By Meteorologist Tom Skilling
Wednesday's chill---fairly moderate by January standards---is but a taste of what's to come Thursday. It's then that a lobe of arctic air is to bring the Chicago area's its coldest winter temperatures yet. If there's any good news in this, it's that the coldest air, which may includes a period of single-digit temperatures and sub-zero wind chills, will be moderating as a pattern shift this weekend into next week across North America mixes arctic-origin air with chill-moderating maritime air off the Pacific. It's a development expected to send daytime temperatures surging above freezing by Sunday and into early next week.
But, with the West under siege by a series of winter storms expected to hammer the region one after another over the next week, prospects these systems will continue east into the heart of the country raises the potential for a period of accumulating snow Friday afternoon and night, and several additional rounds of rain or a mix of rain and ice pellets Sunday afternoon and Monday.
Week's second surge of arctic air to drop daytime temperatures Thursday to single digits over sections of the area; chills headed below zero
The first of the week's two significant punches of air out of Canada has lowered Wednesday morning's temperatures more than 20-degrees below those observed here 24 hours ago. Wednesday afternoon's highs will be more than 10-degrees colder than Tuesday afternoon.
But the REAL chill is to hit behind a polar front expected to settle across the area toward Thursday morning. The air in that front's wake is take low and mid teen readings early Thursday morning and send them falling into single-digits over sections of the area by afternoon. The moderately gusty northwest winds predicted to deliver Thursday's chill will be enough to propel wind chills lower and into sub-zero territory.
North suburbs and Wisconsin see most of Tuesday's snow; 3 inches reported near Beloit
The arrival of colder air was behind Tuesday's snowfall which proved quite limited in the city. Only 0.2 inches fell at Midway Airport with 0.4 inches measured at O'Hare.
The heaviest area snow tallies occurred northwest and north of the city with the Beloit area reporting a 3-inch accumulation and Belvidere checking in with 2.5 inches. Two inches fell at Winnebago and Galena while Kenosha picked up 1.6 inches and Racine, WI was covered by a fresh 1.2-inch layer of snow. The heaviest accumulation to occur in the region was the 3.5 inches reported west of Milwaukee at Waukesha.
Tuesday's 0.4 inches at O'Hare only the 7th measurable snow this season---half the average!
Tuesday's light but measurable snowfall in the city marked only the 7th time this winter season measurable snow has occurred. That's half last year's tally of 14 measurable snows by this date and nearly half the average of 13 measurable snowfalls the past 14 years.
Model snowfall projections on possible late-week system vary, but all suggest some accumulation; exact amount hard to call yet
The disturbance expected to initiate snowfall Friday afternoon and night is an offshoot of a powerful series of storms which are lambasting the Northwest as part of what's referred to as the "Pineapple Express" pattern. The pattern derives its name from the huge expanse of moisture it sends toward and into North America originating over the tropical Pacific not far from Hawaii---a state known for, among other things, its pineapple production.
"Pineapple Express" storms to produce coastal and "upslope" rains topping 1 foot and 5+ ft. mountaintop snows
Wave after wave of rainfall over the next week is to drench sections of northern California, Oregon and Washington with more than a foot of rain in the hardest hit areas while snowfall up against and in the mountains along the coast and into the northern Rockies could exceed 5 feet. Forecasters are warning residents of the region of potential flooding and an extreme avalanche risk as a result.
Seattle could see a season's worth of snow in a single storm
With some sections of Seattle, where just 5.9 inches of snow falls in a typical season, expecting a foot or more, that city could be in line for its heaviest snowfall in decades!
Could the winter's first Greenland Block be on the way longer range?
Global computer forecast models, which are predicting milder overall temperatures across a huge swath over North America over the 7 to 14 day period, are also indicating the build-up of a warm pool of air over Greenland and northeastern North America late in that period. Warmth there often forces cold arctic air south into the Lower 48. For that reason, prospects of the so-called Greenland Block possibly reconstituting itself, even if for a limited period of time, could signal that a temperature downturn may be brewing later this month and/or going into February. That wouldn't be hard to envision given the build-up of a bitterly cold air mass predicted to take place over Alaska and the Yukon in the coming two weeks. It's not at all unusual for such cold air to eventually find its way into the Lower 48.
