872
FXUS63 KGRR 171854
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
254 PM EDT Fri Apr 17 2026
.KEY MESSAGES...
- Line of Storms Crosses Area Tonight, Strong to Severe Possible
- Cooler Sunday, Drier Pattern Ahead
&&
.DISCUSSION...
Issued at 253 PM EDT Fri Apr 17 2026
- Line of Storms Crosses Area Tonight, Strong to Severe Possible
Storms out west across the upper Mississippi Valley will traverse
east through the evening reaching the lakeshore near 9am. HREF/RAP
guidance is less bullish on CAPE than yesterday with MUCAPE on the
order of 500-1000 J/kg by the time storms arrive thanks to a wam
nose just off the surface. 30-45 knots of deep layer, and 0-3 km
shear will be sufficient for the potential of storms remaining
organized as they approach. Damaging winds in any bowing segments
are the main concern, with a non-zero, but low, risk of tornadoes.
The greatest risk will be near and west of US131 where the earlier
arrival will support better instability lessening with eastward
extent. Showers and garden variety storms will follow the primary
line continuing through daybreak. Widespread rainfall of 0.25-0.75"
is expected with isolated totals to around 1.5 inches. The
progressive nature of the storms should limit areal flooding
concerns but any training or heavier swaths will bring that
potential given saturated soils.
- Cooler Sunday, Warmer and Drier Pattern Next Week
Colder air filters in behind the cold front with 850mb temps falling
into the negatives. This will also support breezy conditions later
Saturday with gusts to 30-35 mph. Highs in the 40s and lows in the
20s to low 30s between Sunday Morning and Monday will be a notable
change from recent patterns. The bright side is the incoming ridging
and northwest flow will be much drier than we have been of late. Dry
weather is likely until late next week when the approach of our next
system brings precipitation back into the forecast. Temperatures
then rebound into the 60s and 70s.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 121 PM EDT Fri Apr 17 2026
Fog and low clouds have dissipated and all sites are VFR as of
present. A line of weakening thunderstorms will move in from the
west after 01z with showers behind it, with conditions falling to
MVFR at all terminals, with periods of IFR and lower conditions
possible. LLWS is also expected out of convection given the strong
low-level jet in play. Gusts to 25 knots, higher possible in any
thunderstorms, are expected near and behind the line of
storms/cold front with souhterly winds becoming westerly.
&&
.MARINE...
Issued at 253 PM EDT Fri Apr 17 2026
Webcams show that fog has dissiapted across the nearshore waters so
will be ending the Marine Dense Fog advisory with this package.
Winds and waves increase to levels hazardous to small craft tonight
and continue through the weekend. A Small Craft Advisory goes into
effect this evening continuing into Sunday. A line of thunderstorms
is expected to cross the lake this evening. Wind gusts to 34 knots
are possible as this line moves through.
&&
.HYDROLOGY...
Issued at 253 PM EDT Fri Apr 17 2026
Major flooding continues on the Muskegon River. The good news is
that the river at most locations will be cresting within the next 24
hours (Upstream areas of the river including Evart crested earlier
today). It will likely take until late next week for all locations
to come under flood stage, so the recovery process will be slow.
Meanwhile, water levels continue to rise on the Grand River, and
confidence is increasing that this will end up being another minor
flood event, slightly higher and worse than the one that happened
earlier this month, but not a record flood at any locations.
However, some of the lowest and easily flooded locations on the
river like Comstock Park and Robinson Township will have moderate to
possibly major flooding.
A final round of rain moves back into Lower Michigan tonight, and is
expected to drop around one-half inch of rain over a large area,
with locally higher streaks of 1"+ possible at some locations. Given
the saturated soils everywhere, this could result in some renewed
minor flooding, primarily impacting roadways. Thankfully, this
expected rainfall is not anticipated to make the river flooding
significantly worse at any locations. Beyond this next round of
rain, we dry out for at least the better part of a week going
forward, which will be a very welcome chance for the rivers to begin
the slow process of recovering to more normal levels.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT Sunday
for LMZ844>849.
&&
$$
DISCUSSION...Thomas
AVIATION...Thomas
MARINE...Thomas
HYDROLOGY...AMD
NWS GRR Office Area Forecast Discussion
