What a phenomenal day—one which screams summer (even though, in reality, we have a way to go—the summer solstice, the astronomical beginning of summer, is still 69 days away. It arrives Wednesday, June 21 this year at 9:48 a.m.)
Today’s 82 degree high is the warmest April 12 in 46 years (since an 85 degree high on this date in 1977).
My check of the records shows only three other April 12’s which were warmer in the 153 years of weather records dating back to 1871:
1941: 83 degrees
1971: 86 degrees
1977: 86 degrees
That places today among the warmest 3% of all April 12’s on the books!
We have a rex block in place aloft. That a blocking pattern with a big dome of warm air over Lower 48 deflecting the storm-carrying jet stream to the north and a wet low pressure system on the Gulf Coast to the south. Blocking patterns in the atmosphere slow the progression of air masses, In this base, a blocking pattern is good news because it locks the warm air in over Chicago through Saturday.
In time, the air mass is to humidify—with Gulf moisture gradually moistening the air mass. Dew points, which have been limited to the 40s—indicating dry air in place—-will continue in that range Thursday, which should be another glorious day with limited cloud cover and bountiful sun—but then creep higher, reaching the low to mid 50s Friday and to near 60 later Saturday. A 60-deg dew point indicates enough moisture has moved in to make the air feel more humid.
That too should fuel shower development Saturday and the rains could grow thundery as a cold front approaches Saturday night and jet stream winds shift into the Midwest airspace Saturday afternoon and evening with cooling temps aloft further destabilizing the atmosphere. If some strong t-storms are going to develop, this will be the period to watch.
VERY WINDY, MUCH COOLER WEATHER SHIFTS IN SUNDAY INTO MONDAY. A pool of cold air aloft will keep the atmosphere is a shower generating mode. Temps Sunday night could cool to the extent some mixed snowflakes could put in an appearance at some locations here or nearby.
While this week’s warmth is to produce a weekly temp average of 65-deg—a reading 16-deg above normal and nearly 16-deg warmer than last week—next week’s temps are to drop close to or a tad below normal—a weekly pullback expected to come in around 15-deg cooler—A NOTICEABLE CHANGE TO COOLER WEATHER.
HERE’S MY LATEST WEDNESDAY CHICAGO METRO FORECAST:
TONIGHT: Mainly clear and mild. A southwest flow continues to elevate temps well above the normal low around 40. Low overnight 58.
THURSDAY: Sunny, becoming breezy and continued unseasonably warm. A July level high of 82—a reading 25 degrees ABOVE NORMAL.
THURSDAY NIGHT: Partly cloudy, mild and breezy. Low 57.
FRIDAY: Partly cloudy, breezy and warm. High 79—but closer to the low 70s on area beaches.
SATURDAY: Clouds and some mixed sun, windy, unseasonably warm and more humid. Scattered showers and possible t-storms, mainly in the afternoon—-BUT EVEN MORE LIKELY Saturday night when some heavier storms are possible. High Saturday 80. Turning much cooler by Sunday morning. Low Saturday night 48.
SUNDAY: Variably cloudy, very windy and much cooler. Some showers possible impacting 30% of the area. High 55—but falling into the 40s amid 40 mph wind gusts.
MONDAY: Cloudy spells, quite windy and cool. Several showers possible—a few snowflakes could be mixed in during the morning in spots. High 48.
TUESDAY: Mostly sunny and milder. High 57,
WEDNESDAY: More clouds, chance for some shower. Breezy and milder. High 63—possibly lower on the lakeshore.