572
FXUS63 KDLH 041729
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1229 PM CDT Sat May 4 2024

.KEY MESSAGES...

- Light to moderate rain continues through this morning and
  afternoon before tapering off this evening last in the
  Arrowhead and northwest Wisconsin. An isolated thunderstorm is
  possible (20% chance) near the Iron Range this afternoon.

- Mostly clear skies and a colder air mass overhead tonight are
  expected to aid in fog and frost formation tonight.

- Dry conditions Sunday give way to a warmup near 70 F Monday
  when there is a 40% chance of near-critical fire weather
  conditions as breezy southerly winds occur with minimum
  relative humidity in the low to mid-30% range.

- The next round of rainfall begins Monday night into Tuesday,
  with non-severe thunderstorms most likely in northwest
  Wisconsin.

&&

.DISCUSSION...
Issued at 248 AM CDT Sat May 4 2024

The slow moving, weak cold front that moved into the region
overnight is producing an axis of low to mid-level convergent
flow from the Brainerd Lakes into the Arrowhead early this
morning. Combine this forcing with a southerly moist jet with
Gulf air, the widespread light to locally moderate rainfall
within the convergent axis has brought up to a few tenths of an
inch of rainfall overnight so far. Rainfall rates and amounts
will increase during the daylight morning hours for the I-35
counties in MN and US Hwy 53 counties in WI though as the mid-
level frontal forcing pushes eastward within the deeper mid to
upper level trough to align better with the moisture. A quarter
to half-inch of rainfall is expected for those locations by late
this afternoon. Frontal-associated rainfall exits the region by
mid-afternoon as dry air in the mid-levels pushes into the
southern half of the Northland from the west and the front
exits the region. In far northern Minnesota (north of US Hwy 2),
a secondary vort max drops into north-central Minnesota from the
north by mid-day today. Residual wrap-around moisture (0.5"
PWAT progged in guidance), mid-level lapse rates of 7.5 to 8.5
C/km, around 100 J/kg of MUCAPE and 20 knots of effective shear
may (20% chance) support isolated thunderstorm development from
Bemidji- Grand Rapids- Hibbing and northward. The most likely
hazards in those thunderstorms would be very localized moderate
rainfall and pea size hail. Other locations in the Arrowhead,
Brainerd Lakes and Twin Ports are expected to see another period
of scattered rain showers in this afternoon time period.

As the secondary vort max exits the Arrowhead by mid-evening
later today, dry air subsidence ends all shower chances
overnight tonight. Deterministic guidance progs the 850 mb air
mass from 0 to -2 C for far northern Minnesota. Combine this
cold air mass, light winds under surface high pressure and
residual moisture trapped in the boundary layer, there is
potential (40% chance) of fog development in the region Saturday
night into Sunday morning. If locations closer to the Brainerd
Lakes that see precipitation end earlier today and the dry air
mixes out the surface layer enough, then frost could instead
form tonight for those locations.

A dry day on Sunday sees temperatures rebound into the low to
mid-60s across the region as surface high pressure exits the
region to the east and a mid-level ridge builds overhead from
the west; promoting southerly air advecting into the region
beginning Sunday night.

Gusty southeasterly low-level winds mix out Monday morning to
create breezy conditions around 15 mph with gusts to 30 mph for
parts of east-central and north-central MN. Relative humidity in
the low to mid-30 percent range may (40% chance) create a
period of near-critical fire weather conditions Monday afternoon
as temperatures are forecast to peak around 70 F. The fuel
guidance from land management agencies will also be monitored
for input due to recent rainfall and how the spring "green up"
proceeds in this early week period.

Precipitation chances build Monday evening as a low pressure
moves out of the Northern Rockies and into the Northern Plains
Monday afternoon. The warm front passes over the region Monday
night to create a period of likely (80% chance) widespread
rainfall and possible (30% chance) thunderstorms late Monday
night into Tuesday afternoon as the low pressure retrogrades in
the Northern Plains. The best chance of non-severe thunderstorms
will be in northwest Wisconsin Tuesday afternoon. In all, there
is a 60-70% chance of at least 1/2 inch of rainfall for
northwest Wisconsin and east-central and the Arrowhead in MN.
The upper-bound of isolated rainfall is 1-1.25" with a 20%
chance of occurrence in localized areas of east-central MN and
northwest Wisconsin Tuesday.

Ensemble cluster analysis shows high confidence on the
vertically stacked low pressure center remaining over the
Northern Plains, which may (20-30% chance) keep the Northland
in a continued wet pattern into next week as well before the
deep low ejects eastward by late next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1226 PM CDT Sat May 4 2024

MVFR conditions with a stripe of IFR in rain will transition to
showers this afternoon with IFR becoming less likely. Shower
activity should subside by sunset with high pressure building
in. Clear skies overnight will likely (80% chance) lead to fog
formation, so have included hints of IFR fog in the TAFs. Winds
will be generally light and will eventually become mostly
northwesterly.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 1226 PM CDT Sat May 4 2024

A band of persistent light to moderate rainfall today and
tapering this evening may (60% chance along the South Shore and
40% chance for the North Shore) result in marine fog Saturday
night into Sunday morning. No headlines are expected currently,
but if dense fog does form tonight then some could be necessary.
Otherwise, light winds under high pressure prevail through
Sunday morning before becoming west-southwest at 10-15 knots.

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...None.

&&

$$

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