Warm-up ahead, but weekend cool-down looms

Warming ahead, but temps take a dive over the weekend

Frost and Freeze advisories were hoisted for Tuesday night into early Wednesday for much of the Chicago area, with temps in the 20s expected away from the lake—but sunshine returns “big time” Wednesday and warming follows Thursday and Friday especially away from lake Michigan—but a powerhouse 180 mph jet stream wind max over the Gulf of Alaska is to dive into nation’s mid-section spinning up a chilly late season upper low this weekend into next week with lots of clouds and showers

VIEW SLIDESHOW OF THE UPCOMING CHANGES:

  • FROST ADVISORIES (in light blue) and FREEZE WARNINGS (in areas shaded in dark blue) TUES NIGHT INTO WED MORNING
  • ACTIVE NWS FROST ADVISORIES AND FREEZE WARNINGS TUES NIGHT & WED MORNING
  • PREDICTED LOW TEMPS at daybreak Wednesday morning
  • PROJECTED LOW TEMPS WED MORNING
  • BRIEF BUT NOTICEABLE WARMING for several days later this week. THIS ARE FORECAST HIGHS THURSDAY
  • FORECAST THURSDAY HIGH TEMP DEPARTURES from normal
  • FORECAST FRIDAY HIGH TEMPS
  • PREDICTED HIGH TEMP DEPARTURES from normal FRIDAY
  • FORECAST HIGHS SATURDAY
  • FORECAST HIGHS SUNDAY
  • FORECAST HIGH TEMP DEPARTURES SUNDAY showing a broadly BELOW NORMAL DAYTIME TEMP REGIME taking control over the Midwest
  • FORECAST HIGHS MONDAY
  • FORECAST HIGH TEMP DEPARTURES FROM NORMAL MONDAY
  • Powerful 180 mph JET STREAM WINDS ARE ROARING OFF THE GULF OF ALASKA into Canada–then expected to dive into the central U.S. this weekend developing a huge, slow moving upper air low pressure–home to cold unstable air aloft which fosters widespread cloudiness and showers
  • Here’s a look at the TUESDAY MORNING UPPER AIR ANALYSIS showing the 180 mph jet stream wind max coming off the Gulf of Alaska and headed into British Columbia in western Canada.
  • HERE’S A LOOK HOW OUR COMPUTER MODELS ARE DEVELOPING THE CLOUDY WEEKEND COLD AIR POOL ALOFT. This is the forecast for 7am CDT FRIDAY.
  • THE COLD, UNSTABLE AIR MASS IS SHOWN TAKING SHAPE CENTERED ON THE MIDWEST 7am CDT Saturday morning
  • THE COLD AIR POOL AND CLOSED UPPER AIR LOW PRESSURE IS SHOWN HERE 7am CDT Sunday morning
  • UPPER AIR FORECAST–7am CDT Monday morning
  • May be an image of map and text that says ‘ECMWF EPS| 500 hPa potential Height [dm] Anomaly [m]| Ensemble Mean 20-Year M-Climate Init: 12Z25APR2023 [168] hr –> Valid Tue1 12Z02MAY2023 MIN|MAX: 284.9 186.8 m 500 440 380 320 240 210 180 150 120 60 30 0 30 -60 -90 -120 -150 180 210 -240 -270 300 service based data and products the European Centre for Medium-range Weather Forecasts (ECMWF) 370 -410 450 500 weathermodels.com’ This photo is from a post. View post Tom Skilling npesSoortdim68uf7um61uf 4 3ii57a6 h 6chh9506ihcthl164huilg738ica · 7am CDT Tuesday morning Comments You’re commenting as Jennifer Kohnke. To interact as Tom Skilling, go to Meta Business Suite .
  • 7am CDT Wednesday morning
  • THIS IS THE WARMER PATTERN PREDICTED A WEEK FROM THIS SATURDAY and likely to bring more normal high temps which flirt with 70-deg
  • THIS SEQUENCE OF PREDICTED SURFACE WEATHER MAPS tracks the predicted development of a broad low pressure over the Midwest. This panel is the forecast for 7am CDT Saturday
  • 7pm CDT Saturday evening
  • 7am CDT Sunday morning
  • 7pm CDT Sunday evening
  • 7am CDT Monday morning
  • 7am CDT Tuesday morning
  • FORECAST CLOUD COVER 1pm CDT Saturday
  • 1pm CDT CLOUD COVER Sunday
  • 1pm CDT Monday
  • 1pm CDT Tuesday
  • FORECAST TEMP DEPARTURES for Days 1 to 5 per the National Weather Service GFS ensemble model
  • DAY 6 to 10 FORECAST TEMP DEPARTURES
  • FORECAST 11 to 15 DAY TEMP DEPARTURE FORECAST

A cold Tuesday night-Wednesday a.m. with freezing temps at O’Hare for only the 5th time this month as inland low temps dip into the mid to upper 20s at the coldest locations.

