Lake Vermilion Area Weekend Weather UPDATE – January 18-20

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KEY MESSAGES

– A prolonged period of frigid air is expected. Wind Chill temperatures this morning through Tuesday morning will range from -30F to -50F.
– A prolonged period of lake effect snow will occur along portions of the South Shore this weekend into Tuesday.

DISCUSSION

Issued at 335 AM CST Sun Jan 19 2025

Not much to say this morning as we try to conserve warmth. It`s
cold and will remain cold for the next several days. As of 3 AM
temperatures around the Northland were generally in the low
single digits to 20s below zero. Wind chills so far tonight
ranged from around 20 to 50 below zero. Expect the dangerous
wind chills to persist through the next few days. As
temperatures warm diurnally, there will be several hours each
day when there will be improvement in the wind chills. No
changes to the Extreme Cold Warning were made since the overall
message remains the same. Highs today will reach the single
digits to upper teens below zero, except near the Lake Superior
shore in northwest Wisconsin where temperatures may climb above
zero due to onshore flow from the comparatively warm waters.

Lake-effect snow will continue over northeast Douglas, northern
Bayfield, extreme northeast Ashland, and northern Iron counties
in northwest Wisconsin today. Early morning GOES-East Channel
13 (clean window IR) imagery reveals thin and shallow convective
plumes emanating from all of the inland lakes despite their ice
cover. They remain much warmer than the Arctic airmass in
place. It`s likely these clouds are very thin and transparent to
translucent. Once the sun is over the horizon, visible Channel
2 imagery can reveal their depth. We expect to see light
flurries falling across the Northland wherever the thin, low
stratus remains over the next 36 hours.

We received a report from Gile around 1230 AM with 1.1 inches
of snow so far. It`s likely areas in the northwest Wisconsin
snowbelt will see 1-2 inches of fluffy accumulation every 12
hours until the wind direction and temperatures aloft change. By
noon Tuesday, some locations may pick up 3 to 7 inches with a
few spots perhaps seeing as much as 8 inches. The long-duration,
slow accumulation rate, and limited area of accumulation seem
to preclude snow headlines at this time. Once CoCoRaHS, COOP,
and spotter reports start coming in this morning, we may need to
reassess that course of action if snow accumulation is greater
than we expect. With very dry air upstream of Lake Superior, all
of the precipitation is the result of sensible heat and
moisture flux from the short fetch over the southwest arm of the
lake. Temperatures are cold enough to reveal a snow band
downwind from Madeline Island affecting northern Iron County.
Even across that short fetch, there is sufficient heat and
moisture transfer for accumulating snow.

Another cold night on tap tonight with lows from around 19 to
26 below zero. Minimum wind chills will be in the -35 to -50
degree range. Temperatures stay below zero on Monday, perhaps
even colder than today`s highs as another surge of Arctic air
aloft arrives. Look for highs generally from -5 to -15 degrees.
Lows Monday night and Tuesday morning will dip into the -20 to
-30 degree range, with some typically colder spots possible
as cold as -40. Wind chills will bottom out in the -35 to -50
range again.

A pattern change is expected around midweek as a positively
tilted ridge propagates southeastward across the region Tuesday
followed by a shortwave trough on Wednesday. The ridge will back
winds westerly and southwesterly pushing the Arctic air out of
the region to the east. The shortwave trough will bring a chance
of light snow. While the deterministic and ensemble guidance
all have some amount of precipitation over the Northland
Wednesday and Thursday, the guidance has been overly optimistic
with snow chances for the past month or so. There just isn`t
enough moisture advection ahead of the troughs to generate more
than a brief period of light snow. Think that`s the most likely
outcome with the midweek shortwave.

Temperatures will likely climb above zero either Tuesday night
or Wednesday with highs in the teens and low 20s through next
weekend.

AVIATION

Issued at 532 AM CST Sun Jan 19 2025

Very cold conditions expected today. GOES-East Channel 13
(clean window IR) imagery reveals clouds streaming from inland
lakes over northeast Minnesota and upstream into Manitoba and
northwest Ontario (despite their ice cover). These are likely
thin, almost transparent ice clouds given the temperatures
across the region. LAMP and NAM guidance continues to suggest a
period of IFR or MVFR ceilings late this morning into the
afternoon. With the cold air in place and slight moisture
infusion from the inland lakes, diurnal heating may be enough to
generate shallow convection and low ceilings with snow showers.
Confidence in this scenario is not high. Surface obs from 11Z
over southern Manitoba and northwest Ontario show ceilings
around 5kft AGL. Thus have added another cloud layer at that
height at the terminals later today. At HIB a combination of
anthropogenic and inland lake-effect processes continue to
produce low ceilings and visibility. We expect the visibility
reductions are due to light snow and ice crystals. As
temperatures warm later this morning, the ceilings should lift
and may allow the snow and ice crystals to sublimate yielding
VFR visibility.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR

Issued at 335 AM CST Sun Jan 19 2025

Cold and conditions with gusty northwest winds will persist
through Tuesday morning. Wind speeds and gusts will decrease
slightly today as the pressure gradient relaxes slightly and
cold air advection slows. Conditions will remain hazardous for
small craft through Tuesday morning at least. Winds will back
southwesterly on Tuesday and warmer air will move into the
region. On Wednesday evening and Thursday winds will veer
westerly and weaken bringing an end to the hazardous conditions
for a day or two. Stronger winds are forecast to return by the
weekend.

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