Major Winter Storm/Blizzard, February 23-25, 2007

South central and southeast Wisconsin experienced two rounds of hazardous winter weather during the weekend of February 23-25, 2007...or Friday evening the 23rd through early Sunday morning the 25th.
Round 1- Winter Storm occurred Friday night into early Saturday morning...6 PM Friday To 6 AM Saturday

Ahead of a developing low pressure system over the Rocky Mountains, snow spread across south central and southeast Wisconsin right after sunset Friday.  Accumulations ranged from 2 to 5 inches south of State Highway 18.  North of Highway 18, winter storm conditions developed.  Accumulations ranged from 5 to 8.5 inches.  This snow was more on the dry side with snow to water ratios of 13 to 15 to 1.  For reference, a 10 to 1 ratio means that one inch of snow would melt to .10 inch of liquid.   A lower ratio means a wetter snow, a higher ratio means a drier snow.

Snowfall Friday Night
6 PM Fri - 6 AM Sat

The maximum accumulation of 8.5 inches occurred in Germantown and a couple of miles south of Berlin in eastern Green Lake county.  Milwaukee's Mitchell International Airport measured 4.7 inches and Madison's Truax Field measured 7.0 inches.

Round 2- Blizzard occurred Saturday night into early Sunday...6 PM Saturday to 4 AM Sunday

As the strong low pressure system moved from Kansas through northern Missouri to western Illinois, BLIZZARD conditions developed between 6 PM and 8 PM across most of south central and southeast Wisconsin. The blizzard conditions persisted, especially in open areas, through about 1 AM to 4 AM Sunday, February 25th. 

Blizzard conditions were not observed in the counties of Racine and Kenosha.  Additionally, blizzard conditions were not observed within 5 miles of the Lake Michigan shoreline in the counties of Sheboygan, Ozaukee and Milwaukee.

Periods of moderate to heavy snow and thundersnow, along with east winds frequently gusting to 35 to 45 mph, created the blizzard conditions.  Visibilities were frequently reduced to 1/8 to 1/4 mile, especially in open areas.  Snow drifts of 1 to 4 feet in height developed on some roads, and there were other reports of 5 to 7 foot drifts in some yards.

7' Snow Drift in Beaver Dam 

Snow accumulations from 6 PM Saturday to 6 AM Sunday, in those areas that experienced blizzard conditions, ranged from 6 to 12.5 inches.  The snow was heavy and wet.  The 12.5 inches was measured at the NWS Forecast Office about 3 miles southeast of the village of Sullivan in eastern Jefferson county.

Snowfall Saturday Night 6 PM Sat - 6 AM Sun

2 Day Total 6 PM Fri - 6 AM Mon

3 Day Total 6 PM Fri - 6 AM Tue

Blizzard conditions were observed in the western parts of Sheboygan, Ozaukee and Milwaukee counties.  However, snow and sleet accumulations within a couple of miles of the Lake Michigan shoreline in these counties only ranged from 1 to 3 inches.

A mixture of snow, sleet, freezing rain and rain occurred in the counties of Raince and Kenosha where only winter storm conditions developed.  Snow and sleet accumulations in those two counties ranged from an inch along the Lake Michigan shoreline to 6 inches well inland.  The reason blizzard conditions were not observed in these two counties was because of the sleet, rain and freezing rain that was mixed in with the snow.  The mixed precipitation kept visibilities in the 1 to 2 mile range in these counties, which is above the 1/4 mile blizzard criteria.

Peak wind gusts Saturday night include 47 MPH at Racine, 44 MPH at Milwaukee, 40 MPH at Mineral Point, 39 MPH at Janesville, 38 MPH at Madison, 38 MPH at Sheboygan and 38 MPH at Monroe.

The wind gusts and visibilities did meet or exceed blizzard criteria Saturday night for 6 to 9 hours.

Below are a few images of how this snow impacted the NWS Milwaukee/Sullivan office.  Drifting snow to 3 1/2 feet blocked the entrance to our office.  Forecasters and other members of the staff were stranded at the office due to the hazardous road conditions across rural Jefferson county.  Sleeping quarters were set up in our conference room.

Snowfall Behind Office

Snowfall At Entrance

Camp MKX

At about 3 AM to 4 AM Sunday morning, the wind gusts diminished below blizzard criteria and as a result, visibilities in open areas improved above blizzard criteria.  At that point, the blizzard warning was changed to a winter storm warning.

...HOW A BLIZZARD IS DEFINED...

   - FOR 3 HOURS OR MORE...
         - SUSTAINED WINDS OR FREQUENT WIND GUSTS 35 MPH OR HIGHER
         - VISIBILITIES FREQUENTLY BELOW 1/4 MILE
         - FALLING SNOW AND BLOWING SNOW...OR JUST BLOWING SNOW

Note that temperatures and snow accumulation are not considered in the definition of a blizzard.

Below is a text listing of storm total snow amounts from 6 PM Friday through 7 AM Monday. These amounts were taken from a combination of Cooperative Observer, Ham Radio Operator, Trained Spotter and Public reports.