330
FXUS63 KGRR 011714
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
114 PM EDT Fri Aug 1 2025

.KEY MESSAGES...

- Extended period of quiet, mild, and less humid weather

- Low rain chances return mid-week next week

&&

.DISCUSSION...
Issued at 317 AM EDT Fri Aug 1 2025

- Extended period of quiet, mild, and less humid weather

Lower Michigan (and much of the Great Lakes region) is going to see
an extended period of Chamber of Commerce type of weather for
potentially the next week. This will be the result of a fairly
stable and stagnant upper air pattern over much of North America.
The two main players are a large upper low east of Hudson Bay, and
an expansive upper ridge over the Plains.

We remain under the far SW periphery of the large upper low over
Eastern Canada. This position keeps all of the jet energy north of
the area, but relatively cooler temperatures with the lower heights
overhead. In addition, the associated sfc high will be feeding
cooler and drier air in from the NE around the sfc ridge to our west.

We will see a slow progression of this pattern with slow building
of heights slowly warming our temperatures over the next few
days. A lack of advection of moisture through early next week will
keep dew points low and humidity levels comfortable for most.

The downfalls of this pattern will be that the drought stricken
areas of the state will not see any relief in the form of rainfall,
and the NW flow aloft will keep potential of wildfire smoke from
Western Canada a bit elevated at times.

- Low rain chances return mid-week next week

Ensemble probabilities show that 60F dew points may not arrive until
around Tuesday of next week as the sfc high nudges east, and some
semblance of a southerly flow sets up.

This is important in the sense that maybe enough moisture will be
present by then to increase the chance of rain, albeit slightly.
This advection of moisture will allow for some afternoon
shower/storm chances. These will be mostly of the air mass variety
that form on various mesoscale boundaries like the lake breeze,
terrain influences, etc...

The upper air pattern will not be conducive to any significant rain
chances as the heat dome and any ring of fire storm complexes will
stay SW of the area, and any northern stream waves that could
produce better chances will stay well north of the area. We are
looking at mostly 10-20% chances of showers/storms for Wed/Thu of
next week. That means most areas will stay dry through next
Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 114 PM EDT Fri Aug 1 2025

High confidence in VFR conditions exists for much of the TAF
period with one key caveat. SCT mid-level clouds have been
observed and will dissipate after sunset with brief periods of
high based VFR cigs at LAN/JXN thanks to enhancement of moisture
from Lake Huron. The main concern for any sub VFR conditions
arrives mid to late Saturday Morning, when wildfire smoke mixing
down may send visbys into the 3-6SM range. Given that model
handling of smoke concentrations hasn`t been great in recent days
will not include restrictions in the TAFs but that will be
something to monitor. Expect predominantly northeasterly flow
under 10 knots, with the exception of MKG shifting to
northwesterly each afternoon due to the lake breeze.

&&

.MARINE...
Issued at 114 PM EDT Fri Aug 1 2025

No significant marine concerns over the next several days as high
pressure and weak gradient flow dominate the forecast. A brief burst
of wind is expected along the coast this afternoon associated with a
thermal low developing across the land, though with winds to only
around 15 knots 2-4 foot waves with a moderate swim risk is favored.
Water temps remain on the cool side thanks to upwelling due to
recent northerly flow. Water temps remain in the upper 50s at St.
Joseph and South Haven this afternoon.

&&

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

&&

$$

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