676
FXUS63 KDLH 241143
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
643 AM CDT Mon Jun 24 2024

.KEY MESSAGES...

- A highly conditional threat for severe thunderstorms exists
  for this afternoon into tonight across the Northland. Hazards
  include large hail, damaging winds, and a tornado but is
  dependent on timing and storm mode which is still
  questionable.

- Dry weather expected for most Tuesday and Wednesday.

- Periodic chances for more showers/storms Thursday into next
  week.

&&

.DISCUSSION...
Issued at 335 AM CDT Mon Jun 24 2024

The forecast focus will be on this afternoon into tonight and
the chance for severe thunderstorms, with the possibility of a
more high end severe threat. Most of the Northland remains under
a Slight Risk (2/5) but this is a "higher" end Slight Risk.

A warm front across the Northern Plains early this morning will
move north today and should be just off to the west and south
of the Brainerd Lakes by this evening. A low amplitude upper
ridge will be over the area but will move east and weak height
falls will move over the region this afternoon. Southerly winds
will draw moist air north (PWAT values rising to 1.7-2.0") along
with very warm temperatures. Highs this afternoon will reach
the lower to middle eighties over much of the southern half of
the area. An elevated mixed layer moving in will contribute to
mid-level lapse rates of 7.5-8.5c/km. Very high to extreme
MLCAPE values (2000-4000j/kg) will develop over or very close to
the Northland with a north to south gradient. 500MB westerly
winds around 50 knots will contribute to effective shear of
40kts+. Forecast soundings show plenty of curvature from 0-3km
and 0-1km SRH will be from 150+ m2/s2, with the RAP forecasting
values up to 300 m2/s2 over southern areas.

Most of the ingredients are present for a significant severe
weather event across the Northland. However, one significant
impediment will be the presence of a stout cap, especially over
the southern half of the Northland. 750-800mb temperatures are
forecast to be around 20C and RAP soundings reveal very high MLCIN
values (200-300+ J/kg). The cap is weaker in far northern
Minnesota though. Will the cap be overcome by a subtle shortwave
aloft, frontal convergence, and persistent warm air/moisture
advection from a low level jet (that will strengthen this
evening)? That is the main question and the CAMS offer varying
solutions with all developing some convection but are different
on storm mode and location of the storms. There are two themes
from the CAMS and both make sense with this setup and may
happen. Late afternoon or more likely evening storms should
develop in far northern Minnesota which will be a bit closer to
the larger scale forcing from the low/shortwave. The main threat
from these storms will be large hail, up to 2" in diameter,
damaging winds, and possibly a tornado. Further south closer to
the warm front, severe storms will have a large hail threat like
those further north but also have a greater chance for a
tornado given a better chance for surface based storms. There
are indications that an MCS or a line of severe storms may
develop this evening with higher end damaging winds of 75 mph.
This would be along and north of the warm front and include
areas roughly south of US 2 from the Brainerd Lakes east into
parts of northern Wisconsin. The bottom line is there is
potential for a higher end severe weather outbreak and you need
to monitor forecasts through the day into tonight. If you have
outdoor plans, make sure you know where to go should storms
develop.

One thing that we didn`t mention with the storms is widespread heavy
rainfall. The threat isn`t zero, but it`s also not expected to
be a major issue. This is due to faster westerly deep layer
winds which will lead to faster storm motions and be off the
surface cold front which will minimize training storms. CAM
guidance suggests rather localized rainfall amounts of 1-2",
which is significant, but coverage is expected to be limited.

Looking ahead, Tuesday and Wednesday will be dry for most with
some showers possible in far northern Minnesota Tuesday. Highs
will be 75-84 degrees Tuesday and cool into the upper sixties to
mid-seventies Wednesday.

There will be periodic chances for more showers/storms Thursday
into early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 643 AM CDT Mon Jun 24 2024

Some patchy fog remained over northwest Wisconsin but otherwise
VFR conditions prevailed. Radar showed showers and
thunderstorms over central to eastern North Dakota this morning
moving east. This activity is moving into a more stable airmass,
at least for the morning and we expect much of it will
dissipate but not all. We have a VCSH going at
KHIB/KINL/KDLH/KBRD for a time this morning/afternoon and will
update if showers look more likely. Clouds will thicken some
but will remain VFR today.

A very unstable airmass will develop through the day and a warm
and cold front will move through the region late today into
tonight. Warm air aloft will create a cap and it may be tough to
break given the forcing. We do think storms will develop but
confidence in how widespread they will be is low. The storms
will be capable of all hazards including large hail, damaging
wind, and possibly a tornado. There are some indications that
MVFR or even possible IFR ceilings will develop tonight but
guidance has delayed the onset and HREF guidance forecasts less
than 35% chance for MVFR ceilings. We backed off those ceilings
for now.

A period of low level wind shear will develop...mainly impacting
KHYR/KDLH.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 335 AM CDT Mon Jun 24 2024

Winds will be or become onshore today for most areas. Speeds are
expected to be at or less than 15 knots today. There is a chance
for thunderstorms this afternoon into tonight and some may
produce large hail and winds in excess of 45 knots.

Winds will switch to west or southwest tonight and increase late
to 10 to 15 knots with gusts around 20 knots. The wind will
increase further on Tuesday from the west and conditions may
become hazardous for smaller vessels with gusts around 25 knots
and a Small Craft Advisory may be needed. Winds will veer to
north Tuesday night and diminish to less than 15 knots.

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...Melde
AVIATION...Melde
MARINE...Melde