851
FXUS63 KGRR 140719
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
319 AM EDT Fri Aug 14 2026

.KEY MESSAGES...

- Multiple chances of showers and storms tonight into Sunday

- Cooling off and drying out later Sunday through Tuesday

- Stronger system possible Wednesday

&&

.DISCUSSION...
Issued at 319 AM EDT Fri Aug 14 2026

- Multiple chances of showers and storms tonight into Sunday

Another night, and another round of convection just to our south
over Illinois and Indiana where they don`t need any more damaging
storms or rainfall. Up our way, we remain under a somewhat humid air
mass, with little to no rain chances for one more night.

We do see some minor changes in the upper air pattern that will
bring the better shower/storm chances to Lower Michigan as early as
tonight, and keeping the chances in until Sunday. We see upper
heights build a bit as the long wave trough over the Western U.S.
moves east a little, and we see some short waves come out of the
long wave trough.

This change will allow a short wave/MCV over Western KS early this
morning to move toward the area late Friday night/Saturday. As the
MCV approaches, the moisture advection with the low level jet will
weaken as is typical at that time of the day. This will bring a few
showers and maybe a rumble of thunder in Saturday morning.

We see instability build through Saturday as the front moves north
and the very warm and moist air mass moves back over the area,
coinciding with diurnal peak heating. We see the instability
continue to build Saturday evening as the low level jet with the
next wave pushes right at the area. It looks like this will be the
favored time and into Sunday morning for the best chances of showers
and storms.

CAPEs are shown to climb above 2000 J/kg Sat evening, and maybe even
up to 3,000. Synoptic scale shear may be on the lower side, which
would limit severe potential a bit. There may be some better
mesoscale deep layer shear associated with the short waves/MCV. That
is a bit uncertain at this time, but there is a potential of some
strong to severe storms Sat evening/night. There may be some
training of storms also with somewhat of a persistent low level jet
causing some backbuilding.

- Cooling off and drying out later Sunday through Tuesday

The low jet jet from Saturday night will push east by daybreak
Sunday morning, and the cold front will be poised to steadily move
through the area as the upper flow pushes it. Any lingering rain and
clouds early will slowly improve in the afternoon behind the cold
frontal passage.

We will see upper ridging build in behind the system on Sunday, and
bring dry weather as the low level flow from the north advects drier
weather overhead. Dew points will go down, and temperatures will not
be nearly as warm.

- Stronger system possible Wednesday

The upper ridge will control the weather for Monday and Tuesday, but
we will have nearly a zonal upper jet over the northern half of the
country. What this will do is allow additional short waves ride it
right into the region. There has been a wave shown to bring rain
chances in for late Wednesday and Thursday. The latest data
indicates that this wave may be stronger with a stronger jet
supporting it as it traverses the country. The sfc low is shown to
be relatively stronger, and potentially more impactful.

We will see another break in the weather then for Thursday as the
Wednesday system clears all of the moisture out of the area.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 135 AM EDT Fri Aug 14 2026

Once again, fog is the main focus of the forecasts this morning.
Skies have mostly cleared out from blowoff clouds from convection
to our south earlier. Winds being light along with an air mass
that remains moist is leading to the fog development. Visibilities
should trend down through the next 2-4 hours before stabilizing as
winds aloft increase some.

This will burn off once again this morning after daybreak, with
KJXN likely taking the longest to clear out. Some scattered
cumulus clouds around 5k ft agl along with high clouds will
dominate. The cumulus clouds will disappear toward mid evening.

&&

.MARINE...
Issued at 319 AM EDT Fri Aug 14 2026

Our next possible set of marine headlines look to arrive Saturday
afternoon into much of Sunday ahead of, and behind a frontal system.

Until Saturday afternoon, the gradient will remain light as it has
been for the past few days. Winds should stay below 20 knots and
waves below 3 ft until Saturday afternoon. Waves will build later
Saturday and more so Sunday with cooler air coming in on the
backside of the system, and an onshore flow.

Once the system moves by over the weekend, we should see a few days
with lower winds and waves.

&&

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

&&

$$

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