464
FXUS63 KGRR 052355
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
755 PM EDT Fri Jun 5 2026

.KEY MESSAGES...

- Periods of showers and thunderstorms through Saturday

- Chances for showers and storms Monday night into mid week

- Warm and humid next week

&&

.DISCUSSION...
Issued at 313 PM EDT Fri Jun 5 2026

- Periods of showers and thunderstorms through Saturday

Several rounds of showers and storms are expected across Southwest
Lower Michigan between this afternoon and Saturday evening. The
first threat comes this afternoon and evening as a mesoscale
convective vort (MCV) moves northeast through the forecast area.
The leading edge of this vort max has become diffuse with time,
but is situated near mid lake over the southern bowl of Lake
Michigan. Little in the way of convection is ongoing at this time
associated with it. Most unstable CAPE values are only around 500
j/kg at this time, which is probably the main reason we are not
seeing more activity develop. This is due to fairly widespread
showers today along with lingering cloud cover. There are a few
breaks in the overcast for additional heating, but there are not
many. Overall feeling the threat this afternoon and evening is
fairly low given the lack of building instability. Not out of the
realm of possibilities though that we could see a few strong winds
gusts if storms can organize. We will be watching.

Tonight, instability actually builds in a southwest flow as
unstable air is advected in southwest flow ahead of a cold front.
We are expecting MUCAPE values to reach the 1000-2000 j/kg range
despite the time of day. This is owed to the deep moisture that
moves in. Tonight`s convection actually has more going for it with
better dynamics in play. A shortwave moves in from the northwest
which will be driving a cold front into the unstable airmass over
our area. Deep layer shear is roughly 30-40 knots so severe
weather is very much possible. Actually all hazards are in play
tonight.

The severe weather threat may continue towards daybreak in
Southern Lower Michigan towards I-94 as the deep moisture remains
in place ahead of the cold front. There may be just enough time to
rekindle a few storms near I-94 again into the midday hours before
the cold front sweeps south. The main threat may actually be the
overnight convection though after midnight.

- Chances for showers and storms Monday night into mid week

The upper pattern for several days in a row now has shown
shortwave troughing trying to move into the mean ridge position
across our area. Hard to ignore this continuity. We have chances
for showers and storms from Monday night at least into mid week.

- Warm and humid next week

Warm and humid conditions are expected all next week. 80s for
highs will be common and we will push into the 90s late in the
week. The ECWMF is not as warm as it was a few days ago at 850mb
on Thu/Fri as 24-25C has come down to 21-22C. Bottom line it is
going to feel like summer, but maybe not quite as warm as we were
thinking.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 755 PM EDT Fri Jun 5 2026

The back edge of rain is moving through the LAN and JXN terminals
at the start of this TAF period. In general, other than some light
showers there will be a lull in activity until additional showers
and probably some thunderstorms get going in the 02z-04z time
frame in scattered fashion. This occurs ahead of a more organized
line of storms moving toward our region from Wisconsin, likely
crossing the lake around or shortly after 04z. There is a chance
for some gusts to reach or possibly exceed 30 kts with this line
as it sweeps southeast through the region. Some waning in the
intensity may occur, so uncertainty exists in how strong the
storms will be as they approach the terminals from NW to SE. Good
confidence exists in IFR conditions developing in the 05z-09z time
frame for most if not all terminals as ceilings begin lowering
overnight into early Saturday as moisture-rich air advects into
the region. Expect the threat for IFR to decrease especially after
12z Saturday, and with it the chance for rain also gradually
subsides.

&&

.MARINE...
Issued at 313 PM EDT Fri Jun 5 2026

Have opted to drop the Small Craft Advisory and the Beach Hazards
Statement as conditions are below criteria at this point and not
expected to make a significant increase this evening. There may be
some 3 footers for a time this evening near Muskegon, but all the
nearshore buoys to the north right now are indicating 1-2 foot
waves. The gradient gets more slack as we head into tomorrow, so
we should remain below advisory thresholds heading into the
weekend.

&&

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

&&

$$

DISCUSSION...Duke
AVIATION...Hoving
MARINE...Duke