346
FXUS63 KGRR 030800
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
400 AM EDT Thu Sep 3 2026
.KEY MESSAGES...
- SPC Slight Risk for severe weather over much of the area today
- Thunderstorm chances may linger into Friday
- Dry weather expected over the weekend
&&
.DISCUSSION...
Issued at 400 AM EDT Thu Sep 3 2026
- SPC Slight Risk for severe weather over much of the area today
The pattern continues to support the threat of thunderstorms over
the next 24 hours, including both today and tonight. At the
surface we have essentially a stationary boundary stretching from
east/west near the I-96 corridor. Dew points to the north are in
the 60s and are in the 70s to the south. MUCAPE values are
stratified correspondingly with 2,000 j/kg in place to the south
and 500-1,000 to the north. The upper flow pattern will likely
bring in convectively induced vorticity maxima from the west today
(the IA/MN convection). Tonight models suggest a NW to SE moving
shortwave that may bring additional storms to the area. The best
LLJ orientation and magnitude occur early this morning through
sunrise and again tonight coming up. Confidence in the evolution
remains on the lower side today/tonight, but we do feel we will
likely see additional storms this morning, additional chances this
afternoon, followed by more storms tonight. Wind appears to be the
main threat per machine learning data like NadoCast which is
supported by the SPC outlooks. Early afternoon soundings via the
HRRR in Ottawa County are indicating 1,100 j/kg of DCAPE which
shows the potential for damaging winds.
PWAT values continue to be high both today and tonight with 2.0
values both forecast periods. Storms have the potential to be
moving quickly, but rainfall rates will likely be high given deep
summer values of PWAT. If storms can train over certain areas or
if motion is slower than anticipated hydro concerns will increase
(localized short term flooding).
- Thunderstorm chances may linger into Friday
Models indicate the potential for some storms lingering into
Friday morning in a northwest flow aloft just downstream of the
plains upper ridge. SPC has a marginal threat for severe weather
in our far southwest which makes sense given the moisture will be
pooled in this area as the front likely sags to the southwest.
- Dry weather expected over the weekend
The patterns looks to try and dry out this weekend as high
pressure builds in from the north and northeast. BUFKIT moisture
overviews this weekend are starkly drier than what we have seen
all this week.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 156 AM EDT Thu Sep 3 2026
Skies are partly cloudy as we approach 06z across Southwest Lower
Michigan with VFR bases. The clouds are generally in the 5,000 to
10,000 foot layer and are associated with a weak front in the
area. The front is producing showers and a few thunderstorms
mainly near I-96. There is a chance these showers and storm expand
through the remainder of the night and we will be watching that
closely. Otherwise some patchy light fog has formed across the
area.
As we progress into the daytime hours of Thursday, the showers and
storms that develop overnight will likely end with VFR weather
expected. Another round of heat of the day showers and storms will
be possible during the afternoon 18z-22z.
&&
.MARINE...
Issued at 400 AM EDT Thu Sep 3 2026
The surface pattern remains fairly benign the next few days with
lighter synoptic scale winds expected. Winds should remain at or
below the 5-15 knot range which will result in waves of 2 feet or
less through Saturday. No advisory level wave events are expected.
The one item to keep an eye on though is the threat of
thunderstorms and stronger winds associated with them. We will be
in a pattern conducive for storms and wind today. Winds and waves
can obviously be higher in and near thunderstorms and mariners
will need to remain alert to this threat.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
