NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 171756
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1256 PM CDT Tue Mar 17 2026

Forecast discussion for routine afternoon forecast issuance and
updated aviation portion for 18z TAF issuance

.KEY MESSAGES...

- There is a 40-80% chance of light snow tonight into Wednesday
  morning. Snowfall up to 1 inch is possible, especially across
  central Wisconsin. Snow may taper as light freezing drizzle.

- Additional clipper may bring wintry mix or rain Wednesday night
  into Thursday. At this point, only minimal ice or snow accumulations
  expected. Additional chances for light snow late this week into
  the weekend over the north (20-35%). Any accumulations look to be under
  an inch at this point.

- Temperatures rising back above normal by late week. Warmth peaks
  Friday and Saturday with 40-80% chance of highs over 50 degrees.
  The rising temperatures will lead to snowmelt and increased
  flows and rising levels on rivers and streams. Several rivers
  may reach bankfull or even minor flood stage.

&&

.DISCUSSION...
Issued at 1250 PM CDT Tue Mar 17 2026

A stronger northwest flow with clipper systems keeps the pattern
active through the week. After chilly day today by mid March
standards, gradual warming trend develops into the coming weekend.
At this point, limited impacts expected with these weather systems.
Will have to keep eye on trends with the Wednesday night into
Thursday system.

Sunsplashed day so far today, except some lake clouds and flurries
especially north of Rhinelander. Mid clouds already increasing into
western WI, ahead of warm front with light snow falling from Manitoba to
Minnesota. Low-mid level jets with this fade while arriving over
western Great Lakes, so though it will snow, looks like an inch or
less for most areas late tonight into Wednesday. So, a bit of
fresh snow on the roads, though most roads are still snow covered
from the recent storm. Mid-level moisture strips out mid to late
morning, so maybe this ends as patchy light freezing drizzle.
Impact should be minimal.

Next clipper with a bit more wind energy arrives Wednesday evening.
Some models have more QPF due to overall sharper shortwave and
steeper mid-level lapse rates. Probabilities from NBM for 6hr QPF
do suggest that some of these models may be overdone or at least on
the higher end percentiles. Main question is ptype. Critical thicknesses
point to rain/snow line over far northern WI. There could be a zone
where warm layer aloft will have near or below freezing temps beneath
(FZRA/Sleet). It is also possible that where warm layer aloft is
present, sfc temps will also be above freezing. Tricky setup, but
overall appears impact would be lower even if there is a mix as LREF/NBM
probabilistic guidance not too thrilled for much in way of snow or
ice amounts in our area, with less than 15% chance for even a
coating of ice or snow. Perhaps surface temps in these guidance
sets are too warm to support accumulations, even if there is
wintry mix. Precip that lingers over east-central WI then exits by
mid morning on Thursday. Given current forecast now shows at
least minor ice accums (up to 0.02 inch) and it could impact the
Thursday morning commute, going to add a mention in our HWO.

Another couple clipper systems cross northern Great Lakes Thursday
night into Friday, then again this weekend. Current indications
are that main swath of snow Friday will be farther north across
Upper Michigan, though far northern and far northeast WI could see
up to 1 inch of snow late Thursday night into Friday morning. Clipper
for the weekend could impact more of our area. but probabilities over
the north are very low for even an inch of snow.

Temperatures/Snowmelt: Getting recalibrated, normal highs for mid
March are around 40. Normal lows range from the upper teens
north, to the mid 20s elsewhere. With that in mind, high
temperatures starting off chilly today, will bounce back to reach
normal to slightly above normal by Thursday with readings mainly
in the 40s away from the immediate Lake Michigan shoreline. Friday
and Saturday have the greatest chance of seeing highs over 50F
(40-80%), before temperatures cool back to normal or even slightly
below normal Sunday into early next week. Minimum temperatures
will be mostly below freezing, which should allow for a gradual
melting of snowpack. The only night that shows some signal for
temperatures staying in the mid to upper 30s would be Friday night
(25-35% of min temps >= 35F).

As temperatures warm later this week into the weekend, the snow
melt will no doubt result in increasing fast flows and rising
river levels. Some rivers could reach bankfull or even minor
flood stage. At this point though with lack of a rapid, significant
warmup and heavy rain, widespread flooding is not expected. This will
have to be monitored as we progress through the end of the month.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 1250 PM CDT Tue Mar 17 2026

VFR conditions are expected through early this evening. There will
be a few lake effect stratocu at 030-040 north-central and
northeast this afternoon. Otherwise, mid clouds will thicken from
the west ahead of clipper system that brings light snow over the
area late evening through late tonight.

Bulk of light snow occurs 05z-11z. Visibility will be as low as
IFR as the snow moves through, while cigs will be IFR to MVFR.
The snow may taper as freezing drizzle on Wednesday morning with
IFR-MVFR conditions grudgingly improving to MVFR-VFR mid to late
afternoon.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....JLA
AVIATION.......JLA