WGN Weather Center Blog

Late-season arctic air is on the move Tuesday evan as meteorological spring and March 2005 get underway. The chill is setting in motion a late-season snowstorm which could linger into Wednesday in sections of the Indiana and Michigan snowbelt, centered on LaPorte and Berrien counties to Chicago’s east. With bursts of lake-effect snow likely to continue there for 30 or more hours, accumulations in excess of one foot aren’t out of the question—and a few of the hardest-hit locations could see as much as 20”. The fluffy snow is to be whipped by gusts to 30 m.p.h. at times—a situation which could produce local white-out conditions. Lighter amounts will occur just west in Porter County, Ind. And, the Chicago area can expect spells of flurries Tuesday with most accumulations on the order of a dusting. Longer days and stronger sunlight will keep this cold outbreak from producing the 0° temps which might have occurred in a similar air mass just two months ago.

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For the second week in a row, Chicago is missing a major snowstorm. While no more than an inch or two of wet snow is expected here, much of the Northeast is girding for its third major snowfall in just a little more than a week. A classic nor’easter will bury much of the populace there with a foot or more of snow, while areas just to our east in Northwest Indiana and southwest Lower Michigan will get a similar amount of lake-effect snow as a late-season arctic blast invades the Midwest following the storm.
Though Chicago will miss most of the snow, cold weather will be in ample supply here, with temperatures this week well below the typical lower 40º days Chicagoans can usually expect around the start of meteorological spring. Tuesday and Wednesday should be the week’s coldest days with highs remaining in the 20s with a small rebound into the 30s forecast by the end of the week.

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In a bit of meteorological irony, a mild winter—where December, January and February all logged above normal temperatures—is going to end with cold and snow. February has by far been the mildest of the three meteorological winter months, though its once massive 10-12º temp surplus has whittled away to a still very impressive 6º above normal.
As March prepares to open, a surge of polar air will send temperatures tumbling after today’s mild high in the lower 40s. Maximum temperatures will be limited to the lower 30s on Monday, and the middle and upper 20s on March’s opening days. The chill, coupled with brisk northwest winds and periods of snow showers will be anything but spring like. Not much improvement is expected the rest of the week with highs rebounding only into the 30s, along with the possibility of more snow by the end of the week.

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It’s the fourteenth and final weekend of “meteorological” winter. The season, with just three days remaining, extends from December through February. The deceptively quiet weather pattern now in place masks a significant change in the upper winds which is getting underway. For much of the winter, west winds have dominated, bathing the region is mild temps. The fast fading season has produced weekends with temperatures which have paralleled that trend. Winter weekends have finished milder than normal 64% of the time since early December.
Chicagoans were treated to the 12th February day of temps 40° or higher Friday—and a 13th is predicted Sunday. But big changes lie ahead including surges of cold air, anyone of which could produce sticking snow.
Though chilly temps are predicted overall through mid-March, the month has been known to host mild air. March weather records reveal an average of twelve days at or above 50°—six of them over 60°.
-Tom Skilling

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When the books close Monday night on the three month meteorological winter period, temperature surpluses are likely almost from coast to coast. It’s been mild enough here in Chicago—hard to fathom given often chilly daytime temps in recent weeks, but true—that the demand for home heating is likely to finish 8% lower than normal and 6% below a year ago. The period since Dec. 1 has run 2.5° milder than the same period a year ago.
Snow socked the major mid-Atlantic cities Thursday and Thursday night. Visibilities at New York’s JFK and LGA airports dropped to a quarter mile in heavy snow for several hours at the height of the afternoon/evening rush hour. As much as 5-9” was expected to fall in the hardest hit areas from Philadelphia north to Boston before snows move out to sea early Friday. Washington, D.C. sat beneath a new 4” veil of snow Thursday evening.

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Chicago sits on the severe weather sidelines Thursday. Flurries may occur both early and again later in the day. But, it’s the East Coast’s “BosNYWash” corridor—the heavily populated stretch of territory from Boston south to New York, Philadelphia and Washington, D.C.—under the weather gun and expecting healthy snow accumulations by the time Thursday night ends.

