208
FXUS63 KDLH 301747
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1247 PM 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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1247 PM CDT Tue Apr 30 2024

Stubborn stratocumulus clouds with a few embedded light showers
will be slow to diminish this afternoon, but there is still
potential for there to be a period of VFR ceilings for a few
hours later this afternoon where clouds have not broken yet. As
we go into this evening, rain is expected to quickly spread into
the region from southwest to northeast. Expect ceilings to fall
pretty rapidly to MVFR/IFR and visibility to fall mainly to MVFR
as well and remain so for much of the night. Thunder is not
expected at most terminals, but HYR will have the best chance
(20-30%) at seeing some. After the rain ends from southwest to
northeast Wednesday morning, lingering low-level stratus are
expected to stick around through much of the morning. Winds will
gradually shift to east/northeasterly this evening ahead of the
rain and become breezy at DLH with gusts up to 20-30 kt. Winds
are expected to shift fairly abruptly to westerly Wednesday
morning after rain moves northeast.

&&

.MARINE...
Issued at 1001 AM CDT Tue Apr 30 2024

Some headline adjustments have been made along the South Shore
and Outer Apostle Islands to extend Small Craft Advisories into
mid-day Wednesday as latest models suggest that gusty winds will
persist there with northeast flow. No other changes at this time
from the previous update.

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 PM CDT
     Wednesday for LSZ146-147-150.
     Small Craft Advisory from 10 PM this evening to 4 AM CDT
     Wednesday for LSZ148.

&&

$$

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