Glenn, Michigan Weather Forecast Discussion

103
FXUS63 KGRR 231825
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
225 PM EDT Tue Sep 23 2025
.KEY MESSAGES...
- Scattered Showers/Storms Slowly Press South and East
- Drying out for the Weekend into Early Next Week
&&
.DISCUSSION...
Issued at 224 PM EDT Tue Sep 23 2025
- Scattered Showers/Storms Slowly Press South and East
The upper level pattern changes little into Thursday morning as an
upper low meanders over the region. Abundant low level moisture (ie.
high RH in the 1000-850mb layer) will be featured across much of the
region, leading to extensive cloud cover. Enough moisture and
surface based instability (a few hundred J/kg) will be present
through this evening and then again Wednesday to help generate a
few showers and thunderstorms, mainly along I-94 and also east of
I-69 this evening, then primarily east of US 131 for Wednesday.
The 12z HREF 24 hr QPF LPMM shows some bullseyes of 1"+ from
Wednesday into early Thursday especially toward the US 127
corridor.
A consensus of model guidance for Thursday indicates the upper low
should start exiting, with any leftover showers mainly impacting
areas near US 127 and further east into the thumb region and SE
Lower. There might be just enough elevated instability to support a
thunderstorm, but that would likely be the exception to the rule.
- Drying out for the Weekend into Early Next Week
Ensemble guidance continues to favor a dry weekend as ridging moves
in, with upper heights reaching the 580s dm into early next week
(well above normal). With 850 mb temperatures staying in the 12c-15c
range, upper 70s to around 80 will be achievable this weekend into
early next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 129 PM EDT Tue Sep 23 2025
A broken line of showers with embedded thunderstorms continues to
cross West Michigan this afternoon, with the line moving east of
JXN near 18z. Isolated showers and thunderstorms are possible
behind this line into the evening, with widely scattered activity
supportive of maintaining PROB30s with amendments as needed. Any
remaining MVFR sites will become VFR shortly as cigs climb to near
5kft. MVFR and lower conditions are possible in any showers and
storms. Tonight, widespread fog and low stratus are expected with
widespread MVFR/IFR conditions and a 20-40 percent chance of LIFR.
Have trended the TAFs accordingly with this package. While
visibilities will improve after sunrise, it may be well into the
morning/early afternoon before ceilings improve.
&&
.MARINE...
Issued at 224 PM EDT Tue Sep 23 2025
No marine concerns at present given a weaker gradient across the
Central Great Lakes. Winds increase from the north Wednesday into
Thursday with speeds of 10-20 knots as a low pressure system slides
through the Ohio Valley. Initially offshore flow before the low
moves east will help keep waves in the 1-3 foot range, with flow
becoming onshore Thursday morning. Looking at the 12z ECMWF... the
morning run brings this guidance more in line with other models with
a weaker low tracking more to the east. This would keep winds in
line with the current forecast. Winds subside Friday as high
pressure takes over as the main driver of the forecast. Unsettled
weather will persist through Thursday with scattered showers across
the waters.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Hoving
AVIATION...Thomas
MARINE...Thomas

NWS GRR Office Area Forecast Discussion