Marion, Michigan Weather Forecast Discussion

864
FXUS63 KGRR 052306
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
706 PM EDT Fri Sep 5 2025
.KEY MESSAGES...
- Cool with chances for showers through the weekend
- Small chances for showers Monday night into Tuesday
- Mainly dry with a slow warming trend Wednesday through Friday
&&
.DISCUSSION...
Issued at 339 PM EDT Fri Sep 5 2025
- Cool with chances for showers through the weekend
We will remain under a deep through aloft through much of the
weekend. 850mb temperatures of +2 to +4 C are expected through
Sunday night which means cool weather will continue. Highs will be
in the upper 50s to middle 60s with lows in the upper 30s to
lower 40s. Normal highs are in the 70s and normal lows in the 50s,
so we will be well below normal...the fall feel to the air will
continue.
Lake temperatures are around +20C which puts delta t`s in the
upper teens C over the lake through the weekend. Therefore there
will be plenty of instability over the lake. The instability
combined with cyclonic flow should result in isolated to scattered
rain showers off of Lake Michigan. The deepest moisture will
occur on Saturday and Saturday night when upper shortwaves will be
moving through. We expect the highest chances for rain in those
two periods, increasing into the 30-50 pct range.
- Small chances for showers Monday night into Tuesday
Small chances for rain showers exist Monday night into Tuesday on
the backside of departing high pressure that will be moving off to
the east. Return flow and increasing moisture main bring us some
showers during this time frame as shown by the ECWMF. The GFS is
dry, so confidence in this time frame is on the lower side.
- Mainly dry with a slow warming trend Wednesday through Friday
We look to be mainly dry mid to late week as we have followed the
ECMWF for guidance in this time frame. The ECMWF has a building
ridge. The GFS has a trough moving through the area. Given the
range in the forecast though forecast confidence is on the lower
side. We have a dry forecast at this point from Wednesday through
Friday.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 706 PM EDT Fri Sep 5 2025
Wind gusts to around 20 knots are possible for the
next hour or so at inland terminals, and next few hours at MKG.
Winds diminish overnight, increasing from the west Saturday with
gusts to 20 knots. Expect VFR ceilings over the next 24 hours,
with ceilings scattering out overnight near LAN/JXN. Scattered
lake effect rain showers will develop Saturday afternoon and have
added a PROB30 at MKG to account for this.
&&
.MARINE...
Issued at 339 PM EDT Fri Sep 5 2025
Hazardous winds and waves persist this afternoon with gusts to 30
knots and waves up to 10 ft being recorded at observation sites this
afternoon. Have expired the Gale Warning but conditions hazardous to
small craft will continue through the weekend. Waves of 6-10 feet
with gusts to 30 knots will continue into Saturday before a brief
lull develops late Saturday. With another burst of wind Saturday
night bringing waves of 3-6 feet, the short duration of the lull
warrants keeping headlines in place through the weekend. Have
extended the Small Craft Advisory/Beach Hazards Statement through
Sunday afternoon.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Sunday afternoon for MIZ037-043-
     050-056-064-071.
MARINE...Small Craft Advisory until 5 PM EDT Sunday for LMZ844>849.
&&
$$
DISCUSSION...Duke
AVIATION...Thomas
MARINE...Thomas

NWS GRR Office Area Forecast Discussion