138
FXUS63 KDLH 250537
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1137 PM CST Sun Nov 24 2024

.UPDATE...
Issued at 908 PM CST Sun Nov 24 2024

Primary shift to the forecast with this evening update was to
bump up QPF by around 0.05" across portions of central and
north-central MN, which has led to a subsequent increase in
forecast snowfall amounts of 0.5-1.0 inches from the Brainerd
Lakes up towards International Falls. This has bumped up
forecast snowfall totals from this evening through Monday to
2-4" for Cass, Crow Wing, Aitkin, Itasca, and Koochiching
Counties. The Winter Weather Advisories were expanded into Cass,
Crow Wing, and Koochiching counties to account for this increase
in forecast snow totals. The snow forecast for the remainder of
the Northland remains on track and is largely unchanged.

The main reason for this shift to the forecast is rooted in both
upstream observations and 00Z hi-res model guidance. Area
webcams and surface observations across western and north-
central MN show light snow already ongoing upstream of the
Northland (e.g. Baudette, Bemidji, Park Rapids, etc.) associated
with low-level frontogenesis and increased lift as a result. As
this band shifts east towards 10pm-midnight, expect the
atmospheric profile to quickly saturate from the Brainerd Lakes
up to International Falls, with light snow beginning during that
timeframe, as well.

&&

.KEY MESSAGES...

- Light to moderate snow enters from the west this evening.
  Winter Weather Advisories have been expanded. The heaviest
  snow is expected in the overnight hours across NE MN. Light
  snow is expected to continue through Monday.

- A pattern change is expected to start Tuesday. Off and on snow
  chances will linger through the week as temperatures continue
  to cool.

- Prolonged lake effect snow chances are expected along the
  South Shore.

&&

.DISCUSSION...
Issued at 234 PM CST Sun Nov 24 2024

Synoptic Set Up:

The upper level ridge that has been in place over the region the
past couple days is slowly exiting to the east this afternoon as a
vertically stacked low moves across the Canadian Prairies. There is
also another surface low moving across Iowa. Both of these features
are helping to draw in some moisture to the Northland. ALPW
highlights some gulf moisture in the lower levels being pulled by
the Iowa Low and some upper level moisture from Baja mixed in with
the Canadian Low. The resulting PWATs are around 0.50 inches, well
within the normal climatology for this time of year, but enough to
provide the region with a coating of snow.

Afternoon/Tonight:

Radar has shown a few echoes this afternoon. Primarily transient
plumes of snow occasionally flowing off of Lake Superior. Webcams
have largely shown these small flurries quickly melting after
passage as high temps continue to float just above freezing.
More widespread snowfall will begin to enter from the west after
9pm as an inverted trough/occluded front moves west to east.
Vertical profiles completely saturate overnight as colder air
begins to overtake the region. Lack of a robust forcing
mechanism will lead to largely light snowfall for most of the
region. The exception to this will be along the North Shore and
into the Arrowhead. An impressively long fetch of easterly winds
across a warm lake (8C) will lead to a boost in snowfall rates.
The highest rates of 0.5" per hr are expected after midnight
across the North Shore. Thereafter, winds begin to switch to
the northeast resulting in lighter accumulations.

Monday:

Light snow will continue through most of the day as the system
progresses east. Snow totals with this forecast package have
increased. Overall widespread snow is expected with high confidence
(70%) of at least 2 inches of snow. Thanks to the contributions of
two moisture sources our QPF was boosted once again instigating an
expansion of our Winter Weather Advisories. Still believe we are a
bit shy of hitting 6" anywhere despite the HREF suggesting high
chances across the North Shore and South Shore. A few pockets of 6"
are possible thanks to the terrain boost and Lake effect but
not expecting it to be widespread enough to warrant a warning.
Winds will be backing through the day as the inverted trough
passes with northwest winds expected by the evening hours. This
change in wind direction will see lake effect mechanics switch
from the North Shore to the South Shore.

Tuesday-Weekend:

The main forcing mechanisms will depart Tuesday morning but
lingering moisture with a strong lobe of vorticity aloft will allow
for continued flurries and cloudy skies. Accumulations will be
minimal. Tuesday marks the start of a pattern change with much
colder air seeping into the Northland. By Thanksgiving our 850 temps
are expected to be around -15C. This colder air will have cascading
effects that will need to be monitored in upcoming forecasts.
Persistent NW flow will allow for continued chances for snow showers
along the South Shore. Areas downstream of large inland Lakes may
also see some Lake effect snow showers as ice production has not
settled in for the year. Look for air temperatures to decrease
through the week with highs in the teens by next Sunday.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1122 PM CST Sun Nov 24 2024

Snow showers are moving east from central Minnesota. MVFR will
lower to IFR ceilings once snow intensity increases. These
conditions are expected to last the majority of the night and
into Monday morning. Conditions will begin to improve as snow
comes to an end in the late morning to afternoon. INL will be
right on the edge of the back end of the snowfall, so accounted
for possible continued snow through the afternoon with a PROB30.
Will refine in the next TAF set.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 234 PM CST Sun Nov 24 2024

Enhanced easterly winds are ramping up this evening with Small Craft
Advisories currently in effect. Radar this afternoon has shown a few
lake effect streamers at times impacting the Near Shore waters.
Overnight, a system spreads in from the west which will largely
cause rain across the warm Lake. Winds taper off and back to out of
the northwest tomorrow. These winds are expected to increase
tomorrow evening with another batch of Small Craft Advisories likely
needed.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Winter Weather Advisory until 9 AM CST Monday for MNZ010-011-
     018-019-025-026-033>038.
     Winter Weather Advisory until 2 PM CST Monday for MNZ012-020-
     021.
WI...Winter Weather Advisory until 9 AM CST Monday for WIZ001.
     Winter Weather Advisory until noon CST Monday for WIZ002>004-
     006>009.
MARINE...Small Craft Advisory until 4 AM CST Monday for LSZ142-143.
     Small Craft Advisory until midnight CST tonight for LSZ144>147-
     150.

&&

$$

UPDATE...Rothstein
DISCUSSION...Britt
AVIATION...KML
MARINE...Britt