as the
last couple of the days in the afternoon. This is because the
winds from the SE are picking up, and short term guidance shows
that the smoke will move a bit north today.

There will likely be some cumulus cloud cover for inland locations
this afternoon and evening. Skies should clear out this evening.
Fog does not look as likely with winds up just a little over last
night, and with less expected smoke.

&&

.MARINE...
Issued at 328 AM EDT Mon Aug 4 2025

The main theme for marine interests continues to be lighter winds,
small waves, and cold water temperatures from the recent upwelling
event. We will see another day in which the flow will be from the
east/offshore in nature, and then switch to onshore in the afternoon
as the lake breeze develops.

The gradient will slowly increase slightly through the week, and
gradually shift from the flow from the east, to more from the south
by later in the week. Latest guidance is a little weaker with the
flow for the end of the week, potentially pushing possible headlines
until next weekend.

&&

.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