849
FXUS63 KGRR 241122
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
722 AM EDT Sun Aug 24 2025

.KEY MESSAGES...

- Lake Effect Showers and Cooler

&&

.DISCUSSION...
Issued at 335 AM EDT Sun Aug 24 2025

- Lake Effect Showers and Cooler

An upper level low will circulate over James Bay bringing a series
of shortwave troughs along with colder air aloft. Timing of the
initial shortwave moves through this afternoon bringing shower
chances across the area and triggering lake effect showers to
begin along the lakeshore as 850 mb temperatures drop. Another
shortwave Monday morning will help drive showers farther inland
again. PoPs may need to be increased for Tuesday as well with
another shortwave rotating through before the upper level low
lifts northeast.

With the lake effect showers there could be some rumbles of
thunder as there will be enough instability over the lake with
warm water temperatures around 20 to 25 degrees Celsius. 850mb
temperatures around 5 degrees Celsius will also put us within
thresholds for waterspouts to develop over Lake Michigan. If
waterspouts occur and they happen to move onshore, make sure to
keep your distance as they contain winds greater than 40 mph and
can loft loose objects.

Another front moves through Thursday which may spark off a few
showers and thunderstorms although chances are low (20 to 30
percent) at this time. Otherwise dry conditions are expected
through the remainder of the week with highs in the 60s and 70s
warming up to near 80 for next weekend. Tuesday night currently
looks to be the coldest with lows in the 40s across much of the
area with some isolated spots potentially dropping into the upper
30s.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 718 AM EDT Sun Aug 24 2025

Not much of a change from the previous forecast. Showers develop
this afternoon mainly along the lakeshore with a 20 to 30 percent
chance further inland. Thunderstorms may make it inland off the
the lake this afternoon and evening, therefore added a Prob30 in
MKG`s TAF. Ceilings will generally be in the 4000 to 6000 ft range
as clouds fill in this afternoon and evening. Some areas along the
lakeshore may drop down to 2500 ft during the late afternoon and
evening. Northwest winds will continue through the day with gusts
around 20 knots this afternoon.

&&

.MARINE...
Issued at 335 AM EDT Sun Aug 24 2025

Winds and waves will continue to be hazardous to beachgoers and
small craft within the persistent northwest winds. Gusts to 25
knots are possible mainly during the afternoon and evening with
waves building to 3 to 5 feet. In addition to winds and waves,
lake effect rain showers, thunderstorms, and waterspouts will
also be possible. Make sure to keep your distance from any
waterspout as they contain winds greater than 40 mph and can loft
loose objects. These hazards are expected to continue into Monday
before subsiding late Monday afternoon into Monday night.

The remainder of the week winds largely remain on the lighter
side with mostly dry conditions.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Monday evening for MIZ037-043-
     050-056-064-071.
MARINE...Small Craft Advisory until 8 PM EDT Monday for LMZ844>849.

&&

$$

DISCUSSION...RAH
AVIATION...RAH
MARINE...RAH