859
FXUS63 KGRR 112236
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
536 PM EST Thu Dec 11 2025
.KEY MESSAGES...
- Lake Effect Snow Friday and Saturday
- Arctic Air into Early Next Week
&&
.DISCUSSION...
Issued at 315 PM EST Thu Dec 11 2025
- Lake Effect Snow Friday into Saturday
Inversion heights lower tonight as surface ridging with
subsidence and drying builds in, ending the snow showers except in
the far NW zones. Some clearing is possible inland which would
allow temperatures to drop below 10F and possibly below zero if
skies remain clear for several hours.
An a shortwave trough arrives Friday afternoon and raises
inversion heights to around 10 kft. We expect lake effect snow to
perk up in southwest to west flow during the afternoon. There
could be a brief burst of heavier snow as an arctic front moves
though Friday evening with strong low level convergence with lake
effect continuing in west-norrthwest flow behind the front. Given
onshore flow and strong lake instability, we expect some localized
amounts of 3 to 5 inches of snow before inversion heights fall and
snow showers decrease on Saturday.
- Arctic Air into Early Next Week
A vast area of arctic air pooling across northwest Canada surges
southeast by the weekend, with a lobe of the polar vortex reaching
Lower Michigan by Sunday. 850 MB temperatures plunge below
minus 20C and should result in high temperatures being confined
to the teens on Saturday and Sunday with wind chills approaching
minus 10F, especially Saturday night when the core of the coldest
air aloft comes through.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 536 PM EST Thu Dec 11 2025
TAF sites should climb VFR cigs at or shortly after 00z and remain
there through at least 04z. Uncertainty increases after 04-06z
with two main scenarios possible based on model guidance. First
(and more likely) is that the robust cloud deck holds, possibly
lowering to MVFR with weak subsidence and a lack of notable
thermal advection to break the inversion. Second (lower
confidence) is that breaks in the clouds allow FZFG to form with
visibility restrictions thanks to moisture from the robust
snowpack. Have favored scenario one in the 00z TAF package given
the aforementioned factors leading to questions on if we can break
up the stratocu. However, satellite trends will need to be
watched closely to see if trends towards clearing skies and FZFG
materialize.
Either way, improvement to solid VFR is likely by
late Friday morning/early Friday afternoon. Snow then arrives from
the west near to after 00z, with MVFR conditions possible in any
snow. Low chances at GRR/MKG in the late TAF period warrant a
PROB30 with higher confidence in snow timing after 00z.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Ostuno
AVIATION...Thomas
NWS GRR Office Area Forecast Discussion
