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000
FXUS63 KDLH 192030
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
330 PM CDT Fri Apr 19 2024

.KEY MESSAGES...

- Snow showers will persist through this evening, then taper to
  flurries overnight. Occasional visibilities less than 1 mile
  are possible in the heaviest snow showers, but accumulations
  should be very light.

- Elevated fire weather concerns are expected this weekend due
  to low minimum relative humidity and breezy northwest winds.

- A spring weather system will bring mainly rain but possibly
  some light snow late Monday through Tuesday.

&&

.DISCUSSION...
Issued at 330 PM CDT Fri Apr 19 2024

This afternoon through Sunday:

Scattered snow showers will persist mainly through the evening,
though there may be just enough moisture and low-level mixing to
keep flurries possible through the night. The snow shower
intensity has not been quite as high as was originally
anticipated so far this afternoon, and it seems like this is
largely due to widespread cloud cover that could be tampering
low-level lapse rates and instability. There is a pocket of
mixed clearing and more intense snow showers over northwest
Minnesota and heading east, and that combined with model
consensus suggest that we may see a brief reinvigoration of snow
showers for a few hours this afternoon until around sunset.
During this time, briefly reduced visibilities as low as ~1/2
mile will be possible. Any snow accumulations are expected to be
very minor, and in most cases, should not accumulate on
roadways.

Much drier air will work its way into the region from the
northwest gradually tonight, leading to a cessation of any
lingering snow showers or flurries by Saturday morning and
clearing skies. Mostly sunny skies are expected Saturday
afternoon with the exception of perhaps a few pockets of
cumulus. Winds will remain on the breezy side from the
northwest, gusting to around 20 to 25 mph. With the dry air
moving in, we will move back into the threat for some elevated
fire weather conditions. Min RH values are expected to fall into
the 25-30% range for most of the region, but lowest mainly in
east-central Minnesota. Fortunately, the threat for strong winds
has been lessening slightly.

An even drier day is expected on Sunday as a ridge axis moves
overhead. More widespread min RH values falling to 20-30% are
expected. Breezy northwest winds are again expected, but a bit
less strong than Saturday. Elevated to near-critical fire
weather conditions will be possible with the low min RH values.
With warm air advection developing, temperatures are expected to
warm up into the 50s across the region. Winds will become light
and transition to southerly Sunday night out ahead of an
approaching low pressure system.

Monday through Friday:

A dynamic spring system will be approaching the area for
Monday. The system looks to come down from Canada impacting the
region with a mix of rain and snow. This system per the global
models has quite a bit of cold air coming with it as well. The
geopotential height anomalies are showing a consistent signal of
this cold air advection starting Monday night and lasting into
early Wednesday morning. However, some differences are noted in
the global models with the GFS showing a much more potent (read
vigorous) low-pressure system coming out of Saskatchewan and the
Dakotas. The GFS also shows plenty of forcing at the 700mb
level. However, the Euro global model shows a much weaker system
resulting in less forcing. In addition, the Euro has the low-
pressure system staying further north into Canada. A third
global model, the ICON, shows a solution between the two models
with the low staying right along the Canadian border and
traveling towards the U.P of Michigan.

Winds will pick up during this period as the forecast area gets
caught between a high pressure off to the east and the incoming
low. This tight pressure gradient will result in some strong
southerly winds helping to bring in the moisture from the Gulf
of Mexico. This is shown well with precipitable water values
between .60” and .75”. and moderate integrated vapor transport
showing moisture transport into southern Minnesota. The only
question is where will this low track? If it tracks more south
then snow will be the more dominant precip type. In fact some
models are hinting at some light accumulations across the
Arrowhead of Minnesota due to the cold air being pulled down on
the backside of the system. Though a more northerly track would
result in less cold air and more of a plain rain setup.

Looking at temperatures, 50s look to be common area-wide before
the system approaches with a drop in temperatures due to that
cold air advection on the backside of the low. This system
certainly bears watching as all the main ingredients for
snowfall are there, namely strong forcing, and sub-freezing air
wrapping into the system. However, things can and likely will
change, and any snowfall accumulations are dependent upon the
low track and if snow falls at night versus the day given the
sun angle even through the clouds. After this system departs the
area, high pressure briefly settles in overhead with our next
system approaching the area Friday along with chances for more
rain which is certainly welcome news to the ongoing drought
situation.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1248 PM CDT Fri Apr 19 2024

Scattered showers of snow or mixed snow/graupel/rain will
increase in coverage this afternoon. Visibilities are expected
to be up and down this afternoon between VFR and MVFR, and IFR
can`t be ruled out a time or two if a heavier shower happens to
track over a terminal briefly with visibilities as low as 1/2 to
1/4SM. Predictability is expected to be quite low for timing,
but this was generally handled with tempos when the showers are
expected to be the heaviest and most widespread from 20Z and
00Z. Coverage of showers is expected to gradually diminish
around and after sunset.

Otherwise, expect MVFR to VFR ceilings with some terminals
seeing lowering ceilings tonight, then improving Saturday
morning. Breezy northwest winds will prevail through the period.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 330 PM CDT Fri Apr 19 2024

Gusty west winds abound across the nearshore waters this
afternoon with gusts from 25-30 kt and even approaching 35 kt at
Devil`s Island. We do expect that wind gusts will gradually
decrease this afternoon and evening, so we are not planning to
issue any Gale Warnings. Overall, winds have been trending
slightly downward Saturday into Sunday, and there may be a
period where wind gusts hover around or just under 20 kt
Saturday into Saturday night. We currently have Small Craft
Advisories going through Sunday, when we expect another brief
uptick in winds. However, it may be possible to allow Small
Craft Advisories to expire for a period Saturday afternoon and
night if the winds continue to trend downward. We will continue
to re-assess this in the next forecast updates. Higher wave
heights to around 4 ft are generally expected to remain offshore
with the westerly winds, except that they will affect the Outer
Apostle Islands periodically. Winds become light and variable
Sunday night, becoming southerly by Monday morning.

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 until 4 AM CDT Saturday for LSZ121.
     Small Craft Advisory until 10 PM CDT Sunday for LSZ140>148-150.

&&

$$

DISCUSSION...JDS/CJM/PA
AVIATION...JDS
MARINE...JDS