095
FXUS63 KDLH 212325
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
625 PM CDT Mon Jul 21 2025

.KEY MESSAGES...

- Multiple chances for showers and thunderstorms this week.
  Strong to severe storms Tuesday and Wednesday may create
  large hail and damaging winds.

- Two different periods of heavy rainfall Tuesday evening to
  Wednesday night may lead to flooding. A Flood Watch is in
  effect for most of the Northland in that time period.

- Warm and humid conditions Wednesday inland northwest
  Wisconsin.

&&

.DISCUSSION...
Issued at 345 PM CDT Mon Jul 21 2025

Zonal mid-level flow today builds into the northern periphery
of a mid-level strengthening ridge axis tonight into Tuesday
over the Northland. Multiple weak waves will move through the
ridge to create increasing strong to isolated severe
thunderstorm chance Tuesday morning through Wednesday night. The
first round of strong to isolated severe storms is forecast in
north-central Minnesota first Tuesday early to mid-morning.
Guidance is showing a tight gradient in available instability
from the Brainerd Lakes (more) to Borderlands (less) as a
middling amount of shear and mesoscale forcing are present.
Expect the better chances of any damaging winds and large hail
in the western Iron Range and southward in northern Minnesota
Tuesday morning....highest though overall in the Brainerd Lakes
for the the entire area though. Some high-res model guidance
shows the line of strong thunderstorms that is forecast to
entire north- central Minnesota tomorrow morning falling apart
quickly on the border of northwest Minnesota so this
conditional threat for severe weather in the Leech Lake to
Brainerd Lakes areas will be monitored very closely over coming
forecasts.

An already humid airmass that enters the area tonight further
increases the moisture content Tuesday night as a warm front
lifts northward and stalls out over the Upper Midwest. This
eventual stationary front with the parallel-flow impulses
creates concerns for at least two rounds of heavy rainfall
Tuesday night into Wednesday night. The forecast generally is
showing 1-2 inches areawide at this point, upper-end ranges show
potential of 3-5 inches in localized areas of the region mainly
along and southeast of the Iron Range. With these forecast
amounts of widespread rainfall and pockets of even heavier rain
falling on top of a region which has seen 100-200% of normal
rainfall in the last month and saturated soils in places, a
Flood Watch was issued for all areas except Koochiching, Price
and Iron Counties in the Northland. This Flood Watch lasts from
Tuesday evening to early Thursday morning.

A secondary conditional period of severe thunderstorm chances
sets up again Tuesday night and Wednesday for most areas south
of the Iron Range as more instability advects into the area.
While the primary hazard remains heavy rainfall leading to
flooding potential, any isolated severe thunderstorm could still
cause damaging wind gusts and even lesser chances of large
hail.

By Wednesday, the warmest temperatures will be south of the
region, but very warm and humid conditions are still likely in
the afternoon across east- central Minnesota and inland
northwest Wisconsin. Forecast Wet Bulb Globe Temperatures in
the low-80s for a few hours, apparent temperatures in the
low-90s and a Heat Risk of Level 3 / 4 (or Major) may eventually
result in a limited time-period Heat Advisory for parts of
northwest Wisconsin. What could be a dampener though on these
conditions would be that previously mentioned overnight rainfall
Tuesday night into Wednesday morning with lingering sky cover.

As the stationary front moves eastward Thursday daytime, the
rainfall chances decrease in that time period and end Thursday
evening mainly as a widely scattered showers. A dry and
seasonable Friday leads into the weekend with still seasonable
temperatures but a return of widespread scattered thunderstorm
chances into early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 624 PM CDT Mon Jul 21 2025

A few areas of MVFR ceilings can be seen on satellite this
afternoon with radar showing very isolated showers. Through this
evening ceilings will continue to lower and become more
widespread, eventually encompassing the whole Northland. There
is also potential for showers and storms to enter from the west
out of the Northern Plains tomorrow morning and march across the
region into the early afternoon hours. Confidence is low on
timing and whether or not the storms from the west can sustain
the journey into our region.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 246 PM CDT Mon Jul 21 2025

Easterly winds gusting to 20 knots continue into this evening,
creating waves of 2 to 3 feet along the western waters. Expect
an overnight decrease in wind speeds to again become easterly
around 20 knots Tuesday daytime. Expect potential for gusty and
erratic outflow winds from an area of strong thunderstorms,
especially at the head of the lake in the late morning to midday
hours Tuesday. Heavy rainfall from another possible round of
strong thunderstorms may impact the South Shore to Twin Ports
Tuesday night into Wednesday.

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 Tuesday evening through Thursday morning for
     MNZ011-012-018>021-025-026-033>038.
WI...Flood Watch from Tuesday evening through Thursday morning for
     WIZ001>003-006>008.
MARINE...None.

&&

$$

DISCUSSION...NLy
AVIATION...Britt
MARINE...NLy