681
FXUS63 KDLH 042147
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
447 PM CDT Tue Jun 4 2024

.KEY MESSAGES...

- Dense fog expected over much of western Lake Superior into
  this evening.

- A line of showers and storms along and ahead of a cold front
  will gradually move eastward this evening and will weaken with
  time tonight. Rainfall amounts of a 1-2 inches, with isolated
  3 inch amounts remain possible with the strongest storms.

- Some storms will be strong to severe with hail of pea to half
  dollar coin size and wind gusts of 40 to 60 mph.

- Isolated to scattered showers and storms are expected once
  again each afternoon and evening Wednesday through early next
  week. Rainfall amounts mid-week into the weekend will be
  lighter than what is expected today.

&&

.DISCUSSION...
Issued at 445 PM CDT Tue Jun 4 2024

Surface low pressure stretched from Saskatchewan southeast
through southern Manitoba and into Minnesota and western Iowa
with a center along the north central South Dakota and North
Dakota border. Water vapor imagery depicted an upper low over
the Manitoba/Saskatchewan border and a second lobe of vorticity
over southwest Wisconsin. The upper trough will continue to
propagate east tonight. A cold front will propagate eastward
across the Northland tonight and Wednesday morning.

A warm and moist airmass will precede the cold front tonight
with PWAT values rising to 1.6" and surface dewpoints will climb
into the mid-sixties with a few spots as high as the upper
sixties. MLCAPE values are expected to climb to 1000-2500 J/kg
ahead of the front. Deep southerly flow ahead of the front will
be in place and was aiding in drawing moisture north. Deep layer
shear will be from 25 to 30 knots ahead of the front to 35
knots very close to it. There will be a severe threat,
especially for cells close to the front where the shear is
greatest. Forecast soundings show decent low level curvature in
the hodographs but with a messier appearance above. Given the
stronger forcing with the front and upper trough, storm mode
will be a broken line of discrete storms with stratiform rain
closer to and behind the front. The CAPE and shear profiles
support hail from penny to half dollar size. There will also be
a wind threat, especially as storm mode changes to more linear.
Given the deep layer winds, 2-7 km, and 0-6 km shear vectors are
all parallel or nearly parallel to the front today, heavy rain
will be another threat. Storm motions will have a south to north
component within the west to east line movement. This will lead
to some training and with the higher moisture, flooding may
result. The heavy rain that fell 36-48 hours ago over portions
of the Northland will have soils primed. The HREF is showing the
heavy rain threat with some pockets in the LPMM to 3" and some
larger areas of 1-2". We expanded the Flood Watch to now include
Cass, Itasca, and northern Aitkin counties to account for this
potential.

The main window for severe will roughly be before 9 pm,
guidance is in fairly good agreement on this. The SPC outlook
for severe storms for much of our area is a 2 out of 5.

The upper trough will be over the region Wednesday through
Thursday and cooler temperatures will move in. The cooler
temperatures aloft and upper low will keep chances for showers
going through Thursday but they will be most widespread
Wednesday. Chances will be greatest during the afternoon and
evening hours during and just after peak heating. The rainfall
Wednesday/Thursday will be much lighter than what is expected
today and tonight.

A western upper ridge does build late week into the weekend but
the Northland remains close to the upper low and we carry
chances for showers and a few thunderstorms in spots into early
next week. Rainfall amounts will be relatively light. Highs late
week into early next week will be near normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1240 PM CDT Tue Jun 4 2024

Low stratus and fog have cleared. Look for a period of VFR
conditions before showers and thunderstorms move into the
terminals later this afternoon and tonight. A cold front near
the Dakotas/Minnesota border will progress eastward this
afternoon through tonight. Showers and thunderstorms will
develop along and ahead of the front and will move toward the
north-northeast. Hail, gusty winds, and reduced visibility are
expected with the storms. A few storms may loiter behind the
cold front amongst the widespread stratiform rain showers. Once
the precip clears the MN terminals early Wednesday morning, fog
may develop.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 445 PM CDT Tue Jun 4 2024

Fog, dense in spots, will persist tonight over portions of the
western Lake Superior. Easterly winds will continue tonight and
then turn westerly as a cold front moves through overnight. The
wind switch should aid in ending the dense fog threat. Showers
and thunderstorms will develop along the front as well and some
of the storms could be strong to severe with large hail and
winds to 45 knots possible. Westerly winds on Wednesday will be
strongest from Silver Bay to the Twin Ports to Port Wing and
some gusts of 20 to 25 knots will be possible.

Westerly winds will increase further on Thursday with
widespread speeds of 15 to 25 knots with gusts around 30 knots.
Hazardous conditions will occur, especially for smaller vessels
and a Small Craft Advisory will likely be needed.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch through Wednesday morning for MNZ018-025-026-
     033>036.
     Beach Hazards Statement until 9 PM CDT this evening for MNZ037.
     Flood Watch through Wednesday afternoon for MNZ038.
WI...Beach Hazards Statement until 9 PM CDT this evening for WIZ001.
     Flood Watch through Wednesday afternoon for WIZ001>004-006>009.
MARINE...Dense Fog Advisory until 10 PM CDT this evening for LSZ140>146-
     150.

&&

$$

DISCUSSION...Melde/Huyck
AVIATION...Huyck
MARINE...Melde/Huyck