Toivola, Minnesota Weather Forecast Discussion

673
FXUS63 KDLH 090843
AFDDLH
Area Forecast Discussion
National Weather Service Duluth MN
343 AM CDT Tue Sep 9 2025
.KEY MESSAGES...
- Showers and thunderstorms continue through today, slowly
  sliding southeast into northwest Wisconsin.
- Rainfall, heavy at times, may lead to localized flash flooding
  where storms repeatedly move over the same location this
  morning.
- Areas of dense fog in north-central Minnesota early this
  morning. More widespread dense fog is possible for much of the
  Northland (40-70% chance) for tonight into early Wednesday
  morning.
- Quieter weather takes over for Wednesday and Thursday, with
  shower and thunderstorm chances returning Friday into this
  weekend.
&&
.DISCUSSION...
Issued at 343 AM CDT Tue Sep 9 2025
Today - Tonight:
At the surface early this morning, low pressure is centered over
west-central Minnesota with a stationary front extending
eastward into the Iron Range and western Lake Superior.
Vorticity aloft on the leading edge of a mid/upper-level
shortwave trough interacting with the front and isentropic
ascent into and just north of the frontal zone on the nose of a
low-level jet is continuing to kick off elevated scattered
showers and storms from Grand Rapids east to Two Harbors/Silver
Bay and across parts of the South Shore and much of western Lake
Superior. Hourly rainfall with this precipitation is generally
on the order of 0.5-1.25" per hour due to sfc-freezing level
saturation depths of ~10 kft, above average PWATs of 1.1-1.5",
and unidirectional flow through the depth of the storms being
parallel to the surface front leading to both efficient rainfall
rates and repeated motion of the storms over the same locations.
While widespread heavy rainfall is not expected, ponding of
water and localized flash flooding remains possible east of the
I-35 into the South Shore and portions of northwest Wisconsin
early this morning where storms can repeatedly move overhead. While
effective shear is still 25-30 kt as of 3:30 AM CDT, the low-
level jet is expected to weaken with time as we progress into
the daylight hours today, leading to decreasing storm coverage
and storms becoming less coherent with time. Storms will also
slowly continue tracking southeast into northwest Wisconsin
today as the stationary front also starts to track that
direction, as well. Lighter showers and some embedded storms
persist during the daylight hours before gradually exiting to
the east of northwest Wisconsin tonight.
Another hazard through early this morning is dense fog over
north-central Minnesota as well as along the North Shore north
of Taconite Harbor/Tofte where there has been clearing on the
northern edge of the cloud and precipitation shields,
respectively. Area webcams and surface observations already
show several locations with 1/4 mile visibility or less in
northern Itasca and Koochiching counties. If this fog continues
to expand, Dense Fog Advisories may be warranted.
HREF and RRFS ensembles, as well as even NBM probabilities for
more widespread dense fog (visibilities of less than or equal to
1/4 mile) increase again for tonight into early Wednesday
morning for much of the Northland, generally in the 40-70%
range. If this signal holds or increases, another Dense Fog
Advisory would likely be needed for tonight.
Wednesday - Thursday:
Fog will be dissipating by mid to late Wednesday morning. The
upper-level pattern for Wednesday into Thursday will favor a
ridge moving through the Upper Midwest and surface high pressure
sliding east across Ontario. This should keep the Northland
largely dry during this timeframe, though some lingering low-
level moisture in north-central WI could keep a few
sprinkles/showers persisting into Wednesday afternoon (10-20%
chance). Little to no additional accumulations expected.
Temperatures remain on the more mild side than previous days,
with highs in the mid 60s to mid 70s and lows in the upper 40s
to 50s.
Thursday Night - This Weekend:
Temperatures top out on Friday as the axis of the ridge moves
over the Northland, with highs in the 70s for most to even
around 80F for some locations. Some low-end shower and
thunderstorm chances (20-40%) return for Thursday night through
Friday as some subtle shortwave energy rounds the top of the
mid/upper-level ridge, but the shear/instability parameter space
at this juncture does not appear to support severe weather.
Ensembles show some variation of positively-tilted shortwave
energy/troughing moving back into the Upper Midwest and/or
northern Plains Saturday into early next week, which could bring
additional precipitations chances during that timeframe.
However, there is a fairly strong signal in an omega-blocking
pattern setting up somewhere in the central/north-central CONUS
vicinity, so exact placement of this pattern could still vary
enough that confidence in precipitation potential and timing
this weekend into early next week is low.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1249 AM CDT Tue Sep 9 2025
Most weather models continue to poorly handle the ongoing
convection, so have backed off on prevailing thunderstorm
mention at most terminals overnight and relied heavier on VCTS
and PROB30 groups. With that said, HIB/DLH have the best
potential to see ongoing shower/storm potential overnight given
proximity to a stationary front. Look for generally MVFR to VFR
visibilities for them in showers, with occasional dips to IFR
visibility for any storms that move overhead. Showers and storms
are generally slow moving, but the front should start slowly
sagging south today, pushing farther southeast into northwest
Wisconsin for much of today. Outside of storms, expect current
VFR to MVFR ceilings to plummet to IFR to LIFR towards early
morning for northeast Minnesota terminals towards early morning,
lingering towards midday. This area of IFR ceilings should
shift into northwest Wisconsin later in the morning into
afternoon/evening as the front and precipitation slides
southeast, with conditions gradually returning to MVFR/VFR for
most northeast Minnesota terminals mid to late today. LIFR to
VLIFR conditions in dense fog persist at INL into early this
morning, before gradually improving towards mid to late morning. LLWS
persists towards 08Z for DLH and 10Z for HYR prior to the low-
level jet weakening.
Look for more widespread fog to dense fog and low stratus
potential towards or just after the very end of the current TAF
period Tuesday night given light winds and lingering low-level
moisture.
&&
.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 343 AM CDT Tue Sep 9 2025
Rounds of showers and thunderstorms continue today, though much
of the active thunderstorm activity has now focused along the
South Shore and will continue to slowly trend southeast with
time today. Cloud-to-water lightning and wind gusts up to 30
knots will be the primary threats. South to southwest winds
with with gusts to 20 to 25 knots tonight persist through mid-
morning in the Outer Apostles to Saxon Harbor. Small Craft
Advisories remain in effect. Winds remain southwesterly later
today and decrease to 10 to 20 knots during the afternoon before
further weakening tonight. Winds then turn northeasterly at 5
to 15 knots for Wednesday.
Another concern will be marine dense fog today for areas north
of the precipitation shield along the North Shore. A Marine
Dense Fog Advisory has been issued from Taconite Harbor to Grand
Portage. Weather models show an increasing potential for
widespread dense marine fog across western Lake Superior tonight
into early Wednesday morning, generally a 40-70% chance of
visibilities of 1 NM or less occurring. If this trend holds,
Marine Dense Fog Advisories will likely be needed tonight.
For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory until 10 AM CDT this morning for MNZ010-011-
     018-021-025-026.
WI...None.
MARINE...Small Craft Advisory until 10 AM CDT this morning for LSZ121-
     148-150.
     Dense Fog Advisory until 10 AM CDT this morning for LSZ140-141.
&&
$$
DISCUSSION...Rothstein
AVIATION...Rothstein
MARINE...Rothstein

NWS DLH Office Area Forecast Discussion