218
FXUS63 KGRR 150748
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
348 AM EDT Sat Aug 15 2026
.KEY MESSAGES...
- Chance of showers and isolated thunderstorms this weekend
- Drier and more comfortable Monday
- Midweek shower/storm chance
&&
.DISCUSSION...
Issued at 348 AM EDT Sat Aug 15 2026
- Chance of showers and isolated thunderstorms this weekend
Quasi-stationary front with active convection remains stuck over
Illinois and Indiana. With an 850 mb ridge moving east of the
area, some higher low-level moisture (increasingly muggy dew
points) will drift into southern Lower Michigan this weekend.
Limited upper-level shortwave forcing, thin CAPE, and weak
vertical shear will make for generally meager convection today,
often along zones of temporarily increased surface confluence.
PWAT will be rather high, so despite the model trends to back away
from heavier mean QPF solutions, rain totals around 0.5 to 1 inch
remain possible but will be patchy and isolated, and mainly near
and south of I-96.
Anticipating muggy air with dew points in the lower to mid 70s on
Sunday. Areas of fog are possible in the morning given the moist,
still air and the potential for skies to partially clear Saturday
night. 850 mb temperatures on Sunday will be a little warmer
while 500 mb heights fall as the upper-level ridge flattens out a
bit. As a result, CAPE should climb toward 1000 J/kg during the
day. Scattered thunderstorms may develop in the vicinity of a
cold front and/or midlevel MCV. Heavier downpours will remain the
mode in any thunderstorms, and hit-or-miss heavier totals greater
than an inch are possible.
- Drier and more comfortable Monday
Behind the cold front, high temperatures Monday may not be much
cooler, though will be noticeably less humid as air from the
northern plains flows through. A good amount of sunshine is also
expected.
- Midweek shower/storm chance
Late Tuesday into Wednesday, somewhat increased low-level
moisture returns from the central CONUS, then upper-level heights
fall and a cold front sags through, associated with an upper-
level low over Hudson Bay and a trough digging into Ontario and
the northern Great Lakes. Instability builds and scattered
thunderstorms may develop with hit-or-miss beneficial rain.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 200 AM EDT Sat Aug 15 2026
Generally less favorable flight conditions are expected in
southern Michigan and better conditions in central, while
aerodromes such as MKG, GRR, and LAN may experience more of a mix
of conditions. The onset of worsening flight categories is rather
low confidence in timing as models have not been handling the
weakly forced showers well so far, and later shower development on
Saturday is also expected to be weakly forced. It is possible that
these TAFs are too optimistic, and temporary IFR visibility may
occur today under moderate rain showers, and patchy MVFR ceilings
may develop as the lower atmosphere moistens inconsistently.
&&
.MARINE...
Issued at 348 AM EDT Sat Aug 15 2026
Offshore flow today will keep waves low at West Michigan beaches
while larger waves build in the open waters toward Wisconsin.
More of a west wind at 10 knots is expected on Sunday, making
waves about 1 to 3 feet. Scattered showers and isolated
thunderstorms may occasionally develop over the lake this weekend.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...CAS
AVIATION...CAS
MARINE...CAS
NWS GRR Office Area Forecast Discussion
