937
FXUS63 KGRR 061742
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
142 PM EDT Sat Jun 6 2026

.KEY MESSAGES...

- Dry and seasonably warm this weekend

- Showers and thunderstorms return late Monday into Tuesday

- Hotter and humid late week with chances (30-50 percent) for
thunderstorms


&&

.DISCUSSION...
Issued at 142 PM EDT Sat Jun 6 2026

- Dry and seasonably warm this weekend

Down around I-94, we are not totally out of the woods yet regarding
thunderstorm potential this afternoon. However, satellite water
vapor imagery indicates drier air associated with subsidence is now
overspreading this area and visible imagery indicates that cumulus
convection already looks decidedly less vigorous than it did an hour
ago. Can`t rule out a stray shower or thunderstorm however. By this
evening, precipitation chances should all but disappear for the rest
of the weekend.

A sharp northern stream upper ridge will cross the western Great
Lakes during the remainder of this weekend, yielding dry conditions
and surface pressure ridging. Light northeast surface winds on
Sunday will result in slightly drier conditions with maximum
temperatures highest immediately by the lakeshore.


- Showers and thunderstorms return late Monday into Tuesday

By late Monday, the upper level ridge axis will have progressed to
the eastern Great Lakes, leaving the western Great Lakes beneath
southwest flow aloft. An upper PV max in this flow approaches Lower
MI Monday, bringing favorable mid-level ascent and resultant
destabilization. As noted previously, we remain in a marginal risk
for excessive rainfall on Tuesday. Additionally, some of the NCAR ML
guidance hints at a chance for severe weather on Tuesday across
parts of Lower MI. That said, deep layer shear appears rather
weak as does the mean flow in the cloud bearing layer. This
supports the idea of slow-moving multicell clusters with the
potential to produce locally heavy rainfall and perhaps marginally
severe wind gusts.


- Hotter and humid late week with chances (30-50 percent) for
thunderstorms

The latest round of guidance advertises greater precipitation
chances starting Wednesday at the same time lower tropospheric
temperatures are expected to rise. It should be noted that forecast
highs are strongly based on NBM guidance, which has been a bit of a
warm outlier compared to other sources such as the ECMWF ensemble,
for instance. Diurnally augmented thunderstorms earlier in the day
are quite plausible given persistent background conditional
instability; this would have a damping effect on achieving high
temperatures. So, this becomes a tricky temperature forecast given
that deep moist convection is highly plausible throughout the
period. This will be a very summer-like pattern with the typical
limited predictability issues that accompany it.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 142 PM EDT Sat Jun 6 2026

Cumulus development through early afternoon mainly from BTL to JXN
could support a low chance / PROB30 / for a shower to impact those
terminals through about 20z. Otherwise, expecting some cloud bases
around 3-4k ft this afternoon before clearing this evening and
tonight. Light W to WNW winds this afternoon go light and variable
overnight before turning ENE into Saturday morning.

&&

.MARINE...
Issued at 142 AM EDT Sat Jun 6 2026

No headlines for elevated winds and waves are anticipated, but
marine fog will remain a threat over the open waters. There is some
question regarding how much the nearshore waters will similarly be
affected as we saw this morning. The next couple days will be more
favorable for lake/land breeze circulations that may help to dilute
the marine boundary layer by the lakeshore and reduce the fog threat.
However, even if this happens conditions could be significantly
worse even a couple of miles offshore. We will need to monitor
satellite and webcams to further assess this. Otherwise, thunderstorms
will be a lingering threat from late Monday onward.


&&

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

&&

$$

DISCUSSION...TJT
AVIATION...Hoving
MARINE...TJT