054
FXUS63 KDLH 242137
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
437 PM CDT Mon Jun 24 2024

.KEY MESSAGES...

- Still a conditional severe thunderstorm threat for this
  evening into early tonight for the Northland. Hazards include
  large hail, damaging winds, and a lower (2% chance) tornado
  potential.

- Scattered showers for some on Tuesday and mostly dry
  Wednesday.

- Additional showers and storms Thursday into Saturday and again
  early next week.

&&

.DISCUSSION...
Issued at 435 PM CDT Mon Jun 24 2024

Rest of Today - Tonight:

While the forecast has honed in on the areas of concern for
severe weather potential this evening into early tonight, there
still remains some uncertainty with regards to if and when
severe storms develop this evening. All of the Northland remains
in a Slight Risk for severe weather (Level 2/5) with some
slivers of a "higher end" severe threat.

As of 430 PM CDT this afternoon, elevated scattered showers and
a few embedded rumbles of thunder were present in the Brainerd
Lakes vicinity in an area of very subtle 500-mb troughing
perturbations. This activity will continue to move east through
the remainder of the afternoon. Much of the Northland remains
strongly capped for surface-based air parcels with current RAP
forecast soundings showing 150-300 J/kg, though capping is a bit
weaker farther northwest near a surface cold front over SE
Manitoba/SW Ontario/NW MN. This region is where initial
development of thunderstorms late this afternoon is most likely
where forcing is better, as is hinted at by several short-term
models, including most of the WoFS ensemble members.
Thunderstorms in this region are forecast to see MLCAPE values
of 2000-3000 J/kg where effective shear is 45-55 kt out of the
west. This would be a roughly 45-degree angle relative to the
cold front, so initial convective development would favor a
discrete supercellular storm mode. Given the favored storm mode
and mid-level lapse rates around 7-7.5 C/km, the primary threats
would be large hail (1+") and wind gust up to 60 mph as these
storms move east into north-central Minnesota by 6-8 PM
timeframe, and then moving farther east with time into the
Arrowhead the remainder of the evening into early tonight. Also
can`t rule out a low-end tornado potential (2%) through mid-
evening given 0-1 SRH values of 150-200 m2/s2. The loss of
daytime heating will lead to increasing MLCIN mid to late
evening over north-central MN, so expectations are for severe
potential to diminish as storms move farther into the Arrowhead
towards 10pm-2am timeframe.

The second--and more conditional--area of severe thunderstorm
concern this evening into early tonight is from central MN into
NW WI as this area has been plague by more persistent cloud
cover, lingering showers, and a stronger capping inversion for
much of the day. This area would be closer to the surface warm
front moving northward from its position in SW/south-central MN.
If storms can break the cap, it wouldn`t be likely till a
little later into the early evening hours (looking more towards
8-9 PM in the Brainerd Lakes/east-central MN as another subtle
500-mb shortwave moves through. Storms in this area would have
access to MLCAPE of 2500-4000 J/kg with very steep mid-level
lapse rates, around 50 kt of westerly effective shear, and 0-1
and 0-3 SRH of 150+ and 250+ m2/s2, respectively. These storms
would favor a quicker upscale growth into a cluster of storms or
a bowing line segment given shear being oriented more parallel
to the surface front. The main concern with these storms would
be damaging wind gusts to 60 mph, as well as large hail to 1
inch in diameter initially. The low-level turning/SRH would
support a low tornado threat (2%) for the surface based storms
that don`t become outflow dominant. Short term guidance still
disagrees on where/if these storms develop given the strong cap.
There is also a real potential that these storms may develop
just to the south of our forecast area and remain that way due
to the gradient of higher instability being just south of
central/east-central MN and track east/southeast while remaining
completely out of our area. If storms develop in central/east-
central MN, then these storms could continue to track east into
NW WI, as well. Instability will be less with eastward extent,
so expectation is for storm intensity to weaken with eastward
extent into the later evening and early overnight hours before
storms exit eastern parts of the CWA.

Widespread heavy rain is not expected due to the faster storm
motions and more progressive nature of storms this evening and
tonight. However, PWATs of 1.7-2" will support efficient
rainfall rates, so some localized pockets of 1-2" could be
observed mainly in east-central MN to NW WI.

Tuesday - Wednesday:

Some showers are expected across far Northern MN late Tuesday
and Tuesday night in cyclonic flow aloft. May see an off chance
for a stray shower on Wednesday, but chances are 10% or less.
Temperatures in the mid-70s to mid-80s are expected for Tuesday,
but be cooler in the 70s on Wednesday.

Thursday - This Weekend:

A series of shortwave troughs move through the Upper-Midwest on
Thursday-Saturday, with a surface low pressure moving across the
region on Friday into Friday night. This will bring additional
shower and thunderstorm potential, though severe weather is not
anticipated at this time. We will have to watch for some limited
heavy rain/flooding potential given elevated streamflows and
wet soils, however. Exact amounts and locations are still
uncertain and too low-confidence to pin down at the moment.

There should be a brief break in rain again on Sunday as
ridging/surface high pressure move through.

Early Next Week:

Another active pattern with more shower/thunderstorm chances as
more shortwave energy/surface low moves somewhere through the
north-central CONUS/far south-central Canada.

&&

.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 435 PM CDT Mon Jun 24 2024

Lighter onshore winds with speeds less than 15 knots continue
for the remainder of today. There is a chance for thunderstorms
this evening into early tonight, with a large hail threat and
winds in excess of 45 knots, with the best chance along the
South Shore.

Winds will switch to westerly behind a cold front tonight and
increase late to 10 to 15 knots with gusts around 20 knots.
Winds increase further on Tuesday from the west, with gusts up
to 25 knots and hazardous conditions for small craft for late
Tuesday morning through mid-evening, where a Small Craft
Advisory is in effect. Winds will veer to northeast Tuesday
night into Wednesday 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...Small Craft Advisory from 11 AM to 9 PM CDT Tuesday for LSZ121-
     140>148-150.

&&

$$

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