713
FXUS63 KDLH 121137
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
637 AM CDT Sun May 12 2024

.KEY MESSAGES...

- Scattered showers and a few thunderstorms continue through
  early this morning for the MN Arrowhead.

- Near-critical to borderline critical fire weather conditions
  today for northeast MN.

- As the cold front moves into northwest WI this afternoon, a
  few storms may become strong to severe between 2PM-6PM.
  Localized gusty winds up to 60 mph and hail up to 1" in
  diameter are the main concerns.

- A couple chances for frost tonight, Monday night, and Tuesday
  night.

- Dry conditions on Monday and Tuesday will give way to periodic
  chances for showers and thunderstorms mid to late this
  upcoming week into next weekend.

&&

.DISCUSSION...
Issued at 435 AM CDT Sun May 12 2024

This Morning:

A surface low over far northern Ontario has an attendant cold
front draped back into northwestern MN early this morning. Some
weak MUCAPE ahead of this front will continue leading to
scattered showers and a few embedded thunderstorms across the MN
Arrowhead into the first half of the morning before
precipitation moves east. Rainfall amounts are generally only a
few hundredths of an inch due to significant dry air in the
lower levels of the atmosphere.

Today:

The cold front will quickly trek southeast across NE MN by mid
to late morning, and through NW WI during the afternoon hours. By
early/mid Sunday afternoon, some redevelopment of showers and
thunderstorms is likely in the warm sector just south of the
front. Higher-res model guidance has slowed the front
progression just a bit in NW WI to the point that there is a
narrow window between about 2PM-6PM where storms could initiate
in parts of NW WI, mainly southeast of a Spooner-Hayward-Hurley
line. A few of these storms could become strong to severe given
SBCAPE values rising to 700-1200 J/kg along with 30-35 knots of
effective bulk shear and steep low and mid- level lapse rates.
This would favor some organization to the storms as well. The
main hazards would be wind gusts up to 60 mph and hail to 1" in
diameter. Rainfall amounts won`t amount to much, roughly a
quarter inch or less under the strongest storms. Past 6PM, the
cold front will have moved far enough south for the storm threat
to move south of our NW WI counties.

Another concern on Sunday will be much drier Canadian air
advecting in behind the cold front. Deep mixing will take place
in the wake of the front, leading to RH values dropping into the
15-25% range, predominately in NE MN from the late morning
through early evening. These lower RH values, combined with
northwest winds gusting to 20-25 mph, will lead to near-critical
fire weather conditions, and even some borderline Red Flag
Warning criteria north of the Iron Range where the strongest
gusts will be.

Canadian wildfire smoke will also be moving in behind the front
starting today and continuing into tonight. Have included smoke
mention in the forecast as well as some increase in sky cover
due to smoke aloft. Don`t expect as much of an impact to surface
visibilities at the moment given the deeper mixing today, but
will need to reassess for tonight depending on smoke
concentrations and how much of an inversion develops tonight.

Additionally, a Frost Advisory has been issued for tonight in
the Iron Range and northern Minnesota as winds turn lighter and
temperatures drop into the mid-30s. Temperatures farther south
will be in the upper-30s to low-40s.

Monday - Tuesday:

Dry and more seasonable weather for mid-May returns to start the
work week. High temperatures will be in the 60s for most both
days, albeit a bit cooler near Lake Superior. While northerly
winds on Monday and easterly winds on Tuesday will be gusting to
less than 20 mph given less deep mixing than we have seen the
past couple days, afternoon relative humidities have trended
drier and may approach 25-30% if this drier trend continues.
This could lead to more near-critical fire weather days Monday
and Tuesday.

The drier airmass will also allow for efficient cooling at
night, with some mid-30s for lows likely again Monday night and
Tuesday night in the Arrowhead and parts of NW WI. Therefore,
additional Frost Advisories may be needed.

Wednesday - Next Weekend:

Precipitation makes a return to the Northland on Wednesday-
Thursday as a shortwave trough and surface low slide across the
Upper Midwest. There doesn`t appear to be much, if any,
instability associated with this system, so it should be mainly
just rain showers. Rainfall probabilities are 60-70% for >0.1"
of rain with the midweek system, with a 30-40% chance for
greater than 0.25", so these amounts have trended down.
Ensembles show an additional series of shortwave troughs sliding
across southern Canada/northern CONUS Friday into next weekend,
but timing and tracks still have large spread. These troughs
would bring additional shower/storm chances for next weekend
(30-50% chances).

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 637 AM CDT Sun May 12 2024

Predominately VFR conditions for today with winds veering to
northwesterly behind a cold front that has already moved into
north-central MN. Some gusts in NE MN could reach up to 20 to 25
knots where mixing will be the deepest, with the highest gusts in
far northern MN. Some Canadian wildfire smoke moves south into
the region behind the front today into tonight. Depending on how
much of the smoke gets mixed to the surface, we could see the
smoke lead to some visibility reductions. Put 6SM in the TAFs
for now, but how low visibility gets is uncertain. Winds turn
light tonight out of the north-northwest to north.

Isolated to scattered showers/storms remain possible in parts
of NW WI (including KHYR briefly), but mainly southeast of a
KRZN to KHYR to KIWD line during the mid to late afternoon
along a cold front. The front quickly moves south of NW WI by
this evening, bringing precipitation chances to an end with it.
Could see some brief MVFR visibilities in the heaviest
precipitation if it moves directly over a terminal, as well as
erratic thunderstorm winds.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 601 AM CDT Sun May 12 2024

Showers and isolated thunderstorms continue along the North
Shore and possibly as far south as the Apostle Islands into the
early portion of this morning. Strong to severe thunderstorms
are not expected, although cloud- to- water lightning remains
possible at times.

Southwest winds in the morning turn northwesterly behind a
passing cold front this afternoon. The stronger winds should
remain over land due to warmer temperatures, though some gusts
up to 20 knots are possible along the immediate North Shore this
afternoon into early evening.

Light northeast winds are expected for western Lake Superior on
Monday, but increase on Tuesday with gusts approaching 20-25
knots in the head of the Lake. There is a 40-60% chance that
Small Craft Advisories may be needed from Two Harbors to the
Twin Ports to Port Wing Tuesday afternoon.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Frost Advisory from 2 AM to 8 AM CDT Monday for MNZ010>012-018-
     019.
WI...None.
MARINE...None.

&&

$$

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