The nighttime chill followed a day which saw wet flakes of snow mixed with morning rain showers—something (i.e. snow) that’s happened on April 25th only 7 of the past 138 years dating back to 1885, the year our official Chicago snow records began. The most recent April 25th snowflakes occurred 7 years ago in 2016.

The frost and freezing temps Tuesday night also followed a day in which temps failed to make it out of the 40s. Daytime temps THAT CHILLY have’t been regular occurrences on April 25th’s here. In fact, only 33 of the 151 April 25’s for which we have records (our official temp record goes back further than the snow record here—all the way back to 1871)—that’s just 22% of them—have produced highs which have failed to break above 50-degrees.

Despite Recent Chill. April 2023 To-Date Ranks Among Warmest on Record…

WHAT’S INTERESTING—AND YOU MAY FIND THIS SURPRISING GIVEN THE RECENT CHILL HERE—IS THAT APRIL, 2023 ACTUALLY RANKS AMONG THE WARMEST 6% OF ALL APRILs TO DATE since the early 1870s. IT’S THE 9th WARMEST APRIL OF THE PAST 151.

Above normal APRIL 2023 average daily temps have outnumbered ones which have finished colder than normal 14 to 11. And for 2023 to date, the dominance of warmer than normal days is even more striking. Chicago has experienced ABOVE NORMAL DAYS since Jan 1 at more than twice the pace of below normal days—75 to 35 respectively–with 4 days coming in “normal”.

Late-Week Reprieve From The Chilliest Temps Won’t Last

A STUBBORN COLD, UNSETTLED UPPER AIR LOW PRESSURE SYSTEM, HEMMED IN AND THEREFORE SLOW MOVING AND LIKELY TO LAST FOR DAYS HERE–IS TO TAKE SHAPE OVER THE WEEKEND

HERE’S A LOOK HOW OUR COMPUTER MODELS ARE DEVELOPING THE CLOUDY WEEKEND COLD AIR POOL ALOFT. This is the forecast for 7a.m. CDT FRIDAY through 7 a.m. CDT Wednesday:

Instrumental to the development of this STUBBORN CENTRAL U.S. UPPER LOW is a 180 mph jet stream speed max making its way across the Gulf of Alaska toward British Columbia in western Canada. Once ashore, these powerful high altitude winds will plunge southward into the Plains spinning up a cold upper low pressure which is to become trapped in a complex blocking pattern which will, for all intents in purposes, lock it in place well beyond this weekend–very possibly into the middle part of next week. That means a whole set of days dominated by clouds, unseasonably chilly temps and sporadic showers.

THIS SEQUENCE OF PREDICTED SURFACE WEATHER MAPS tracks the predicted development of a broad low pressure over the Midwest

This panel is the forecast for 7am CDT Saturday through 7am CDT Tuesday morning

THE GOOD NEWS IS there continue to be indications of a temp rebound to something closer to normal late next week with daytime highs within striking distance of 70 a good bet.

MAY 2023’s ONLY 5 DAYS AWAY—IT BEGINS NEXT MONDAY—LIKE ITS PREDECESSOR—MAY IS A STUDY IN CONTRASTS WEATHER WISE

In looking over the records, I’ve found a trace of snow has occurred in a quarter of the past 151 Mays for which we have records—that’s 48 of the Mays since 1873. Fortunately, only 8 of the 48 have produced “measurable” snow—defined at 0.1″ or more. And measurable snow doesn’t stick around in May.

But while SNOW CAN OCCUR–SO CAN WARM, EVEN HOT WEATHER: 135 of the past 151 Mays have generated 80-degree high temps—and 45 of the 151 Mays have even produced 90s. So hang in there warm weather enthusiasts. It may not seem like it—but nature has the Chicago area on a track toward warmer days to come. With a chilly lake next door, it takes a bit of time some years.