688
FXUS63 KGRR 131930
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EDT Mon Oct 13 2025

.KEY MESSAGES...

- Mostly Dry Until Late Week

- Weekend Shower/Storm Chances

&&

.DISCUSSION...
Issued at 330 PM EDT Mon Oct 13 2025

- Mostly Dry Until Late Week

A weakening cold front is coming through mostly dry today, but
some mid and low level cloud cover will persist into Tue morning.
May have fog develop Tue morning again especially around
Lansing/Jackson where fewer clouds are expected, and projected low
temperatures may fall a few degrees below this afternoon`s
minimum dew points.

The next chance of rain showers, Tue night, is trending up in
probability to about 30-50 percent with the support of more ECMWF
ensemble members and now the HREF models. However, this is likely
to be an inconsequential rain event. Worth noting this time that
the PoPs express the chance of receiving at least 0.01 inch of
precip. Narrow swaths of over 0.10 inches of rain are possible but
do not appear to be the most common outcome for any particular
location. This precipitation will be produced amid midlevel lift
and moisture (above 700 mb) crossing the ridge and spreading over
relatively dry low-level air.

There will be a midweek cooldown under northerly flow ahead of an
advancing surface high. Wed is expected to be the coolest day of
the week with highs in the lower 60s, which is pretty close to mid
October normals. The center of the surface high will be in close
proximity Wed night, setting up a frost/freeze scenario. Mimicking
the frost/freeze of last week, a freeze is likely in the interior
highlands of Central Michigan. Widespread frost is likely around
Jackson, while patchy/areas of frost are possible elsewhere. Parts
of Southwest Michigan may escape frost again.

- Weekend Shower/Storm Chances

The synoptic pattern translates eastward later in the week,
bringing upper level troughing closer to Michigan with chances for
rain from Friday through the weekend. The upper level ridge will
cross Michigan around Friday with a chance of warm advection rain
showers, but amounts are not favored to be very significant.
Better chances for appreciable rain, and perhaps some
thunderstorms and blustery winds, arrive during the weekend, as a
digging shortwave trough rounding the base of the midcontinent low
may develop a relatively strong Ohio Valley / Great Lakes surface
cyclone.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 213 PM EDT Mon Oct 13 2025

Low clouds have lifted and vsbys have lifted. A weakening frontal
boundary is infiltrating from the west. This is draping a cloud
deck across Western MI. Dry forecast through the period. The only
question is the potential for IFR and lower cigs and vsbys at the
TAF sites. Biggest concern will be at the central TAF sites of LAN
and JXN. There remains question on how east the clouds make it. If
clearing occurs there is a good potential for another round of fog
at JXN and LAN.
 While less likely, there remains a chance of fog/mist at AZO and
BTL. with calm winds, it will be tough to mix out any reducing
conditions. So any MVFR to IFR cigs and vsbys could continue to 14
to 15Z Tuesday.

&&

.MARINE...
Issued at 330 PM EDT Mon Oct 13 2025

Fog remains possible tomorrow morning though given the passage of
the front it will be less likely. Winds will shift to the north
behind the front. Expect gusty winds tomorrow afternoon with winds
potentially reaching 20 to 25 knots after 20Z Tuesday. Winds will
then shift to more northeast which will be offshore flow. So will
hold off for now but there is the potential for SCY tomorrow
afternoon for the points.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...CAS
AVIATION...Ceru
MARINE...Ceru