• Mid-continent atmospheric blocking pattern is to stall major weather systems in place over the coming week setting the stage for a Memorial Day weekend of warming temps and rain-free weather in Chicago within a building dome of warm air. Day-to-day temp increases are in store here with highs flirting with 90-degrees Tuesday, Wednesday and Thursday next week
• The most important rule of thumb as ATMOSPHERIC BLOCKING PATTERNS come together is what’s happening across the central United States: the weather system in control as the blocking pattern gets underway 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 find ourselves smack dab in the middle of a sprawling Canadian high pressure. We had Friday afternoon relative humidities as low as 22%, about as dry as it gets this time of year. The dry in the heart of this high pressure is to down ANY PROSPECT OF RAIN for the foreseeable future, and that includes the Memorial Day holiday weekend  — a rain-free pattern which is to extend well into next work week.

PATCHY FROST IN SOME COLDER NORTHWEST SUBURBS FRIDAY MORNING

• The high pressure’s strong south flank northeasterly winds are responsible for delivering the chill we felt Thursday and overnight. Frost-level chill in colder locations away from Lake Michigan north and west of Chicago Friday morning have shifted south of Chicago.
• They’re setting the stage for a major wind-driven precipitation event — a multi-day spell of heavy wind-driven rain, some of it thundery, as well as gale winds sending huge ocean swells likely to pound the Caroline Atlantic coast for days.

COOL DOWN TO HIT NEXT WEEKEND INTO THE FOLLOWING WEEK

• The high pressure’s strong south flank northeasterly winds are responsible for delivering the chill we felt Thursday and overnight. Frost-level chill in colder locations away from Lake Michigan north and west of Chicago Friday morning have shifted south of Chicago.
• The warm dome to develop over the coming week over the Midwest is to retrograde (shift westward) as the blocking pattern breaks down late in the coming week and next weekend—and this could lead to a cooler weather regime next weekend going into the following week.

• Temps recovered nicely from the chilly morning lows Friday—low enough to produce patchy frost in some north and northwest suburbs. Low dropped to 45 at O’Hare and 50 at Midway at a time of year that 54 is normal.
• But, colder inland temps included 33 at McHenry, 34 at Richmond in McHenry County and 34 at Odell in Livingston County with interior northwest Indiana Friday morning minimums as low as 36 at Chesterton and Michigan City in Indiana.
• Friday saw 100% of its possible sunshine in a May which has been as sunny as it’s been dry. The month has produced nearly 20% more sun than normal. At the same time, it’s 11% of normal rainfall—just 0.42” to date versus the normal of 2.68” to date. May is headed for a Wednesday night midnight close as Chicago’s 2nd driest May of the past 153 years.
• Warming has begun. Today’s near 70-degree high has come in 8 degrees warmer than yesterday, and warming is slated to continue through the upcoming Memorial Day weekend with NO RAIN in sight here until late next week at earliest. EVEN THAT RAINFALL ISN’T LOOKING IMPRESSIVE.

• In fact, model estimates of rainfall over the coming 2 weeks look paltry. One estimate covering the period through Friday, June 9 suggests less than a quarter of the normal rainfall may occur, continuing a dry stretch which has persisted more than 5 weeks.
• As indicated for days, numerical model forecasts continue building a REX-BLOCKING pattern, featuring a dome of moisture-deflecting warming air well into next week. The effect of such blocking is to essentially trap large scale weather features where they are. With high pressure over our area, that suggests an air mass stalled in place and likely to warm slowly but steady over the coming week. That would produce Chicago highs of 75 Saturday, 80 Sunday and 84 Memorial Day (Monday).  
• The air is to remain dry with dew points ranging from the upper 30s to the upper 40s over the holiday weekend. Dry air cools at night—so cool nights and warm days are expected this holiday weekend.
• The air is to remain dry with dew points ranging from the upper 30s to the upper 40s over the holiday weekend. Dry air cools at night—so cool nights and warm days are expected this holiday weekend.
• One interesting forecast trend will be the increase in mainly HIGH clouds which is to take place after Saturday’s sunny start. A HIGH overcast is likely to be in place by the end of the day and may linger into Sunday morning. But, the expectation is these high clouds will break allowing mixed sun to emerge after a cloudy start Sunday and that Memorial Day will be sunny. Those clouds are therefore not expected to impede the slow warming which has commenced.
• Lake breezes will cool shoreline locations each day of the coming week with east winds strengthening next weekend into the following week. This suggests the warming will carry Chicago area INLAND temps to within striking distance of 90 Tuesday, Wednesday and Thursday next week. But, the strength of these easterly winds will be weaker than in recent days limiting the distance lake cooling is likely to head inland.
• Weekend mariners planning to head out onto Lake Michigan will find a 1-foot chop since the easterly winds projected won’t be covering the LONG STRETCH OF WATER that the NNE winds of recent days have. It’s that trip over LONG STRETCHES of water which permit waves to build—and that’s NOT to happen over the weekend.
• THE BLOCKING PATTERN is BAD NEWS for sections of the Atlantic coast—in particular, for the Carolinas where strong east winds traveling over a huge fetch of the Atlantic are to bring rains ashore through the holiday weekend while large waves pound the shoreline. Rainfall estimates suggest local 2 to 6-inch rains may drench sections of wide swaths of the Carolina.

WHAT A THRILL: Tom is featured in an NPR podcast!

• “I’ve been featured in a ‘THIS IS LOVE’ podcast episode! How cool is that?! “I was contacted late last year by ‘THIS IS LOVE’ podcast producer Katie Bishop out of New York and asked if I would consider participating as the subject of an episode of ‘THIS IS LOVE.’ To say the least, I was surprised to have been asked—and flattered at the interest in my work. 
• “Many of the ‘THIS IS LOVE’ staffers have NPR (National Public Radio) backgrounds—and I LOVE NPR. So I knew this was going to be well done (IT HAS BEEN) — and one which would be fun (which it WAS!) I had no idea precisely what would result, but Katie Bishop had been so nice in the follow-up phone call that I SAID YES! 
• “What followed was an interview with the podcast’s wonderful host Phoebe Judge, who grew up in Chicago and had watched my weather programs over the years. She now lives in North Carolina, and I’ve since learned Phoebe is an Edward R. Murrow and Associated Press award-winning journalist and am not at all surprised by this. Phoebe’s journalistic and investigative work over the course of her amazing career is amazing. Not surprisingly, talking with Phoebe was a joy.
• “I have to tell you, the podcast has been beautifully done. The work and research which has gone into this episode is clear. The ‘THIS IS LOVE’ crew has entitled the episode, ‘The Weatherman’ and recalls moments in my career I had filed so far back in my mind, I wouldn’t have remembered them had Phoebe not asked about them during our interview. 
• “The program features comments from longtime Chicago Tribune columnist—Pulitzer Prize winning Mary Schmich—whose work I loved all these years and whose kind words mean the world to me. THANK YOU more than I can possibly say, Mary! I’m humbled at your comments. And thank you to Stefani Klein, who has provided me the most beautiful weather photos here on Facebook and whose photos I’ve posted here and used on my WGN weather programs over many years, was contacted and interviewed for the podcast by Phoebe Judge. THANK YOU TOO, Stefani.”