985
FXUS63 KDLH 020534
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1234 AM CDT Sun Jun 2 2024

.KEY MESSAGES...

- Widely scattered showers and isolated thunderstorms this
  afternoon last into early evening today.

- Fog is expected to form tonight in parts of inland northwest
  Wisconsin and especially across north-central Wisconsin,
  potentially reducing visibility to 1/2 mile into early Sunday.

- Isolated general storm chances Sunday gives way to the next
  round of possible severe weather and expected heavy rainfall
  starting Sunday evening in north-central Minnesota and
  spreading eastward Sunday night.

- The active pattern continues Tuesday daytime into Tuesday
  night for possible severe weather again and heavy rainfall.
  Scattered rain showers last into the end of next week.

&&

.DISCUSSION...
Issued at 356 PM CDT Sat Jun 1 2024

A shortwave trough centered in northwest Ontario this afternoon
is rotating through a deep central Canadian mid- to upper-level
low pressure center and dragging a weak cold front across far
northern Minnesota this afternoon. Pre-frontal, diurnally-aided
rain showers have formed as a result right ahead of the front.
Surface observations show high cloud bases from 5000-7000 feet
above ground level, with a very dry air mass in the low levels
underneath those showers very likely limiting any rainfall to
sprinkles a few hundredths of an inch of rain into early evening
today. Those showers and isolated thunderstorms exit the area
then by the mid to late evening hours.

Weak surface high pressure sets up tonight over northern
Wisconsin to create calm winds. Some moisture from rain showers
that wrapped up over the last few hours should remain trapped
under that surface high and aid in fog formation later tonight
for inland northwest Wisconsin and mainly north-central
Wisconsin. Have placed patchy and areas of fog in the grids for
most Wisconsin zones through 8-9 AM Sunday morning. Some
guidance has visibility dropping down to 1/2 mile so an
overnight land-based Dense Fog Advisory cannot be ruled out for
our far southeastern counties (highest chances in Price or Iron
Counties bordering WFOs Green Bay, LaCrosse and Minneapolis).

While fog is ongoing in northern Wisconsin tonight, a 30-35 knot
low-level southerly jet builds into western Minnesota tonight
to rapidly increase precipitable water values Sunday from west
to east. The exception will be in the eastern Arrowhead where a
drier Canadian high-pressure dominated airmass lingers Sunday
afternoon to keep minimum relative humidity still down to the
mid-20 percent range. Blended in 10th percentile guidance into
the dewpoint forecast for that part of the Arrowhead as a
result.

Isolated strong thunderstorm chances (capable of near-severe
hail) build first in the afternoon hours Sunday in north-
central Minnesota along the warm front of a deepening surface
low pressure centered in southern Manitoba. In this time period,
severe thunderstorms fire over central North Dakota and slowly
spread eastward into northwest Minnesota as the low pressure
lifts into the Manitoba/Ontario border region of Canada by late
Sunday afternoon and the cold front trailing into the Red River
Valley of the North basin. The severe thunderstorms eventually
are progged to form a line of severe thunderstorms reaching
north- central Minnesota between 7-10 PM Sunday evening. In this
time period, damaging wind gusts of 70 mph is the primary
hazard and is most likely in the greater Itasca / Cass / Crow
Wing / Aitkin County region of north- central Minnesota lasting
into the early overnight hours (12-2 AM). Depending on
environmental stability factors and the organization of the line
of storms, a tornado (also large hail) could not be ruled out
in this general locations of Cass to Crow Wing to southern
Itasca County either. Further eastward into northeast Minnesota
still has the potential to see damaging wind gusts to 60 mph,
but the southern trend of this severe weather tomorrow evening
keeps those lower.

Heavy rainfall is likely (80% chance) to create anywhere from
0.5 to 1 inch of rainfall with this system tomorrow evening and
overnight. An few reports of 1.5 inches would not be surprising
either in the Brainerd Lakes or east-central Minnesota region by
Monday morning, creating minor ponding of water. Scattered
showers and storm chances last into Monday, but the next
potential round of severe weather sets up Tuesday daytime as a
deep trough digs through the US Plains and a surface low
pressure over the Dakotas deepens to create an even more moist
and unstable environment over the Northland. The best
instability and shear to support severe weather hazards would be
placed across northeast Minnesota and especially northwest
Wisconsin with the Tuesday round of storms that has potential to
last into early Tuesday night depending on how fast the support
aloft lingers or speeds up to eject out of the Northland Tuesday
evening.

An area of strong to possibly isolated severe thunderstorms
will have to be monitored for Wednesday daytime as the deep low
pressure is currently progged to move through northwest Ontario.
This scenario may then create an environment over mainly north-
central and northeast Minnesota with meso-forcing aloft,
increasing mid-level lapse rates to 7.5 C/km, CAPE of 800-1200
J/kg and shear of 25-30 knots to support a large hail threat
Wednesday daytime.

Ensemble guidance shows a 40-50% chance of west-northwest winds
gusting 35-45 mph beginning Wednesday night into Thursday and
may need a future Wind Advisory if this scenario persists,
largely dependent upon the synoptic pressure gradient from a
building high in the central CONUS and low over the Great Lakes.

Scattered thunderstorms and shower chances last into the end of
next week as slightly above normal temperatures persist.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1228 AM CDT Sun Jun 2 2024

VFR conditions for tonight into Sunday. Fog chances have moved
east, and are no longer expected to get flight restrictions from
fog. Scattered storms ahead of a cold front will affect our
western terminals, with some strong to severe storms possible.
As the cold front moves east, a large line of storms will move
with it. This line may produce strong to damaging winds and
small hail. Ceilings will lower to MVFR with the line and there
may be some visibility restriction with heavy rain.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 1000 PM CDT Sat Jun 1 2024

Dense marine fog lingers along the North Shore north of Taconite
Harbor this evening, and is expected to continue tonight. We
have continued the Advisory into early Sunday morning for the
expectation of lingering dense fog. Guidance brings reduced
visibility back into the Apostle Islands tonight though it does
not appear to have developed there so far this evening. Have
continued the Dense Fog Advisory which runs from now until
early Sunday morning. Winds shift to easterly tomorrow, gusting
towards 20 knots in the southwestern arm of the lake and builds
wave heights to 2 feet tomorrow afternoon. The next round of
heavy rain and strong thunderstorms likely affects the lake
after Midnight Sunday night and lasts into Monday morning.
Easterly winds 10 to 20 knots last into Monday with wave heights
from 2 to 3 feet.

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...Dense Fog Advisory until 7 AM CDT this morning for LSZ140-141-
     147-150.

&&

$$

DISCUSSION...NLy
AVIATION...KML
MARINE...LE