620
FXUS63 KGRR 150702
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
301 AM EDT Thu Oct 15 2026
.KEY MESSAGES...
- Becoming wet, windy, and colder through Friday
- Extended dry period with moderating temperatures next week
&&
.DISCUSSION...
Issued at 301 AM EDT Thu Oct 15 2026
- Becoming wet, windy, and colder through Friday
Everything remains on track for the evolution of our weather from
today through Friday evening, with no major changes noted at this
time.
Plenty of clouds remain from the stratocumulus clouds that moved
overhead on Wednesday. There are some breaks in this, but high
clouds are widespread, and the holes in the lower clouds are filling
in. We will see deep moisture advect over the area this afternoon as
the strengthening low level jet associated ahead of the upper wave
and developing sfc low will approach late this afternoon. It is with
this feature that we will see the most widespread rain with this
entire system. The sliver of instability (elevated in nature based
between 850 and 700 mb) that may affect the I-94 corridor would also
be maximized at that time. All of this would be through just before
06z when the low level jet peels away and the occluded front moves
through.
The next wave of showers will then come right ahead of the secondary
cold front/cold conveyor belt that will surge in from the NW. This
comes through centered around 12z Friday give or take a couple of
hours depending on the northern or southern portion of the forecast
area. This is associated at the leading edge of the upper trough and
cyclonic flow arriving. The passage of these features will
ultimately shift the mean low level flow to become from the NNE.
Lake effect rain showers will be likely initially from the NW, and
will shift offshore by late afternoon. It is from mid morning until
the wind shifts offshore when the best chance of lake induced
thunder will be possible with just short of 1,000 J/kg of CAPE
available.
Wind will be another aspect of this system. Right now, it looks like
most places will see gusts to around 40 mph Friday. May just be
short of advisory criteria inland, where instability will be a bit
less than over the warmer waters.
A few showers will remain possible inland through the daylight
hours, and a few may linger into mid-evening. It will be shortly
after 00z Saturday the the upper trough moves out, and the flow
becomes anti-cyclonic.
- Extended dry period with moderating temperatures next week
Strong subsidence will build in quickly behind the departure of the
upper trough by Saturday morning. The upper air pattern over the
CONUS then transitions to a much more amplified trough/ridge/trough
pattern from the West Coast to East Coast in almost an Omega block.
The strong upper trough on Friday will close off along the East
Coast, and strong energy moves toward the West Coast from the
Pacific. This will place Michigan in between under the influence of
the strong ridge. This means plenty of dry weather, with sunny days
and cool nights. There will be attempts of short waves trying to
flatten the ridge. It seems that the ridge should remain intact
through at least mid-week.
Later in the week, there have been indications that there may be a
trough that tries to close off overhead next Thursday. Way too much
uncertainty seven days out to try to pin down the details. Generally
speaking, we will see above average temperatures, and below average
precipitation.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 156 AM EDT Thu Oct 15 2026
We are seeing a variety of conditions at the terminals this
morning, ranging from some small areas of clear skies to lower
clouds in the MVFR category. The trend for the night will be for
the lower clouds to become more widespread as they expand. The
clouds should end up mainly MVFR. There may be some breaks at
times, but will side on the pessimistic side. The clouds will then
hold on into the afternoon.
We will see widespread showers move in over the area from West to
East after about 18z. Conditions will then deteriorate late
afternoon and this evening as we go down into the LIFR category
with visibilities and ceilings. Showers will continue the majority
of the time, but may scatter out a bit right at the end of the
period.
Low level wind shear is expected at all but the KMKG terminal
after 00z as the wind core aloft moves overhead. The winds at the
sfc will be from the SE at less than 10 knots, while 45 knots or
so from the SW at 2k ft agl.
&&
.MARINE...
Issued at 301 AM EDT Thu Oct 15 2026
We will be issuing a Gale Warning for the core of the upcoming
wind/wave event, with a Small Craft Advisory on the front end of it
from this evening through the beginning of the Gale Friday morning.
Winds will increase quickly with the first surge of colder air late
this evening, and overnight. The strongest of the winds will come
with the deep colder air that arrives Friday morning. Very unstable
conditions over the lake will allow all of the wind aloft to reach
the sfc. Waves will build quickly also.
After a break on Saturday with high pressure overhead, winds will
increase once again Saturday night through Sunday night under a
tight gradient from the high to our south, to a strong low across
Canada.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 11 PM this evening to 11 AM EDT
Friday for LMZ844>849.
Gale Warning from 11 AM Friday to 2 AM EDT Saturday for
LMZ844>849.
&&
$$
DISCUSSION...NJJ
AVIATION...NJJ
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
