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000
FXUS63 KDLH 211101
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
601 AM CDT Sun Apr 21 2024

.KEY MESSAGES...

- Near-critical fire weather concerns today due to low minimum
  relative humidity and breezy northwest winds.

- A clipper system will bring light rain Monday PM through
  Tuesday. Some light snow could mix in late Monday night into
  Tuesday, possibly even an embedded thunderstorm or two, as
  well.

- Additional precipitation chances late next week into next weekend.

&&

.DISCUSSION...
Issued at 327 AM CDT Sun Apr 21 2024

Today:

Shortwave ridging moves through the Upper Midwest today with
clear skies early this morning giving way to some scattered
diurnal cumulus and some mid/high-level clouds for most of the
Northland northeast of a Grand Rapids to Moose Lake line. Areas
southwest of that line should remain sunny. Deeper atmospheric
mixing today to around 6000-7000 ft will result in another day
of breezy northwest surface winds to around 20 mph from mid
morning through this afternoon. Expect minimum afternoon RH
values to dip into the 20-25% range for much of central/north-
central MN into the Iron Range and extending southward into the
Pine Barrens of NW WI. This combination of low RH and breezy
winds will result in near-critical fire weather conditions for
this afternoon into early evening. High temperatures will also
be much warmer today, ranging from the upper 40s/low 50s in the
tip of the MN Arrowhead where cloud cover will be highest to mid
50s to around 60 degrees elsewhere. Winds weaken and become
light this evening and tonight.

Monday - Tuesday:

An upper-level trough currently located over the British
Columbia will close off and track east into southern
Saskatchewan by 12Z Monday and then open up into a trough again
as it dives southeast through the Northland from Monday night
through Tuesday. There is some drier low-level air that the
precipitation will initially have to fight through Monday
morning, but expect precipitation to start in the form of rain
Monday afternoon with precipitation continuing through Tuesday
before ending by Tuesday evening. Strong southerly winds on
Monday will push high temperatures into the low to mid 60s, with
50s near Lake Superior. Some colder air aloft and at the surface
wrap in on the backside of this system, which should result in a
light rain/snow mix late Monday night into Tuesday. This mix
should primarily be north of Highway 2 in MN, but could be seen
for most of NW WI on Tuesday afternoon. There also may even be
enough instability (MUCAPE ~100-400 J/kg) to produce a few
embedded non-severe thunderstorms Monday night and again late
Tuesday morning into Tuesday afternoon in east-central MN into
NW WI. Expect cooler high temperatures on Tuesday as breezy
winds shift to out of the north, with highs ranging from the
low/mid-40s near the International Border to low/mid-50s in
east-central MN and NW WI. Clearing skies and a colder airmass
Tuesday night should push low temperatures down into the 20s.

Snow accumulations would be a wetter dusting at best on grassy
or elevated surfaces. Meanwhile, liquid precipitation amounts
have trended lower, with a tenth of an inch or less for
central/north-central MN and a tenth to one-quarter inch for
NE MN and NW WI.

Wednesday:

Upper-level ridging and surface high pressure moves through the
region Wednesday and Wednesday night, leading to quiet weather,
mostly sunny skies, and high temperatures in the 50s for most
(40s in the MN Arrowhead and near Lake Superior). This will be
another day with low RH values in the 20-25% range in spots, so
this will need to be watched for additional near-critical fire
weather potential. Right now southerly winds look lighter for
Wednesday afternoon, with gusts generally to 15 mph or less.

Thursday - Next Weekend:

An upper low over southern California on Wednesday will move
through the southwestern States through Thursday night before
ejecting northeast into the central Plains on Friday and into
the Northland vicinity as a negatively tilted trough on Friday
night into Saturday. Ensemble clustering of the low track in the
Northland vicinity is actually in fairly good agreement for
being 6-7 days out, with forecast surface low centers at 12Z
Saturday ranging from the far eastern Dakotas to as far east as
western Wisconsin, though the large majority are in MN at that
time. This system will bring our next chance at more widespread
precipitation potential. As of now, it appears that most of
Thursday will remain dry with highs in the upper 50s to low 60s.
A similar pattern of highs in the mid-50s to low 60s on a daily
basis for Friday into the weekend are also possible depending on
the exact track of the low. Precipitation chances peak on
Friday/Friday night before diminishing late Saturday.
Ensembles/deterministic global models point to air being warm
enough aloft for all of the precipitation with this system to be
in the form of rain aside from a stray 3 to 5 out of 100 ensemble
members across the CMC/GEFS/EPS ensembles mixing in some very
light snow Friday night. Still a bit too soon to discuss exact
rainfall amounts, but NBM 72-hr probabilities (7 AM Thursday - 7
AM Sunday) are as follows and likely to change:

>0.5": 40-60% chance SE of a Brainerd-Twin Ports-North Shore
           line, with 20-40% NW of this line.

>1.0": 10-30% and 0-10% for the same respective areas.

>1.5": less than 10-15% everywhere.

Models then diverge more significantly as to whether or not
another trough/low moves into our region for Sunday into early
next week, which would bring additional precipitation chances if
it does so.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 602 AM CDT Sun Apr 21 2024

VFR conditions throughout the TAF period. Development of
isolated to scattered diurnal cumulus with bases around
6000-7000 ft develop from late morning through the afternoon for
most of NE MN and NW WI terminals. BRD/central MN should remain
far enough southwest that cumulus doesn`t develop due to lower
humidity at the top of the mixed surface layer. Light westerly
winds early this morning turn northwesterly throughout much of
the day/afternoon, sustained around 9-13 knots with gusts up to
16-20 knots before weakening again this evening/tonight and
backing to south-southwesterly. Breezier conditions pick up
again on Monday ahead of an approaching clipper system, with the
strongest gusts over NW WI.

&&

.MARINE...
Issued at 327 AM CDT Sun Apr 21 2024

Today will be fairly quiet on the Lake as warmer air results in
more stable lake conditions and southwest wind gusts remaining
under 20 knots. Winds turn light this evening and most of
tonight at less than 10 knots before picking up a bit more on
Monday into Monday night. Small Craft Advisories may be needed
again at the head of the Lake and along portions of the South
Shore Monday afternoon for southwest winds gusts around 20-25
knots, though these winds have been trending downwards prior to
previous forecasts. Stronger winds arrive for much of western
Lake Superior on Tuesday as winds shift to northeasterly on the
backside of a low pressure system moving through. Some gusts up
to 25 to 30 knots and waves building to 4-7 feet cannot be ruled
out.

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...Rothstein
AVIATION...Rothstein
MARINE...Rothstein