420
FXUS63 KGRR 190048
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
848 PM EDT Thu Jun 18 2026

.KEY MESSAGES...

- Cooler Than Normal with Rain Possible Sunday into Monday

&&

.DISCUSSION...
Issued at 155 PM EDT Thu Jun 18 2026

- Cooler Than Normal with Rain Possible Sunday into Monday


The weather pattern continues to be dominated by zonal flow being
steered by a large quasi stationary upper level low situated over
central Canada. That low will continue to bring north westerly
flow through the region, along with anomalous cold air advection.
NAEFS mean temperature anomalies show -1 to -2 standard
deviations through the mid levels. That means while the region
will see a mix of sun and clouds, the temperatures will struggle
to get into the mid 70s. Max temperatures through the weekend and
into early next week will be 5 to 10 degrees below normal. Models
continue to be in good agreement on the passage of a few weak
shortwave traversing the previously mentioned upper level low as
it shifts to the south. Those shortwaves will trek through the
Great Lake Saturday. This will allow for a chance of precipitation
Saturday. Precipitation should be fairly light and will make its
way eastward as the day continues. Chances for precipitation of
over a tenth are best along the lakeshore Saturday morning. The
better chance for heavier precipitation continues to be as a upper
level low, currently over the Pacific, filters through the upper
level pattern, stamps down a ridge through the intermountain west,
and finally makes its way through the midwest. That wave and mid
level and surface low will advect good moisture with it. However
latest ensembles struggle with its position and track. The best
chance for heavy rain remains south of Michigan, though Southern
lower could see some rainfall late Sunday into Monday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 848 PM EDT Thu Jun 18 2026

VFR weather is in place across all of Southwest Lower Michigan
at 00z. That is expected to remain the case through the duration
of the forecast period. We do see some upstream clouds and showers
working this way from Wisconsin, but we expect showers to
dissipate this evening with the setting sun and remain west of the
TAF sites. We will see some VFR clouds move in however tonight
with bases of 7,000 to 10,000 feet. On Friday we will likely see
some fair weather cumulus clouds develop with bases in the 3,500
to 6,000 foot range. Winds have already settled down this evening
with the loss of deep mixing. Winds through tonight will be less
than 10 knots. Winds will become gusty again on Friday after 15z
with 10-20 knots expected and gusts towards 25 knots from the
west and northwest.

&&

.MARINE...
Issued at 155 PM EDT Thu Jun 18 2026

 The west to northwest winds continue as advertised. Waves of 3 to
6 feet continue along the lakeshore. The winds will slacken as the
day continues and with it the waves will slowly subside. This will
occur from the north to the south into Thursday evening. The SCA
and Beach hazards will then end accordingly. Winds tomorrow are
trending low but there could be a brief period of higher waves, 2
to 4 feet, early in the day.

&&

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

&&

$$

DISCUSSION...Ceru
AVIATION...Duke/Thomas
MARINE...Ceru