159
FXUS63 KGRR 270611
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
211 AM EDT Sun Sep 27 2026

.KEY MESSAGES...

- Beautiful Fall Conditions through Tuesday

- Rain Chances Return Tuesday Night and Continue through Week

&&

.DISCUSSION...
Issued at 225 PM EDT Sat Sep 26 2026

- Beautiful Fall Conditions through Tuesday

High pressure remains in place with troughing to our east and
west. Mostly sunny conditions are expected through Tuesday with
highs in the upper 60s along the lakeshore to mid 70s further
inland. Lows overnight will mainly be in the 40s with a few spots
potentially dropping into the upper 30s tonight toward US-10.

- Rain Chances Return Tuesday Night and Continue through Week

Cluster analysis and long range ensembles all point to high
pressure weakening over the area midweek with a trough moving
through late Tuesday night into Wednesday. Instability is low
therefore not expecting thunderstorms at this time. Moisture
increases with precipitable water values around the 90th
percentile (1.6 inches) shown in the mean of each cluster in the
cluster analysis. There are some isolated members that approach 2
inches (record precipitable water levels) as mentioned in the
previous discussion, however those probabilities are low.

Additional shortwaves move through the area for the remainder of
next week. There are some differences in the extended with the
timing of each of these shortwaves, but ensembles show agreement
that most will see some rain accumulations each day. WPC
highlights rainfall amounts in the 1-2 inch range Tuesday through
Saturday. Some isolated higher amounts are possible (20 percent)
as highlighted by individual ensemble members.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 211 AM EDT Sun Sep 27 2026

Main concern with this set of TAFs is the threat of fog and
stratus between mainly 09z and 13z this morning. Fog is already
occurring however and that may mean that the fog may be a bit more
widespread than anticipated. A moist northeast flow off of Lake
Huron, especially in the lowest 1k to 2k feet will spread moisture
into a cool airmass leading to fog formation. As of 06z, little to
no low clouds are seen, so the fog at this point is very local and
raditional. Again, we anticipate an increase in the fog as we head
through the night with some LIFR or VLIFR ceilings as well. We may
not have gone pessimistic enough and will amend as necessary this
morning. After any fog lifts this morning VFR weather should
prevail the rest of the TAF period with little in the way of cloud
cover. Winds will be northeast to north in most areas today at
5-10 knots. A lake breeze will back the winds at MKG to northwest
this afternoon.

&&

.MARINE...
Issued at 225 PM EDT Sat Sep 26 2026

Tranquil conditions continue with low wave heights and light
easterly winds. Winds will become more onshore each afternoon as
the lake breeze develops. Winds turn to the southwest Tuesday then
turn to the northwest Thursday night behind the front. Winds and
waves may approach Small Craft Advisory criteria at times
Wednesday into Friday.

&&

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

&&

$$

DISCUSSION...RAH
AVIATION...Duke
MARINE...RAH