522
FXUS63 KDLH 211726
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1226 PM CDT Tue May 21 2024

.KEY MESSAGES...


- Heavy rainfall rates combined with saturated soils may produce
  flooding in the Northland.

- Severe weather is possible this afternoon, mainly in northwest
  Wisconsin. However, an isolated severe storm in far eastern
  portions of Minnesota is not out of the question. The
  northwest Wisconsin threat has increased.

- Rain chances continue in the late week and into the weekend.

&&

.DISCUSSION...
Issued at 244 AM CDT Tue May 21 2024

Easterly flow off Lake Superior and a low level inversion is
leading to dense fog in the Twin Ports. In addition, high
humidity from rain yesterday and radiational cooling overnight
has lead to patchy fog inland as well. Inland fog should
dissipate throughout the morning as temperatures increase. The
marine fog could take a couple hours longer as easterly flow off
the lake continues.

This system will be somewhat of a double whammy as both severe
weather and flooding are possible. PWATs at or above the
climatological maximum (about 1.2 inches) will bring heavy
rainfall region wide. Highest rainfall amounts are expected in
the wrap-around region of the low, and totals up to 3 inches are
possible by Wednesday evening. Current totals suggest that
today`s record for precipitation could be tied or broken at
Duluth and International Falls.

This afternoon and evening, a warm front will move through the
eastern half of the CWA. An increase in instability 1000-2000
J/kg combined with 0-6km wind shear of around 40 kts will lead
to strong to severe thunderstorms. Lapse rates are pretty
modest, but high enough to allow for convective initiation.
Soundings show the long and skinny CAPE and saturation
throughout the column that is common for storms that could
produce heavy rain. Wet microbursts are also possible for this
setup, and could produce damaging winds. There are signals for
an isolated tornado or two from SRH values 400-500 and model
hodographs showing nice turning in the low levels. Hail up to an
inch is also possible, but winds and flash flooding will be the
main threats. Rain showers and thunderstorms will come to an
end south to north on Wednesday.

Models already start to diverge after Wednesday, but show signs
for more rainfall Thursday night into Friday across a stationary
front in the Northern Plains ahead of another system that will
bring more chances for rain showers and thunderstorms this
weekend.

&&

.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 244 AM CDT Tue May 21 2024

Northeast winds will increase as the system that will bring
moderate rain to the area approaches western Lake Superior.
Gales are possible in the Twin Ports and along the North Shore
with waves up to 11 ft. Storms this evening over western Lake
Superior (especially the South Shore) are possible, with strong
winds as the main threat. Tonight, as the low center passes,
winds will temporarily decrease below gales as winds turn to the
southwest. Then winds increase to gales again early Wednesday
morning. Winds will start to decrease Wednesday evening, but
will remain hazardous to small craft into Thursday.

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-
     026.
     Flood Watch through Wednesday morning for MNZ025-033>038.
WI...Flood Watch through Wednesday morning for WIZ001-006.
     Flood Watch from 5 PM this afternoon to 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.
     Gale Warning from 4 PM this afternoon to 7 PM CDT Wednesday
     for LSZ140>146-150.

&&

$$

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