878
FXUS63 KDLH 211145
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
645 AM CDT Tue May 21 2024

.KEY MESSAGES...

- Dense fog in the Twin Ports and patchy fog across the
  Northland this morning should dissipate during the mid
  morning.

- Heavy rainfall rates combined with saturated soils may produce
  minor 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.

- 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 /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 632 AM CDT Tue May 21 2024

Fog from Lake Superior lingers this morning, leadint to low
ceilings at DLH and HYR. Visibilities may occasionally lower at
DLH, but should largely remain MVFR or above. Conditions will
lower this afternoon as the rain system for today moves in. IFR
ceilings and MVFR to IFR visibilities are expected at all
terminals with the heaviest rainfall. Thunderstorms will be in
the vicinity of the terminals this afternoon and evening. Some
storms at or near DLH and HYR could be severe, and capable of
producing strong gusts. LLWS is possible late this evening, but
confidence is not high enough to include in the TAF.

&&

.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 from 1 PM CDT this afternoon through Wednesday
     morning for MNZ010>012-018>021-026.
     Flood Watch from 10 AM CDT this morning through Wednesday
     morning for MNZ025-033>038.
WI...Flood Watch from 10 AM CDT this morning through Wednesday
     morning for WIZ001-006.
MARINE...Small Craft Advisory from 1 PM this afternoon to 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 from 10 AM this morning to 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.
     Dense Fog Advisory until 10 AM CDT this morning for LSZ144-145.

&&

$$

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