383
FXUS63 KDLH 230603
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
103 AM CDT Sun Jun 23 2024

.KEY MESSAGES...

- Periods of rain and some thunderstorms continue through the
  weekend. Severe weather is not expected.

- Severe thunderstorms expected (risk level 2 out of 5) Monday
  evening and night.

- Quieter weather Tuesday and Wednesday before thunderstorm
  chances return late next week.

&&

.DISCUSSION...
Issued at 118 PM CDT Sat Jun 22 2024

Rain showers and embedded thunderstorms in association with a
shortwave/MCV across west central Minnesota will continue to
propagate east-northeast through the afternoon and into this
evening. This will represent the next more widespread round of
precipitation for northwest Wisconsin and northeast Minnesota.
Buoyancy is modest and severe weather is not expected. A close
eye will be kept on rainfall amounts and rates with this round
of precipitation given the sensitive hydrologic situation
across the Northland. The highest rainfall amounts through this
evening are favored across northwest Wisconsin where the
shortwave/MCV will track along a 1.5-2.0 inch precipitable
water gradient. CAM trends and upstream rainfall analysis
suggest 0.5 to 1.0 inches of rainfall across northwest Wisconsin
is most likely. Across the Twin Ports one quarter to one half
inch of rainfall is the most likely rainfall range through this
evening, with amounts decreasing further north across the Iron
Range and Borderlands. The axis of heaviest rainfall will have
to monitored based on radar and satellite trends through the
afternoon. With high pressure in place tonight at the surface
with weak winds and plentiful remnant moisture, fog will be
likely across most of the Northland tonight into Sunday morning.
A Dense Fog Advisory may be needed (30-50% chance) across
northwest Wisconsin, the Twin Ports and I-35 corridor.

The next wave arrives in northwest flow from Canada late tonight and
will propagate across the Northland through Sunday. Numerous rain
showers and a few thunderstorms are likely with this wave and its
associated cold core aloft with residual precipitable water values
around 1 inch. Again, buoyancy is modest so severe weather is
unlikely. Although some small hail (half inch or less diameter)
is not out of the question with low freezing levels.

Attention on Monday turns to the severe thunderstorm threat,
especially for Monday evening and Monday night across all of the
Northland. SPC has the area in a Slight Risk for severe
thunderstorms. How the scenario for Monday evening and night
will unfold is somewhat conditional based expected capping in
the warm sector, how far north the warm sector is able to
establish itself, and subtle forcing in the mid levels with
smaller impulses embedded in fast westerly flow aloft south of
the more significant wave across Canada. In the warm sector, mid
to upper 60s dewpoints beneath steep mid level lapse rates
support moderate to strong buoyancy with MLCAPE values of
2000-3000+ j/kg. However, model soundings indicate an
appreciable cap through the afternoon and into the early
evening that will likely hold until the arrival of the cold
front from the west. Like SPC stated, all threats are in play
with any supercells that are able to break the cap Monday
evening with strong deep layer shear largely perpendicular to
the cold front. This includes damaging wind gusts in excess of
70 mph, and a tornadic threat with hodographs with significant
low level curvature. This significant low level curvature may
limit how large hail is able to grow as initial hail embryos
would be quickly removed from the favored hail growth curtain.
Still hail to 2 inches is certainly possible. CSU Machine
Learning probabilities confirm these threats. Upscale growth
into an MCS is possible Monday night into northwest Wisconsin,
though that is uncertain based upon how much convective coverage
there will be to congeal. The flash flood threat is non-zero,
although not as significant as was seen last Tuesday as the
overall setup is much different with a lower coverage of storms
also expected. Impressive rates are likely where storms track,
although the lower coverage makes the widespread flash flood
threat much less.

A much needed two days of quiet weather is expected on Tuesday
and Wednesday with surface high pressure. Thereafter,
thunderstorm chances return for late in the week beneath fast
zonal flow aloft.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 103 AM CDT Sun Jun 23 2024

Fog and stratus is expected overnight with some lingering mid
and higher clouds. KHYR the most likely to be affected by fog,
with IFR conditions likely between 09z-12z. Have included MVFR
visibilities in fog at most of the other terminals, though some
mid clouds and showers should keep fog from developing for KINL,
so have instead included a VCTS group for overnight. Conditions
should return to VFR during the morning hours, with all sites
VFR by 18z. Additional showers and possible storm development
expected for KINL, KHIB, KDLH and KHYR, during the day on
Sunday, and have included some VCSH/VCTS groups. Some short
periods of MVFR conditions are possible during the afternoon
hours as cells pass by.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 118 PM CDT Sat Jun 22 2024

Dense fog will continue for the Twin Ports and through all South
Shore zones through Sunday morning and a Dense Fog Advisory is
in effect. Fog may (40-60% chance) expand along the North Shore
today, and especially tonight. Northeast winds with gusts
around 25 kts and waves of 2-4 feet will continue for Taconite
Harbor, through the Twin Ports and along the South Shore through
the afternoon, with winds and waves slowly subsiding tonight.
Scattered rain showers with a few embedded thunderstorms will
continue today through Sunday.

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 LSZ121-
     146>148-150.

&&

$$

DISCUSSION...PA
AVIATION...LE
MARINE...PA