Wednesday's chill---fairly moderate by January standards---is but a taste of what's to come Thursday. It's then that a lobe of arctic air is to bring the Chicago area's its coldest winter temperatures yet. If there's any good news in this, it's that the coldest air, which may includes a period of single-digit temperatures and sub-zero wind chills, will be moderating as a pattern shift this weekend into next week across North America mixes arctic-origin air with chill-moderating maritime air off the Pacific. It's a development expected to send daytime temperatures surging above freezing by Sunday and into early next week.
But, with the West under siege by a series of winter storms expected to hammer the region one after another over the next week, prospects these systems will continue east into the heart of the country raises the potential for a period of accumulating snow Friday afternoon and night, and several additional rounds of rain or a mix of rain and ice pellets Sunday afternoon and Monday.
Week's second surge of arctic air to drop daytime temperatures Thursday to single digits over sections of the area; chills headed below zero
The first of the week's two significant punches of air out of Canada has lowered Wednesday morning's temperatures more than 20-degrees below those observed here 24 hours ago. Wednesday afternoon's highs will be more than 10-degrees colder than Tuesday afternoon.
But the REAL chill is to hit behind a polar front expected to settle across the area toward Thursday morning. The air in that front's wake is take low and mid teen readings early Thursday morning and send them falling into single-digits over sections of the area by afternoon. The moderately gusty northwest winds predicted to deliver Thursday's chill will be enough to propel wind chills lower and into sub-zero territory.
North suburbs and Wisconsin see most of Tuesday's snow; 3 inches reported near Beloit
The arrival of colder air was behind Tuesday's snowfall which proved quite limited in the city. Only 0.2 inches fell at Midway Airport with 0.4 inches measured at O'Hare.
The heaviest area snow tallies occurred northwest and north of the city with the Beloit area reporting a 3-inch accumulation and Belvidere checking in with 2.5 inches. Two inches fell at Winnebago and Galena while Kenosha picked up 1.6 inches and Racine, WI was covered by a fresh 1.2-inch layer of snow. The heaviest accumulation to occur in the region was the 3.5 inches reported west of Milwaukee at Waukesha.
Tuesday's 0.4 inches at O'Hare only the 7th measurable snow this season---half the average!
Tuesday's light but measurable snowfall in the city marked only the 7th time this winter season measurable snow has occurred. That's half last year's tally of 14 measurable snows by this date and nearly half the average of 13 measurable snowfalls the past 14 years.
Model snowfall projections on possible late-week system vary, but all suggest some accumulation; exact amount hard to call yet
The disturbance expected to initiate snowfall Friday afternoon and night is an offshoot of a powerful series of storms which are lambasting the Northwest as part of what's referred to as the "Pineapple Express" pattern. The pattern derives its name from the huge expanse of moisture it sends toward and into North America originating over the tropical Pacific not far from Hawaii---a state known for, among other things, its pineapple production.
"Pineapple Express" storms to produce coastal and "upslope" rains topping 1 foot and 5+ ft. mountaintop snows
Wave after wave of rainfall over the next week is to drench sections of northern California, Oregon and Washington with more than a foot of rain in the hardest hit areas while snowfall up against and in the mountains along the coast and into the northern Rockies could exceed 5 feet. Forecasters are warning residents of the region of potential flooding and an extreme avalanche risk as a result.
Seattle could see a season's worth of snow in a single storm
With some sections of Seattle, where just 5.9 inches of snow falls in a typical season, expecting a foot or more, that city could be in line for its heaviest snowfall in decades!
Could the winter's first Greenland Block be on the way longer range?
Global computer forecast models, which are predicting milder overall temperatures across a huge swath over North America over the 7 to 14 day period, are also indicating the build-up of a warm pool of air over Greenland and northeastern North America late in that period. Warmth there often forces cold arctic air south into the Lower 48. For that reason, prospects of the so-called Greenland Block possibly reconstituting itself, even if for a limited period of time, could signal that a temperature downturn may be brewing later this month and/or going into February. That wouldn't be hard to envision given the build-up of a bitterly cold air mass predicted to take place over Alaska and the Yukon in the coming two weeks. It's not at all unusual for such cold air to eventually find its way into the Lower 48.
