144
FXUS63 KDLH 301119
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
619 AM CDT Tue Apr 30 2024

.KEY MESSAGES...

- Fog creating areas of low visibility around 1/2 mile very
  early this morning lifts from mid to late morning today.

- Another quickly moving system will create 1/4 to 1 inch of
  rainfall across the Northland beginning this evening in north-
  central and northeast Minnesota and exiting the region early
  Wednesday morning. Thunder and lightning is possible (30%
  chance in east-central MN and northwest WI), but severe storms
  are not expected.

- A second system is likely (70% chance) to bring a late week
  round of rainfall from Thursday morning into Friday, with
  continued off-and-on rain and thunderstorm chances into the
  weekend and early next week.

&&

.DISCUSSION...
Issued at 357 AM CDT Tue Apr 30 2024

Infrared satellite imagery shows the low pressure that brought
the Northland a wet half of Sunday and foggy/drizzle Sunday is
now located in far northwest Ontario early this morning.
Trailing rain showers have all but moved out of the Arrowhead
over the last few hours, with only drizzle, fog and mist ongoing
across the region under very low sky decks behind the low
pressure. These low clouds stick around through this morning,
but gradually scour out into this afternoon as drier air aloft
is already working overhead from mid-level ridging moving from
the Northern Plains into the Upper Midwest. That mid-level ridge
is very short-lived though as the next low pressure lifts
northward from the Central Plains into the Upper Midwest by late
this afternoon.

The incoming moisture plume on southerly low to mid-level flow
increases sky cover again from southwest to northeast late this
afternoon and into the evening ahead of the next band of
rainfall. The low tracking from south-central Minnesota to
northwest Wisconsin tonight favors the best chances for
widerspread thunderstorm activity south of the forecast area.
Mid-level lapse rates around 7 C/km and available MUCAPE up to
50 J/kg indicate limited thunder/lightning potential (30%
chance) though for east-central Minnesota to northwest Wisconsin
late this evening and early overnight. Model sounding data
shows precipitable water values of 0.9-1.1 inches in the column
(about the 90-95th percentile for today) in east-central MN and
across northwest Wisconsin favoring a 20% chance of a maximum
location of 1-1.25 inch rainfall total by early Wednesday
morning. The rest of the Northland is expected to see 1/4 to
3/4 of an inch of rainfall as the vort max within the quick-
moving low pressure exits the forecast area by Wednesday mid-
morning. For locations at the Head of the Lake and along
lakeshores, increasing easterly winds are likely (80% chance)
too. Wind gusts of 25 to 30 mph (60% chance) are expected at
this time in the mid evening hours to early overnight time
period as the low pressure center crosses through northwest
Wisconsin.

Deep mid-level troughing that has been in place over the
northern Rockies and Pacific northwest moves towards the middle
of the Continental US by mid-week.

Sunny skies setup under a period of subsidence by Wednesday late
afternoon and evening, so these late afternoon dewpoint
temperatures were decreased towards the 10th percentile guidance
to create around a 5-10% drop in forecast relative humidity for
that day over base guidance. Recent moderate to heavy rainfall
should help to minimize fire weather concerns though even with
increasing westerly winds starting late Wednesday morning.

As that mean troughing enters the Northern Plains into Wednesday
night, a southerly low-level jet increases moisture south to
northward Thursday daytime. Thursday late morning into the night
is the second chance for widespread rainfall chances this week.
Another few tenths of an inch of rain may (40 to 60% chance)
fall in this late week system before off-and-on rain chances
last into this weekend and early next week. Near-seasonal
temperature prevail in this active and somewhat wet period.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 616 AM CDT Tue Apr 30 2024

IFR to LIFR ceilings and fog/drizzle creating MVFR to LIFR
visibility begins to clear from 14 to 17Z today as an area of
low pressure further lifts into northern Ontario. Light
southwest winds under 10 knots today back southeasterly after
21Z ahead of the next incoming quick moving shortwave; breezy
southeasterly winds 10-20 knots after 00Z Wednesday along the
lakeshore terminals. That shortwave brings a shield of moderate
rainfall to the Northland from southwest to northeast 23Z to 04Z
this evening. Thunder is most likely south of US Hwy 2,
including BRD and HYR. After the shortwave exits the area after
09Z Wednesday, a quick wind shift occurs back to southwesterly
to end this TAF period.

&&

.MARINE...
Issued at 315 AM CDT Tue Apr 30 2024

Lingering elevated swell tapers in height through the mid-
morning hours today so the earlier Advisories were cancelled
early this morning. A period of mild conditions quickly gives
way to increasing northeast winds early this evening, first at
the head of the lake, as a strong, quick low pressure moves into
Minnesota. As the low passes immediately south of the lake this
evening, accelerating easterly to northeasterly winds could
reach near-gale force strength, depending on the track of the
low pressure through NW WI. For now, Small Craft Advisories have
been hoisted for this evening and overnight as winds gust 25 to
30 knots at the head of the lake and along the North Shore. A
quick wind shift to westerly occurs late Wednesday morning low
lifts northeast of the lake. Another round of Small Crafts may
be necessary again for the South Shore Wednesday.

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...Small Craft Advisory from 10 PM this evening to 10 AM CDT
     Wednesday for LSZ140>142.
     Small Craft Advisory from 7 PM this evening to 10 AM CDT
     Wednesday for LSZ143.
     Small Craft Advisory from 7 PM this evening to 4 AM CDT
     Wednesday for LSZ144-145.
     Small Craft Advisory from 10 PM this evening to 4 AM CDT
     Wednesday for LSZ146>148-150.

&&

$$

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