505
FXUS63 KGRR 130836
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
336 AM EST Sat Dec 13 2025
.KEY MESSAGES...
- Lake effect snow and cold tonight into Sunday
- Turning warmer this week with rain in the forecast Thursday
&&
.DISCUSSION...
Issued at 336 AM EST Sat Dec 13 2025
- Lake effect snow and cold tonight into Sunday
Main forecast focus this morning was on the Arctic air intrusion
combined with lake effect snow. Specifically the concern is the
threat of impacted travel. We have issued a Winter Weather
Advisory from this afternoon through tonight and into Sunday
morning. The advisory is not for heavy snow, but instead impacted
travel. We will see 1 to 3 inches of snow in the lakeshore
counties during the aforementioned time frame with an isolated 4
inch amount not out of the question. The issue however is the fact
that temperatures will continue to plummet throughout the day. A
strong mid level shortwave will work through the region tonight
which will give a boost to the lake effect snow. Again, heavy snow
is not expected but the combination of very cold air, small/fine
snowflakes and blustery conditions/blowing-drifting snow (NW
15-25 mph) will create impacted travel.
When 850mb air of -20C or colder works into the area it correlates
to surface temperatures below 15F. At these temperatures salt
becomes less effective. Any light snow production, whether it is
heavy or not is pasted into a glaze of ice many times due to a
constant refreezing process. Therefore, the main concern is
impacted travel from this afternoon through Sunday morning for
slick conditions. People will need to slow down and allow extra
travel time. We do not see these conditions (very cold
temperatures and snowfall) all of the time and folks can be
unprepared. The HRRR shows temperatures dipping to +5F tonight
in portions of the Winter Weather Advisory. Again, those surface
temperatures with a consistent light snow is the concern with
regard to travel.
As for some of the meteorological parameters agree with previous
discussions that the depth of moisture is shallow, but it does
increase this evening and tonight with a healthy mid level
shortwave working through. At the lakeshore BUFKIT points, the DGZ
is off the deck so there should be consistent light snow
production. Lift is fairly strong within the shallow cloud layer.
The heaviest snow will certainly be tonight. Delta T`s will reach
the mid 20s C which is extreme.
- Turning warmer this week with rain in the forecast Thursday
The remainder of the forecast shows the upper pattern becoming
more zonal with a system forecast to move through the Great Lakes
region on Thursday. Southerly flow ahead of this system will push
us back into the 30s and even some 40s mid week. At this point,
the precipitation looks to be mainly rain with amounts that do not
look too significant on the order of a half inch.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1125 PM EST Fri Dec 12 2025
Radar shows light snow developing over central Lower ahead of the
arctic cold front that`s moving across central Wisconsin. We`ll
see visibilities fall to 1.5sm - 4sm in light snow as this initial
burst of snow moves through. Accumulations around an inch are
possible, especially along the I-96 terminals.
Once the arctic air moves overhead, extreme instability over the
lake will develop and produce lake effect snow. However, the
dendritic growth zone will plunge to near the surface resulting
in a dgz that`s only 2-4k ft thick. In addition, moisture isn`t
all the plentiful either. Flake size will likely be pretty small
in the lake effect but visibilities are likely to fall to IFR at
times along/west of US-131. While accumulations won`t be
significant, the lower vsbys will likely impact aircraft
operations to some degree.
GRR Airport DSS Update
No changes to the airport briefing information provided from the
day shift.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 4 PM this afternoon to 11 AM EST
Sunday for MIZ037-038-043-050-056-064-071-072.
MARINE...Small Craft Advisory until 7 PM EST Sunday for LMZ844>849.
&&
$$
DISCUSSION...Duke
AVIATION...04
NWS GRR Office Area Forecast Discussion
