995
FXUS63 KDLH 210543
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1243 AM CDT Tue May 21 2024

.KEY MESSAGES...

- Dry this evening and into tonight with areas of fog developing
  overnight.

- A large spring storm will bring widespread rainfall and
  thunderstorms for Tuesday into Wednesday with most areas
  seeing at least an inch. A few strong to severe storms will be
  possible across mainly northwest Wisconsin Tuesday as well.

- Dry conditions return Thursday with rain chances for Friday
  into the weekend.

&&

.DISCUSSION...
Issued at 352 PM CDT Mon May 20 2024

Weak low pressure was analyzed near the Twin Cities this
afternoon with a stationary boundary trailing to another area of
low pressure in west-central Kansas. Another stationary boundary
extended from the low over the Twin Cities into northeastern
Iowa and northern Illinois. As a trough moves through the
Rockies tonight, a stronger area of low pressure will develop in
the lee of the Rockies across eastern Colorado/western Kansas.
This low will then be the focus for our heavy rainfall event for
Tuesday into Wednesday.

This low will move to the northeast Tuesday along a warm front
and spread rainfall across the region Tuesday morning into
Tuesday afternoon. High pressure over the eastern CONUS will
help bring a surge of Gulf moisture northward into the Upper
Midwest ahead of the low. Forecast soundings across northeastern
Minnesota are saturated almost throughout the entire column
with very skinny CAPE. This will favor efficient rainfall
production with PWATs continuing to be around 1.25-1.50" plus
over the region, which is two standard deviations above normal.
During the afternoon hours, CAMs show a bit of a dry slot
working into northwest Wisconsin which may help build some
instability. Forecast CAPE of 500-1000 J/kg may develop in this
area, especially if any breaks in the clouds can be realized.
Effective shear will be in excess of 50 knots, so some storm
organization is possible if the instability can develop.
Damaging wind gusts from wet microbursts will be the primary
threat with these storms. Large hail is also possible, given
long hodographs in the lower levels and steep low-level lapse
rates, but this threat looks higher south of our forecast area.
SRH will be supportive of an isolated tornado as well, but a
lack of instability will reduce this threat.

Rainfall will continue into Wednesday and then taper off
Wednesday afternoon. Rainfall amounts of 1 to 2 inches will be
possible across northwest Wisconsin with 1 to 3 inches possible
across northeastern Minnesota. A corridor of higher rainfall
amounts is expected from the Grand Rapids area through the Iron
Range and into the Arrowhead and North Shore. Given the recent
rainfall and forecasted amounts, the WPC has outlined the entire
CWA in a slight risk for excessive rainfall for Tuesday into
Wednesday. Rivers look to have enough capacity to handle most of
the forecasted QPF, but culverts, back roads and fast responding
creeks and streams may be overwhelmed. As such, a Flood Watch
has been issued for all of northeastern Minnesota along with
Burnett and Douglas counties in northwest Wisconsin. With the
abundant cloud cover and rainfall, temperatures will trend
cooler for Tuesday and especially Wednesday with highs in the
50s and 60s, although some low 70s will be possible in northwest
Wisconsin Tuesday.

Thursday looks to be dry currently as upper level ridging passes
through, but the active pattern looks to persist for the end of
the week and into the weekend. Additional chances for rainfall
arrive Friday and linger into Saturday before models diverge
with additional chances for the late weekend into early next
week period. Near normal temperatures are expected for the
latter half of the forecast period.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1233 AM CDT Tue May 21 2024

Areas of fog across the Northland makes for a tricky forecast
tonight. Fog from radiational cooling after passing rain showers seems
to be occurring in central Minnesota, and could affect INL,
HIB, and BRD. Fog will clear where mid level clouds move
overhead. In addition, marine fog has moved inland to DLH, HYR,
and could also affect the HIB terminal. The progression seems to
be slowing, but with an inversion in place, this fog and low
ceilings are not expected to dissipate until morning. There is
remaining uncertainty whether this marine fog will reach HIB.
There may be improvement in the morning as fog and stratus
dissipates as we start mixing in the lower levels but before the
next system arrives. Then, MVFR to IFR ceilings and visibilities
will persist for the remainder of the TAF period due to moderate
rainfall. There is signals of LLWS Tuesday night, but not
confident enough to include in the TAFs.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 352PM CDT Mon May 20 2024

Light winds will prevail for tonight generally out of the north
at 10 knots or less. As low pressure approaches the region
tomorrow, winds will turn northeasterly and increase to 15 to 25
knots with gusts to 30 to 40 knots for Tuesday afternoon into
Tuesday evening. Winds then diminish slightly overnight as the
low center moves along the North Shore and winds swing around
from the southwest by daybreak Wednesday. Winds will be
sustained at 15 to 25 knots with gusts to 30 to 35 knots
Wednesday before slowly weakening Wednesday night into Thursday.
Gale Watches have been posted for most of western Lake Superior
for Tuesday afternoon into Wednesday. Rainfall Tuesday into
Wednesday may be heavy at times leading to low visibilities. A
few storms will also be possible, mainly along the South Shore
Tuesday afternoon. These storms could bring gusty winds and
small hail.

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 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.
     Dense Fog Advisory until 6 AM CDT early this morning for
     MNZ037.
WI...Flood Watch from 10 AM CDT this morning through Wednesday
     morning for WIZ001-006.
     Dense Fog Advisory until 6 AM CDT early this morning for
     WIZ001.
MARINE...Small Craft Advisory from 1 PM this afternoon to 1 AM CDT
     Thursday for LSZ121-148.
     Gale Watch from this afternoon through Wednesday evening for
     LSZ140>146-150.
     Dense Fog Advisory until 6 AM CDT early this morning for
     LSZ144-145.

&&

$$

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