National Weather Service Raw Text Product

752 
FXUS63 KGRR 231924
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
324 PM EDT Wed Jul 23 2025

.KEY MESSAGES...

- Hot and Humid through Thursday

- Storms possible, mainly Thursday afternoon/evening

- Humidity and additional rain chances through the weekend

&&

.DISCUSSION...
Issued at 324 PM EDT Wed Jul 23 2025

- Hot and Humid through Thursday

As expected, temperatures are making a run into the upper 80s
today. Humidity also continues it's steady climb, with 70+
dewpoints near the Michigan/Indiana line as of this writing. This
is producing heat index values in the mid 90s today. Tomorrow will
feel about 5 degrees warmer, with 100+ heat index values still
expected to reach generally up to a line from Muskegon to Mt
Pleasant (and all points southward). There remains some question 
about how much cloudcover creeps into the area from the northwest 
during the day tomorrow, potentially cooling things down every so 
slightly, so the northern-most counties along this line 
potentially may not quite hit the 100+ mark, but regardless it 
will be very hot and humid in these areas tomorrow. There are no
changes to the ongoing Heat Advisory.


- Storms possible, mainly Thursday afternoon/evening

There's a small chance of a few popup showers or storms this
evening and overnight - mainly along parts of the US-10 corridor,
where proximity to an ongoing LLJ may help kick off a few
updrafts. Confidence is low in this happening, though, so wouldn't
be surprised if nothing at all happens up there. Meanwhile, the 
thunderstorm forecast for Thursday remains challenging. The most 
likely scenario continues to be a few clusters of strong - to 
possibly severe - thunderstorms developing by mid afternoon. 
Working in favor of storms is the heat and humidity providing 
instability, along with a weak upper wave and associated weak cold
front providing some lift. Working against storms will be the 
timing of that lifting mechanism. Models have slightly sped up the
arrival, which may limit whether parcels can overcome lingering 
capping inversion associated with the large-scale ridge pattern. 
SPC has maintained all of Lower Michigan in a marginal (Level 1 of
5) severe risk for tomorrow, with primary threats being damaging 
wind gusts. Of course, with PWAT values exceeding 2 inches 
tomorrow, locally torrential rain rates and localized flooding 
will also be possible if/where storms do get going.


- Humidity and additional rain chances through the weekend

The aforementioned weak cold front will clear through Lower
Michigan Thursday night and Friday and stall south of the state 
border before lifting northward again for the late week period.
This will produce unsettled and still notably humid weather Friday
and Saturday, even though temperatures will be a bit cooler in the
mid 80s. As our area resides on the periphery of broad ridging on
the "ring of fire", we expect multiple rounds/risk periods for
MCS-type activity to move through the area Friday through
Saturday. While it's hard to pin down the most likely timing for
rain at this time, suffice it to say most areas should end up with
some decent measurable rains, with a few localized heavier (1"+)
rain totals possible during this time - especially in the southern
areas that are closer to the frontal boundary.


&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 145 PM EDT Wed Jul 23 2025

Presently there are MVFR ceilings at Ludington (LDM) from what's
leftover from thunderstorms that dissipated over Wisconsin.
Otherwise expecting mostly VFR with a few clouds 4,000 to 5,000
feet this afternoon.

There is about a 20 percent chance of a thunderstorm in the 
vicinity of Muskegon (MKG) this evening 02 to 05 Z.

A few models are creating ceilings around 3,000 feet late 
tonight, which is more probable around Big Rapids (RQB) and Mount 
Pleasant (MOP), but could develop as far south as Grand Rapids 
(GRR) and Lansing (LAN).

Between 06 Z and 12 Z, there may be 25 knots of LLWS between 
1,000 feet and the ground due to winds 220 at 30 knots, 1000 feet
AGL.

&&

.MARINE...
Issued at 324 PM EDT Wed Jul 23 2025

Marginal hazards to small craft and moderate-high swim risk 
continues through tonight north of Muskegon, particularly around Big 
and Little Sable Points. South winds in the nearshore have been 
about 15 knots gusting to 20, which is a bit lower than advertised 
in the models, though this is not unexpected given the relatively 
warm air temperatures flowing over the lake and relatively stable 
conditions limiting the ability for stronger winds aloft to mix 
down. Generally 2 to 4 ft waves, longshore currents at many beaches, 
and structural currents on the south side of south piers do pose 
at least a moderate hazard for swimmers.

Thursday, winds become southwest of similar strength, and moderate 
to possibly high swim risk continue through a good portion of the 
day. Extending the small craft advisory / beach hazards and possibly 
adding Ottawa County (Holland to Grand Haven) will again be a 
marginal call based on observed conditions early in the morning.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through late tonight for MIZ037-043-050.
     Heat Advisory from 11 AM to 8 PM EDT Thursday for MIZ046-051-052-
     056>059-064>067-071>074.
MARINE...Small Craft Advisory until 5 AM EDT Thursday for LMZ847>849.

&&

$$

DISCUSSION...AMD
AVIATION...CAS
MARINE...CAS