997
FXUS63 KDLH 212015
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
315 PM CDT Tue May 21 2024

.KEY MESSAGES...

- The threat for severe thunderstorms has increased for late
  afternoon into late evening, mainly for northwest Wisconsin
  and Pine County in Minnesota. Primary threats are damaging
  wind and a tornado with a secondary threat of a large hail.
  Flash flooding will also be possible.

- The deep low pressure system will continue to produce rain
  tonight which could lead to flooding over central to northern
  Minnesota and parts of northwest Wisconsin.

- Chances for showers will continue Thursday into the weekend
  with Friday having the highest chance for widespread showers
  and thunderstorms (60-80%).

&&

.DISCUSSION...
Issued at 315 PM CDT Tue May 21 2024

A 995MB low was centered in southwest Iowa as of 20Z with water
vapor showing a shortwave moving out of Nebraska. The low will
deepen further as it moves north tonight. These features along
with robust moisture and warm advection with a low level jet
acting on high PWAT values will produce strong forcing. The RAP
wraps PWAT values around 1.6" into northwest Wisconsin by early
evening which are anomalously high for this time of year. There
was partial clearing surging north through southern Minnesota
which would arrive into our southern Wisconsin zones yet this
afternoon. Instability was not impressive over the Northland as
of early afternoon but it is forecast to increase late afternoon
into the evening, especially from around Burnett County east
northeast into at least southern portions of Ashland/Iron
Counties. Favorable shear profiles exist with forecast
hodographs showing plenty of low level curvature. Confidence has
increased for severe thunderstorms affecting east-central
Minnesota into northwest Wisconsin late this afternoon into late
evening. The main threat will be damaging wind but given the
hodographs, a tornado threat will exist along with some hail.
CAM guidance supports the severe threat although there remains
some uncertainty on storm mode. Discreet storms are possible but
given the forcing, we`d expect the storms to congeal into a
line. The tornado threat will remain even if a linear mode
prevails given strong southerly 0-3KM shear vectors of 30 to 40
knots and a southerly storm motion. The severe threat should
wane by late evening.

Strong northerly winds will develop on the backside of the low this
evening/overnight and they will become westerly on Wednesday.
Forecast soundings at Walker and Brainerd show 40-50knot northerly
winds 1-2kft off the surface by late evening they will back late
into Wednesday morning as they move across the region. We increased
winds some but don`t feel confident to issue a Wind Advisory at this
time. It will be something to watch for though for much of the
Northland.

A flood threat will continue as well and we expanded the Flood Watch
further into northwest Wisconsin to account for the threat with the
strong to severe storms late afternoon/evening. Heavy rain has
already fallen over portions of the Northland with spotter reports
of 1-2" across the Brainerd Lakes region. Addition rainfall from
this afternoon and tonight will be 1 to 3 inches, highest in far
northern Minnesota and the North Shore.

The surface low will move just north of the Arrowhead in northwest
Ontario by 12Z Wednesday, continuing northeast through the day.
Showers and a few thunderstorms will occur through the day,
especially in northern Minnesota. It will be windy with gusts of 30
to 40 mph with the possibility of even higher gusts.

Looking ahead, there will be additional shower/storm chances (20-
30%) on Thursday with a frontal boundary across the area.
Another stronger shortwave will deepen the surface low Thursday
night into Friday causing higher chances (60-80%) for
showers/storms. A strong storm will be possible Friday and expected
rainfall will be from a half to one inch for much of the Northland.

We do continue some low POPS, 20-40%, through the weekend but
coverage looks more limited.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1226 PM CDT Tue May 21 2024

IFR conditions covered most of the Northland and are expected to
prevail through most of the period with some improvement at the
end of the period. A strong low pressure system is still on
track to produce widespread showers and thunderstorms this
afternoon into Wednesday. The thunderstorm threat will be
greatest this afternoon into the late evening hours. The threat
for severe thunderstorms has increased over northwest Wisconsin
with all hazards on the table, including damaging winds and a
tornado.

Fog will occur at times, especially around Lake Superior into
tonight.

Strong winds will occur around Lake Superior today and as the
low pressure system moves through, strong northerly then
westerly winds will develop for all areas.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 315 PM CDT Tue May 21 2024

Strong easterly winds with gale force gusts to around 40 knots will
continue or develop this evening. The wind will briefly diminish
late evening or early morning as they switch from easterly to
westerly as low pressure moves through the region. West to southwest
winds will ramp up with strong gusts of 40 to 45 knots on Wednesday.
Winds will diminish Wednesday night into Thursday. Widespread rain
and some thunderstorms will continue tonight but gradually decrease
in coverage late tonight into Wednesday.

Some fog will remain possible at times, especially when winds are
easterly and we issued a Dense Fog Advisory from the Twin Ports
to the North Shore.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch through Wednesday morning for MNZ010>012-018>021-
     025-026-033>038.
WI...Flood Watch through Wednesday morning for WIZ001-006.
     Flood Watch until midnight CDT tonight for WIZ002-007-008.
MARINE...Small Craft Advisory until 7 AM CDT Wednesday for LSZ121-147-
     148.
     Gale Warning from 7 AM to 7 PM CDT Wednesday for LSZ121-147-
     148.
     Small Craft Advisory until 4 PM CDT this afternoon for
     LSZ140>146-150.
     Dense Fog Advisory until 7 AM CDT Wednesday for LSZ140>143.
     Gale Warning until 7 PM CDT Wednesday for LSZ140>146-150.
     Dense Fog Advisory until 3 AM CDT Wednesday for LSZ144-145.

&&

$$

DISCUSSION...Melde
AVIATION...Melde
MARINE...Melde