Small Craft Advisory 39, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
314 PM EDT Thu Jun 4 2026

.KEY MESSAGES...

- Periods of showers and thunderstorms Friday through Saturday

- Potential chances for rain early next week

- Building heat mid to late next week

&&

.DISCUSSION...
Issued at 220 PM EDT Thu Jun 4 2026

- Periods of showers and thunderstorms Friday through Saturday

Convection upstream in the Plains states tonight driven by an
increasing low level jet will try to spill eastward into Western
Lower Michigan after about 500am in a decaying non-severe mode.
HREF 4hr reflectivity shows areas from Holland northward standing
the best chance at rainfall through 800am.

After 800am, the area of rain will spread eastward through the
GRR forecast area. During the midday into the afternoon on
Friday with some building weak instability (500-1000 j/kg) we
expect convection to increase, initially on the southern end of
the activity which will occur south of I-96 and then over much of
the area. The activity in the afternoon will be aided by a weak
shortwave trough in the mid levels. It is not out of the question
that there may be strong to severe storms Friday afternoon and
evening across Southern Lower Michigan especially. Near and south
of I-96 stand the best chance at severe storms during this time.
Given stronger winds noted at both 850mb and 500mb, damaging winds
will likely be the bigger severe threat. Machine learning tools
like Nadocast also support winds being the primary threat.

There will likely at least somewhat of a lull in the activity
Friday night as the low level jet and its associated convection
peel off to the east. We have been monitoring the chance for
additional convection on Saturday ahead of the southward moving
cold front. The front may be a bit quicker in the latest model
runs and we wonder how much airmass recovery can occur before it
begins to push out of the area. The threat area on Saturday will
be near/south of I-96 once again, especially down towards I-94.
Deep layer shear near the front is fairly strong 30-40 knots so
severe weather is not out of the question.

- Potential chances for rain early next week

Early next week and potentially into the middle of the week,
models are trying to show an upper low moving into the mean ridge
position aloft over the Great Lakes. At this point will side
towards the ECWMF which does not have as pronounced of an upper
low. At this point we have low pops in the forecast from Monday
night into Wednesday. Could see these pops needing to be lowered
with time with the ridge holding firm.

- Building heat mid to late next week

The upper ridge builds after Wednesday with heights pushing into
the 590s late in the week. If that verifies and it is our current
forecast that it will, we are looking at highs in the 90s. Even
early in the week highs will remain in the 80s so summer warmth
looks like it is here.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1259 PM EDT Thu Jun 4 2026

VFR continues into tonight ahead of a front that will move through
the region on Friday. Showers and possibly a few thunderstorms
could begin impacting mainly MKG/GRR/AZO by 18z Friday. Given some
uncertainty regarding intensity and coverage, PROB30s are the
appropriate way to handle the threat until getting into the
16z-18z time frame for these sites when SHRA may be predominant.
With questions regarding the degree of instability present, will
hold off mention on TSRA for now through the 18z ending of these
TAFs.

&&

.MARINE...
Issued at 220 PM EDT Thu Jun 4 2026

We will be issuing a Small Craft Advisory from Holland northward
to Manistee. South winds increase tonight and into Friday to a
point where south winds of 15 to 25 knots should become common.
Some gusts should push towards 30 knots at times. This will push
waves into the 3 to 5 foot range. The Small Craft Advisory may
need to be expanded in area to the south and in time as there is
some indication that winds could hang on a bit longer and/or be
aided by thunderstorms. A period of lighter/offshore winds will
occur Saturday night into Sunday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 8 AM to 11 PM EDT Friday for
     LMZ846>849.

&&

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