The ATMOSPHERIC RIVER STORM sweeping California—the 11^th such storm since Dec 22—will cross the Rockies, plug into Gulf moisture and bring Thursday afternoon and nighttime rains to Chicago amid strong southerly winds expected to begin boosting city temps tomorrow (Wednesday).

Wed’s predicted 50-deg high is to be 15-deg warmer than today’s 35—and will occur as south/southwest winds ahead of the approaching storm take hold and gust by afternoon and into Thursday to 30 mph.

An average of a set of computer forecast model rainfall projections puts likely Chicago rainfall around 0.50″–with rains commencing Thursday afternoon—but clouds on the increase in advance of the storm as early as tomorrow (Wed) afternoon. 

While Wednesday is to open bright and sunny with daybreak cloud coverage minimal—covering perhaps 9% of the sky— an overcast will have assembled by mid-afternoon Wednesday announcing the storm system’s approach and drive home Wed evening will take place beneath largely cloudy skies—but WITHOUT PRECIP.

While temps are to surge close to 50 Wednesday, Thursday and into Thursday night—the “warming” will be short lived. Powerful winds on the storm’s backside will send temps plummeting noticeably lower Friday.  A pre-dawn 42-deg high Friday is likely to drop to the upper 20s or low 30s by nightfall Friday amid 40 to 45 mph wind gusts.

And rain and snow showers Friday may give way to sporadic snow flurries Friday night into Saturday in what appears likely to be another COLD WEEKEND with daytime 30s likely.

The parade of storms is to continue next week as will a MODESTLY BELOW NORMAL TEMP REGIME. Temps last week averaged 3-deg above normal—but will come in close to 5-deg below normal this week and close to 4-deg below normal next week.

An estimated 30-million California residents are being impacted by this 11th atmospheric river system to hit the state since Dec. 22. Forty of California’s 58 counties are under a State of Emergency as the latest Pacific storm system sweeps in with drenching rains, high winds and, above 8,000 ft. 3 to 5 feet of additional snow. And from all indications, it won’t be the last. Severe more are to hit in the the next week and a half.

Ominously, the NWS Weather Prediction Center (WPC) assesses as a HIGH RISK the threat of flooding and notes that 40% of the country’s flood fatalities have occurred in regions declared at HIGH RISK for excessive rainfall. WPC also notes that the the assessment of a HIGH RISK for flooding is made on average in only 4% of days annually.

The storm will cross the Rockies and redevelop in eastern Colorado then track across Wisconsin and Michigan–place Chicago is the system’s “warm sector” Thursday into Thursday night with windy rains and possible isolated thunder before its powerful backside winds hit Friday–a day in which temps are likely to fall from a predawn 40-deg highs to the upper 20s or low 30s by nightfall amid some backside rain and snow showers. Current modeling suggests rainfall in Chicago may come in around a half inch–but snows well to the north could be significant across the North Woods–including northern Minnesota, far northern Wisconsin and Michigan’s Upper Peninsula.

HERE’S MY LATEST TUESDAY CHICAGO METRO FORECAST

TONIGHT: Clear and cold. Light winds shift southerly before morning. Low 23 in the city—but mid to upper teens colder inland locations.

WEDNESDAY: Sunny in the morning, but clouding over in the afternoon. Turning breezy and milder with gusty south winds approaching 30 mph in gusts during the afternoon. High 50.

WEDNESDAY NIGHT: Cloudy, windy and milder. Low 41.

THURSDAY: Windy with rain developing by or during the afternoon. Isolated thunder possible. High 48.

THURSDAY NIGHT: Rainy and windy. Isolated thunder possible. Mild—but beginning to turn cooler by morning. Low 42.

FRIDAY: Cloudy, quite windy and sharply colder. Several rain or snow showers. High 42—but falling to 30 by nightfall.

SATURDAY: More cloudy than not, blustery and colder. Passing snow flurries. High 35.

SUNDAY: Sunny, breezy and cold. High 38.

MONDAY: Cloudy spells, not quite as cold. High 45.

TUESDAY: Mostly cloudy and chilly. High 43—but colder along Lake Michigan.