For the first time since last Thursday, southern California faces no additional flooding. There are signs this reprieve may be a short one. Computer models hint that another wet system may be on the way late this weekend into next week. That news comes just as Los Angeles establishes a new seasonal rain benchmark. The 33.87” of rain on the books since July 1—more than triple the 10.15” dubbed “normal”—is the largest seasonal rain tally there since the 1889-90 season. It’s makes this the third wettest water year on record and puts the area 4.31” short of the all time record.

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Californians and other waterlogged residents of the Southwest have been at the mercy since last Thursday of driving downpours produced by an all-but-stationary storm system. A relatively infrequent jet stream orientation in the region has led to the system’s incredibly sluggish movement. Referred to as a “rex block” by meteorologists, the storm-slowing pattern features a pool of warm air to the north of the storm which separates high altitude steering winds into two distinct bands. The storm stalls in the much calmer air between as pressures build to the east. It’s a set-up which has subjected the Southwest to repeated waves of rainfall—including downpour-generating t-storms—for days. A rare tornado watch covered southern California Tuesday. 5-day rain totals reached 21” at Opids Camp in the mountains surrounding Los Angeles. L.A.’s 10.24” for February, 2005 is more than all the rain of the past three February’s combined.
-Tom Skilling

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This past weekend’s damp, overcast weather spilled over into Monday. Chicago recorded none of its possible sunshine Sunday and Monday—allowing February’s overall sunshine to slip to just 42%. Though sun won’t be completely absent in coming days, the lackluster 42% tally strongly suggests the month may be headed for its lowest percent of possible sunshine of any February since 1999.
Snow, with the same storm which only sideswiped Chicago over the weekend, hit New York City late Sunday into Monday morning, producing 5” of snow in Central Park—but as much as 8” of snow to the city’s north in Montgomery.
A twister touched down in Sacramento, Calif., Monday—part of the same storm which has swamped the state since late Thursday. In Hollywood late Monday, all lanes of Freeway 101 were shutdown near Sunset Boulevard due to the standing water left by driving rains.

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Chicagoans awoke to a 1 to 2 inch snowfall Sunday then watched it quickly turn to slush as temperatures warmed into the middle and upper 30s and a steady rain moved into the area. However, residents of southeast Wisconsin were digging out of a 4-8” snowfall that targeted areas from Milwaukee north as the storm system responsible for the precipitation shifted its track further north than was expected, sparing Chicago a major snowfall.
A rather cold week appears in the offing for this area with daily highs hovering in the lower and middle 30s. Other than some passing snow flurries later in the week, dry weather is expected. This is in sharp contrast to the plight of Southern California, where a Pacific storm of epic proportions continues to bring waves of heavy precipitation ashore.

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Until this morning, Chicago’s ground had been snow-free for nearly 10 days since the last of January’s ample 28 inch snowfall total melted away earlier this month. This morning’s snowfall was expected to total from 1 to 3 inches south of the city to up to 6 inches north of Chicago near the Wisconsin state line rewhitening the area’s landscape. However, warmer air moving into the region, both surface and aloft, should turn the snow to a slushy mess this afternoon as precipitation changes to light rain and drizzle. With Sunday afternoon highs reaching the upper 30s, much of the newly fallen snow should melt away.

Weekend storms continue to pound southern California, where torrential rains are causing flooding and mudslides and in the higher elevations of the Sierra Nevada the already impressive snow pack is expected to increase by at least another two feet.

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Much could change in the predictions of snowfall Saturday night and Sunday. It appears four or more inches is a good bet from Chicago north. But, it’s possible at least sections of the Chicago metro area may see as much or more snow with an incoming storm than the 6.5” which fell in the entire month of February a year ago. “Big” snows (i.e. snowfalls of 6” or more) have been in short supply for decades during the latter half of February. Since 1970, the month’s final two weeks have hosted only three half foot or greater accumulations. The total amount of snow measured here in the last four Februarys combined has amounted to just 12”—half the snow which fell last month.
With the Southwest and West Coast under the weather gun a second weekend in row, rain totals continue growing in places like Los Angeles. The city has measured 25.51” since Oct. 1—already enough to rank as 8th wettest rainy season there since 1877.

