738
FXUS63 KDLH 030642
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
142 AM CDT Sun Aug 3 2025

.KEY MESSAGES...

- Stagnant weather pattern remains in place with a strong high
  pressure over the region trapping smoke at the surface. Air
  Quality Alerts remain in effect across the Northland

- A slow pattern change begins this afternoon with precipitation
  chances of 20-40% entering from the west.

- A Rex blocking pattern sets up over the Northland leading to
  off and on rain and thunderstorm chances through the mid week,
  largely for the MN side.

&&

.DISCUSSION...
Issued at 134 AM CDT Sun Aug 3 2025

Current Conditions/Today:

The anomalously strong surface high pressure that has been present
over the region for the last several days has begun to weaken and
will slowly shift to the southeast through the day. Return flow
on the backside of the air mass will bring southerly winds into
the region. Aerosol optical depth from yesterday afternoon
showed that the Canadian Wildfire smoke had penetrated as far
south as central MI. While winds turning out of the south would
normally flush the region of smoke, these antecedent conditions
may lead to extensions in the Air Quality Alerts.

Sunday Night - Tuesday Night:

With the return of southerly winds we will see an increase in
moisture advection and warming temperatures. Ridging aloft moves off
as well with some shortwaves moving in from the west. 00Z guidance
shows an upper level low currently over western ND slowly
encroaching on the Northland late Sunday. High pressure aloft over
Manitoba will act as a Rex Block leading to slow movements with this
system. Overall synoptic forcing looks to be on the weak side with
showers and storms getting the best boost from diurnal processes.
The expectation at this time will be for scattered showers with an
isolated storm or two through Tuesday. This will primarily take
place over MN as WI will still have subsidence in play
suppressing potential for rain. The convective parameter space
is lacking in overall bulk shear and instability remains weak
leading to no severe weather anticipated at this time.

Midweek:

Late Tuesday the blocking pattern begins to break down as surface
low moves across the Canadian Prairies. An increased low level jet
will also help to pivot the baroclinic zone out of the Red River
Valley an into the Northland. A slight uptick in instability may
help to produce some stronger storms Wednesday evening, but bulk
shear is still on the marginal side clocking in around 33 kts.

End of the Work Week:

As head into the latter parts of the work week the forecast becomes
a bit more uncertain. Looking at water vapor transport we will see a
surge from the Central Plains up into the Northland, likely a
combination of some Gulf moisture and evapotranspiration. This added
moisture will leave us with an unstable environment. Most of the
uncertainty is with the upper pattern and what shortwaves will be
rounding the dominant anti-cyclone over the desert southwest. The
GFS is the most robust with it`s latest run for Thursday and it has
some agreement from the GEFS ensemble as the CSU ML severe
probabilities begin to light up for Thursday. For now we will have
to wait and see if this signal stays consistent and if any other
ensembles begin to lean this way as well.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1221 AM CDT Sun Aug 3 2025

Areas of smoke continue to impact the Northland with reduced
visibilities at the surface. While there has been some improvement
from the previous day there is still potential for fog to mix with
the smoke overnight and drop visibilities towards IFR. After
daybreak fog will disperse and with smoke lingering. High pressure
will be departing tomorrow and an area of light rain will move in
from the west. Coverage is expected to be scattered with a few
embedded thunderstorms possible in the afternoon.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 134 AM CDT Sun Aug 3 2025

Light southwest winds to start the day with speeds generally less
than 5 kts. High pressure will be departing today which will make
winds more variable in the afternoon. Speeds will continue to remain
on the low side. By Monday winds will switch to out of the east
around 10 knots. Additionally, there may be areas of smoke across
the Lake.

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...Britt
AVIATION...Britt
MARINE...Britt