Chicago's mild winter will continue for at least a few more days before a slug of arctic air arrives, bringing the city its coldest weather in nearly three weeks. Temperatures should reach the middle 40s Sunday, and upper 40s on Monday with a few locations likely to reach 50 degrees. Colder air accompanied by some snow showers will arrive on Tuesday, dropping readings to more typical early-February levels in the lower and middle 30s, followed by a reinforcing shot of cold air on Friday with another round of snow showers.
 
Saturday storm splits Chicago area

Substantial rainfall with a total approaching one half-inch at Romeoville soaked southern portions of the Chicago Metro area Friday night and Saturday, while little if any rain fell across the north. In addition the rain changed to snow over the far southern and Indiana portions of the metro area with slushy accumulations ranging from just 0.2 inches at Peotone to an inch at Crown Point and 1.2 inches at Valparaiso. The snow got much heavier to the east in Indiana with up to 7inches blanketing the Fort Wayne area. Heavy snow also fell to the west of Chicago where the same storm brought 9 inches of snow to Des Moines and nearly a foot of snow to Omaha. In Louisiana, the storm's warm southern flank brought more than 3 inches of rain to Alexandria, and spawned a tornado at DeRidder, about 70 miles to the southwest.

Dear Tom,
What is the latest date that Chicago's temperature dropped below zero?
--Richard L. Ettlinger, Highland Park

Dear Richard,
While the heart of Chicago's below-zero season runs from late December to mid-February, the city has logged subzero weather as early as Nov. 23, 1950, (minus 1) and as late as March 22, 1888, (minus 1). Subzero weather in March is rare having occurred only 15 times in 141 years dating back to 1871, with all but three of the occurrences falling between March 1 and March 8. During the final stages of the winter of 2001-02, when it appeared that the city was headed for its first winter without subzero temperatures since 1982-83, frigid air arrived in the wake of a 10-inch snowstorm March 1-3 and the mercury plunged to minus 7 on March 4 ---the season's lone subzero day.

by Mike Hamernik   twitter @Mike Hamernik

Rain changed over to snow last night on the northern fringe of a large precipitiation shield that still stretches from Texas to the Midwest.  The majority of the rain, snow and sleet fell along and south of the I-88/Eisenhower corridor.  While there was little or no accumulation in northeast Illinois, the snow did stick just to the southeast of Chicago.

Fort Wayne hit the hardest

Over six inches of snow fell in Fort Wayne, Indiana this morning.  As of 8AM, radar indicates the heaviest snow has shifted east into Ohio.  Periods of light rain and snow will persists this afternoon, mainly along and south of Interstate 80.  However any additional accumulation will be limited to one inch or less.  Recent snowfall reports include:

6.8"  Fort Wayne, IN

5.5"  Columbia City, IN

1.2"  Valparaiso, IN

1.0" Crown Point

0.9"  La Porte, IN

0.6"  South Bend, IN

0.6"  Crete, IL

0.4"  Homewood, IL

0.2"  Peotone, IL

TOP RIGHT: A wet, slushy snow in Akron, Indiana.

TOP BOTTOM: Parkview Field in Fort Wayne, Indana.

By Meteorologist Tom Skilling

    Prospects that sunshine may manage to break through Saturday's thick morning clouds increase during the day. The gray open, which could produce patchy light rain or ice pellets in some areas south of the city, is the product of moisture streaming off a huge winter storm responsible for burying sections of Colorado's Front Range under a huge accumulation of snow. As much as four feet fell there Friday and wind-blown 12+inch snow accumulations extended east into portions of Nebraska.
     Any other eastbound storm with a center over southwest Missouri Saturday morning, might be expected to bring the Chicago area a healthy dose of precipitation.  But, some of this storm's energy is being deflected south in a gradually dissipating state across downstate Illinois and Indiana by what meteorologists refer to as a "blocking pattern" over the Rockies.
    Such a pattern allows some of the storm's energy to propagate eastward--but locks a pool of cold air, around which upper winds spin--producing the "lift" which creates the storm in the first place--farther west.  The result is, the initial surge of eastbound energy, responsible for clouds and precipitation, eventually shears away from its primary energy source and begins to lose strength.
    While precipitation continues for a while in such an environment, eventually, the area of rain and snow begins to shrink in areal coverage and intensity.
     It's at that point northwest upper winds coming into the Chicago area are to begin importing milder, drier Pacific air, encouraging clouds to break and daytime sunshine to emerge. The slow clearing will permit sunshine to appear first in northern suburbs then settle into other sections of the metro area Saturday afternoon as precipitation shifts downstate.


Northeast winds off Lake Michigan waters to lend Saturday a "chilly" feel lakeside

    Thursday's 39-degree high at O'Hare wasn't "warm"--but it does qualify as "mild' for this time of year.  The reading exceeded the date's "normal" high by 7-degrees.  And, while northeast winds promise a chill as they flood into the area off mid 30-degree lake waters, the appearance of some mixed sun and complete lack of snow cover bodes well for some highs in the 40s away from the lake Saturday--the 14th consecutive day of above normal temperatures!
     This process is to accelerate Sunday as the northeast flow weakens and even more sunshine follows the exit of possible early clouds. 
    By Monday, gusty southwest winds and compressional warming ahead of a southbound cold front, expected to pass late Monday night, could push temperatures within striking distance of 50-degrees in typically warmer locations.


