036
FXUS63 KGRR 051757
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
157 PM EDT Sat Sep 5 2026

.KEY MESSAGES...

- Fair Weather through Labor Day

- Chance for showers and Thunderstorms Tuesday and Wednesday

&&

.DISCUSSION...
Issued at 157 PM EDT Sat Sep 5 2026

- Fair Weather through Labor Day

An Omega block develops across the CONUS this weekend as the
central U.S. upper high is bookended by cut off lows across the
NE and NW CONUS. This lowers heights across the central Great
Lakes and allows surface high pressure ridge to build in from the
northeast with lower temperatures and dew points. Showers end this
afternoon and clearing pushed south this evening with it becoming
noticeably cooler overnight. Morning lows on Sunday and Monday
expected to be in the upper 40s to lower 50s across the northern
forecast area.

- Chance for showers and Thunderstorms Tuesday and Wednesday

The surface high retreats east eastward by Tuesday. The Omega
block breaks down as a low across the Pacific NW kicks east and
flattens the upper high, with surface low pressure tracking across
southern Canada. Return flow of moisture and a surface warm front
should kick off some showers and thunderstorms late Tuesday into
Wednesday. Another round of storms will be possible as a cold
front moves through late Wednesday and shear profiles suggest
strong storms are possible if instability is sufficient.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 135 PM EDT Sat Sep 5 2026

Rain showers with local/temporary IFR stretch from MKG to south of
GRR and are slowly moving south. These showers should gradually
diminish with time. MVFR ceilings along and southwest of MKG-GRR-
LAN should gradually improve to above 3,000 feet and/or scatter
out this afternoon, though there may be patchy MVFR ceilings
hanging on through 00 Z. Will also have to evaluate patchy fog
potential on Sunday 09 to 13 Z.

&&

.MARINE...
Issued at 157 PM EDT Sat Sep 5 2026

Light offshore winds, generally less than 15 knots, can be
expected through Monday. High pressure will move east on Tuesday
and winds will be on the increase, with a Small Craft Advisory
probably being needed for Tuesday and Wednesday.

&&

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

&&

$$

DISCUSSION...Ostuno
AVIATION...CAS
MARINE...Ostuno