543
FXUS63 KDLH 241751
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1251 PM 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 /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1252 PM CDT Mon Jun 24 2024

VFR ceilings with mid/high level clouds aloft and diminishing
showers continue for parts of central MN. Have periodic light SHRA/VCSH
mention at KDLH/KHIB/KBRD through much of the afternoon, though
coverage is becoming more isolated to scattered.

The cloud cover is expected to lead to some hindering of the
daytime heating, but a warm and cold front moving northeast out
of eastern SD later today into tonight will still bring moist
and unstable air to the area. Still some uncertainty on how much
a capping inversion aloft will hold into this evening as it is a
stout inversion, but short term model guidance still does hint
at storm development along the warm front this evening somewhere
across central MN, and a thinner area of convective development
over north-central MN mid to late evening if storms are able to
develop and then quickly track towards the east into late
evening/early overnight. Any storms that do develop could
produce large hail, damaging wind gusts, and potentially a
tornado, particularly for the storms closer to the warm front.
Amendments are likely as forecast trends through the afternoon
hone in on when/where storms are more likely to form. For now,
am maintaining VCTS/PROB30 mention for the periods of time when
storm potential is highest. Any storms moving directly over a
terminal could produce MVFR to IFR conditions. Some MVFR
conditions, potentially IFR, are hinted at again by model
guidance for tonight before skies clear out behind the cold
front. Confidence in IFR conditions are 40% or less, with the
highest potential at KDLH and KHIB.

Some LLWS develops this evening into early tonight, mainly at
KDLH/KHYR. Winds turn westerly later this evening behind the
cold front, and turn gusty Tuesday towards the end of the
current TAF period.

&&

.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...Rothstein
MARINE...Melde