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February couldn’t be more different than January in terms of Chicago area snowfall. Measurable snow fell on 11 days last month and totaled 29.1” at Midway Airport, making it the site’s fourth snowiest January since 1928. At the other end of the city, O’Hare’s 27.8” tally finished nearly two and a half times normal for the month! The total was equivalent to nearly three-quarters (73%) the normal snowfall for an entire snow season.. What a difference we’ve seen in just the past few weeks! February, 2005—nearly three weeks old—has hosted only 0.5”. The tally is so paltry that only 14 other Februarys (of 120 on record) have hosted similarly anemic totals in the opening two and a half weeks of the month.
Thursday’s 27° and 19° extremes produced this month’s first sub-normal daily average temp—the first time a sub-normal reading has been logged here since Jan. 27.
-Tom Skilling

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A February cold spell of Thursday’s intensity is long overdue. Though not even close to the +1° high on this date 102 years ago—the coldest Feb. 17 daytime reading on record in 135 years of official weather observations—today’s 25° high is the first February maximum temperature which has failed to reach 30°. Eight such days had occurred by this time last February and an average of nine readings below 30° have occurred in February since 1871. It’s the coldest daytime temp to grip the city in two and a half weeks. In a winter noteworthy for the limited number of truly frigid days, a 25° Thursday high would rank among the 15 coldest temps since Dec. 1.

The chill occurs in the wake of a jet stream shift. Upper steering winds are blowing into the Midwest from the NW. The air which has arrived in Chicago Thursday originated over Duluth, Minn. and Winnipeg, Canada 24 hours ago.
-Tom Skilling

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An unseasonable surge of 70° warmth into downstate Illinois Tuesday—30 degrees above normal and the highest readings there since November—aided the development of thunderstorms in parts of the Chicago area. By 4:22 p.m. Tuesday, lightning and thunder were observed at O’Hare Airport—the first time that’s happened in February since 2001.
Tuesday’s rainfall, totaling 0.36” at Midway Airport, pushed the month’s total to 1.58”—nearly the total amount of precipitation which has fallen in Chicago over the past three Februarys combined (1.78”).
More impressive is the 6.90” of rain which has fallen at the South Side site since the first of the year. Never, in 77 years of Midway weather observations (dating back to 1928), have the first 45 days of a year opened any wetter. It’s little wonder rivers at a number of locations across the Midwest are out of their banks.

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February 2005’s unusually mild temperatures continue to raise eyebrows in the meteorological community. The month maintains a 10° temperature surplus as it passes the halfway mark, and not a single day this month has finished with a normal or below normal reading. That’s a fairly remarkable streak at a time of the year in which much of Canada remains ensconced in a sea of cold air which has taken months to form over a vast snowpack in the weak (or non-existent) sunlight indigenous to the arctic latitudes in winter. Only six other Februarys in Chicago since 1871 have opened with so many (14) consecutive days of above normal readings. This month’s persistent mild air makes it the 9th mildest February open since 1871—only three Feb. 1-14 periods since 1940 have been warmer than this year.
The rain (0.93” at Midway, 0.76” at O’Hare) which fell here Sunday into Monday morning amounted to more than all the precipitation which fell last year in February.

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As low pressure pulls away to the northeast, rain (totaling 0.25 to 0.50 inches) will end with a break in the clouds possible this afternoon; however, the approach of a cold front is expected to bring a quick return of cloudiness and a good chance of rain again later tonight. The warmest temperatures for this date may have already been recorded by sunrise, but if clouds break and the sun comes out this afternoon, readings could jump back into the mid to upper 40s. With the passage of the cold front Tuesday, colder, more seasonable air will return and stick around the remainder of the week. After temperatures drop below freezing Tuesday afternoon, Chicagoans may not see 32° again until Friday.
Meanwhile, California is preparing for another onslaught of rain that may well persist most of the week ahead—another 3 inches or more may fall in many areas of the Golden State between today and Friday.

