770
FXUS63 KDLH 110846
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
346 AM CDT Tue Jun 11 2024

.KEY MESSAGES...

- Rain showers and a few thunderstorms move eastward across the
  Northland this morning into early afternoon. A few isolated
  strong to near-severe storms are possible later in the
  afternoon into early evening over portions of northeastern
  Minnesota and NW WI.

- Severe weather is expected on Wednesday, primarily during the
  late afternoon into evening. The main concerns will be very
  large hail (2"+ diameter) and damaging wind gusts. There is a
  lower-end threat for an isolated tornado that cannot be ruled
  out during the evening, but the potential is low (5% chance
  or less).

- An active warm and wet weather pattern going forward, with
  additional shower and thunderstorm chances on Thursday, late
  Saturday into Sunday, and next week.

&&

.DISCUSSION...
Issued at 347 AM CDT Tue Jun 11 2024

Today:

Moisture advection ahead of an approaching occluded front
associated with a shortwave trough/surface low over southern
Manitoba early this morning is bringing an area of light to moderate
showers into central and north-central MN early this morning.
This activity will continue moving eastwards across the
Northland this morning though early afternoon, with a general
window of 3-5 hours of rain for any one location as the showers
move east. There could be a few embedded thunderstorms with this
activity this morning into early afternoon, but no strong or
severe weather is expected with this initial round of
precipitation. Rainfall amounts of around 0.1-0.25" are expected
with this initial round.

There will be a brief break in precipitation behind this rain.
Depending on how much clearing occurs behind the initial rain, a
narrow pocket of 500-1100 J/kg of MUCAPE could develop by mid-
afternoon amongst 0-6 km bulk shear values of 20-30 knots as the
main forcing with the shortwave aloft moves overhead. Should
this sufficient instability occur, isolated thunderstorms
would develop along the occluded front in the mid-late
afternoon in the vicinity of the I-35 corridor, with storms then
moving east into the Arrowhead and NW WI into early this
evening. The instability/shear combination would support a
couple of these storms becoming strong to marginally severe
before storms diminish past the early evening. The main hazards
would be hail up to 1 inch in diameter and wind gusts up to
50-60 mph, with the best severe potential (5% chance) in
Burnett, Washburn, and Sawyer counties in NW WI where
instability looks to be highest.

Wednesday:

A few showers and non-severe storms could occur again later tonight
into Wednesday morning in the wake of this low pressure system,
but little in the way of additional rainfall is expected.

Otherwise, the focus turns towards the more likely severe
thunderstorm potential for later Wednesday afternoon into
evening. Strong moisture advection from the Gulf of Mexico will
be ongoing throughout the day, pushing dewpoints into the 60s by
the afternoon along with high temperatures soaring into the 80s.
This will make it feel like the muggiest day the Northland has
seen so far this Spring. An approaching shortwave trough and surface
low/cold front from the Canadian Prairies will eventually kick
off shower and thunderstorm development later Wednesday
afternoon. These storms will have access to a very buoyant warm
sector with this system ahead of the front, denoted by MUCAPE
values of 1500-3000 J/kg and locally higher amounts due to steep
low and mid-level lapse rates. 0-6 km and 0-10 km bulk shear
vectors of 45-55 knots and 75-90 knots, respectively, will be
generally parallel with one another, favoring initial
thunderstorm development as discrete supercells.

The high amount of instability, shear, and supercellular storm
mode will favor the primary threat during the afternoon being
very large hail to 2"+ in diameter. The potential for supercells
will be mainly in north-central and northeast Minnesota during
the afternoon, but the best potential for the very large hail
will be where instability is expected to be highest, which is an
area generally bounded on the north by the Brainerd Lakes to
Duluth to Siren. These supercells will also pose a threat for
damaging wind gusts as well. While there will be some SRH values
in excess of 100 m2/s2, LCLs during the afternoon will initially
be a bit too high to favor much tornado development. Hodographs
do show a little bit better low-level turning along with
lowering LCLs heading into the early evening, so a low end
threat (5% chance or less) for a tornado or two cannot be ruled
out heading into the evening. Heading towards sunset and later
into the evening, storms are expected to grow upscale into more
of a line of storms, leading to the threat becoming primarily
wind at that point. However, the farther we progress into the
evening, instability will be on the downward trend with storm
intensities gradually weakening and eventually moving southeast
out of the area prior to Wednesday night. Updates to the favored
locations of storm development are still likely as highlighted
by the various placement of storms in short-term model guidance
with the 06Z model suite.

