542
FXUS63 KGRR 052320
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
720 PM EDT Thu Jun 5 2025

.KEY MESSAGES...

- Near Normal Temperatures with Some Late Weekend Rain Chances

- Warming Up Later Next Week

&&

.DISCUSSION...
Issued at 336 PM EDT Thu Jun 5 2025

- Near Normal Temperatures with Some Late Weekend Rain Chances

Temperatures near normal with highs in the mid 70s and lows in the
mid 50s (cooler near Lake Michigan) should persist until mid next
week. High pressure will generally be in place over the region
through Saturday. On Friday, lingering moisture / higher humidity
over southern Michigan, and proximity to the stationary front and
weak low draped across Indiana/Ohio, may allow a few light rain
showers to develop near I-94.

There are a couple chances for showers and possibly a thunderstorm
between Saturday night and Sunday night. A weak shortwave trough and
associated surface low moving through the southern Great Lakes
Saturday night to Sunday morning may touch off showers depending on
its exact track, with chances for precip about 30 percent in
southern Michigan. On its heels is a larger and robust upper-level
low diving in from south-central Canada with a leading cold front
arriving later Sunday. Precipitation chances are greater than 60
percent near I-96 and to the north. CAPE progged around 500 J/kg is
worth a mention of a chance of a thunderstorm Sunday evening. There
will be some wind shear present also, supporting a threat of some
gustier winds.

- Warming Up Later Next Week

Ensembles are broadly in agreement of a warming trend next week
Wednesday into Friday with southwesterly low-level flow from the
south-central Plains toward the Great Lakes. Temperatures are
looking to climb into the 80s possibly Wednesday and likely Thursday-
Friday. With many ensemble members showing increasing PWAT, surface
dew points, and CAPE late in the week going into the weekend, both
heat/humidity and chances for thunderstorms will become more of the
story.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 720 PM EDT Thu Jun 5 2025

VFR conditions are ongoing at all terminals as earlier stratus and
smoke have mixed out. MKG, GRR, and LAN are forecast to remain VFR
through the TAF window. Model soundings suggest MVFR cigs/fog
develop after 6-8z at AZO, BTL, and JXN where low-level moisture
is better. A period of IFR cigs is favored at JXN near daybreak
as dewpoints/crossover temps are notably higher due to stratus
persisting well into the afternoon today. Conditions will slowly
improve after daybreak with these three sites forecast to reach
VFR in the early afternoon Friday. Otherwise expect northeast
winds aob 10 knots, with the exception of MKG where a lake breeze
Friday afternoon will result in northwest winds.

&&

.MARINE...
Issued at 336 PM EDT Thu Jun 5 2025

Weak gradient flow from a high pressure system will keep conditions
below hazardous levels through the rest of the week on Lake
Michigan. Winds and waves increase Sunday/Monday as a low pressure
system moves over the Great Lakes. Periods of reduced visibility are
possible at times through Friday morning due to wildfire smoke on
the water.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until noon EDT Friday for MIZ037>040-043>046-
     050>052-056>059-064>067-071>074.
MARINE...None.

&&

$$

DISCUSSION...CAS
AVIATION...Thomas
MARINE...Thomas