FIRST, THURSDAY WEATHER HEADLINES
–We managed 21% of our possible sun Thursday, reports veteran NWS observer and Chicago climate guru Frank Wachowski—but we also had a few squally snow showers.
–The chill was heightened today by the arrival of gusty WSW winds which reached 35 mph at O’Hare and 39 mph at Midway.
–A record level warm air pool over Alaska and the Yukon is behind a highly amplified (i.e. “wavy”) North American jet stream pattern—one in which steering winds aloft are roaring down the warm pool’s eastern flank—blowing all the way from the North Pole and arctic regions of the continent into the Lower 48. The effect has been profound. More than 40% of the continental U.S. now boasts a cover of snow. And the 70-deg temps in the country—which covered more than 30% of the U.S. only days ago has shrunk to just 1.5% of the country. The 40.6% snow coverage is nearly 5 times the area covered by snow (just 8.7%) one year ago.
–The strong northerly flow aloft means the southward flood of early season arctic air is to continue and that the cold air will tighten its grip on the area in coming days. Highs both Friday and Saturday will only reach the upper 20s—levels nearly 20-deg below normal—and a far cry from the mid 40s which are “normal” this time of year.
–The atmosphere is to remain quite unstable—thus clouds and sporadic flurries will linger. We should actually be glad that’s the case because were clouds not present, nighttime temps would be EVEN COLDER.
–A BIG TEMP TURNAROUND is in our future. High temps will surge back to the 40s Monday, Tuesday and Wednesday as we head toward Thanksgiving Day next Thursday.
–I mentioned early indications of a potential storm system toward Thanksgiving. The prospect for such a system today appears muddled based on overnight and daytime global model runs from the major meteorological centers. Whereas there was some model continuity yesterday, machine projections are all over the map as I send this out today. One thing you look for with developing systems—even at this distance in time from the potential event—-IS CONTINUITY. It simply isn’t there at this point. The morning’s NWS GFS model develops a respectable snow Thursday night and Friday—a forecast radically different from its overnight forecast. At the same time, not a hint of a storm system now on the European Centre’s model today. THAT model had kicked out quite a storm yesterday. At the same time, the European Centre’s ensemble model does place an inverted trough over the area and hints at precipitation Thu night into Friday—but not strongly at this point. Bottom line—IF THERE’S SOME KIND OF STORM OUT THERE—modeling sure hasn’t followed through and connected with it in its latest runs. Does that mean chances for such a system reappearing in subsequent forecast runs is completely dead? Not necessarily. But the evidence we’re presented today is not impressive at this point. Let’s see where this goes. We have days to keep an eye on any development.
–Averaging across forecasts out 1 to 2 weeks produces temps which move from this week’s MUCH COLDER THAN NORMAL LEVELS—to something closer to or only modestly BELOW NORMAL in the coming 15 days.
HERE’S THE THURSDAY CHICAGO METRO FORECAST (11/17/2022)
TONIGHT: Clouds dominate, cold and breezy. Sporadic snow flurries. Low 22.
FRIDAY: More often cloudy than not, windy and unseasonably cold. Snow flurries at times. Wind gusts top 30 mph at times. High 28–but full day wind chills range from 10 to 14 degrees.
FRIDAY NIGHT: Clouds linger—but a few cloud breaks, blustery and chilly. Chance of several flurries. Low 22.
SATURDAY: Clouds break for some mixed sun at times, windy and continued unseasonably cold. High 28—a reading 19-degrees below normal. Full day wind chills: 3 to 16 ABOVE.
SUNDAY: Partly sunny and windy. Still cold—a few degrees above Saturday’s highs. High 35.
MONDAY and TUESDAY: Partly cloudy, breezy and noticeably milder. High 43.
WEDNESDAY: Mostly cloudy, cooler. Winds shift off Lake Michigan. High 44.
THURSDAY (Thanksgiving): Cloudy and colder. Chance of snow later in the day or at night. High 42.