779
FXUS63 KDLH 280849
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
349 AM CDT Sun Apr 28 2024

.KEY MESSAGES...

- Freezing rain is expected along the higher terrain of the
  North Shore and for most of Cook County tonight. Total ice
  accumulations of around one tenth of an inch are expected.

- A little snow is possible north of highway 2.

- Strong northeast winds gusting up to 50 mph are expected this
  afternoon through Monday morning in the Twin Ports and along
  the North Shore. Wave heights will also be large due to the
  strong winds.

- Widespread rain this afternoon into Monday will give up to
  1.25" of rainfall.

- Active weather continues through the week with rainy systems
  on Tuesday and Thursday.

&&

.DISCUSSION...
Issued at 345 AM CDT Sun Apr 28 2024

There`s a lot going on with high winds and also mixed ptypes.

The most concerning aspect of the forecast is the potential for
significant icing along the North Shore and in Cook County where
hi-rez guidance is flogging them with ice storm warning criteria
amounts. Coordinated pros and cons with the WPC and we were both
thinking along the same lines. Here is what we came up with: it
appears that HREF is overdoing the ice accretion, but there
does appear to be a window between 06Z-15Z Monday where some
icing could occur. The precipitation type algorithm has 3 models
that use wet-bulb temperature and these all agree for some low
probability of ice as a weather type. The meteorological setup
is just not that great for efficient freezing rain with wet bulb
temps right around freezing, and strong forcing which drives
heavier precip rates which suppress icing potential. These
together without a clear signal of dry advection suggests that
the forecasts of ice approaching 0.25 to 0.5" are too
aggressive. While the trend for higher ice amounts in the hi-rez
guidance has been increasing, it feels like a low probability
of occurrence due to the aforementioned conditions unless the
temperature is not being handled properly. Furthermore, I can`t
recall a good freezing rain event when wet bulb temperatures are
around 30. The best ones seem to be 28 and below. In my mind, I
was thinking around a tenth of an inch seems like a good path
forward. We can adjust if necessary as we near the time of the
event if obs come in colder, but for now raised a Winter Weather
Advisory to cover up to 0.10" of ice which I believe is most
likely. Note that any ice accumulations should be away from Lake
Superior as the environment is already marginal mainly due to
the temperature near freezing component. To add to this, winds
will be strong, so if the more dire scenario plays out, it could
make a mess though again, this more dire event has a low
probability of occurrence especially climatologically for this
time of year.

Remaining in the winter mindset, some ptypes keep a fair bit of
this precipitation snow in International Falls, so if that does
occur, thinking it may up to an inch on grassy surfaces, but
road temperatures are expected to be too warm for any
accumulation on them. Even some guidance starts the snow off as
far south as the Twin Ports, but a look at soundings suggests
that the snow algorithm is off and my interpretation is it`ll
just be really cold rain with a warm nose aloft and surface
dewpoints above 32F.

Not much change in the wind forecast, they still look strong
with the NBM mean coming in around 50 mph this evening in the
Twin Ports - have slightly less than that in the forecast, but
wouldn`t be surprised to see some exposed areas hit 50 mph.
Maintained the Wind Advisory.

Opted to forego any Lakeshore Flood headlines. Thinking the
fetch residence time is not long enough to cause the piling up
of water enough to overcome the current water level of 601` -
where we need 603`. It would require quite the push with
stronger winds than forecast or a longer period of those winds
to exceed that. Large waves to 10 to 14 feet and beach erosion
are expected though.

Rainfall forecast remains on track with another 3/4 to 1 1/4"
for this wave. If this is not enough, we`ll get more rain on
Tuesday and potentially a very similar system to the one today
to end the week helping to squash fire weather concerns for
awhile. :)

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1230 AM CDT Sun Apr 28 2024

MVFR most places this morning. Slowed down the timing of the
rain in this package and improved ceilings as obs are coming in
a bit above guidance, but this is the difference between IFR and
MVFR this morning. Ceilings lower towards morning falling below
this threshold before they pop up for the morning before falling
again to IFR this evening as the rain approaches. Winds will
begin to pick up out of the east and become gusty as the next
system approaches.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 345 AM CDT Sun Apr 28 2024

A low pressure system will arrive this afternoon bringing rain
and very strong northeasterly winds. Winds will strengthen this
morning with gales expected this afternoon. Winds will be
strongest tonight into Monday morning. This is expected to be a
high-end gale event with gusts to 45 knots. In addition, wave
heights around 10 to 14 ft are expected, especially along the
North Shore and Outer Apostle Islands. Breezy conditions and
high wave heights will persist into Monday night. Much calmer
conditions are expected Tuesday.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Winter Weather Advisory from 1 AM to 1 PM CDT Monday for
     MNZ012-021.
     Wind Advisory from 4 PM this afternoon to 4 PM CDT Monday for
     MNZ020-021.
     Wind Advisory from 4 PM this afternoon to 10 AM CDT Monday for
     MNZ037.
WI...None.
MARINE...Small Craft Advisory until 4 PM CDT Monday for LSZ121-148.
     Small Craft Advisory until 4 PM CDT this afternoon for
     LSZ140>147-150.
     Gale Warning from 4 PM this afternoon to 4 PM CDT Monday for
     LSZ140>143-146-147-150.
     Gale Warning from 4 PM this afternoon to 10 AM CDT Monday for
     LSZ144-145.

&&

$$

DISCUSSION...Wolfe
AVIATION...Wolfe
MARINE...Wolfe