588
FXUS63 KDLH 311036
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
436 AM CST Fri Jan 31 2025

.KEY MESSAGES...

- Widespread snowfall is expected Saturday afternoon and Sunday
  across the Northland. Confidence remains high for 2 to 5
  inches over most of the area. There is also a 60 to 90 percent
  chance of 6 inches or more along the North Shore due to lake
  and terrain enhancement.

- Colder temperatures return early next week as modified Arctic
  air arrives. Overnight lows will be in the single digits above
  and below zero from Sunday night into at least the middle of
  next week.

&&

.DISCUSSION...
Issued at 436 AM CST Fri Jan 31 2025

Northerly winds and cold air advection in the wake of a
southward moving cold front will bring cooler temperatures
compared to the record and near-record highs from yesterday.
Some locations may have reached their daytime high temperature
shortly after midnight over far northern Minnsota. High pressure
over the Canadian Prairies will drift east-southeastward today.
Look for skies to clear from north to south as drier air
arrives. Mostly clear early tonight before clouds return
overnight. Lows will tumble quickly after sunset over northern
Minnesota with lows in the single digits and teens below zero
possible before clouds arrive and push temperatures warmer.

Attention then shifts to Saturday when a fast-moving low
pressure system will begin to be felt in the Northland.
Widespread snow is forecast from late Saturday morning into
Sunday. There may be a second round of light snow Sunday
afternoon and evening as the system departs. Most of the
precipitation is forecast ahead of the low track. Thaler QG
omega and Q-vector convergence is maximized south of our area
across eastern South Dakota east toward Green Bay. There is
ample moisture aloft for snow. Questions linger regarding
amounts. The difference in snow totals from the North Shore to
central Minnesota is driven almost entirely by lake and terrain
enhancement, which is susceptible to length-of-fetch and
residence time problems. It seems the snow totals in the
Arrowhead have the greatest potential to bust on the low side of
the forecast.

That being said, the NAM, ECMWF, and GFS deterministic 31.00Z
runs all feature a deep nearly isothermal layer in the dendritic
growth zone of -12 to -18 C along the North Shore Saturday
afternoon into Sunday morning. The ECMWF and NAM are closer to
the -12 C side of the zone while the GFS is approximately in the
middle. Deep but modest ascent and marginal supersaturation may
result in snow ratios of 15-20 to 1 for several hours, which
would produce snow rates of 0.5 to 1.0 inches per hour.

No changes to the Winter Storm Watch with this forecast.

There is a potential for a period of freezing drizzle to
develop Sunday as drier air moves in to the mid-levels, thus
reducing ice crystal genesis chances. As the system`s cold front
moves in from the northwest late Sunday morning through Sunday
evening, another period of snow is likely. Additional
accumulation of an inch or two is possible. Total snow for the
event will likely be from 2 to 5 inches for most of the
Northland with higher amounts in the 5 to 8 inch range for the
Arrowhead. A few spots may see as much as 10 inches of snow
(about a 30% chance), though that depends on the perfect
alignment of lift and dendritic growth with sufficient sensible
heat and moisture flux from Lake Superior.

Modified Arctic air arrives in the wake of the clipper and will
drop temps below normal for the first half of the work week.
Highs will be in the teens and single digits above zero while
overnight lows fall into the single digits above zero to the
teens below zero.

A shortwave trough is forecast to move across the region
Tuesday into Wednesday which will bring another chance of light
snow.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1052 PM CST Thu Jan 30 2025

VFR conditions with increasing chances for MVFR ceilings
tonight into Friday morning as a cold front drops south tonight.
There will be some MVFR ceilings that develop along and behind
it for several hours. Some flurries or light snow could
accompany the MVFR ceilings. There also are some indications
some fog may develop. The possible fog and ceilings will lift
to mostly VFR conditions through the day Friday. The exception
will be in northern Wisconsin which will see lake processes
develop Friday leading to more MVFR ceilings and some flurries
or light snow under northerly winds.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 436 AM CST Fri Jan 31 2025

Winds will veer northwesterly over western Lake Superior by
sunrise and wind speeds will increase to 10 to 20 knots by noon
CST. The long fetch over western Lake Superior from near the
southern shore of Isle Royale to the south shore of Northwest
Wisconsin will result in waves building to 2 to 5 feet. A Small
Craft Advisory remains in effect for the Outer Apostle Islands
and from Oak Point to Saxon Harbor from late this morning until
early evening when winds and waves will decrease.

Winds veer easterly and southeasterly by Saturday morning ahead
of an approaching low pressure system. The fast-moving clipper
will increase wind speeds and gusts Saturday afternoon and
evening. Conditions will become hazardous for smaller vessels
over much of the waters. There is a small chance of gales from
Grand Portage to Grand Marais Saturday afternoon and evening.
Additional Small Craft Advisories will be needed.

Snow, heavy at times, is forecast Saturday afternoon through
Sunday. Visibility will be less than 1 mile at times in heavy
snow.

Winds will back northwesterly and strengthen again Sunday. Cold
air advection will increase the risk of gales Sunday night and
Monday morning along the North Shore due to downslope processes.
Heavy freezing spray remains a risk as the colder modified
Arctic air pours into the region Monday.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Winter Storm Watch from Saturday afternoon through late
     Saturday night for MNZ020-021.
WI...None.
MARINE...Small Craft Advisory from 10 AM this morning to 6 PM CST this
     evening for LSZ148-150.

&&

$$

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