217
FXUS63 KDLH 012322
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
622 PM CDT Sat Jun 1 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 /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 622 PM CDT Sat Jun 1 2024

Decaying showers should pass north of KHYR in the next few
hours, but for now do not anticipate any impacts to the
terminal. Breezy west winds with gusts up to 20kts to diminish
to less than 10 kts by 03z, then remain light for the overnight
hours. Radiational fog is expected to develop around KHYR later
this evening, reducing visibilities to IFR. There may also be
additional fog development in the vicinity of Lake Superior
which may also affect KDLH, but the probability is low enough at
this time and have left it out of the TAF forecast. Winds will
pick back up out of the south to southwest on Sunday, and may
become breezy with gusts up to 20 kts after 22z. Showers and
storms developing west of the area during the day should also
spread east to near KBRD and possibly also KINL after 22z. Due
to timing uncertainties have only put a VCTS into KBRD for now,
but anticipate additional storms after the end of the TAF
period.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 245 PM CDT Sat Jun 1 2024

Dense marine fog lingers along the North Shore today and
expected into tonight. Extended the far North Shore fog Advisory
into early Sunday morning for the expectation of overnight
linger dense fog. Some guidance brings similar reduced
visibility back into the Apostle Islands later tonight again so
altered those zones to run from late evening today to early
Sunday morning as well in a fog Advisory. 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 Sunday for LSZ140-141.
     Dense Fog Advisory until 8 PM CDT this evening for LSZ142-143.
     Dense Fog Advisory from 10 PM this evening to 7 AM CDT Sunday
     for LSZ147-150.

&&

$$

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