167
FXUS63 KDLH 170838
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
338 AM CDT Tue Jun 17 2025

.KEY MESSAGES...

- The best chance for more organized severe storms is Friday
  into Saturday when many ingredients align nicely for severe
  weather.

- Heat wave Saturday into early next week. Looking to be a hot
  and sticky Sunday.

- Plenty of chances for largely diurnal thunderstorms this week.

&&

.DISCUSSION...
Issued at 337 AM CDT Tue Jun 17 2025

Continued northwest flow aloft through the mid-week period,
with a few embedded shortwave troughs expected to trigger
scattered showers and a few thunderstorms. The primary focus for
this activity will remain across the Minnesota Arrowhead where
moisture and instability will be greatest, though not great, as
these showers are not anticipated to be severe or particularly
widespread, with many locations remaining dry.

A more significant weather system is forecast to arrive for the
latter half of the week. A deeper upper-level trough is progged to
dig southeastward from Canada, pushing a cold front into the region
Wednesday night into Thursday. This front will provide the focus for
more organized showers and thunderstorms across the Northland.
Global models, including the GFS and ECMWF, are in fair agreement
regarding the timing of this feature. The feature begins to move
into our forecast area reaching far west Kooch and Itasca counties
where the SPC has a Marginal Risk for severe thunderstorms Wednesday
afternoon. Then activity wanes a little before instability builds
again Thursday. The primary concern with the Thursday system will be
the potential for some stronger to severe thunderstorms,
particularly across the southern third of our forecast area Thursday
afternoon. Forecast soundings indicate increasing surface-based
instability and effective bulk shear values supportive of organized
convection. The exact magnitude of the severe threat will become
clearer as the event nears and mesoscale features become better
resolved.

The most significant period will be Friday into Saturday. Heading
into the weekend, attention turns to a warming trend and
another round of thunderstorms. A warm front is expected to
lift northeastward into the area Friday night into
Saturday bringing potentially 70F+ dewpoints and a
strengthening low-level jet (LLJ) under a sharp upper level wave
with synoptic forcing supplied by a 996 mb low-pressure system
tracking northward through Minnesota and into Canada. Strong and
most likely severe thunderstorms are expected, especially
during the evening and overnight hours. CAPE values exceed 2000
J/kg with 0-6 bulk shear > 40kt with a 50 kt LLJ. PWATs of 1.5
to 2" and modest mid-level lapse rates all point to a spicy
system.

Behind the warm front, a significantly warmer and more humid airmass
will become established for Sunday. High temperatures are forecast
to climb into the upper 80s, with dewpoints in the 60s. This
combination will lead to hot and sticky conditions. The increase in
heat and humidity will also provide ample fuel for additional shower
and thunderstorm development throughout the day on Sunday though
ridging may push the action up into Canada. Given the expected
instability, some of these storms could again become strong. An
active weather pattern is certainly on tap for the foreseeable
future. So much weather!

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1212 AM CDT Tue Jun 17 2025

A soupy night with a lot of low clouds. Satellite shows a lot of
low stratus, but wherever holes develop in the stratus, fog then
becomes a quick possibility with all of the low level moisture
from the past system. Right now, played the TAFs with only hints
of low visibilities given the prevalence of stratus. By 12Z,
conditions should improve rapidly to VFR with daytime heating.
Winds decreasing through the period and remaining westerly.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 337 AM CDT Tue Jun 17 2025

Fairly light SW winds and small waves with on and off chances
for general thunderstorms continue for the next couple days.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Dense Fog Advisory until 7 AM CDT this morning for LSZ121-
     140>148-150.

&&

$$

DISCUSSION...Wolfe
AVIATION...Wolfe
MARINE...Wolfe