Winter Weather Advisory 13, NWS Duluth, MN

Area Forecast Discussion
National Weather Service Duluth MN
411 PM CDT Sun Apr 25 2021

.DISCUSSION...(This evening through Saturday)
Issued at 405 PM CDT Sun Apr 25 2021

Summary: Precipitation is moving in from the southwest this evening
and will spread across the Northland overnight. A wintry mix is
likely as we lose sunlight with snow favoring northern MN. The
higher elevations along the North Shore could see 1-3 inches. Warmer
temperatures across our southwest counties could result in some ice
accumulation tonight and in the morning hours. Monday a warm front
will promote the chance for some elevated thunderstorms in the
afternoon.

A surface high pressure has moved east across Lake Superior with
clouds slowly moving in from the southwest. A band of FGEN and
isentropic lift is set to move across the Northland late this
afternoon and spread northeast throughout the night. The arrival
of the precipitation will initially be rain but as the night
progresses and the surface cools we will see a rain/snow mix
across the region. The challenging part of this forecast will be
the precipitation type. There is a very strong warm nose of air in
the lower levels that will sufficiently melt most ice crystals
that happen to fall into it for the southern half of our CWA. The
question is how far will this warm nose extend north. For now, it
looks like it may stall a bit across northern MN where cooler air
will prevail in the overnight hours leading to more snowfall.
Snowfall totals for the area will range from less then an inch
across most of the Arrowhead to around 1-3 inches on the higher
elevations along the North Shore. The latest high resolution
models are favoring a freezing rain mix with sleet across Price,
Iron, and Ashland counties. Confidence is not high in this
solution with wet bulbs teetering on freezing. Additionally, the
higher sun angle in April may promote more warming than the models
are hinting at. Regardless, the morning commute may be slick.

There is another batch of precipitation on tap for Monday. A low
pressure moving across the High Plains has its warm front arching
into the Northland. An influx of warm air and moisture surges north
along a low level jet. The strong warm air in the lower levels will
still be present but the elevated mixed layer arriving from the west
will increase the mid level lapse rates and we could see some
elevated thunderstorms in the afternoon. MUCAPEs are are less than
500 J/kg but a low freezing level should promote some glaciation for
a few rumbles of thunder.

The rain chances continue into the midweek with temperatures slowly
on the rise. By Wednesday highs will be in the upper 50s and
lower 60s. Longer range models do not have a good consensus of the
weather pattern heading beyond Thursday. There is good agreement
of a cold front pivoting through but timing and weather or not it
will carry enough moisture for precipitation is still in question.
The 850mb temperatures do show a slight warming trend into the
weekend with highs climbing into the lower 60s across our southern
CWA.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1235 PM CDT Sun Apr 25 2021

VFR conditions are currently over the Northland this afternoon but
clouds are quickly encroaching from the west. BRD will be the first
terminal to see conditions deteriorate to MVFR as ceilings build in
with light rain this evening. A rain/snow mix will spread across the
region throughout the night with ceilings dropping to IFR.
Additionally, a band of enhanced low level winds over HYR/BRD
overnight will generate the threat for low level wind shear through
the early morning hours. More rain and the chance of thunderstorms
will be possible tomorrow afternoon.

&&

.MARINE...
Issued at 405 PM CDT Sun Apr 25 2021

The surface high pressure is slowly moving to the east and was
located over the center of Lake Superior this afternoon. Further
west the pressure gradient is slowly beginning to tighten. A Small
Craft Advisory has been issued for tonight for increasing
southeasterly winds and building waves. This advisory is further
expanded tomorrow as winds back to the northeast. Additionally, a
rain/snow mix will move across the Lake beginning this evening
and continue into tomorrow. Monday afternoon there is a chance for
some thunderstorms across northern WI and the South Shore.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  31  38  36  49 /  80  90  50  30
INL  30  42  34  54 /  50  70  50  10
BRD  35  49  40  55 /  80  70  30  30
HYR  32  49  40  56 /  70  70  40  50
ASX  32  44  37  49 /  70  80  50  40

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory from 2 PM Monday to 5 AM CDT Tuesday for
     LSZ143>146.

     Small Craft Advisory from 4 AM Monday to 5 AM CDT Tuesday for
     LSZ140>142-150.

&&

DISCUSSION...Britt
AVIATION...Britt
MARINE...Britt

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