624
FXUS63 KGRR 152243
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
643 PM EDT Thu Oct 15 2026
.KEY MESSAGES...
- Fall Storm System to bring Wind, Rain and Lightning to the area
- Rather benign weather expected this weekend into early next week
&&
.DISCUSSION...
Issued at 245 PM EDT Thu Oct 15 2026
- Fall Storm System to bring Wind, Rain and Lightning to the area
Low pressure is centered just east of Des Moines Iowa at 18Z with
widespread rain located to the north of the low over Minnesota and
Wisconsin. Two upper shortwaves from both the northern stream and
southern stream are phasing off to the west over the upper midwest
at this time. As such, the low will deepen as it moves east
through the Lower Peninsula. Widespread/deep lift will sweep
through Southwest Lower Michigan between roughly 400pm this
afternoon and 400am tonight. The bulk of the rain will fall during
this period. The lift is driven by the right entrance region of an
upper jet that will be located overhead which will drive a low
level response of strong isentropic lift and significant moisture
transport.
Sounding climatology for DTX shows the max PWATs for today being
1.55 inches. We will be north of 1.75 inches this evening. Given
abnormal moisture in the depth of the column tonight we expect
efficient rainfall production. Most areas will see 0.50 to 1.00
amounts. Amounts may exceed an inch up towards Ludington. Given
low river levels and amounts that are not overly concerning not
expecting flooding issues.
Thunderstorms are a possibility this evening, especially along
I-94 between 800pm and 200am. The instability is not strong,
several hundred j/kg, but given the dynamics, thunder is a
distinct possibility.
Wind is the next concern and we have Gale Warnings out on the big
lake. As for the land, we feel we will stay just below wind
advisory criteria with most gusts in the 30-40 mph range. It will
very much feel like fall with a wet, windy and rainy system
working through the state.
The second portion of the event will come on Friday as a strong
cold front sweeps south around daybreak. Showers will accompany
the front and usher in cold enough air for lake effect rain.
Midday into the afternoon CAPE over the lake is maximized, pushing
towards 1,000 j/kg. We are likely looking at thunderstorms off the
lake given the significant moisture boost this time of the year
via the warmer water. Some diurnally driven showers and storms
will be possible inland as well given the cold air aloft. The most
concentrated rain will be working down the length of the lake
though in northerly flow.
- Rather benign weather expected this weekend into early next week
Quiet weather conditions will persist over the weekend into early
next week as high pressure dominates the scene both at the surface
and aloft.
The main item of note is that frost and freezing temperatures are
possible both Friday night and Saturday night.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 643 PM EDT Thu Oct 15 2026
Deterioration of conditions has been a bit slower than originally
forecast, however greater radar signatures over the lake suggest
deterioration to IFR, potentially LIFR at times. Can`t rule out
widespread LIFR if conditions overperform but current trends
suggest TEMPO is the way to go for now. A brief break in
precipitation is expected early from 05z-09z roughly as winds go
from southeast to northwest (also resulting in a period of LLWS)
before lake effect rain showers ramp up into the morning Friday.
In addition, wind gusts climb to 25-30 knots with the wind shift.
Lake effect rain showers then continue through mid to late Friday
afternoon when winds go northerly keeping higher coverage over
Lake Michigan.
&&
.MARINE...
Issued at 245 PM EDT Thu Oct 15 2026
A deepening fall storm system is still expected to pass through
the Great Lakes in the next 24-36 hours. The low will reach 995mb
to 999mb Friday morning and early afternoon as it passes east from
Ontario into Quebec. To the west a stout high pressure will be
sliding south through the plains at a magnitude of 1040+ mb. Even
though the distance between these two features is fairly wide,
a tightening pressure gradient will reach its peak on Friday. The
strongest winds will likely occur from midday into the evening
hours with Gales likely along with the possibility of some Storm
Force gusts. 40-45 knot gales look very reasonable over the water.
Given the flow is north or even just east of north, the largest
waves will be out over the open waters. That said, we are looking
at 8 to 13 footers in the nearshore waters. Given along shore flow
and water levels (near 579ft) that are 2.5 feet below advisory
(582.5ft) we are not expecting any lakeshore flood issues in our
area.
Small Craft Advisory begins this evening and lasts into Friday
morning. A Gale Warning is in place from Friday morning into
Friday night. Two items we will be watching are... 1) do we need
to jump into the Gale earlier as some models are showing gales in
the 06Z-12Z time frame tonight and 2) how much will the wind touch
storm force tomorrow. Do not see either as a high probability at
this point and will leave the headlines unchanged.
Waterspouts will be possible over the lake late tonight and Friday
morning before the wind truly ramps up. The stronger winds tends
to shear apart waterspouts. Much of this activity will remain over
the lake given northerly flow.
&&
.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...Duke
AVIATION...Thomas
MARINE...Duke
NWS GRR Office Area Forecast Discussion
