846
FXUS63 KDLH 172346
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
646 PM CDT Sun Aug 17 2025

.KEY MESSAGES...

- Another round of rain and thunderstorms begins this afternoon
  and continues overnight into Monday morning.

- High pressure and drier conditions build into the area for
  Tuesday into Thursday morning with near normal temperatures.

- The next chance for precipitation is late in the work week.

&&

.DISCUSSION...
Issued at 258 PM CDT Sun Aug 17 2025

Today has been almost fall like, with strong easterly winds,
stratus clouds streaming off Lake Superior, and cool
temperatures. A low pressure system developing over South Dakota
with a warm front extending east over central Minnesota and
into Wisconsin. This system will push east-northeast today
through tomorrow, with the low center and warm front staying
just south of the forecast area. This will cause a surge of
warm, moist air up over the front, and is currently producing a
large area of showers and thunderstorms over eastern North and
South Dakota and western Minnesota. These will push into the
forecast area this afternoon and tonight in waves of showers and
embedded thunderstorms tonight and Monday morning before
exiting off to the east Monday afternoon and evening. The
probability of getting more than a half inch of rainfall by
Monday evening is over 50 percent for northern Minnesota and
most of northwest Wisconsin. The most rain should fall in a
corridor from the Brainerd and Mille Lacs lakes area east
through the Twin Ports and Bayfield Peninsula, where rainfall
amounts of over an inch and a half are possible.

A ridge of high pressure noses into the area Monday night into
Tuesday and lingers over the area through Wednesday night,
giving us a period of quieter and drier weather with near normal
temperatures.

Active weather with several precipitation chances returns
Thursday into Friday with a strong upper low that moves across
the Canadian Prairies, across Ontario and into Quebec Thursday
through Saturday. Confidence is increasing in this general
scenario, but the details of the strength of the system as well
as timing have yet to be narrowed down. For now, precipitation
chances have increased for Thursday night into Friday. We should
have some warmer than normal temperatures Thursday and Friday,
shifting to cooler than normal for next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 646 PM CDT Sun Aug 17 2025

East to southeast winds will persist tonight. Orographically
enhanced clouds are not expected to go away at DLH, though they
may scatter out briefly at times for the next few hours.
Elsewhere, an approaching trough will bring showers and
thunderstorms to all terminals tonight through Monday morning,
starting at BRD in approximately a couple hours, then spreading
northeast elsewhere through the night. Coverage is expected to
be scattered, so rain and storms are not expected continuously
through the night, but they should still be frequent with
periods of heavy rain that may result in MVFR visibilities.

Low clouds are expected to develop everywhere gradually through
the night and persist into most of Monday, leading to IFR
ceilings for a prolonged period later tonight through around
midday Monday with some ceilings lifting and scattering out
during the afternoon, leading to some improvement to MVFR/VFR.

Winds will be gusty through tonight, especially at DLH, though
speeds and gusts will gradually decrease a bit by morning. Winds
become lighter and variable in direction as a surface low passes
through.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 318 PM CDT Sun Aug 17 2025

Northeast winds continuing to blow hard, with gusts of up to 36
knots so far. Wind gusts should be strongest now through 8pm.
This is being caused by a tightening pressure gradient over
western Lake Superior between high pressure over Ontario and
incoming low pressure passing through South Dakota and southern
Minnesota later today. Sustained wind speeds around 20 knots
with gale force gusts, mainly for the southwest tip of the lake.
These winds will build large wave heights, which is unusual for
this time of year, across all waters ranging from 3 to 6 feet.
Expect dangerous conditions for small craft and vessels through
this evening with Advisories in effect. The Gale Warning
continues through 10 pm this evening. A Small Craft Advisory
will be needed after 10 pm. The Small Craft Advisories have been
extended tonight into Monday morning, though an extension may be
needed longer on Monday as elevated swell lingers. The next
round of thunderstorms builds west to east this evening and
general thunderstorm hazards are likely tonight into Monday mid-
day.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Beach Hazards Statement until 10 PM CDT this evening for
     MNZ037.
WI...Beach Hazards Statement until 10 PM CDT this evening for
     WIZ001.
MARINE...Small Craft Advisory until 4 AM CDT Monday for LSZ121-146>148-
     150.
     Small Craft Advisory until 10 AM CDT Monday for LSZ140-141.
     Gale Warning until 10 PM CDT this evening for LSZ142>145.

&&

$$

DISCUSSION...LE
AVIATION...JDS
MARINE...LE