143
FXUS63 KDLH 152337
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
637 PM CDT Tue Jul 15 2025

.KEY MESSAGES...

- Several rounds of showers and thunderstorms are expected
  today into Wednesday. Rainfall amounts of 1-3" with locally
  higher amounts may lead to flash flooding concerns this
  afternoon into tonight in east-central Minnesota, the
  Arrowhead, and northwest Wisconsin.

- Strong to severe thunderstorms will be possible this afternoon
  and evening with damaging winds to 65 mph and large hail up to
  1.5" in diameter being the primary hazards. A low-end
  potential for a tornado or two also cannot be ruled out.

- Temperatures for the latter half of the week into the weekend
  will be more mild with additional chances for precipitation Friday
  into Saturday.

&&

.DISCUSSION...
Issued at 248 PM CDT Tue Jul 15 2025

This Afternoon - Tonight:

An initial round of thunderstorms has developed in far east-
central MN into northwestern WI this afternoon in an area of
low- level warm advection on the warm side of a surface
stationary front. Storm motion has generally been parallel to
the front here in a high PWAT environment (1.6-1.9") with storms
slowly traveling northeast and training over the same
locations. Effective shear has been about 30-35 kt, which
should be enough for some of these storms to become organized
and produce up to 60 mph wet-downburst winds, large hail to
1-1.5" in diameter, and a low-end (2% SPC outlook) for a
tornado. Heavy rain rates with the training here could produce
flash flooding, but will more likely prime portions of Douglas
and Bayfield Counties for flash flooding potential with an
additional round of storms this evening.

Otherwise, expect the primary strong to severe storm potential
to develop with and on the warm side of the slow-moving front
draped from the Brainerd Lakes to around the Twin Ports later
this afternoon and evening as model soundings point to MLCAPE of
1700-2700 becoming uncapped as subtle 500-mb shortwave energy
traverses over the front. This environment will also be
characterized by decent low and mid- level lapse rates around 7
degC/km, PWAT values around 1.6-2" (towards the upper-end of
climatology for July), and effective bulk shear around 35-40 kt.
This environment looks favorable enough for organized discrete
(supercells) thunderstorm development initially, though front-
parallel flow aloft should result in these storms growing
upscale into a linear segment of storms towards this evening.
Initial concerns with the discrete storms should be hail up to
1.5 inches in diameter and 60 mph damaging wind gusts in
addition to heavy rainfall potential leading to flash flooding.
As storms grow upscale into a line towards this evening and
tracks southeastward into east-central MN and northwest WI, the
threat should transition to damaging wind gusts up to 65 mph,
hail up to quarters (though this threat decreases rather
rapidly), and heavy rain that could lead to flash flooding.
There will also be some more modest levels of 0-1km and 0-3km
storm-relative helicity (SRH), but low-level vorticity in the
vicinity of the front that could be stretched by strengthening
updrafts and lead to a low-end (SPC 2% outlook chance) for a
tornado or two this afternoon into early evening. Thunderstorm
intensity should then diminish into late this evening over
northwest WI as instability weakens and surface-based inhibition
increases.

Regarding the heavy rainfall potential, storms should
repeatedly move over the same locations with efficient rates
(1-2"+ per hour), leading to concerns for flash flooding due to
rapid runoff. The 12Z HREF guidance shows 24-hour localized
probability matched mean QPF of 1-3" with localized amounts to
4+ inches, with the best potential for the higher end of these
rainfall amounts where the Flood Watch has been issued for in
east-central MN into the Twin Ports, most of the Arrowhead, and
northwest Wisconsin. The flash flooding threat should
transition into east-central MN and northwest Wisconsin this
evening as storms track southeast with time. While rainfall
intensity in storms should drop off overnight, moderate rainfall
rates on areas that already see heavy rain this afternoon and
evening could keep the flooding/flash flooding threat persisting
into the overnight hours, particularly in northwest WI.

Wednesday:

Rainfall will be slow to exit the Northland Wednesday into
Wednesday night as a couple shortwave 500-mb troughs continue to
traverse the Northland, though very modest instability should
preclude any strong to severe thunderstorm development.

Wednesday should also be much cooler as cloud cover and rainfall
lingers, with highs in the upper 50s to upper 60s. Prominent
northeast winds off of Lake Superior will also likely produce a
high risk of rip currents at the Minnesota and Wisconsin Point
Beaches, so a Beach Hazard Statement will likely be needed on
Wednesday.

Thursday:

Brief surface high pressure with zonal flow aloft should give us
a mild and dry day on Thursday, with high temperatures in the
low to mid 70s.

Friday - This Weekend:

Zonal flow aloft continues on Friday, turning slightly more
northwesterly on Saturday into Sunday. Weaker 500-mb shortwave
energy will move across the Northland through this flow on
Friday into Saturday, leading to additional shower and
thunderstorm potential Friday and Saturday. At this juncture,
there doesn`t appear to be much of an overlap between bulk shear
and instability to produce any strong to severe storms for
Friday into Saturday.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 637 PM CDT Tue Jul 15 2025

The cold front is now slowly moving towards the southeast, with
a line of strong to marginally severe storms now present along
and just ahead of the front in much of northwest Wisconsin.
Threats with these storms continue to be small hail, wind gusts
to 30 to 40 knots and heavy rain. These storms will continue to
move southeast through the remainder of the evening, with
lingering showers and some embedded thunderstorm potential in
their wake across northeast Minnesota and northwest Wisconsin.
IFR to LIFR visibilities and MVFR to IFR ceilings remain
possible in the heaviest rainfall. More broad IFR to LIFR
ceilings develop for tonight for much of the area, with some
improvement to ceilings towards mid to late Wednesday afternoon
for all but HYR. INL, being northwest of the rain, largely
remains MVFR to VFR for ceilings and visibilities tonight into
Wednesday.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 248 PM CDT Tue Jul 15 2025

Winds today will be around 10 knots or less the rest of today
before increasing tonight out of the northeast at 10 to 20
knots with gusts to 25 knots, highest in the western arm of Lake
Superior and the Apostle Islands. These winds will lead to
increasing wave heights of 2 to 5 feet. A Small Craft Advisory
continues for these nearshore waters starting late this evening
and persisting through Wednesday. Winds weaken to 5 to 15 knots
Wednesday night through Thursday.

Several rounds of thunderstorms are expected today into
Wednesday. A few stronger storms remain possible this afternoon
and evening across western Lake Superior. Large hail and wind
gusts to 50 knots are the primary concerns in stronger storms,
as well as cloud to water lightning and heavy rainfall.

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 MNZ020-037-038.
WI...Flood Watch through Wednesday morning for WIZ001>004-006>008.
MARINE...Small Craft Advisory from 11 PM this evening to 7 PM CDT
     Wednesday for LSZ121-143>148-150.

&&

$$

DISCUSSION...Rothstein
AVIATION...Rothstein
MARINE...Rothstein