Thursday:

A stationary front and subtle shortwave trough may lead to
additional shower and thunderstorm chances on Thursday in the
wake of the Wednesday system. Despite strong shear vectors
continuing, this will be a much less moist airmass, with very
meager instability to tap into as a result. Therefore, severe
weather is not expected on Thursday.

Friday:

Surface high pressure and shortwave ridging aloft bring a brief
break from the rainy pattern for Friday into early Saturday.
Expect sunnier skies, light winds, and high temperatures in the
mid-70s to around 80 degrees on Friday.

This Weekend:

The active weather pattern rears its head again later on
Saturday into Sunday as the ridge shifts off to our east and
global model guidance hints at a southern stream shortwave
trough moving across the Upper Midwest in phase with a more
robust shortwave/closed low moving northeastward across southern
Saskatchewan into northern Manitoba. This pattern should set up
southwesterly flow once again across the Northland, advecting a
much more moist airmass into the region once again. Still a bit
to early to get into the details, but the synoptic parameter
space (sufficient instability and bulk shear vectors around 30
knots) could support a severe weather threat, particularly on
Sunday given the longer duration of moisture and temperature
advection. Sunday could even see widespread high temperatures in
the 80s once again. Given still wet soils and near to above-
normal streamflows, PWATs potentially approaching 2 inches, and
model soundings showing deep saturation with temperatures above
freezing to above 10 kft, this system could also pose a low-
end threat for heavy rainfall and minor flooding across much of
the Northland as highlighted by the Day 5 Marginal WPC Excessive
Rainfall Outlook.

Early Next Week:

Global ensemble guidance diverges into next week, with the
timing of additional shortwaves/low pressure systems becoming
increasingly uncertain. However, the generally southwest to
quasi-zonal flow pattern aloft would favor periodic impulses,
and additional shower/thunderstorm chances as a result, into
next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1244 AM CDT Tue Jun 11 2024

VFR conditions to start. Rain moving in from the west later
during the current overnight hours through Tuesday morning will
bring high confidence in IFR or lower ceilings with it, and some
MVFR to perhaps at times IFR visibilities. There is a 10% chance
for some thunder in the vicinity of KBRD between 09-12Z, but
potential is too low to include in the TAF at this time, though
amendments may be needed. Also expect some wind shear early this
morning for KINL an KBRD before winds pick up during the day.

There will be a brief break in precipitation behind the morning
showers before a narrow window of time/area for isolated
thunderstorms develops along an occluded front mid-afternoon
along the I-35 corridor and pushes east into the Arrowhead and
NW WI into early evening. Given the more isolated nature of the
storms, kept thunderstorm mention primarily in PROB30 or VCTS
groups. Conditions quickly improve to VFR later this afternoon
and evening as skies clear behind the front.

Light southeast winds during the current overnight will veer to
westerly behind an occluded front later this morning through
afternoon from west to east. Daytime winds around 10-12 knots
will gust up to around 20 knots through the afternoon before
turning light into this evening and tonight.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 347 AM CDT Tue Jun 11 2024

Winds will be southerly along the South Shore and northeasterly
along the North Shore today, with gusts remaining less than 20
knots. A few isolated storms are possible this afternoon into
early evening, though no strong to severe storms are expected
when they move over the Lake. Winds turn light out of the
southwest this evening and tonight.

As another low pressure system and cold front approach from the
west on Wednesday, winds will increase out of the southwest with gusts
up to 20 kts. Hazardous small craft conditions are not
currently expected given the warmer air temperatures over land
and more stable marine layer over the Lake, but will need to be
monitored. Another round of storms Wednesday evening may be
strong to severe over western Lake Superior.

Winds turn breezy out of the west on Thursday behind a departing
cold front, which will lead to a 50-60% chance for Small Craft
Advisory level wind gusts of 20-25 knots during the late morning
and afternoon.

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