By Meteorologist Tom Skilling
Were it mid March--more than a month later than it actually is--the near 50-degree high predicted Friday afternoon would be right at home. Such a reading is equal to Chicago's normal high on March 23!
But it's not March--we're still trudging through February. A 48-degree high, like the one predicted at the official O'Hare thermometer Friday, will be 12-degrees ABOVE normal.
A host of factors contribute to abnormal warmth this time of year. High latitude blocking, known to force cold arctic air bodily southward into the Lower 48, has been a "no-show" this winter--a development in marked contrast to the pattern which dominated the past four winters.
In addition, sunlight is pouring down on bare ground because of this season's frequent lack of snow cover. With just 10 days this winter with a snowpack of an inch or more compared to 67 such days a year ago, the chance for incoming sunlight to warm ground level air has increased dramatically this season. This winter has recorded the smallest number of snow-covered days in the 63 years since the 8 days recorded in the winter of 1948-49.
Snow can reflect as much as 90 percent of incoming energy back into space, whereas non-snow-covered ground actually enhances lower atmospheric heating. When snow is absent, the dark colored ground heats more than snow does, allowing it to transfer warmth to the layer of air immediately above it.
In addition, Friday will see 94 minutes more sunlight than back on Dec 21, the northern hemisphere's shortest day. That plus the sun's daily trek across the sky farther above the horizon this time of year means the sunlight reaching the city has more than doubled in strength.
Lakefront and Gary reach 50-degrees Thursday; 109 of the past 141 years have seen an official 50-degree high in the city by February 17
Temperatures Thursday hit 50-degrees at both the lakefront and in Gary. O'Hare and Midway recorded 47-degree highs.
A review of Chicago's weather records indicates 50-degree temperatures by this date in February aren't rare at all. 109 of the past 141 winters--77 percent of them--have generated a 50-degree temperature by now.
Warmer temperatures creeping ever closer
The average first dates of 60 and 70-degree temperatures have been edging closer as well. Since 1870, the city's first 60-degree temperature has occurred on or about March 2 while the Chicago's first official 70-degree temperature has taken place on or about March 31.
Storm to spin up over the western Gulf; drenching rains, an outbreak of severe weather and the threat of heavy snow are all threats accompanying this storm
A wet storm is to take shape in the western Gulf Friday and Friday night, then track northeast toward the central Appalachians. Its impact on Gulf States and Southeast region weather will be considerable with as much as 4 inches of rain falling by the weekend in some locations. Severe weather becomes will be a threat across the Southeast this weekend and a ribbon of accumulating snow may assemble on the storm's north side in the mountains of West Virginia, Maryland and southern Pennsylvania.
Forecasters in Mid-Atlantic cities, including Washington D.C, Philadelphia and New York, are monitoring this storm closely.
Storm's interaction with a chilly Canadian high could set up lake clouds, flurries and possible snow showers here later Saturday into Sunday
Though the storm's direct precipitation will stay well south of Chicago, the metro area may not completely escape some impact from the system's reach. A north to northeast wind flow is to come together between the intensifying storm system and a sprawling Canadian high pressure to this area's west and north later Saturday into Sunday. This could produce clouds and possible lake-effect snow flurries or snow showers at that time.
A few non-storm related rain or snow showers threaten Friday night into Saturday morning.
Were it mid March--more than a month later than it actually is--the near 50-degree high predicted Friday afternoon would be right at home. Such a reading is equal to Chicago's normal high on March 23!
But it's not March--we're still trudging through February. A 48-degree high, like the one predicted at the official O'Hare thermometer Friday, will be 12-degrees ABOVE normal.
A host of factors contribute to abnormal warmth this time of year. High latitude blocking, known to force cold arctic air bodily southward into the Lower 48, has been a "no-show" this winter--a development in marked contrast to the pattern which dominated the past four winters.
In addition, sunlight is pouring down on bare ground because of this season's frequent lack of snow cover. With just 10 days this winter with a snowpack of an inch or more compared to 67 such days a year ago, the chance for incoming sunlight to warm ground level air has increased dramatically this season. This winter has recorded the smallest number of snow-covered days in the 63 years since the 8 days recorded in the winter of 1948-49.
Snow can reflect as much as 90 percent of incoming energy back into space, whereas non-snow-covered ground actually enhances lower atmospheric heating. When snow is absent, the dark colored ground heats more than snow does, allowing it to transfer warmth to the layer of air immediately above it.
In addition, Friday will see 94 minutes more sunlight than back on Dec 21, the northern hemisphere's shortest day. That plus the sun's daily trek across the sky farther above the horizon this time of year means the sunlight reaching the city has more than doubled in strength.
Lakefront and Gary reach 50-degrees Thursday; 109 of the past 141 years have seen an official 50-degree high in the city by February 17
Temperatures Thursday hit 50-degrees at both the lakefront and in Gary. O'Hare and Midway recorded 47-degree highs.
A review of Chicago's weather records indicates 50-degree temperatures by this date in February aren't rare at all. 109 of the past 141 winters--77 percent of them--have generated a 50-degree temperature by now.
Warmer temperatures creeping ever closer
The average first dates of 60 and 70-degree temperatures have been edging closer as well. Since 1870, the city's first 60-degree temperature has occurred on or about March 2 while the Chicago's first official 70-degree temperature has taken place on or about March 31.
Storm to spin up over the western Gulf; drenching rains, an outbreak of severe weather and the threat of heavy snow are all threats accompanying this storm
A wet storm is to take shape in the western Gulf Friday and Friday night, then track northeast toward the central Appalachians. Its impact on Gulf States and Southeast region weather will be considerable with as much as 4 inches of rain falling by the weekend in some locations. Severe weather becomes will be a threat across the Southeast this weekend and a ribbon of accumulating snow may assemble on the storm's north side in the mountains of West Virginia, Maryland and southern Pennsylvania.
Forecasters in Mid-Atlantic cities, including Washington D.C, Philadelphia and New York, are monitoring this storm closely.
Storm's interaction with a chilly Canadian high could set up lake clouds, flurries and possible snow showers here later Saturday into Sunday
Though the storm's direct precipitation will stay well south of Chicago, the metro area may not completely escape some impact from the system's reach. A north to northeast wind flow is to come together between the intensifying storm system and a sprawling Canadian high pressure to this area's west and north later Saturday into Sunday. This could produce clouds and possible lake-effect snow flurries or snow showers at that time.
A few non-storm related rain or snow showers threaten Friday night into Saturday morning.
