410
FXUS63 KGRR 121739
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
139 PM EDT Mon Oct 12 2026
.KEY MESSAGES...
- A round of showers and non-severe storms tonight
- Additional chances of rain into Friday
- Cooling down Thursday and beyond
&&
.DISCUSSION...
Issued at 258 AM EDT Mon Oct 12 2026
- A round of showers and non-severe storms tonight
We will see another very nice autumn day with temperatures actually
quite warm by mid-October standards. The low clouds on the periphery
of the remnants of "Isaias" from yesterday have moved out, allowing
for much more sunshine, although it will become filtered with high
clouds streaming in. 850 mb temps will warm from around 13C on
Sunday, to almost 18C which will support highs near 80.
The cold front currently north of the area will drop down into the
area this evening and overnight as a short wave over the northern
portion of the state pushes it overhead. Also ahead of the short
wave and sfc low will be a 40 knot low level jet nose aimed right at
the area. This moves in between 00z and 06z tonight. We would expect
a good area of showers with embedded scattered storms. The storms
are not expected to be severe as they will be elevated in nature
(limiting wind and tornado potential) and mid level lapse rates
neutral around 6.0 C/km and updraft strength will be limited with MU
CAPEs a few hundred J/kg.
- Additional chances of rain into Friday
The showers and storms will move out before daybreak Tuesday as the
short wave moves by, and the cold front sinks south of the area. The
front will stall out as it becomes parallel to the upper flow with
the cutoff low out west pumping up the ridge over the area. Much of
Tuesday should remain dry with no organized short waves expected to
move through.
We do see the next short wave ejecting from the western low Tuesday
night along the front, which will be by that time just north of the
Ohio River valley. This sets up the best chance of rain across the
south, closer to the front. We will be on the cool side of the front
by then, so thunder chances will diminish a bit. The same thing
happens around Thursday with the front even a tad further south. A
better low is forecast to develop and move along the front, which
will help bring a bit better rain chances into more of the area.
Fast on the heels of the Thursday southern stream system, a strong
northern stream wave will drop in by Friday and usher in much cooler
air on fairly strong winds. This will bring another chance of rain
with the front, and could produce some brief lake effect rain
showers while the upper jet core briefly drops below our area.
The upper trough then moves out quickly Friday, helping to bring
high pressure to the area. This will clear things out for the
weekend.
- Cooling down Thursday and beyond
We will see cooler air first arrive on Wednesday as the cold front
sinks far enough south. Much cooler air will move in Thursday and
Friday with more clouds and showers with the upper cold pool
overhead. Highs may struggle to get out of the 50s. Temperatures
will recover a bit then starting Sunday as return flow sets up on
the backside of the ridge.
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 129 PM EDT Mon Oct 12 2026
Skies are mostly clear across the region. Low pressure will move
east from Wisconsin tonight and push a weak front across the
terminals. We included a 30 percent chance of thunderstorms during
the late evening and early overnight period. After the
precipitation moves through, we`ll return to VFR conditions.
&&
.MARINE...
Issued at 258 AM EDT Mon Oct 12 2026
We are expanding the Small Craft Advisory further north through our
last marine zone. We are also extending the headline to start
earlier this morning, and last a little longer this evening.
High pressure is moving away from the area, and the next frontal
system will be approaching to ramp up the southerly winds. The winds
will be warm winds, so we will not see the full potential with a lot
of the wind remaining elevated.
There will be a short break then this evening and early tonight as
the front leans in. The winds will increase again with a sfc low
coming through and a good gradient on its periphery.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ847>849.
&&
$$
DISCUSSION...NJJ
AVIATION...04
MARINE...NJJ
NWS GRR Office Area Forecast Discussion
