539
FXUS63 KDLH 172019
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
319 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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1254 PM CDT Sun Aug 17 2025

Current VFR conditions to be slowly overcome by MVFR ceilings as
waves of showers and thunderstorms spread in from the southwest
later today and this evening. All terminals to eventually
deteriorate this evening to predominantly MVFR conditions, then
to IFR ceilings and MVFR visibilities after 05z/midnight as
widespread rain with embedded thunder spreads in. Periods of
LIFR ceilings are also possible, but have only included that for
KBRD and KINL for now. Expect a gradual improvement beginning
late morning/early afternoon, but confidence is low and have not
included for now. &&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 1254 PM CDT Sun Aug 17 2025

Northeast winds are strengthening so far today, with gusts so
far staying under 33 kts, but I do not expect that to last long,
and winds should be strongest between the 2pm to 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 today
with Advisories in effect. The Gale Warning has been expanded to
the Duluth to Port Wing zone, for now through 10 pm. While the
current Advisories expire this evening currently, an extension
in time can be expected for most zones is likely into 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.

&&

.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...LE
MARINE...LE