Area Forecast Discussion
Issued by NWS Duluth, MN

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326
FXUS63 KDLH 182153
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
453 PM CDT Sat May 18 2024

.MESOSCALE...
Issued at 452 PM CDT Sat May 18 2024

Quick update on the storms as we`re about halfway through this
short-duration severe weather event. We have received a few
reports of hail thus far in northwest Wisconsin, ranging from
dime to quarter size. In Wisconsin, cells have been largely
discrete, and are now showing some signs of congealing into a
somewhat organized line in Iron/Price counties. As these storms
exit the region to the east over the next hour, hail will remain
the primary threat, but couldn`t rule out some gusty winds as
well. Storms may backbuild a little bit behind the initial line
as there`s still plenty of instability present out ahead of the
cold front, which is still working its way through
Douglas/Burnett/Washburn counties. But, instability should
pretty quickly fall off over the next hour or two.

Storms over the Arrowhead have been less impressive, which
isn`t surprising with less instability overall there. A few
cells have popped up around the lake breeze boundary and are
moving towards Canada. There will still be a threat for some
large hail mainly for the next hour or so, but the threat is
starting to decrease overall as the cold front advances.

&&

.KEY MESSAGES...

- Isolated to scattered strong to severe storms in the Arrowhead
  and northwest Wisconsin this afternoon. Hail up to 1.5" in
  diameter and wind gusts to 60 mph possible.

- Short dry spell Saturday night and Sunday morning before our
  active weather pattern returns next week with multiple periods
  of rain through the week.

&&

.DISCUSSION...
Issued at 348 PM CDT Sat May 18 2024

We`re still expecting a threat for severe weather through about
7 PM this afternoon. Current observations out ahead of the cold
front in northwest Wisconsin are pretty warm and moist;
temperatures hovering near 80 degrees and dew points in the 50s
to low 60s. One caveat has been some fairly robust stratocumulus
coverage, but this is starting to erode over
Douglas/Burnett/Washburn counties. We`re starting to see a
couple cells pop up along the lake breeze boundary over in
Bayfield/Ashland counties. In the Arrowhead, conditions are
cooler but nonetheless instability is building out ahead of the
front. Around or slightly above 1000 J/kg of SBCAPE is out
there, and we`re looking at favorable 0-6km wind shear from
40-50 kt as well. It is now a waiting game for the cap to bust
everywhere, and once it does, storms should fire pretty
quickly. We will be looking at a pretty short window where
strong to severe storms will be possible until about 7 PM when
the cold front clears the region. Until then, discrete cells
will largely be favored, which will keep large hail as the
primary threat (up to around 1.5" in diameter, though it
wouldn`t be surprising to get a report or two a little larger
than that). Could see wind gusts to 60 mph as well, and perhaps
70 mph which would be more likely (if it happens at all) further
east (Iron/Price counties) where storms may start to
consolidate. The risk for tornadoes remains very low, but a
brief spinup couldn`t be ruled out, again mainly in Iron/Price
counties.

As the cold front passes through by around 7 PM, the storm
threat is expected to quickly diminish, leading to a quiet
night. On Sunday, another low pressure system will approach from
the southwest and bring more rain to the region as early as
Sunday afternoon. This will mainly be a synoptically-forced
rain, but a few embedded rumbles of thunder can`t be ruled out.
This will be a fairly quick-moving system ending on Monday, so
heavy rain amounts are not expected. Totals generally around or
less than an inch with heavier amounts more likely in northwest
Wisconsin.

Another potentially larger system is looking likely to make its
way into the region Tuesday into Wednesday, and model ensembles
with this one suggest some pretty hefty rainfall amounts may be
possible. We could be looking at fairly widespread totals around
an inch or two, and perhaps locally higher. This will be another
situation where, right now, the convective threat appears low,
but the main threat will be localized minor flooding with some
of these higher rainfall amounts. Depending on the storm track,
rainfall amounts and convective potential could go up or down
from where they`re at now. The active pattern looks to continue
through the end of the week with more rain chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1247 PM CDT Sat May 18 2024

A cold front is passing through this afternoon. At DLH, wind
direction is expected to become more westerly through the next
hour or two before direction settles at westerly later in the
afternoon. The chance for thunderstorms at DLH has diminished
considerably. Maybe a 5-10% chance that a storm could erupt
close to the terminal within the next hour and a half or so,
but more likely to remain dry at this point with storm
initiation further west. Otherwise, blustery winds continue
through early evening before weakening. VFR conditions expected
through the period.

Elsewhere in MN, anticipating dry VFR conditions with only the
slightest chance for a pop-up shower this afternoon since the
cold front has passed already. At HYR, there is about a 30-40%
chance for a thunderstorm just before the cold front passes.
Latest models suggest storms will develop further east, but
there remains a possibility that a storm could impact the
terminal. Expect winds to shift to westerly at HYR this
afternoon and decrease in speed overnight.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 348 PM CDT Sat May 18 2024

Winds are expected to shift to west to southwesterly this
afternoon as a cold front passes through, and gusty winds from
20 to 25 knots are expected around the head of the lake through
this early evening as that happens. Another threat will be
isolated to scattered storms that could be strong to severe
through about 7 PM with large hail to 1.5" in diameter and wind
gusts to around 50 kt possible. Winds become lighter through
Sunday and Sunday night following the cold front. Wind direction
will become northeasterly again ahead of low pressure going into
Monday.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Small Craft Advisory until 10 PM CDT this evening for LSZ121-
     144>148-150.

&&

$$

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