968
FXUS63 KGRR 080202
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
902 PM EST Fri Feb 7 2025

.KEY MESSAGES...

- Snowfall Saturday into Sunday

- Winter continues through next week

&&

.UPDATE...
Issued at 902 PM EST Fri Feb 7 2025

Snow currently in western Wisconsin to the Dakotas will gradually
shift east overnight into Saturday. Dry air will impact snowfall
initially and may limit accumulations in the morning before the
better lift with the 500mb wave and positive vorticity advection
move through during the afternoon. Within the Advisory, 3 to 5
inches of snow is expected. Higher amounts are possible with
probabilities of 6 inches or more in the 30 to 50% range north of
US-10.

To the south there is a question of if we saturate enough for
precipitation. Latest hires soundings still struggle with eroding
the dry air. Therefore did adjust the probability of precipitation
lower (30 to 50%) south of I-96.

&&

.DISCUSSION...
Issued at 215 PM EST Fri Feb 7 2025

- Snowfall Saturday into Sunday

Bottom line up front: Have issued a winter weather advisory for
the periods of heavy snowfall expected through the northern half
of the lower Peninsula Saturday into early Sunday. Heaviest
snowfall is expected Saturday afternoon, especially along the US
10 corridor. Snowfall of 3 to 5 inches expected with locally
higher amounts possible.

Zonal flow will bring an upper level shortwave through the region
Saturday through Saturday night. a large mid level low will be
moving from the southwest to the northeast during this timeframe.
A negatively tilted boundary should allow for southeasterly flow
which should allow for increased frontogenetic forcing Saturday
afternoon. Some of the dynamics seem disjointed with weak flow
aloft. However, there will be more than enough moisture provided
by the SE flow. Couple that with cold air advection of around -9C
by Saturday afternoon and periods of increased snowfall is
expected. Still looking at 3 to 5 inches but some areas in
stronger frontogenetic forcing could overperform. Snow should
taper off Saturday evening with linger snow showers into early
Sunday.

As the above mentioned low moves from the southwest through the
Michigan- Indiana border there is a chance that the warm frontal
boundary could allow for wintry mix along and south of the I 94
corridor. It remains low probability but surface temperatures
should remain below freezing, so a snow/freezing rain wintry mix
is possible Saturday afternoon. Soundings for Kalamazoo keep it
dry however, there is an unsaturated DGZ Saturday afternoon with
cloud bases around 6KFT. So while a snow/freezing rain wintry mix
is low it remains possible.

- Winter continues through next week

Cold air will continue to stream through the region through next
week with below normal temperatures expected. This will keep Max
T`s in the 20s with lows dipping into the teens by mid next week.
Forecast pattern looks fairly dry with the next chance for precip
mid to late next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 605 PM EST Fri Feb 7 2025

VFR conditions will lead to minimal impacts to aviation until the
last 6 hours of the TAF period. Westerly winds today will back
easterly by the morning. After 18z, two areas of snow arrive, the
first north of MKG/GRR/LAN and the second from the south towards
JXN/AZO/BTL. High confidence the southern area will bring IFR
visibilities and MVFR to IFR cigs to JXN/AZO/BTL. For MKG/LAN/GRR,
the two areas of snow will approach these terminals, but
confidence is lower in direct impacts thanks to ambient dry air.
Have used a mix of PROB30 and prevailing at these terminals
depending on confidence with MVFR to IFR conditions under snow showers.
There is a low chance that FZDZ could mix in at JXN/BTL/AZO but
confidence is too low to include in the TAF.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 7 AM Saturday to 7 AM EST Sunday
     for MIZ037>040-043>046.
MARINE...None.

&&

$$

UPDATE...RAH
DISCUSSION...Ceru
AVIATION...Thomas