FXUS63 KGRR 240455
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1255 AM EDT Mon Aug 24 2026

.KEY MESSAGES...

- Afternoon Showers Today

- Dry Monday/Tuesday, Showers and Thunderstorms Wednesday

&&

.DISCUSSION...
Issued at 149 PM EDT Sun Aug 23 2026

- Afternoon Showers Today

Moisture from Lake Michigan, steep low level laps rates providing
around 200 J/kg of CAPE, along with mid level support from the
upper level low are sparking off isolated to scattered showers.
These will be largely north of a Ludington to Jackson line before
the inversion builds in this evening and we lose our surface based
instability. Thunderstorms are not expected.

- Dry Monday/Tuesday, Showers and Thunderstorms Wednesday 

Pressure heights increase Monday into Tuesday as the upper level
low over the eastern Great Lakes shifts east. Northwest winds will
continue for Monday with gusts to 20 mph. Tuesday winds will be
lighter and more variable. High temperatures will be in the 70s
Monday and warm to around 80 for Tuesday. Low temperatures will be
in the 40s and 50s.

Southerly winds build in ahead of our next shortwave trough that
is expected to slowly move through Wednesday. Warm air advection 
and the low level jet will feed into the area with instability 
around 1000 J/kg. Shear values only look to be around 25 knots, 
therefore confidence in storms becoming severe is low. Long range 
ensemble clusters are in good agreement that most of the rain ends
by Thursday morning, although we could see another round of 
diurnal showers similar to today Thursday afternoon. The 
probability of a half inch of rain in 24 hours during this time is
less than 20 percent.

Friday ensembles are in good agreement to expect dry conditions
but confidence decreases over the weekend as we remain in
transitional flow where a few weak shortwaves could bring
additional chances for showers and thunderstorms.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1252 AM EDT Mon Aug 24 2026

VFR conditions for this TAF period with some few/sct cumulus
developing after about 14z. Winds will be less gusty today
compared to Sunday, but still holding fairly steady from the WNW.
Just beyond this TAF period, we may see some fog development into
Tuesday morning. Will take a closer look for the 12z TAF issuance.

&&

.MARINE...
Issued at 149 PM EDT Sun Aug 23 2026

Wave heights around 4 feet have been observed this afternoon with
northwest winds gusting around 20 knots. Expect Small Craft
Advisory and High Swim risk conditions to continue into this
evening before winds and waves subside tonight. Wave heights could
remain around 4 feet north of Big Sable after midnight.

Northwest winds 10 to 20 knots Monday will keep wave heights
around 2 to 3 feet. Moderate Swim Risk conditions are expected
through Monday afternoon before wave heights fall below 2 feet
Monday night into Tuesday. The next chance for Small Craft
Advisory and High Swim Risk conditions will be Wednesday which
matches up with our next chance for showers and thunderstorms.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

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