200
FXUS63 KGRR 081834
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
234 PM EDT Thu Oct 8 2026
.KEY MESSAGES...
- Brief chance of rain Friday night; then warm and sunny Saturday
- Rain chances with Isaias diminishing for Sunday
- Strong cold front Monday night/Tuesday with colder air to follow
&&
.DISCUSSION...
Issued at 234 PM EDT Thu Oct 8 2026
- Brief chance of rain Friday night; then warm and sunny Saturday
Really no changes with the forecast through Saturday night for the
area. various sources of model data all show a small and brief
chance of rain coming through Friday evening into early Friday
night. This remains associated with a sfc warm front and low level
jet core of almost 30 knots passing through. Rainfall with this will
be quite limited as moisture below 6k ft is quite limited, as is the
window of opportunity with the forcing.
It will be noticeable on Saturday that we will be in the warm sector
with steady warm winds blowing, and sfc temperatures well into the
70s. 850 mb temperatures around 16C will support those warm October
temperatures.
- Rain chances with Isaias diminishing for Sunday
The most uncertain time frame in the forecast for the last few days
has been centered around the Sunday time frame, due to the
uncertainty with "Isaias" and the upper low that will be merging
with it as it becomes extra-tropical in nature after making landfall
along the Gulf coast.
The latest trend for it is to turn eastward a little quicker, and
bringing just a chance of rain to the SE portion of the forecast
area. We have been saying for days that the merging with a non-
tropical upper low, and the movement of upper lows is quite
uncertain. The 00z runs of the global models all trended east with
it, after having trended NNW the previous couple of days before
that. The latest trend is likely due to the atmosphere to its west
being blocked up with a stronger ridge over the Mississippi River
Valley, and the strong upper trough over the Western U.S..
- Strong cold front Monday night/Tuesday with colder air to follow
The other trend we have noticed is that the rainfall amounts with
the stronger cold front coming through Monday night and Tuesday have
diminished a bit. The timing of the cold front has remained similar
as previous runs, but qpf is on the lighter side overall. This looks
to be a result from a lack of good Gulf moisture with Isaias taking
much of it, and another good moisture feed not able to become
established with the ridge immediately out ahead of it.
Much of the precipitation also looks to be right along, and behind
the front as short waves in the upper flow ride along the front. We
will see much cooler air advect in on the low level flow from the NE
around an area of Canadian high pressure.
Beyond Tuesday/Wednesday has become more complicated as the large
upper trough could possibly close off a low over the SW U.S., and
potentially send more energy to the NE.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 111 PM EDT Thu Oct 8 2026
VFR expected through the TAF period with diurnal Cu in the 4-6kft
range this afternoon giving way to mid and high clouds tonight.
Northwest winds gusting to around 20 knots this afternoon favored
to become light and variable tonight before increasing from the
southwest Friday.
&&
.MARINE...
Issued at 234 PM EDT Thu Oct 8 2026
We will hold on to the current Small Craft Advisory until the 5 pm
expiration, as waves will still be up right around 4 feet until then
for a few of the marine zones.
We will see a little bit longer of a break in the advisory
conditions compared to the last break of only a few hours. The break
should run from this evening into Friday evening, before winds and
waves come up behind a warm front moving through. This period of
wind will likely last through much of Saturday night before coming
down on Sunday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for
LMZ844>849.
&&
$$
DISCUSSION...NJJ
AVIATION...Thomas
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
