044
FXUS63 KGRR 231749
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
149 PM EDT Sun Aug 23 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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 149 PM EDT Sun Aug 23 2026
VFR conditions will prevail at all West Michigan TAF sites through
the 24 hour TAF period. Daytime warming coupled with cooler air
aloft will continue to support SCT-BKN CU this afternoon /4-5 kft/
particularly east of a GRR to BTL line. Isolated brief showers will
also be possible (20-30%) in vicinity of LAN. CU will diminish this
evening, with a few CU returning again by late Monday morning,
though coverage should be less than today.
Winds will remain NW throughout TAF period. Gusts of 20-25 kt are
likely this afternoon. Winds will subside to around 5 kt this
evening, then increase again to 10-15 kt by late Monday morning.
&&
.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...Beach Hazards Statement until 11 PM EDT this evening for MIZ037-
043-050-056-064-071.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ844>849.
&&
$$
DISCUSSION...RAH
AVIATION...Smith
MARINE...RAH
NWS GRR Office Area Forecast Discussion
