634
FXUS63 KDLH 192246
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
546 PM CDT Tue Aug 19 2025

.KEY MESSAGES...

- Areas of dense fog are expected tonight.

- Sunny and warm weather Wednesday and Thursday

- A cold front comes through late Thursday through Friday and
  will bring a chance for showers and storms. A few storms may
  be strong to severe Thursday evening.

- Behind the front expect much cooler temperatures for the
  weekend with highs in the 60s and lows in the 40s.

&&

.DISCUSSION...
Issued at 101 PM CDT Tue Aug 19 2025

This Afternoon:

Low clouds have been rather persistent this afternoon, but
there have been some pockets of clearing. Expect that trend to
continue into the afternoon with some sunshine (or at least
peeks of sunshine) for most places before the sun sets this
evening.

Tonight:

High pressure settles in with drier air moving in aloft. Therefore,
the weather should be quiet tonight with the exception of fog
developing. With more of the mid and higher clouds clearing out, we
should have a good radiational cooling night that should allow for
fog to form somewhat similar to last night. There are widespread 40-
70% chances of visibility falling to half a mile or less for much of
the region per HREF probabilities. There will likely be dense fog
with coverage widespread enough to warrant some Dense Fog
Advisories, though at this time it`s difficult to pinpoint where
exactly that may happen, so no headlines will be issued with this
update. Interior areas of northwest Wisconsin and northeast
Minnesota seem to be the best candidates for the lowest visibilities
at this time, affecting the typical low spots especially so.

Wednesday and Thursday:

We will remain under the influence of high pressure and thus quiet
weather Wednesday and into most of Thursday. Winds are expected to
be pretty light on Wednesday with plenty of sunshine expected after
fog mixes out gradually during the morning.

We get into more southerly flow on Thursday, so high temperatures
will remain on the warm side with highs in the low to perhaps mid
80s. A potent cold front and weak upper level trough will be on the
move from the northwest and reaching north-central Minnesota by late
Thursday afternoon into Thursday evening. With this, we can expect
some showers and thunderstorms with a fairly narrow corridor of up
to 1-2 kJ/kg of MUCAPE. Timing is the trick with this one in terms
of any severe weather threats. Shear profiles don`t look favorable
for tornadoes at this time, but there could be 30-40 kt of 0-6 km
bulk shear that may be favorable for some large hail and damaging
winds for north-central and northwest Minnesota. Right now, the
timing of the front appears to be such that it`ll be entering our
CWA from the northwest just before sunset, so we may only see a
sliver of an opportunity for stronger storms in the early evening
before the sun sets and storms start to weaken as they move
southeast into an environment where surface instability more or less
goes away after diurnal heating ends. The SPC has maintained a
marginal risk (level 1/5) for some strong to severe storms Thursday
late afternoon and evening.

Friday and this weekend:

The cold front will gradually clear the region into WI/MI on Friday,
so any lingering showers and storms will be more likely in northwest
Wisconsin with sunshine building in northern Minnesota.

Cool air advection is expected with breezy northwest flow through
the weekend. This will bring a taste of fall weather to the
Northland with widespread highs in the 60s to maybe low 70s.

A broad upper-level closed low over Ontario with several short waves
attached will bring some synoptic lift that will be favorable for
some wraparound showers Friday night through Sunday. Essentially, we
can expect scattered showers at times to accompany the cooler
temperatures. In fact, the air may be cool enough to introduce the
"l" word (lake-effect). Lake Superior surface water temperatures
around 15-20C and 850 hPa temps falling to around 5-7C may bring
just enough instability for a bit of lake-effect or lake-enhanced
showers for South Shore locations at times. Through this period, the
unstable layer looks to be confined below ~10 kft, so thunder is not
expected at this time.

Monday and Tuesday:

Cooler air lingers on Monday, but high pressure may pass by to the
south going into Tuesday, bringing a return to more west/southwest
flow and allowing temperatures to moderate a bit into early next
week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 545 PM CDT Tue Aug 19 2025

Most of the area should see cloud cover diminishing this
evening, though some BKN to OVC MVFR ceilings continue to hang
around over far northern Minnesota through around 02Z. With
clearing skies and calm to very light winds tonight as high
pressure moves overhead, expect a radiational fog/low stratus
setup to occur tonight through early/mid Wednesday morning.
Models show a widespread signal for IFR to LIFR conditions in
fog tonight across the region, though some terminals could also
see VLIFR conditions (particularly visibility). For now, have
highlighted KDLH/KHIB/KINL with the VLIFR visibility tonight
where dense fog probabilities are highest (50-60%). Expect this
fog to dissipate and low stratus to scatter out into Wednesday
morning, with MVFR ceilings hanging around longest at KHYR. VFR
conditions return late Wednesday morning after fog and low
stratus dissipate.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 101 PM CDT Tue Aug 19 2025

Expect light and variable winds through Wednesday night with high
pressure settling in. Winds will trend a bit breezier Thursday night
into Friday with southwest winds becoming northwest as a cold front
passes through. Scattered non-severe showers and storms will be
possible Thursday night as well. Wind gusts are expected to hover
around 15 kt Thursday night into Friday. 20-25 kt gusts are possible
going into Saturday for most nearshore zones as more cooler air
moves in from the north.

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...None.

&&

$$

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