556
FXUS63 KGRR 222037
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
337 PM EST Fri Nov 22 2024

.KEY MESSAGES...

- Light lake-effect showers this evening

- Showers Monday and Tuesday

- Colder Weather and Potential Winter Weather For The Holiday Weekend

&&

.DISCUSSION...
Issued at 337 PM EST Fri Nov 22 2024

- Light lake-effect showers this evening

Cyclonic flow, residual moisture and marginal lake to 850 mb
delta Ts will bring rather light rain showers this evening across
the western zones. The showers diminish late tonight as inversion
heights lower and moisture becomes more shallow.

- Showers Monday and Tuesday

Our next significant chance of precipitation arrives Monday and
continues into Tuesday as a upper-level trough crosses into the
Great Lakes. Warm air advection ahead of this trough sends highs
into the lower 50s before a cold frontal passage marks the start of
our next cooldown. The rain looks to be in two waves. The first will
be with a weak leading wave followed by the secondary wave and
associated cold frontal passage. Rain looks to be light, generally
under 0.25 inches. Much colder air will provide lake enhancement to
precipitation on the back side of the developing low to our east in
this timeframe. This precipitation will mix with or switch to snow
as we dry out.

- Colder Weather and Potential Winter Weather For The Holiday Weekend

Confidence is high in much colder air infiltrating the area late
next week bringing our first true taste of winter. Longwave
troughing from Canada diving south brings a modified arctic air mass
across the Great Lakes region sending 850mb temps plummeting to near
-10C. Cluster analysis shows that questions on both the magnitude of
this troughing, as well as potential interaction with downstream
ridging exist. This could develop a low pressure system over the
southern United States that brings synoptic snowfall to the upper
Great Lakes or the northeastern United States, however specifics in
this pattern remain limited at this time. Regardless of any synoptic
potential, the modified arctic air over our still very warm lakes
and overall longwave pattern are supportive to the potential for
lake effect snow in the latter part of next week. Given the upcoming
thanksgiving holiday and associated travel this will need to be
monitored.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1216 PM EST Fri Nov 22 2024

Northerly low-level flow off of Lake Huron fortifies the ongoing
sub 2kft MVFR cloud deck this afternoon. Cigs in this range are
forecast to persist through the end of the TAF window as low-level
moisture quality remains impressive. West to northwest winds will
be gusty, to around 25 knots, today before subsiding to near 10
knots overnight. Isolated lake effect showers will persist in the
vicinity of GRR, AZO, and MKG through this evening. If one does
clip the terminals they will be light enough to keep visbys VFR.

&&

.MARINE...
Issued at 337 PM EST Fri Nov 22 2024

No changes to the SCA. After a brief lull late Saturday into
Sunday, winds and waves will increase again early next week.

&&

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

&&

$$

DISCUSSION...Ostuno/Thomas
AVIATION...Thomas
MARINE...Ostuno