372
FXUS63 KDLH 282025
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
325 PM CDT Sun Apr 28 2024

.KEY MESSAGES...

- A spring storm will bring widespread rain to the Northland
  through Monday (accumulations around 0.25" to 1")

- Localized freezing rain is expected for the higher terrain of
  the North Shore tonight into Monday (accumulations to around
  0.10")

- Light snow will mix with rain for parts of northeast Minnesota
  tonight into Monday (accumulations up to 1" mainly on
  grassy/elevated surfaces around and north of the Iron Range)

- Strong northeast winds up to 50 mph are expected along the
  North Shore of Lake Superior.

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

&&

.DISCUSSION...
Issued at 324 PM CDT Sun Apr 28 2024

Rain has begun spreading northward ahead of a low pressure
system that will affect the region through Monday night. The
forecast remains mostly on track in terms of expected rainfall
amounts, albeit with a bit of a westward shift in the highest
amounts expected. Totals are still expected to range from around
0.25" to 1" with perhaps some locally higher amounts possible
through Monday evening.

Models still continue to strongly suggest some localized
accumulations of freezing rain along the higher terrain of the
North Shore with orographic lift and adiabatic cooling. Several
models continue to be unrealistically high with ice
accumulations around or higher than 0.25", but there are several
factors that weigh against that, including occasionally moderate
to heavy rainfall rates that would limit icing potential, a
limited window tonight into early Monday morning where
temperatures will be cold enough for icing, and a high sun angle
that will limit further accumulations during the day on Monday.
Note also that any ice accumulations are expected to remain
inland and in higher elevations from the MN-61 corridor, where
precipitation will be all rain, and even in the higher terrain,
icing is expected to be pretty localized. Localized icing to
around 0.15" is expected, and a Winter Weather Advisory is in
effect tonight through Monday morning for the Arrowhead. Note
that many places within the advisory may not see any icing,
especially right near Lake Superior.

There has also been a continuing trend among models suggesting a
mix or changeover to snow for a good chunk of northeast
Minnesota late tonight through Monday morning (a few models keep
enough cold air around aloft to keep snow possible into the
afternoon). Similar to the North Shore freezing rain potential,
there are some models that are suggesting advisory-level
snowfall amounts that, at this point, seem largely unrealistic
given the narrow time window that snow accumulation will be
possible and temperatures that are just cold enough to support
snow. Places that may see a mix or changeover to snow will be
along the Iron Range and points north towards the International
Border where enough cold air may be present. Thermal profiles
are nearly isothermal around or a degree or two below freezing
though, so snow will be of the wet/heavy consistency and will
likely be more efficient at accumulating on grassy and elevated
surfaces versus roadways. The time range for this changeover
will be late tonight (3-4 AM or so), then the best chances for
any accumulation (up to around 1") between then and 9-10 AM,
then mixing back with rain as temperatures warm up through
Monday afternoon.

The strong northeast winds have already started up around the
head of the lake and are expected to persist tonight through
Monday morning with gusts to 45-50 mph along the North Shore.
Latest guidance does suggest that winds may start to drop a
little earlier than expected mid-day Monday. A Wind Advisory
remains in effect along the North Shore until 4 PM Monday
afternoon, but there is a possibility that it may be allowed to
expire a little earlier if this trend continues.

Lingering rain or mixed precipitation may become a bit more
showery Monday afternoon. There may be the slightest amount of
instability possible to prompt a rumble of thunder or two, but
this is not expected to be common. Otherwise, as low pressure
departs northeast, the rain or mixed rain/snow will taper to
sprinkles/flurries Monday evening before ending. There may be
some residual fog Monday night into Tuesday morning.

Attention then turns to yet another system that`s expected to
pass through Tuesday into Tuesday night. This one looks like it
will be quick-hitting, but a bit more potent in terms of dynamic
forcing as a negatively tilted trough aloft combines with some
convective instability. We`ll likely see some heavier rainfall
rates, and thus the WPC has parts of the Northland under a
marginal risk for excessive rainfall. Many areas will likely see
another quick 0.25" to near 1". Couldn`t rule out a few locally
higher totals, but that will depend on how much instability ends
up being available to produce thunderstorms.

We may see a break with some dry weather on Wednesday before the
active pattern continues in full swing Thursday into Friday.
Several models hint at another broad-scale low-pressure system
that could bring more rainfall to the region.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1230 PM CDT Sun Apr 28 2024

Tricky forecast at DLH over the next few hours as some fog has
developed. Webcam and surface observations suggest it is
somewhat localized and likely driven by orographic lift. With
that, it`s difficult to pinpoint how persistent it may be.
Models are having a hard time picking up on it, but a few
suggest a few hours of MVFR and occasionally IFR visibility for
the next 3-4 hours, then perhaps some brief improvement as rain
starts to move in. We will continue monitoring this trend and
amend as needed. Otherwise, northeast winds will continue
strengthening and IFR ceilings are expected to persist through
the period.

Elsewhere, MVFR ceilings this afternoon and rain will start to
move in from south to north this afternoon and evening.
Visibility will gradually deteriorate from VFR to MVFR as rain
moves in. Snow is expected to mix in at INL later tonight, so
occasional IFR visibilities will be possible late tonight into
Monday morning. This snow will be of the wet and heavy variety,
but any accumulations are expected to be limited mainly to
grassy and elevated surfaces with temperatures hovering around
freezing. Snow may mix in at HIB as well, though confidence is
lower there (~40% chance). Breezy east to northeast winds
through the period at all terminals.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 324 PM CDT Sun Apr 28 2024

Strong northeast winds gusting from 35 to 45 kt are expected for
most nearshore waters through Monday morning, and Gale Warnings
are in effect. Waves around 8-14 ft are expected as well. Rain
is expected through Monday afternoon. Models have trended
slightly downward in winds mid-day to afternoon Monday, so it`s
possible that gale-force gusts may end a little early. But,
blustery winds will still persist into the evening before
direction changes to northwesterly late Monday night and winds
lessen. Wind speeds and gusts are expected to remain below 15 kt
through 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 until 4 PM CDT Monday for MNZ020-021.
     Wind Advisory until 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>143-146-147-150.
     Gale Warning until 4 PM CDT Monday for LSZ140>143-146-147-150.
     Gale Warning until 10 AM CDT Monday for LSZ144-145.

&&

$$

DISCUSSION...JDS
AVIATION...JDS
MARINE...JDS