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For the second straight Saturday high temperatures warmed into the 50s over much the area yesterday, even reaching the upper 40s downtown before light east winds off cold Lake Michigan kicked in. By 4 p.m. lakeshore readings had dropped to 37° at Northerly Island and 40° in Waukegan, while the rest of the metro area held in the upper 40s to lower 50s. Today east winds 15 to 25 m.p.h. will drive colder air well inland and along with the rain will make readings in the lower 40s “feel” more like 30°. As low pressure driven by the upper air mechanisms that brought havoc to the southwestern U.S. approaches tonight, winds will shift southerly and temperatures will slowly rise, despite the rain, with perhaps the day’s highest readings occurring just before midnight. After a cloudy but mild Monday, a cool-down will begin Tuesday with more seasonable high temps in the 30s the remainder of the week.

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For the second time in just a month and a half, the U.S. Southwest is reeling from the effects of a downpour-generating storm. Flood watches and warnings are out in perennially dry cities including Phoenix, Tucson and Las Vegas. There, more rain may fall by late Saturday than usually comes down in two Februaries combined. Southern Californians are being warned of mud slides through Saturday.

With heavy rains falling late Friday, Opids Camp, in the mountains near Los Angeles, had recorded 4.55” of rain while Beverly Hills received 2.05”. The rain story over the past four months in Los Angeles has been stunning with 24.54” down since Oct. 1—nearly three times normal! The same period a year ago recorded just 3.89”. Friday’s 1.67” within the city limits set a new record for Feb. 11.
Chicago has had an incredible run of mild temps. Friday marked the 14th consecutive day of above normal readings—the longest such stretch since late October.
-Tom Skilling

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Snowfall reached 17.5” late Thursday at Hartford, Maine, 14” at New London, N.H. and 13.4” at Peru, N.Y. The storm responsible heads out to sea Friday, but wraparound snows will linger in northern New England. Gusty NW winds on the system’s backside have sent chilly air deep into Florida. Wind chill advisories continue from Jacksonville south to Orlando Friday morning. On the other side of the continent, 12”+ was down in another storm late Thursday in Anchorage, Alaska with an additional 6-8” on the way.
This week marks the 135th anniversary of the National Weather Service which began as a unit of the Signal Service Corps on Feb. 9, 1870. Coincidentally, NOAA has just deployed a new $180-million weather and climate forecasting supercomputer. It increases computational speed from 450-billion to 1.3-trillion calculations per second.

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Februarys in recent years just haven’t produced the weather that seemed indigenous to the month through the 1960s and 1970s. Snowfall has diminished while temps have surged. The multi-decade trend toward milder, less snowy winters, which began after the 1970s, has had quite an impact on February weather stats. A total of more than 80-days of measurable February snow fell in the 1960s and again in the 1970s. But, Februarys in the 1990s saw just half that number—only 44 instances of measurable snow. During the same period, average February snowfall at Chicago’s Midway Airport, which was 10.4” in 1960s, 10.5” in the 1970s and 12.6” in the 1980s plumetted to just 7.5” in the 1990s. February snowfall has been averaging just 4.4” from 2000-2004.
Mild days have been surging. February temps above 40° occurred on 68 days in the 1960s but soared to 118 in the 1990s.
-Tom Skilling

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For the 9th time this season, snow is falling measurably across the metro area. While hardly a major storm here, the system generated an impressive 9” accumulation at Morganville, Kan., and up to 6.6” in sections of the Omaha, Neb., area. Chicago is to pick up 1-3” before snowfall diminishes to flurries mid-morning. February’s normal 8.3” of snow makes it the city’s third snowiest month behind January (11.3”) and December (8.7”).
The snow is falling despite this month’s impressive 10.9° temperature surplus. Even more impressive is the fact February’s opening 8 days have run 13.3° warmer than the same period a year ago. This is a time of the year in which temps have been barbarically cold. In 1899—106 years ago—brutally cold air settled in for five bone-chilling days from Feb. 8-12 with these daily temp. extremes: -4°/-7°, -8°/-21°, -1°/-18°, 1°/-7° and 3°/-17°. Only a trace of snow was on the ground.

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