042
FXUS63 KGRR 161136
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
736 AM EDT Mon Jun 16 2025

.KEY MESSAGES...

- Shower/storm chances begin Tue; Severe weather possible late Wed

- Rounds of storms Thursday through Saturday

- Heat and humidity build next weekend

&&

.DISCUSSION...
Issued at 332 AM EDT Mon Jun 16 2025

- Shower/storm chances begin Tue; Severe weather possible late Wed

Generally speaking, the most likely period of quiet weather for the
area will be the first 24 hours of the forecast into Tuesday
morning. This is a result of weak ridging in place over the area
between low pressure out over the Plains states, and the stalled out
frontal boundary to our south with the deep moisture locked up well
south.

That said, we will have a decent amount of mid and high clouds
today, and decent cumulus development away from Lake Michigan.
Forecast soundings actually show that the cumulus clouds could have
some depth, and you can not rule out a pop up shower/sprinkle inland
where mesoscale troughing will take place between Lakes Michigan and
Huron.

More legit rain chances will begin as early as very late
tonight/very early Tuesday morning over the NW portion of the
forecast area. This results from a sfc low moving by to our NW. The
front will stay west of the area through tonight, but the NW portion
of the area will be on the eastern edge of the better low level
jet/moisture advection ahead of the front.

The sfc front does eventually drop down over the area by Tuesday
night. This will only increase the shower/storm chances with the
better convergence settling in. In addition, we will see a stronger
area of low pressure organize over the Plains as a fairly potent
upper trough swings in from the SW. We will see a stronger low level
jet take shape to our west, and intersect the front, developing more
elevated convection over the region.

What we think is more likely to happen is that convection will be
around Tuesday night and Wednesday morning. Then, we are likely to
see a break as the warm front with the developing low to our SW
pushes through at least the southern half of the forecast area. This
could be setting the area up for potential severe weather Wednesday
evening if we see some decent heating in the warm sector. The strong
upper wave will be pushing right over the area around or just after
peak heating. We agree with the SPC continuing to highlight the area
for Wednesday in the new Day 3 outlook.

- Rounds of storms Thursday through Saturday

The likelihood and strength of showers/storms will be much lower on
Thursday compared to Wednesday, but not zero. The main short wave
with the longer wave trough moving through will remain over the
area. Some heating, and troughiness continuing will keep the chance
in for Thursday.

Things then start looking more interesting in the Friday through
Saturday time frame. We will see the Wednesday/Thursday trough move
out, and then see an upper ridge out over the Plains start to build
toward the area. For the Friday and Saturday time frame, we will be
right on the edge of the heat dome, with the ridge building. This
scenario will provide multiple rounds of MCS activity in a ring of
fire type of pattern. Tough to tell where the axis of MCS ends up
setting up exactly. It is close enough to our forecast area that we
will have pops in the forecast.

- Heat and humidity build next weekend

The upper ridge is expected to build enough by Sunday, that the area
will be firmly under the heat by then. Warm air aloft with the high
heights will cap our atmosphere, with the ring of fire likely moving
north into Canada. We could be looking at some 90 degree
temperatures with enough moisture to have heat indices a bit higher
than sfc temperatures.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 736 AM EDT Mon Jun 16 2025

Mid and high clouds are currently moving over the area this
morning. They will continue to be present, and cumulus clouds will
develop this afternoon with the heating of the day. The cumulus
clouds will likely become bkn inland, and stay scattered near the
lakeshore. All in all, VFR conditions will still dominate.

The cumulus clouds will dissipate toward sunset, and mid and high
clouds will persist. There is a chance of a few dying showers
approaching KMKG after 07z. Have handled this with VCSH. Not
expecting them to be strong enough to drop conditions below VFR.
They will likely not reach the other terminals.

&&

.MARINE...
Issued at 332 AM EDT Mon Jun 16 2025

No marine headlines expected through at least Tuesday morning. There
is a generally weak pressure pattern over the area through Tuesday
morning, especially over the cooler lake waters.

An area of low pressure will move by to our NW on Tuesday. A
stronger flow associated with this could affect the northern marine
zone or two, and could necessitate a Small Craft Advisory and Beach
Hazards Statement for Tuesday afternoon.

The other wind event we are looking at is on the backside of the
area of low pressure that moves through on Wednesday. Small
Craft/Beach Hazards looks likely, with some Gales even possible.

&&

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

&&

$$

DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