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589
FXUS63 KDLH 030047
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
747 PM CDT Sun Jun 2 2024

.MESOSCALE...
-- Changed Discussion --
Issued at 747 PM CDT Sun Jun 2 2024

An update on the evolution of thunderstorms this evening. We`re
some elevated showers and storms pop up across central Minnesota
and moving northeast. These are being generated with assistance
from warm air advection north of a quasi-stationary warm front
across southern Minnesota. With these initial storms being
elevated and instability aloft less than 1000 J/kg and mid-level lapse
rates marginally favorable to strong storms (~6 to 6.5 J/kg), we
don`t anticipate severe weather for several hours. There could
be some sub-severe hail and gusty winds along with heavy rain.

As we get towards 10 PM and midnight, the chances for severe
weather will increase as a cold front passes through. Lingering
surface-based instability over the Dakotas/Minnesota border
around 1 to 2 kJ/kg will migrate east, though as it does, we
lose daytime heating and thus convective potential. The main
threat for severe weather has been drifting a bit south,
attendant with warmer air. We will maintain favorable 0-6 km
shear for much of the Northland, but the main instability axis
will likely stay put in central Minnesota this evening once the
stronger storms eventually make it east. This is where the
greatest threat for strong straight-line winds will be (up to
60-70 mph possible; 15% chance). Tornadoes will be unlikely, but
a stray weak tornado can`t be completely ruled out (<2%
chance). Hail up to quarter size will be possible as well,
though with instability decreasing as storms are expected to
arrive later into the evening, this threat is decreasing some
(10-15% chance).

The severe threat is expected to be of limited time duration,
lasting until ~2 AM or so, by which time instability isn`t
expected to be supportive for severe weather for the rest of the
night, though storms will continue to work through the region
from west to east through early Monday morning. Heavy rain will
be a threat with storms tonight, but flash flooding risk will be
minimal as storms are not expected to train over any one area
for any exceptional duration. Minor flooding or ponding locally
remains possible through Monday morning.
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&&

.KEY MESSAGES...

- System bringing heavy rain for portions of the Northland and
  severe weather in north-central Minnesota will arrive this
  evening and last through Monday morning before showers become
  more localized in coverage Monday daytime.

- The threat of tornadoes in north-central Minnesota from severe
  weather this evening has decreased as of this morning, with
  damaging wind gusts to 70 mph and large hail around an inch in
  diameter as the primary hazards late this evening and early
  tonight remaining mainly in north-central Minnesota.

- Areas of dense fog are very likely (60-80% chance) Monday
  night into early Tuesday morning.

- Another system will bring more heavy rain and severe weather
  Tuesday daytime. This time the better chances are along and
  south of the Iron Range across much of the Northland.

- Localized strong thunderstorms are expected Wednesday daytime,
  first in northern Minnesota before moving into northwest
  Wisconsin and central Minnesota later in the afternoon.

&&

.DISCUSSION...
Issued at 315 PM CDT Sun Jun 2 2024

Low pressure over the northern High Plains is lifting a warm
front into the Upper Midwest this afternoon. Radar shows a very
weak line of pre-warm frontal rain showers in the Borderlands
exiting into northwest Ontario over the next hour or two. So far
today, this has been the only rain showers or storms in the
Northland, but this is expected to change into the 4-6 PM CT
hours today as a cluster of general thunderstorms presently in
western Minnesota moves northward into the Brainerd Lakes area
and eventually into inland northwest Wisconsin in the early
evening hours. These thunderstorms move north-northeastward into
the mid-evening hours, but severe weather is not generally
expected from this first round of showers and general storms.

As the low pressure moves eastward though into the eastern
Dakotas, a line of strong to locally severe thunderstorms is
expected to be moving into northwest Minnesota late this evening
(8-10 PM hours). The current Slight Risk for severe weather
highlighted by the Storm Prediction Center covering Crow Wing
and Cass Counties (highest of all chances, about 15% for severe
weather) and Itasca and Koochiching (still some chance, but
lesser than counties immediately southward) does a fair job of
showing the location where that line of strong to locally severe
thunderstorms could (10-15% chance, but confidence has decreased
over the last 24 hours) impact first in north- central
Minnesota around the 10 PM - Midnight hours. Damaging wind
gusts to 70 mph and large hail up to a half-dollar in size are
the primary hazards for late evening into early overnight
tonight in the Brainerd Lakes and north- central Minnesota
region. The limiting factors on whether this line of
thunderstorms does impact Cass/Crow Wing and other parts of the
Northland will be if the isolated storms earlier in the evening
highly limit instability and whether the line of strong/locally
severe storms moves off of the cold pool and dissipates in
strength from the northeast sector and shifts primarily
southwestward into mainly central Minnesota.

