014
FZUS81 KCLE 041825
ICEGL

GREAT LAKES FREEZE-UP OUTLOOK
NATIONAL WEATHER SERVICE CLEVELAND OH
126 PM EST Thu Dec 4 2025


...Great Lakes Ice Season for 2025-2026 expected to Be Near Average
Ice Cover...


For this issuance, we will keep the outlook at near average for the
seasonal ice coverage despite the recent cold snap across all of the
Great Lakes.


Over the past couple of weeks, the longwave pattern has set up so
that colder airmasses are easily and frequently dropping into the
Great Lakes region with colder than normal conditions area wide. It
has also been characteristic of intense low pressure systems with
frequent gales for all of the Great Lakes, and even storm conditions
at times for some of the lakes as well. During these events, surface
water temperatures have responded accordingly to the more
active/colder weather and winds in terms of heat removal, and we
will see this continue tonight into December 5th in the wake of an
Arctic cold front and another reinforcement of very cold air. As a
result, efficient temperature drops over all of the lake waters have
been observed as we head into December. General lake water
temperatures are in the 40s for all of the lakes with colder waters
along much of the coastlines in the 30s. Areas of the northern Great
Lakes are showing these coastlines, smaller bays, and smaller inlets
with temperatures that are now supportive of freezing with continued
cold air outbreaks. Satellite data is showing minor shoreline ice
formation in Big Bay/Little Bay de Noc and down into the southern
end of Green Bay with the majority of water temperatures in the mid
30s. The St. Marys River also sits in the low to mid 30s.

With the colder pattern, the lakes are still trending above average
on the whole for early December, with Lakes Superior and Michigan at
2-3F above average, while Lakes Huron and Erie are around 1F above
average. Saginaw Bay on Lake Huron is also down into the mid 30s,
and the shallow western basin of Lake Erie is in the mid to upper
30s. Sandusky Bay, a large and very shallow area of Lake Erie, is
showing signs of ice formation as well along the shorelines.

Over the next couple of weeks, there does not appear to be much in
the way of changes to the overall weather patterns for the Great
Lakes with the colder trend persisting. Long range model ensembles
are pointing to weak upper level ridging over the
southwestern/southern Pacific coast of the United States, pairing up
with upper level troughing over the eastern third of the continent.
This set up in the pattern aloft will continue to allow colder
airmasses to spill into the Great Lakes heading into mid December.
Opportunities for holding back additional surface water cooling will
be few and far between, meaning mild spells are not anticipated, and
if they do occur in the next couple of weeks, they will be very
short lived. Overall, significant ice formation outside of the bays
and inlets and St. Marys River is not expected as water temperatures
in the open waters are still too warm for now. Otherwise, expect
shoreline ice to increase, and smaller bays and inlets will likely
start to freeze with subfreezing weather.


Ice formation is determined by two factors: The amount of heat
stored in the water from the summer and how fast that heat can be
removed by arctic outbreaks of Polar/Arctic air and high winds. Long
range outlooks do not consider the "storminess" factor which can
significantly alter the thermal structure of the lakes over short
periods of time.


        Temperature  Forecasts for Selected Cities

 Location   12/04   12/05   12/06   12/07   12/08   12/09
   Duluth  -4  15  10  26   5  14   1  14   5  19  10  23
Marquette  10  19  12  28  17  23  12  21  12  24  17  26
 GreenBay  -1  12   5  24  12  23   8  21   8  23  14  26
Milwaukee   1  14   6  24  17  26  14  26  14  26  17  32
  Chicago   8  19   8  28  21  30  23  30  19  28  23  33
 Muskegon  17  28  17  32  26  32  19  28  15  30  21  32
   Alpena  12  21  14  28  21  30  14  23  12  26  17  28
  Detroit  17  23  10  26  19  33  19  28  15  28  17  30
   Toledo  17  23   6  24  19  30  19  28  15  26  15  30
Cleveland  23  30  12  32  23  35  26  33  23  30  19  33
  Buffalo   21  28  12  32  24  35  21  28  14  26  15  30


FREEZING DEGREE DAY ACCUMULATIONS AT SELECTED STATIONS
COMPARED TO NORMAL CALCULATED ON Tue Dec 2:

LOCATION           DATE   NORMAL CURRENT
----------------------------------------

   DULUTH,   MN  DEC    1   93   79
MARQUETTE,   MI  DEC    1   68   55
SAU_S_MAR,   MI  NOV   28    6   10
 GREENBAY,   WI  DEC    1    6   42
MILWAUKEE,   WI  DEC    1    0   22
  CHICAGO,   IL  DEC    1    0   19
 MUSKEGON,   MI  DEC    1    0   12
   ALPENA,   MI  NOV   28    0    6
  DETROIT,   MI  DEC    1    0   10
   TOLEDO,   OH  DEC    1    0   19
CLEVELAND,   OH  DEC    1    0    7
  BUFFALO,   NY  DEC    1    0    7


          Freezing Degree Day Accumulation Forecast

 Location   12/04   12/05   12/06   12/07   12/08   12/09

Duluth       106     120     152     184     209     241
Marquette    73      85      97      113     127     138
GreenBay     74      104     119     140     172     189
Milwaukee    54      83      95      107     119     130
Chicago      51      79      87      93      101     108
Muskegon     22      30      33      42      52      58
Alpena       22      33      40      54      67      77
Detroit      22      36      42      51      62      71
Toledo       31      63      95      127     159     191
Cleveland    13      23      26      29      35      41
Buffalo       15      25      28      36      48      58



THE NEXT FREEZE-UP OUTLOOK WILL BE ISSUED IN APPROXIMATELY TWO WEEKS.

$$

Marsalek