Winter 2011-12 now the mildest to date here in 80 years
 
      Chicago's average meteorological Winter 2011-12 temperature from Dec. 1 through Friday, February 3, has reached 32.9-degrees, making this the mildest meteorological winter period in Chicago of the past 80 years!  The reading ranks 9th warmest of 141 comparable meteorological winter periods on record since 1871 and places this winter among the warmest 6 percent on record here since 1870. The temperature is 6.6-degrees milder than the long term average and over 11-degrees warmer than a year ago.


Greenland Blocking, noticeably absent thus far this season, looms big-time on latest global model runs later next week into Week #2; that's a "cold signal" for the Midwest

      The potential that winter is may still target the Chicago area with cold air has received a big boost from global computer model runs in recent days. Not one, but a suite of these forecasts are now predicting strong warming over Greenland and the North Atlantic in the next 1-2 weeks.
    The appearance of unseasonably mild air aloft there hints strongly that the winter season's first truly significant round of blocking--a "cold signal" for the Midwest--could be the harbinger of a temperature downturn of some import later next week and beyond.
    The first punch of blustery cold air is to hit behind a southbound cold front late Monday night.  But what follows late in the week and the following weekend could be significantly stronger. We'll keep you posted!


Plains & Denver area hit hard by blizzard while another snowstorm sweeps southern Alaska; Anchorage's seasonal tally tops 100 inches--twice normal; the Valdez total passes 337 inches
 
     Midwest snowfall tallies may be running far below recent years, but any snow drought is noticeably absent in the Plains and Colorado Rockies after the area was hit by heavy snows Friday.  In the Denver area, as much as 4 feet of snow buried nearby Front Slope communities.  Denver itself measured 13 inches of snow--but observers in nearby Blackhawk reported a 48 inch accumulation.
     Even more extraordinary are seasonal snow tallies being reported out of southern Alaska--a region hit by yet another snowstorm Friday. Up to 18 inches of snow was predicted in sections of the Anchorage area of south-central Alaska.  There the 2011-12 seasonal total has reached 100.9-inches--nearly twice the normal of 50.7-inches to date. Even more noteworthy is Valdez, Alaska's 337.4-inch seasonal total to date. There, normal winter snowfall through February 3 is just 199.8-inches.


Deadly European/Russian cold wave rolls on; temps dip 20-30-below; 101 dead in Ukraine alone; concerns about natural gas supplies
 
      The deadly European/Russian cold wave continued unabated Friday with concerns Russian natural gas supplies were being cut to European countries because of increased domestic usage. The death toll for the region was cited at more than 220 by some news agencies there--with 101 deaths reported in the Ukraine alone.
    Snowfall in Rome was the heaviest since the 1980s and a foot of snow is reported to have accumulated over recent days in Istanbul, Turkey. 
    Western Russian and eastern European temperatures have dropped to under 30-below zero in recent nights.

Dear Tom,

A friend in North Pole, Alaska, (260 miles north of Anchorage), indicated the temperature was 51 degrees below zero and at the same time a weather observation at nearby Eielson Air Force Base reported light drizzle. Can drizzle occur at that temperature? Can that observation be correct?

--Marty Becker, Schaumburg

Dear Marty,

It was an error. Drizzle occurring at 51 degrees below zero should have been reported as freezing drizzle (tiny liquid droplets that freeze upon contact with exposed surfaces). The larger issue is this: Is drizzle even possible at that temperature? The answer, surprisingly, is yes. The surface tension that exists in tiny water droplets is so great that it can prevent the formation of ice crystals even when the droplet is cooled far below the usual freezing point of water (32 degrees) if the droplet is in a calm, undisturbed environment. However, 50 below is pushing the theoretical limit.

This snowy shot was taken at the Steamboat Ski Resort near Steamboat Colorado.

Thanks to Diane for submitting this photo montage depicting the beauty of a foggy, early February morning in Bourbonnais.


Photo by Diane

The ground hog had his day yesterday and his bold prediction of six more weeks of winter doesn't seem like much of a threat.   Most of us could handle six more weeks of the kind of winter we have seen so far.  According to Illinois State Climatologist Jim Angel the average temperature for December/January was 33.4º for Illinois, making it at the 6th warmest December/January period on record going all the way back to 1895.  So Arctic air has been elusive this winter.  There have only been ten days with temperatures below average. Snowfall has been scarce also.  At O'Hare we would normally have 21.5" of snow by now but so far this winter we have picked up just 13.19".

We put our number crunchers to work to see if a a warm winter normally is followed by a hot summer.  We looked at the past 83 winters at Midway for consistency's sake.  Of those 83 winters, 26 had above average temperatures for the months of January and February (like this winter).  15 of those summers (months of June, July & August)  that followed had temperatures above the average of 73.2º. 

We then narrowed it down to summers that followed winters that were well above average.   This winter has been +6.8º above average.  There were four winters at least that warm and three out of the four summers that followed were also warmer than average.

         Year                     above/below avg.

   summer of 1931                   -0.5º

   summer of 1982                  +2.8º

   summer of 2001                  +3.0º

   summer of 2006                  +0.9º

So in conclusion, statistically speaking, there appears to be a correlation between a warm winter and warmer than average summer.  58% of summers following warmer than average winters were also warmer than average. 75% of summers that followed the four warmest winters  (given it is a small sample size) were also warmer than average.

Special thanks to Frank Wachowski & Richard Koeneman for their help.

http://twitter.com/WGNWeatherGuy

http://www.facebook.com