Eureka, Michigan Weather Forecast Discussion

416
FXUS63 KGRR 241950
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
Issued by National Weather Service Detroit/Pontiac MI
350 PM EDT Wed Sep 24 2025
.KEY MESSAGES...
- Substantial fog expected again Thursday morning
- Lesser rain chances on Thursday
- Dry and warmer into the weekend and next week
&&
.DISCUSSION...
Issued at 350 PM EDT Wed Sep 24 2025
- Substantial fog expected again Thursday morning
The 12Z DTX sounding showed a very deep saturated layer that is
not liable to go anywhere anytime soon. The ground remains quite
soaked from rain yesterday as well. Widespread fog seems likely again
tonight, especially east of US-131. Widespread visibilities below a
quarter of a mile are what we issue dense fog advisories for and
there likely will be at least some spots in the generally favored
areas that achieve this. Regardless, people can expect very
comparable visibility restrictions Thursday morning that they
observed this morning.
- Lesser rain chances on Thursday
Flow becomes somewhat more phased with the passage of a trough
across northern Ontario at the same time the very positively tilted
trough over our area trends closer to neutral and starts progressing
eastward. The vast majority of available guidance shifts PoPs to our
eastern forecast area closer to the US-127 corridor for the day.
However, the 12Z HRRR does show a signal for afternoon shower
development along a north-south axis west of US-131, apparently
associated with a lake breeze convergence boundary. There is not
much corroborating evidence for this among other model guidance,
except perhaps for the 24/06Z REFS, which shows a weak
(~10 percent) signal for measurable precipitation during this time
in this area.  The good news is that conditional instability should
be negligible; hence, no thunderstorms are anticipated with any
isolated showers that do manage to develop.
- Dry and warmer into the weekend and next week
The upper low/trough responsible for the rain chances on Thursday
will be pushed well SE of the area by Friday. Upper ridging will be
building over the area from the NW, with one small short wave trough
trying to spill over the building ridge. This short wave will produce
a non-zero chance of an isolated shower on Friday over the higher
terrain of Central Lower, and maybe where some enhanced lake breeze
convergence may be found. Most of the moisture will be swept out
by Friday, so most areas should stay dry.
Confidence is quite high, and only increasing then for an extended
dry period from Saturday through the end of this forecast period
on Wednesday, and likely beyond.
Initially the upper ridge will be broad in nature across much
of the middle portion of the 48 states, with upper lows over
the SE and SW portions of the CONUS. This will ensure plenty
of subsidence, with temperatures mild in nature. We will see
temperatures warm to almost 80F early next week as the upper
ridge builds a bit over the area and heights rise.  This ridge
will become more entrenched with the upper low over the SE and
possible tropical systems over the Western Atlantic, and a
long wave trough reinforcing the lower heights over the SW.
The only change expected around mid-week next week might be a
slight cooldown of temperatures. This would be the result of
the strong sfc ridge to our north pumping in slightly cooler
air in from the NE.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 205 PM EDT Wed Sep 24 2025
Ceilings continue to improve with a mix of IFR and MVFR ceilings
across the TAF sites this afternoon. Expect conditions to improve to
MVFR for all sites in the next 1-2 hours with many sites potentially
reaching VFR for a time this evening. Isolated showers are possible
in the vicinity of GRR/LAN for the next few hours and an isolated
storm cannot be ruled out though confidence is too low for TAF
inclusion. Beginning lake this evening, conditions will be favorable
for widespread IFR to LIFR conditions across the TAF sites given the
abundant moisture in the form of both fog and low ceilings. Dense
fog is possible at LAN, JXN, AZO, and BTL where low level moisture
is greatest. By late morning Thursday visibilities will begin to
improve, however similar to today it`ll likely be into the early
afternoon before conditions improve to MVFR or better for all of our
sites except MKG. With winds just off the surface a bit higher at
MKG would expect conditions to reach MVFR by mid morning.
&&
.MARINE...
Issued at 350 PM EDT Wed Sep 24 2025
The driver of our current marine pattern is the enhanced
pressure gradient between an Upper Great Lakes high and Ohio
Valley low. There looks to be localized enhancement of winds
due to the lake breeze this afternoon between Whitehall and
Holland with MKGM4 reporting 20-25 knot winds. Webcams suggest
waves are likely in the 3-5 foot range near Grand Haven and
Mona Lake as well. Will go ahead and issue a Small Craft
Advisory/Beach Hazards Statement this afternoon from Whitehall
to Holland/Muskegon and Ottawa Counties through late this
evening given this. A similar brief increase in the wind
across this region is expected Thursday afternoon to around
15 knots, slightly weaker than today, which should keep waves
a bit lower. Lighter winds are then expected Friday into the weekend.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until midnight EDT tonight for MIZ050-
     056.
MARINE...Small Craft Advisory until midnight EDT tonight for LMZ846-847.
&&
$$
DISCUSSION...NJJ/TJT
AVIATION...Thomas
MARINE...NJJ/TJT

NWS GRR Office Area Forecast Discussion