508
FXUS63 KGRR 152327
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
627 PM EST Mon Dec 15 2025

.KEY MESSAGES...

- Dry and warmer through Wednesday

- Warmer and rainy Thursday, roadway ponding possible

- Colder with snow possible Thursday night through Saturday

&&

.DISCUSSION...
Issued at 250 PM EST Mon Dec 15 2025

- Dry and warmer through Wednesday

Radar shows a few lingering snow showers over the northern half
of the cwa, the result of a weak short wave moving over Lower MI
along with some lake enhancement. H8 temperatures will continue
to warm through the rest of the day which will end the lake
contribution.

Strong southwest flow aloft will result in H8 temps warming to
+8c by Tuesday evening; we`ll see highs Tuesday and Wednesday climb
into the mid 30s.

- Warmer and rainy Thursday, roadway ponding possible

Strong low pressure moving east along the US-Canada border will
create a strong 65kt llj which will advect moisture and warmth
into the cwa Thursday ahead of the trailing cold front. Strong
isentropic lift on the 290k sfc will saturate the lower atmosphere
early Thursday and rain will develop shortly prior to sunrise.
QPF has seen good model-to-model consistency as of late and
0.3-0.4 inches of rain seems plausible. The roughly half foot of
snow on the ground should be able to absorb that without too much
problem. A bigger issue may be what happens on the roads,
especially secondary roads. We are in the middle of snow-clogged
storm drain season and the expected rainfall may have difficulty
finding a storm drain that`s clogged by plowed snow, resulting in
ponding.

Hydrologic ensemble forecast system shows that rivers will rise
with the expected rainfall and a few may reach action stage.
However, flooding is not expected.

- Colder with snow possible Thursday night through Saturday

Another surge of cold air will quickly follow fropa Thursday
night. Any lingering precipitation will change over to both
synoptic light snow and lake effect as h8 temps quickly fall to
-17c. But, that won`t last long either as boundary layer winds
 quickly become southwesterly and h8 temperatures warm to -9c by
 late Friday. A quick succession of lows/cold fronts will result
 in short periods of light show...none of which looks particularly
 heavy.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 627 PM EST Mon Dec 15 2025

MVFR conditions expected overnight with a persistent layer of
stratus clouds. Bases are generally 1800 to 2500 feet AGL with
tops around 4 kft. The clouds will slowly break up Tuesday morning
with VFR expected at most places by 18Z.

&&

.MARINE...
Issued at 250 PM EST Mon Dec 15 2025

Wind will diminish to sub gale force mid afternoon today, but
waves will remain high; we issued a small craft advisory until 1
AM tonight earlier this morning to account for the waves.

Another small craft advisory may be needed mid morning Tuesday as
the pressure gradient tightens ahead of the next cold front and
gales may follow Wednesday and Thursday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 1 AM EST Tuesday for LMZ844>849.

&&

$$

DISCUSSION...04
AVIATION...Ostuno
MARINE...04