Tom Skilling: Second coldest weekend of 2023 arrives

2nd COLDEST WEEKEND OF 2023—THE COLDEST WEEKEND IN 8 WEEKS (since late January) IS ON THE WAY WITH NEAR ZERO WIND CHILLS BY SATURDAY MORNING–SNOW SHOWERS TO DEVELOP LATE SATURDAY MORNING AND AFTERNOON IN AN ATMOSPHERE RENDERED EXPLOSIVELY UNSTABLE BY UNUSUALLY FRIGID TEMPS ALOFT.

IT’S WINDY FRIDAY–and IT’S COLD–and it’s going to stay windy this weekend and get even colder Friday night and Saturday!

The strong winds are being driven by a tremendous pressure gradient across the Plains and Midwest. A HUGE change in barometric pressure between a powerful storm (989 mb=29.20″) near James Bay at the south end of Hudson Bay in Canada and a formidable late season Canadian high pressure over the Dakotas by Saturday morning (central pressure 1040 mb=30.71″) is to be in place. This pressure imbalance leads to strong winds as nature attempts to bring pressures into balance. It’s an effort which is only slowly achieved–thus winds are to remain elevated well into the coming weekend.

Marry thermometer temps predicted to drop to the mid teens by morning to strong west winds sustained around 18 mph but gusting at times as high as 35 mph Saturday morning and the result is WIND CHILL TEMPS due to drop to NEAR ZERO as Saturday dawns—-impressive any time of the year but even more so past mid March–and we’re going to do that with NO snow on the ground! That’s not an everyday occurrence this late in the season.

We’ll have what amounts to early January-levels temps Saturday–only they’ll be occurring past mid March.

Here’s something else which will be interesting to watch–THE EXPLOSIVE GROWTH OF SNOW SHOWERS in Saturday’s “unstable” atmosphere. When weather folks refer to an “UNSTABLE ATMOSPHERE”—that “weathereeze” for a MORE RAPID THAN USUAL DROP IN TEMPS WITH HEIGHT. That’s important because a rapid drop in temps with height causes the air here in the lower atmosphere to become buoyant and WANT TO RISE. When air ascends, it cools–and cooling air like Saturday’s is like to SATURATE—meaning CLOUD AND SNOW SHOWERS ARE LIKELY TO FORM. These could be “convective” in nature–meaning the cloud towers from which these snow showers originate will be fairly tall and apt to produce some interesting bursts of snowfall. They’ll come and go–but when they’re over an area–snow showers like this have been known ti produce temporary visibility reductions.

Sunnier weather returns Sunday as the cold pool aloft moves on.

HINTS OF THE FIRST CHICAGO 60s APPEAR TO BE GROWING TOWARD THURSDAY NEXT WEEK–though rains, some possibly thundery, are likely to arrive at the same time with a new storm system’s SOUTHERLY WINDS.

And it appears the “warmth” will be transient–in other words, temporary! While temps turn down again beyond that system, we’re getting to the time of year when visits by warmer temps will be on the upswing–a wonderful prospect!

AND REMEMBER–The VERNAL EQUINOX–the ASTRONOMICAL (some would say “official”) start to the SPRING SEASON arrives at 4:26pm CDT this coming Monday (March 20th)!

HERE’S MY FRIDAY CHICAGO METRO FORECAST (3/17/2023)

TONIGHT: UNSEASONABLY COLD! Partly cloudy and windy with wind gusts topping 30 mph at times and wind chills by morning dropping to within a few degrees of ZERO. The low thermometer reading drops to 15 by morning.

SATURDAY: Opens with mixed sun—but clouds build and gusty snow showers develop late morning and afternoon amid unseasonably chilly January-level temps. The bursts of snow in some snow showers may cut visibilities and coat the ground with snow at some locations amid the day’s 35 mph wind gusts. High 29—nearly 20-degrees below normal.

SATURDAY NIGHT: Clouds break, snow showers end. Cold and continued blustery. Low 20—with low to mid teens colder inland locations.

SUNDAY: Becoming mostly sunny, continued breezy. Temps recover a bit—but remain nearly 10-deg below normal. High 40.

MONDAY: Clouding over, breezy and milder. Temps closer to seasonal norms. Sprinkles possible. High 49.

TUESDAY: Mostly cloudy, mild and breezy. Chance of some mainly afternoon sprinkles. High 52.

WEDNESDAY: Cloudy, breezy, seasonably mild. Some showers possible. High 50.

THURSDAY: Rainy, windy and mild. Possible thunder. High 60.

FRIDAY: Rainy spells likely. Not quite as mild. High 55—but in the 40s along Lake Michigan.