751
FXUS63 KGRR 260704
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
304 AM EDT Wed Aug 26 2026
.KEY MESSAGES...
- Chance for Showers and Thunderstorms Today
- Warmer Next Week, Occasionally Humid and Stormy
&&
.DISCUSSION...
Issued at 304 AM EDT Wed Aug 26 2026
- Chance for Showers and Thunderstorms Today
The bottom line is that most thunderstorms that develop today will
not be severe, but will need to watch the 18z-22z window east of
US 131 for some scattered thunderstorm wind gusts of 40-60 mph
(isolated 60+ mph), mostly sub-severe hail, and perhaps enough low
level shear / SRH to stretch and tilt some horizontal vorticity to
get some mesocyclonic development. That latter risk, however,
seems to be unlikely at this point though a short-lived spin up
tornado can`t be ruled out east of US 131 this afternoon/evening.
We feel that most locations should get through the day without
storm damage, but would not be surprised if some scattered pockets
of tree damage and power outages do develop.
Beyond 22z and through about 03z or so, an isolated shower or
storm may redevelop over central Lake Michigan into central Lower
MI and move SE with time, though these are unlikely to be strong
as peak daytime heating will be in the rearview mirror.
- Warmer Next Week, Occasionally Humid and Stormy
Quiet days are anticipated from Thursday (aside from a rogue pop
up daytime shower) through at least Saturday before changes begin
to take shape into next week. First, the warmth. Ensemble
guidance supports above normal temperatures next week with a
subset of "grand ensemble" (ECE/GEFS/CMC) membership supporting
highs in the 90s at times. In fact, roughly 1/3 of all members
indicate highs getting into the 90s early next week. Ensemble mean
500 mb heights keep climbing a bit higher and now it appears even
590 dm could be in play for southern Lower MI. However, any MCS
influence via a ridge rider pattern could alter the ridge`s
northern extent and put us in a subsequently stormier and
somewhat cooler pattern. Currently, ensemble mean 850mb temps are
quite high for early September with 20C+ being shown especially
early next week. With outdoor school activities getting into full
swing, there may be some uncomfortable periods of heat/humidity to
deal with depending on how this pans out.
Second, occasionally humid air and associated MCSs / warm frontal
storm development are likely to occur across the Midwest and
potentially Great Lakes as well. PWAT values look anomalous for
early September with waves of 2.00"+ looking plausible into next
week. Deterministic guidance agrees that LLJ development of 40 kts
or greater will occur somewhere in the Midwest starting as early
as Sunday. How far this angles into Lower MI is unclear at this
point, but we`ll be close enough to have some periodic threats for
both nocturnal and daytime thunderstorms. Too early for
specifics, and part of the time we may be capped, but pattern
recognition would say we should have periodic rain chances. NBM
POPs are not high at this point (20-30%) but those may go up with
time.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 115 AM EDT Wed Aug 26 2026
A line of showers is likely to arrive at MKG around 12z this
morning, with embedded thunder possible. Some of this line may
survive as it presses east toward GRR and AZO after 14z. HREF
guidance suggests the 18z-21z period is where TSRA is most likely
to develop between AZO and LAN especially, then move east into
late evening. An isolated shower or storm may also redevelop
across central Lower MI and head SE after 23z, though it is
difficult to pinpoint where that activity may be. Any TSRA
activity could produce wind gusts in the 30-40 kt range. Once
radar trends better emerge, amendments may be needed to include
some of these higher gusts.
&&
.MARINE...
Issued at 304 AM EDT Wed Aug 26 2026
Increasing SW flow over the lake at 15-20 kts today (some gusts
over 20 kts) will help generate waves of 3 to 6 feet though can`t
rule out some 7 footers north of Grand Haven. As a result, both
Small Craft Advisories and Beach Hazards Statements are in effect
today into tonight. Winds and waves should decrease into
Thursday, though we may be looking at a short duration Small Craft
Advisory (and Beach Hazards Statement) potentially needed south
of Muskegon during the afternoon with waves potentially getting
into the 3 to 5 foot range.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through this evening for MIZ037-043-050-
056-064-071.
MARINE...Small Craft Advisory until midnight EDT tonight for LMZ844>849.
&&
$$
DISCUSSION...Hoving
AVIATION...Hoving
MARINE...Hoving
NWS GRR Office Area Forecast Discussion
