Wisconsin Winter Storms & 2010-2011 Winter Outlook

Although the number of winter storms that affect at least a small part of Wisconsin varies from year to year, during the past couple decades Wisconsin has averaged about 12 winter storms each season.  In fact, since the 1982-83 winter season, 4 and 19 have been the minimum and maximum number of winter storms, respectively.

A winter storm, for the purpose of this story, is defined as consisting of one of the following events affecting at least one county:

1. Snow accumulations of 6 inches or more,

2. Blizzard conditions for 3 hours or more - visibility below 1/4 mile due to falling and/or blowing snow with frequent wind gusts 35 mph or higher,

3. Ice accumulations of 1/4 inch or more in 12 hours or less due to freezing rain

4. Sleet accumulations of 2 inches or more in 12 hours or less,

5. Snow accumulations of 3 to 6 inches with sustained winds or frequent gusts of 25-34 mph and intermittent reductions in visibility to less than 1/2 mile resulting in closed roads, etc.

A winter storm affected northwestern Wisconsin on Saturday, November 13th.  This is not unusually early.  In fact, it seems that some part of Wisconsin usually has a winter storm sometime in November, or even October!  A major blizzard-winter storm affected much of Wisconsin December 11-12th.  So far, we've had at least 4 winterstorm systems affect Wisconsin in the 2010-11 winter season.

Date of First Winter Storm in Wisconsin

Winter

Date

Winter

Date

Winter

Date

Winter

Date

82-83

Nov 4-5

90-91

Oct 10

00-01

Oct 6-7

10-11

Nov 13

83-84

Nov 23

91-92

Oct 31

01-02

Oct 25-26

11-12

 

84-85

Dec 1-2

92-93

Nov 1-2

02-03

Oct 20-21

 

 

85-86

Nov 8-9

93-94

Nov 4-5

03-04

Nov 22-24

 

 

86-87

Feb 5

94-95

Nov 27-28

04-05

Nov 27-28

 

 

87-88

Dec 14-15

95-96

Nov 23

05-06

Nov 15-16

 

 

88-89

Nov 5-6

96-97

Nov 9-11

06-07

Oct 11-13

 

 

89-90

Oct 19-20

97-98

Dec 4-5

07-08

Nov 5-6

 

 

 

 

98-99

Nov 15-16

08-09

Nov 6-7

 

 

 

 

99-00

Nov 23-24

09-10

Dec 8-9

 

 

The table above indicates that the first winter storm to affect Wisconsin occurred in November in 15 years, followed by 7 years for October, 4 years for December, and 1 year each for September and February.

Below is a graph showing the number of winter storms to affect Wisconsin each winter season.  

Wi Winter Storm Count

Below is a map showing the general origins of different types of winter storms that affected the city of Milwaukee during the period of 1954 through 2007.  This map would be applicable for any location in southern Wisconsin.  This map was taken from a slide set developed by Bill Borghoff, and is part of a research project he worked on while a Meteorological Intern here at the Milwaukee-Sullivan NWS Forecast Office.  He has since then moved on to the Memphis, TN, NWS Forecast Office as a journey forecaster.

The map shows typical paths of various low pressures after they become organized in different parts of the country. Of course, the exact path of each low pressure will vary.  Alberta Clippers generate the driest snow while Gulf Lows usually have heavy, wet snow.

Winter Storm Types 

Below is an image from Bill's research that shows the exact path of the low pressures that produced major winter storms for Milwaukee, WI.

Exact low pressure paths 


2010-11 Winter Outlook

Click here  to access all of the outlooks produced by the Climate Prediction Center.

La Nina Update

The bullseye of above normal precipitation  chances over the Ohio River Valley is a typical impact of a moderate to strong La Nina, of which a moderate episode is ongoing, and is expected to become a strong event (as defined by the 3 month average Nino 3.4 index of -1.5 degrees Celsius or colder). It is expected to last through at least Spring 2011. Depending on how the temperatures work out in the Midwest, this La Nina may lead to increased chances for above normal snowfall in southern Wisconsin for the December 2010 through February 2011 time period.

Click here for a discussion on the current La Nina event.



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