451
FXUS63 KGRR 052324
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
724 PM EDT Sun Oct 5 2025

.KEY MESSAGES...

- Chances for showers and storms Monday through Tuesday

- Cooler and mainly dry the remainder of the 7 day forecast

&&

.DISCUSSION...
Issued at 340 PM EDT Sun Oct 5 2025

- Chances for showers and storms Monday through Tuesday

Another warm day today with temperatures well above normal in the
lower to middle 80s across the area. We are in deep southwest flow
into Monday with one last warm day in the forecast. Forecast highs
on Monday remain in the lower to middle 80s across much of the
area, the exception being the far northwest towards Ludington
which will be in the clouds and advancing precipitation zone
tomorrow.

The main forecast focus is centered on really the only
precipitation chances in the 7 day which occurs from Monday into
Tuesday. At 19z, the front stretches north to south across
Minnesota, into NW Iowa and into Kansas. This front will make
steady progress in our direction tonight driven by an upper
shortwave trough moving across southern Canada. By daybreak on
Monday the front will be poised just upstream over Wisconsin
stretching from near Green Bay to southeast Iowa. The front will
move into our northwest forecast area near Ludington Monday
afternoon and slow Monday night across the area as the front
becomes more parallel to the upper flow. It will gradually push
out of the area to the south on Tuesday. Scattered pops of 20-50
percent seem warranted on Monday, increasing to 60-90 percent
Monday night as the front slows to 20-40 percent on Tuesday.

Embedded thunderstorms are expected especially Monday afternoon
into Monday evening as a diurnal boost occurs. Instability
parameters are nothing significant, but enough for a few
storms...500-1000 MUCAPE and 850 LI`s of zero to -2C. PWAT`s near
1.5 inches are high for this time of year. 850mb dew points
increase to +10C. The surge in moisture combined with a slowing
front may lead to some locally heavier amounts of rain. A few
swaths of 0.50 to 1.00 are certainly possible. The HREF would even
suggest very small areas of 1.5 inches by 12Z on Tuesday. Not
expecting any hydro issues though given dry soil moisture, low
river levels and rainfall amounts that are not overly high. Threat
for severe weather is low as well given the better shear lags the
front and instability is on the low side. SPC general thunder
outlook is in line with our thoughts.

- Cooler and mainly dry the remainder of the 7 day forecast

Beyond the exiting front and diminishing precipitation on Tuesday
there is no significant weather to speak of. Surface high pressure
builds in and really remains in the area from Wednesday into next
weekend. A taste of true fall shows up behind the cold front as
low temperatures dip into the 30s Tuesday night and Wednesday
night. We could see frost/freeze headlines mid week. The ECWMF
actually has 850mb temperatures dipping to zero C on Wednesday.
Highs mid week will be much closer to normal in the 60s.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 724 PM EDT Sun Oct 5 2025

VFR will continue to dominate. A few high clouds remain this
evening, but skies are mostly clear at all of the terminals. Skies
will stay this way until very late tonight at KMKG as some mid
clouds ahead of the front start moving in. These clouds will then
gradually spread SE through early tomorrow afternoon. It appears
at this time that any rain will not start until right at the end
of this forecast period at KMKG, and after at the other sites.

Winds have diminished this evening after the gusty winds all day.
Winds will pick up around midnight at KMKG as a core of at 2-3k ft
agl moves overhead and mixes down near the warmer lake. Elsewhere,
this core of wind is likely to cause some minor low level wind
shear, but the magnitude is not enough to put in the forecast at
this time.

&&

.MARINE...
Issued at 340 PM EDT Sun Oct 5 2025

No changes are needed to the current set of marine headlines that
are in effect from South Haven northward. The worst of the
conditions this afternoon are north of Grand Haven in the flow from
the SSW. The flow will gradually shift to more from the pure SW, and
bring the higher waves further south on Monday. The current
expiration time of 16z looks good as the gradient will weaken by
Monday afternoon, and the waves will subside correspondingly.

We could see some elevated wind and waves remain on Tuesday behind
the front and as the next sfc ridge builds in. Right now, the
magnitude of that event would likely just fall short of needing
headlines. We will continue to monitor that event.

After Tuesday, we will likely go the rest of the week without any
potential headlines as we get into another quiet weather pattern.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Monday afternoon for MIZ037-043-
     050-056-064.
MARINE...Small Craft Advisory until 5 PM EDT Monday for LMZ845>849.

&&

$$

DISCUSSION...Duke
AVIATION...NJJ
MARINE...NJJ