987
FXUS63 KGRR 120800
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
400 AM EDT Wed Aug 12 2026
.KEY MESSAGES...
- Chance for Scattered Thunderstorms Today
- Saturday and Sunday is the Next Good Chance for Storms
- Seasonable Temperatures Expected
&&
.DISCUSSION...
Issued at 359 AM EDT Wed Aug 12 2026
- Chance for Scattered Thunderstorms Today
High resolution models all have a signal for scattered storms
today and the SPC outlook agrees with general thunder and a
marginal risk across the forecast area. Looking at the 24 hour max
reflectivity from the HREF there are two main zones for convection.
The first is in the SPC marginal risk across Central Lower
Michigan. Storms may both develop this morning and again this
afternoon over Central Lower, peeling to the southeast into the
thumb with time. The second area of focus is really just to the
south and west of the area like yesterday. The RAP is showing
1000-2000 j/kg of MUCAPE at max heating. Stronger mid level winds
are noted over Central and Northern Lower, so if there are chances
for severe weather today it will likely be up in Central Lower
with wind being the main threat.
- Saturday and Sunday is the Next Good Chance for Storms
We will largely be dry after this evening until we get to Saturday
night and Sunday when our next system will be working through the
state. A mid level shortwave looks to be the driver of this
convection as it tops the Central Plains ridge and moves through
the Great Lakes. Dew points surge into the 70s with MUCAPE values
in excess of 2000 j/kg so stronger storms are certainly possible,
especially given mid level flow around 40 knots.
- Seasonable Temperatures Expected
No major changes in temperature are expected. Highs look to be in
the 80s right through the 7 day forecast.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 217 AM EDT Wed Aug 12 2026
The beat goes on in terms of aviation weather concerns today, they
are the same as they have been the last few days, fog and storms.
Variable conditions are in place to start the TAF period once
again with LIFR to VFR weather occurring in close proximity. In a
light wind / high moisture setup this is to be expected as
radiational cooling allows for rapid fog formation and
dissipation. We do expect a downward trend the remainder of the
night however with fairly widespread IFR and LIFR forecast by 11Z.
The fog and stratus should lift quickly once again today with VFR
weather returning by 15Z-16Z.
Storms are once again in the forecast today, but the signal is not
as strong for certain thunderstorm development. We feel many of
the TAF sites may stay storm free today with the bulk of the
activity staying to the north, east and south of the TAF sites. A
zone of storms are expected from portions of Central Lower
Michigan into the Thumb today with another zone sweeping the MI/IN
border once again. Therefore, we currently have dry TAFs going,
but know given a scattered nature to the storms it is not out of
the realm of possibilities to see some activity today. The better
bet is for dry though.
&&
.MARINE...
Issued at 359 AM EDT Wed Aug 12 2026
Limited concerns in the next few days in terms of winds and waves.
We are in a fairly slack pressure gradient through the remainder
of the week so waves should be 2 feet or less. Otherwise, the two
main concerns are fog and thunderstorms. Thunderstorms are
possible today over Lake Michigan so mariners and beach goers will
need to keep that in mind as winds and waves are usually higher
in and near storms. Fog will remain a threat over the water until
we can bring in drier dew points. That does not really happen this
week so the threat of fog will continue.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
