843
FXUS63 KGRR 092044
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
344 PM EST Thu Jan 9 2025
.KEY MESSAGES...
- Accumulating snow for Friday into Friday night
- Arctic air arrives early next week with more snow
&&
.DISCUSSION...
Issued at 253 PM EST Thu Jan 9 2025
- Accumulating snow for Friday into Friday night
Southwest winds will be on the increase later tonight and into
Friday as a deeper trough approaches from the west. Moisture
advect in and is shown to deepen up through 500 mb Friday morning
over the entire area. This axis of deeper moisture shifts east
through the CWA during the day. Models are in good agreement in
showing and area of light snow spreading into the CWA with inland
locations seeing 1 to 3 inches of snowfall. However, closer to
Lake Michigan, enhancement is forecast to lead to higher amounts
and more impacts. The southwest low level flow during the morning
will favor the Holland to Muskegon and possibly southern Newaygo
County area for a band of heavier snow. Then as the low level
winds shift northwest later in the afternoon and evening the
bands should align with this flow and that would support banding
into the cities of Holland, Allegan and Kalamazoo. Ensemble snow
amounts have been trending up with this system, especially to the
southwest of Grand Rapids. We do believe the snow ratio will be a
factor in the snow amounts and 10 to 1 is likely a conservative
value. Based on all this, we have issued a Winter Weather Advisory
for the region we are most confident to see higher snow amounts
and associated impacts, which includes Muskegon, Ottawa, Allegan,
Van Buren and Kalamazoo Counties. We will have to monitor the next
set of counties inland as the western parts of these counties
could be impacted by the bands of snow. We did use the term
occasional snow as there will likely be some breaks in the snow.
- Arctic air arrives early next week with more snow
A deeper upper level low drops slowly southward through Ontario
Sunday into Monday. This feature is shown to be just north of Lake
Superior Monday night. Models are in decent agreement with this
scenario. As a result arctic air wraps in south of this feature
and into the CWA through this period. The DGZ moistens up here in
Michigan later Sunday and it remains moist into Tuesday. In
addition, with a tighter pressure gradient, gusty winds can be
expected. Ensemble temperature trends have been colder. Given
all this, the potential for winter related impacts are on the
increase for early next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1233 PM EST Thu Jan 9 2025
The first 12 hours of the forecast will feature little impact to
aviation as VFR conditions dominate the forecast. Southerly to
southwesterly winds of 7-12 knots are expected with gusts to 20
knots near the lakeshore tonight. After 06z MVFR cigs arrive at
MKG ahead of our next system. The arrival of deeper moisture and a
cold front will generate snow after 12z and through the rest of
the TAF period. MVFR cigs are likely in any snow with IFR cigs
possible at MKG and GRR. Visbys will fall to IFR and lower at all
terminals as snow expands across the area.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 8 AM Friday to 4 AM EST Saturday
for MIZ050-056-064-071-072.
MARINE...Small Craft Advisory until 7 PM EST Friday for LMZ844>849.
&&
$$
DISCUSSION...MJS
AVIATION...Thomas
NWS GRR Office Area Forecast Discussion
