Lake Vermilion Area Weather – February 19-21

KEY MESSAGES

– Dangerously cold wind chills are expected tonight into Wednesday morning. Extreme Cold Warnings and Cold Weather Advisories go into effect at midnight.
– Light snow will move into the Arrowhead tonight and northwest Wisconsin early Wednesday morning. Snow amounts will range from a dusting to around 2 or 3 inches in the Arrowhead and a dusting up to 4 or 5 inches in northwest Wisconsin.
– Significantly warmer temperatures are expected late this weekend into early next week with above-freezing temps very likely (80+% chance).

DISCUSSION

Issued at 324 PM CST Tue Feb 18 2025

An interesting and unusual upper-level pattern was found over
the region this afternoon. A retrograde 300 mb low was drifting
westward over northeast North Dakota. Easterly winds were found
over southern Manitoba and northern Ontario as far south as
Upper Michigan on the 18Z RAP analysis at 300 mb with westerlies
over southern North Dakota into central Minnesota and northern
Wisconsin. A channel of cyclonic vorticity was found at 500 mb
in the zone between these airstreams. An east-west oriented 700
mb trough stretched from New England west into Montana and
northern Wyoming. Arctic high pressure remained in place at the
surface over the region.

The 700 mb trough axis will sag southward this evening as the
trough slowly deamplifies. Northerly winds north of the trough
will usher in warm air advcection and isentropic ascent tonight.
In addition to the isentropic lift, an area of omega will sag
southward into the Arrowhead. Upstream surface obs and radar
imagery across northern Ontario reveal light snow was falling as
of 230 PM CDT. Look for that area of light snow to spread
slowly southwestward with time tonight. The northerly low-level
flow and cold air aloft will encouraged organized lake-effect
snow to develop for the South Shore. The cloud cover and warm
air advection should keep temperatures several degrees warmer
than the past few nights. Winds should be a little higher than
the previous few nights, too, generally between 3 and 10 mph.
The insulation of the clouds and mixing from the light winds
will also help keep the temps a bit warmer. Wind chills
overnight have risen several degrees with this forecast. Even
so, we will keep the existing Cold Weather Advisories and
Extreme Cold Warnings in place.

Light snow will gradually spread farther southwest into the
Twin Ports and more of northwest Wisconsin Wednesday morning.
Forcing for ascent will diminish during the day and snow should
slowly taper off, except along the South Shore where LES will
persist into early Thursday morning. Total snow accumulation in
the Arrowhead of a dusting up to 2 inches with a few spots
possibly seeing 3 inches is forecast. Over the South Shore,
portions of northern Iron County may see 3 to 5 inches, with a
dusting up to 3 inches elsewhere in NW WI.

A steady warming trend will being on Wednesday and continue
through the weekend. The upper-level trough will continue to sag
southward with warm air advection aloft. Highs will climb into
the single digits and low teens above zero on Wednesday. There
is a small chance we may need additional cold weather headlines
Wednesday night over portions of central Minnesota into the St.
Croix valley in Wisconsin.

A progressive upper-level pattern will return for the latter
half of the week into early next week. Several weak waves will
propagate across the region with alternating warming and cooling
periods. Unfortunately it appears the warmest air during each
cycle will pass over the Northland overnight and during the
morning. High temps should climb above freezing on Sunday and
perhaps a few 40s on Monday. There a few clipper-ish systems
Saturday into early next week which could bring light snow.

AVIATION

Issued at 1146 AM CST Tue Feb 18 2025

Stratocumulus clouds are expected to develop once again this
afternoon and linger into this evening. Cloud bases should be
between 3000 and 3500 ft AGL. A few flurries may occur under
those clouds. Anthropogenic clouds and flurries may drop HIB to
IFR visibility this afternoon. It`s more likely they will be VFR
to MVFR in flurries. High clouds will gradually lower tonight
as an westward moving trough approaches from northeast Ontario.
Light snow will accompany that system Wednesday morning.
Visibility in snow should decrease to IFR at HIB and DLH with
MVFR visibility at INL. Snow may not reach BRD or HYR before
19.18Z.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR

Issued at 324 PM CST Tue Feb 18 2025

Downslope winds are forecast over the waters of the North Shore
again tonight. Gusts of 25 to 30 knots are expected and may
reach 35 knots for brief periods. Small Craft Advisories are in
effect.

Warmer air aloft begins to move over the region Wednesday
through the end of the week. Wind speeds and gusts will not be
as strong in general with shallower mixing expected.

A clipper is forecast to move across northern Ontario Friday
and Saturday. The tightening pressure gradient and stronger
winds aloft should create conditions hazardous for smaller craft
starting Friday. There is a small chance of a few gales along
the cold front Friday afternoon and evening.

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

WATCHES/WARNINGS/ADVISORIES

MN…Cold Weather Advisory from midnight tonight to 9 AM CST
Wednesday for MNZ010-011-018-019-026-035-037.
Extreme Cold Warning from midnight tonight to 9 AM CST
Wednesday for MNZ025-033-034-036-038.
WI…Cold Weather Advisory from midnight tonight to 9 AM CST
Wednesday for WIZ002>004-008-009.
Extreme Cold Warning from midnight tonight to 9 AM CST
Wednesday for WIZ001-006-007.
MARINE…Small Craft Advisory until 10 AM CST Wednesday for LSZ140>142.