Either way on the severe weather side, there are good signals in
precipitation guidance for most locations in the Northland to
see a quarter of three-quarters of an inch of rainfall by early
Monday morning as the then-mainly moderate rain showers and
isolated general thunderstorms exit last through north-central
Wisconsin. Very localized instability rain showers are still
expected though for most of northeast Minnesota and northwest
Wisconsin Monday daytime, but less than a tenth of an inch of
rain would be expected.

A short-lived and weak high pressure Monday night sets up in
northeast MN and northwest Wisconsin between the departing and
shortly- incoming low pressure for Tuesday. Calm surface winds
aided by enough of a low-level inversion trapping the moisture
from earlier Monday is expected to create areas of dense fog
Monday night into early Tuesday. Advection fog off Lake Superior
could even produce widespread dense fog into the Twin Ports and
across the Arrowhead in this time period. A stronger southerly
gradient over north-central Minnesota by early Tuesday morning
helps to limit all but patchy fog potential in those western
forecast locations. Dense Fog Advisories may be needed over the
next few forecast packages covering Monday night into Tuesday
morning visibilities down to 1/4 mile.

The previously-mentioned mid-levels low pressure for Tuesday
enters the southern Canadian Prairies, while retrograding and
deepening to become negatively tilted as a surface low extends
into the MN/ND/Manitoba border region by Tuesday early
afternoon. This setup creates a possibly even better severe
storm environment for much of the Northland Tuesday compared to
this evening. Deterministic guidance points to available
instability around 1500 J/kg of CAPE, very deep southerly flow
advecting in high precipitable water of 1.3-1.6 inches in the
column aloft and bulk 0-6km shear of 35 to 40 knots supporting
storm growth high enough for large hail, wind gusts to 60 mph
and heavy rainfall (localized amounts around 2") in localized
parts of the Northland along and south of the Iron Range.

The cold front moves through the region Tuesday evening to bring
an end to storm chances last in northwest Wisconsin and the
Arrowhead by later Tuesday evening.

As the mid-level low pressure over southern Canada shifts
eastward on Wednesday, expect localized strong to near-severe
thunderstorm potential mainly in northern and central Minnesota
Wednesday afternoon potentially moving into northwest Wisconsin,
depending upon the location of mid-level steering flow from
where the low pressure sets up, later Wednesday afternoon into
the evening hours. Deterministic forecast soundings show
potential for pea to dime size hail and wind gusts to 50 mph
currently, but the strength of if the storms can break a cap
aloft could produce the near-severe concerns. Marginal lapse
rates aloft currently for Wednesday daytime do not show great
potential for anything above near-severe at this point though.

Gusty west-northwest winds are expected to gust from 35 to 40
mph Wednesday into Thursday evening, with a 40% chance of gusts
around 45 mph in mainly near and south of US Hwy 2 in northern
Minnesota and across northwest Wisconsin.

Temperatures about 10 to 15 degrees below normal for early June
on Thursday warm to only slightly or near-normal for the weekend
as off-and-on general thunderstorm chances (20-30%) persist
mainly in the Arrowhead and northwest Wisconsin.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 656 PM CDT Sun Jun 2 2024

Ceilings and visibility gradually deteriorate through the
evening as showers and thunderstorms move in from the west. For
the next 3 to 5 hours, VFR conditions are expected to prevail
with brief MVFR conditions possible (mainly visibility) as
showers pass by. Couldn`t rule out some thunder in this period,
but thunder will become more likely (90% chance) around and
after midnight. Ceilings are also expected to fall to IFR as
thunderstorms pass through. Low ceilings are expected to persist
into the morning, then clearing skies in the afternoon as dry
air moves in. Breezy south winds are expected this evening,
gusty and erratic at times as thunderstorms pass by, and then
becoming light from the southwest on Monday.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 235 PM CDT Sun Jun 2 2024

East-northeast winds gusting 15 to 20 knots in the southwestern
arm continue into this evening and are creating wave heights to
2 feet. Strong thunderstorms may (20% chance) move over the
Twin Ports and South Shore, much lesser chances along the North
Shore, after 10 PM this evening and last into the pre-dawn
hours Monday morning. After a forecast 0.2 to 0.4 inches of
rainfall over the lake, patchy fog is expected to form Monday
and linger into Monday night. Dense fog is most likely Monday
night into Tuesday and could, in-time, require a Dense Fog
Advisory for much of the western waters. Better chances for
strong to isolated severe thunderstorms build Tuesday afternoon
and evening.

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.

&&

$$

MESOSCALE...JDS
DISCUSSION...NLy
AVIATION...JDS
MARINE...NLy