US weather movement slows due to ‘blocking’ aloft; Rainless high pressure with approaching high/mid level clouds in Chicago for Memorial Day weekend as temperatures continue to rise

• Mid-continent atmospheric blocking will shut down major weather systems for the next week, setting the stage for a warming Memorial Day weekend with rain-free weather in Chicago in a warm air dome. Daily temperatures are expected to rise here, with highs flirting with 90 degrees on Tuesday, Wednesday and Thursday next week
• The most important rule of thumb when ATMOSPHERIC BLOCKING PATTERNS come together is what happens over the central United States: a weather system that controls as the blocking occurs is likely to stick around. Blocking patterns, by their very nature, slow the movement of weather systems.
• In the case of Chicago and the Midwest, we found ourselves in the middle of high pressure in Canada. Friday afternoon was below 22% relative humidity, about as dry as it gets this time of year. A dry spell in the heart of this high pressure reduces ANY PROSPECTS FOR RAIN for the foreseeable future, including the Memorial Day holiday weekend – a rain-free pattern that will continue into the next work week.

STORAGE FROST FOR SOME COLD NORTHWEST AREA FRIDAY MORNING

• Strong south-northeasterly winds driven by high atmospheric pressure are causing the cold snap we experienced Thursday and overnight. Freezing levels in colder areas from Lake Michigan north and west of Chicago moved south of Chicago Friday morning.
• They are setting the stage for severe wind-driven precipitation — a multi-day period of heavy rain with wind, sometimes thunderstorms, and gusty winds that cause huge ocean waves that are likely to batter the Carolinas’ Atlantic coast for several days.

GET COOL FOR NEXT WEEKEND NEXT WEEK

• Strong south-northeasterly winds driven by high atmospheric pressure are causing the cold snap we experienced Thursday and overnight. Freezing levels in colder areas from Lake Michigan north and west of Chicago moved south of Chicago Friday morning.
• A warm dome that will develop over the Midwest over the next week will retrograde (move west) as the blocking pattern breaks down late next week and into next weekend, and that could lead to a cooler weather pattern next weekend and next week.

• Temperatures recovered well from Friday morning’s chilly lows – low enough to cause light frosts in some northern and northwestern suburbs. Lows dropped to 45 in O’Hare and 50 in Midway at a time of year when 54 is normal.
• But cooler inland temperatures included 33 in McHenry, 34 in Richmond in McHenry County and 34 in Odell in Livingston County, and inland northwest Indiana Friday morning with lows of 36 in Chesterton and Michigan City, Indiana.
• Friday saw 100% of the sunshine possible for May, which was as sunny as it was dry. The moon produced almost 20% more sun than usual. At the same time, that’s 11% of normal rainfall — just 0.42 inches for today, compared to the normal amount of 2.68 inches for today. May is approaching midnight Wednesday night as Chicago’s second driest May in 153 years.
• Warming has begun. Today’s temperature near 70 degrees is 8 degrees warmer than yesterday, and the warming is set to continue through next Memorial Day weekend, with no rain expected until late next week at the earliest. EVEN THESE RAINS DON’T LOOK IMPRESSIVE.

• In fact, the model estimates for precipitation over the next 2 weeks look scant. One estimate, covering the period through Friday, June 9, suggests less than a quarter of normal precipitation could fall, extending a dry patch lasting more than 5 weeks.
• As shown over the past few days, numerical model forecasts continue to line up the REXAM BLOCKING pattern, showing a dome of warm air deflecting moisture into next week as well. The effect of such locking is to essentially capture large-scale weather features where they exist. With the high pressure over our area, this indicates that the air mass has stalled and will likely warm slowly but steadily over the next week. That would put Chicago highs at 75 on Saturday, 80 on Sunday and 84 on Memorial Day (Monday).
• Air should remain dry with dew points in the 30s to 40s over the holiday weekend. Dry air cools overnight, so cool nights and warm days are expected over the holiday weekend.
• Air should remain dry with dew points in the 30s to 40s over the holiday weekend. Dry air cools overnight, so cool nights and warm days are expected over the holiday weekend.
• One of the interesting forecast trends will be an increase in mostly HIGH clouds following Saturday’s sunny start. HIGH CLOUDS are likely to persist for the remainder of the day and may continue into Sunday morning. But those high clouds are expected to break up, and after a cloudy Sunday, some sunshine will appear early Sunday, and Memorial Day will be sunny. Therefore, it is expected that these clouds will not interfere with the slow warming that has begun.
• Lake breezes will cool coastal areas each day next week, with easterly winds picking up next weekend and into next week. This suggests that Tuesday, Wednesday and Thursday of next week will bring temperatures inland to Chicago in the 90s. But the strength of those easterly winds will be weaker than in recent days, limiting the distance the lake cooling can travel inland.
• Boaters planning to head out on Lake Michigan over the weekend will find a 1-foot drop as the forecasted easterly wind will not cover the LONG BLOOD OF WATER that the N-N winds of recent days have. This is the kind of ride on LONG stretches of water that allow the waves to build up and it should NOT happen on the weekend.
• THE BLOCKING SCHEME IS BAD NEWS for parts of the Atlantic coast, particularly the Carolinas, where strong easterly winds moving over a large swath of the Atlantic should bring rain ashore over the holiday weekend while large waves batter the coastline. Precipitation estimates show that 2 to 6 inches of localized rain could drench large swaths of the Carolinas.

WHAT A HIT: Tom is featured on an NPR podcast!

• “I was featured on an episode of THIS IS LOVE podcast! How cool is that?! “Late last year, I was contacted by the producer of the THIS IS LOVE podcast, Cathy Bishop, from New York, and asked if I would consider being on an episode of THIS IS LOVE. I was surprised, to say the least, that I was asked and delighted by the interest in my work.
• “Many of the staff at THIS LOVE have experience with NPR (National Public Radio) and I LOVE NPR. So I knew it would be well done (IT WAS) — and that it would be fun (and it WAS!). I had no idea what was going to happen, but Kathy Bishop was so good on the phone call that I SAID YES!
• “This was followed by an interview with the wonderful podcast host Phoebe Judge, who grew up in Chicago and watched my weather programs for years. She now lives in North Carolina, and I’ve since learned that Phoebe is a reporter for Edward R. Marrow and the Associated Press, which doesn’t surprise me at all. Phoebe’s journalistic and investigative work throughout her amazing career is amazing. No wonder Phoebe was a joy to talk to.
• “I have to tell you, it’s beautifully done. The work and research that went into this episode is evident. The THIS LOVE crew called the episode “The Weatherman” and it brings back moments from my career that I’ve had so long in my mind, I wouldn’t have remembered them if Phoebe hadn’t asked about them during our interview.
• “The program features commentary from longtime Chicago Tribune columnist — Pulitzer Prize winner Mary Schmich — whose work I’ve loved all these years and whose kind words mean everything to me. THANK YOU more than I can say Mary! I am humbled by your comments. And thanks to Stephanie Klein, who gave me the most beautiful weather photos here on Facebook, and whose photos I’ve posted here and used in my WGN weather programs for years, contacted and interviewed for Phoebe’s podcast Judge. THANK YOU TOO, STEPHANIE.”