Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 261121
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
621 AM CDT Tue Mar 26 2024

.KEY MESSAGES...

- Large winter system continues to bring heavy snow and mixed
  precipitation to the Northland through this afternoon.

- Freezing rain chances over portions of the I-35 corridor and
  northwest Wisconsin have increased (60-100%) as have ice
  amounts (trace up to 0.35") before 10 AM this morning.

- Snow showers, with occasional visibility of less than 1 mile,
  are forecast Wednesday and Wednesday evening.

&&

.DISCUSSION...
Issued at 502 AM CDT Tue Mar 26 2024

Freezing rain chances have increased early this morning over
portions of the I-35 corridor from Pine City to Duluth, up the
North Shore to Silver Bay, and east across northwest Wisconsin
to WI-13 including Solon Springs, Drummond, Spooner, and Cable.
The likelihood of freezing rain over these areas is now 60 to
100%. Ice accumulation of a trace up to 35 hundredths of an inch
are forecast between now and 10 AM. The greatest ice
accumulation will be from near Hinckley and Sandstone to
Dairyland to Solon Springs and Gordon to near Drummond.

With the increased risk of significant icing (greater than one-
quarter inch) and additional snowfall late this morning through
the afternoon, we have upgraded Pine and Bayfield counties to a
Winter Storm Warning.

Warm air aloft, marked by 850 mb temperatures warmer than 0
degrees Celsius extended from northwest Wisconsin west into the
I-35 corridor, perhaps as far west as Aitkin and McGregor, and
north past Duluth to the interior of the Arrowhead including
Brimson, Isabella, and Eagle Mountain per the 08Z RAP analysis.
KDLH WSR-88D dual-pol data reveals a partial melt signature
between 5300 and 3800 ft AGL. Observations at our office early
this morning revealed various crystal habits, sleet, and even
freezing rain or freezing drizzle for a time. As of 405 AM,
small to medium needles and needle aggregates were dominant with
sleet pellets mixed in.

Surface temperatures were above freezing south of a line from
near Cambridge to Grantsburg to Barnes to Clam Lake to near Park
Falls. There was also a zone of above freezing temperatures
along the Lake Superior shoreline. Between those areas is where
the greatest ice accumulation is expected this morning. Similar
to yesterday there are likely pockets of freezing drizzle where
radar echoes diminish between bands of more intense
precipitation. Mixed precipitation may advance as far west as
Brainerd before 12Z.

The surface low will continue to strengthen as it advances
north-northeast across northern Wisconsin into northeast Ontario
by early Wednesday morning. GOES-East water vapor and IR
satellite imagery reveal a zone of enhanced divergence oriented
from south-southwest to north-northeast from southwest Minnesota
to Cass and Itasca counties. Radar reflectivities in that area
show a corresponding increase in intensity suggesting moderate
to locally heavy precipitation falling. That area is between
several WSR-88D sites, so a bit of inference is needed to
interpret the signal. As the low continues to wrap up and lift
north-northeast today, expect that area of enhanced forcing for
ascent to pivot and then lift northeastward as well.
Precipitation rates over central Minnesota into the Arrowhead
will increase and a period of one-half to one inch per hour snow
rates is likely (70-90%).

Cold air advection will push the melting line eastward late
this morning and this afternoon. At this time it appears likely
we`ll see a change back to all snow over all of northwest
Wisconsin before precipitation tapers off late this afternoon
and evening. Mixed precipitation in northeast Minnesota will
change back to all snow even earlier, likely in the 12Z to 15Z
timeframe.

Precipitation will gradually come to an end this afternoon and
tonight as the system departs. Cold air advection and cyclonic
flow aloft should result in a return of snow showers and
flurries Wednesday and Wednesday evening. The 00Z NAM solution
reveals a non-zero risk of snow squalls late Wednesday afternoon
into Wednesday evening generally near and south of US-2 in from
the I-35 corridor east across northwest Wisconsin. Drier air is
forecast to arrive on Wednesday which should bring an end to
snow chances for a day or two.

The potential for a Friday night through Saturday night clipper
remains in the forecast. Temperatures appear split across the
area. A bout of light snow seems likely, although it may be
mixed with rain or freezing rain. The zone of precipitation is
somewhat narrow, similar to the frontogenetic band of snow which
affected portions of South Dakota, central and southern
Minnesota, northern Iowa, southern Wisconsin, and northern
Illinois late last week. Therefore, portions of the Northland
may not see any precipitation. The track of the system will
govern where the relatively narrow band of precipitation occurs.
Several inches of snow accumulation appear possible by Saturday
evening, although specific details and location of the greatest
amounts are yet to be determined given the wide range of
forecast solutions this morning.

It would seem that since the atmosphere remembered how to make
precipitation over the Upper Midwest in the last week, it`s
become a favorite activity. Yet another round of wintry mixed
precipitation appears likely for portions of the Upper Midwest
and northern Plains Sunday night through early Tuesday morning.
Will the Northland receive additional light snow or wintry mixed
precip during that time? It`s hard to bet against it at this
point.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 618 AM CDT Tue Mar 26 2024

IFR or lower flight cats expected the first 12 hours of the TAF
forecast in mainly snow in MN and rain in WI with a mix in
between. The low pressure that has been lingering for days will
finally move north through the Northland and over Lake Superior
in the next 18 hours causing winds to switch directions and
vary in speed quite a bit over relatively small areas.
Conditions improve quite a bit after 06Z though MVFR snow
showers may creep in from the north for the end of the TAF
period.

&&

.MARINE...
Issued at 502 AM CDT Tue Mar 26 2024

Northeast gales continue this morning. Winds will gradually back
northwesterly this afternoon and evening. As winds switch, the
gale potential will subside for most of the waters. Cold air
advection and downslope winds along the North Shore should see
another round of gales late this afternoon through this evening
for the North Shore waters. We expanded the Gale Warning into
Chequamegon Bay and Oak Point to Saxon Harbor areas for this
morning as model guidance shows the gale potential will increase
quickly and then decrease by early afternoon. Conditions will
remain hazardous for smaller vessels over western Lake Superior
through Wednesday and perhaps into Thursday.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Winter Storm Warning until 7 PM CDT this evening for
     MNZ010>012-018>021-025-026-033>038.
WI...Winter Storm Warning until 7 PM CDT this evening for WIZ001-
     002.
     Winter Weather Advisory until 7 PM CDT this evening for WIZ003-
     006.
MARINE...Gale Warning until 1 PM CDT this afternoon for LSZ121-144>148-
     150.
     Gale Warning until 1 AM CDT Wednesday for LSZ140>143.

&&

$$

DISCUSSION...Huyck
AVIATION...Wolfe
MARINE...Huyck


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