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  • Tim McGill

More Muggy August Weather But No Extreme Heat

Some Sun With A Few Storms Possible

Tuesday's high of 84° was the warmest since we hit that same high temperature on Friday. It felt a bit warmer than 84° because of higher humidity. We will continue to slowly but surely warm up a degree or two through Friday while dew points also climb. No extreme heat and humidity expected but it will be more uncomfortable the next few days.

The HRRR Model has our highs today in the middle to upper 80s for most areas. A breeze off the lake will hold highs in the upper 70s along the lakefront. Average highs for today's date are around 83°.

We continue to be spared the thicker smoke from wildfires out west. The HRRR Model vertically integrated smoke forecast has relatively lower levels of smoke here today. I expect the concentration of smoke aloft will build a bit though the next few days as the jet stream starts to direct it more towards the Midwest.

Rising heat index or apparent temperature values the next few days but nowhere near the 110°+ levels some of us saw last week. Today's heat index may approach 90° or the lower 90s with middle 90s possible in a few spots by Friday.

Lake Michigan will continue to act as Mother Nature's air conditioner for the lakefront. Highs will be held down lakeside to the upper 70s today and tomorrow.

An isolated shower or thunderstorm can't be ruled out this afternoon or evening and again during the same time frame tomorrow. A lake breeze may produce some convergence (piling up the air) as cooler air sweeps inland and into warmer more unstable air. The chances are relatively small and most areas should be rain free.

The dew points have climbed back into the 60s and may take a run at 70° the next few days with the high humidity expected Saturday. They drop late Saturday into Sunday as a cold front brings in drier air. Sunday could be just as warm as Saturday but it will feel less humid. A more dramatic drop in dew points could be coming by the middle of next week as cooler more comfortable air arrives.

Relative humidity is one way to express the amount of water vapor in the air but dew points are the preferred measurement of moisture in the air for meteorologists like me. We started the week with dew points at "delightful" levels (50s) but they have now moved between "sticky" to "uncomfortable" levels. They will rise to "sweltering" levels Saturday.

Our highs continue to climb the next few days and top out near 90° Thursday through at least Saturday. Some models are suggesting a high near 90° Sunday too. The National Blend Of Models show a cooler pattern kicking in by the middle of next week as highs eventually slip back into the 70s.

Our warmer than average pattern may be shifting back below average overall by the end of the month. The 6-10 day forecast has outlooked Chicago for above average temperatures from August 23rd through August 27th. The longer range 8-14 day forecast favors us for cooler than average temperatures overall from August 25th through August 31st. This is the first below average forecast I have seen in some time. This suggests a cooler pattern kicking in towards the middle of next week. Average highs are in the lower 80s for this part of August.

The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts suggest a warmer than average end to August and start to September. The forecast for the week ending on September 3rd has us outlooked for above average temperatures. The forecast for the week ending on September 10th also favors us for above average temperatures overall. It takes a close inspection of both graphics to see the pixel representing the Chicago area is yellow. That corresponds to a temperature anomaly of .15° to .45° Celsius above average.

Mostly Hit Or Miss Rainfall

Today will be the 7th straight day without measurable rainfall at O'Hare. 1.33" of rain has fallen there so far this month which is down just over an inch from average. O'Hare is now .19" below average since June 1st. Both the short term and long term forecast isn't offering much hope for help with our northern suburbs ongoing drought.

Here is a recap of my Friday update on drought conditions based on numbers from last week's US Drought Monitor analysis:

It's another case of mostly good news from the latest US Drought Monitor analysis. The best news is that portions of Illinois in a severe drought dropped almost in half. 1.19% of the state is now in a severe drought (level 2 out of 4 levels) down from 2.19% last week. The bad news is 6.05% of the state is now in a moderate drought (level 1 out of 4 levels) up slightly from 6.00% last week. Northern Illinois is the only part of the state reporting drought conditions. There is more bad news. The portion of the state considered "abnormally dry" has increased to 15.20% from 10.99% last week.

The latest GFS model still hints at a spotty shower or thunderstorm today with a better chance for some scattered showers and thunderstorms late Saturday into early Sunday morning.

Adding up the rainfall that might come from those two chances on the GFS model yields about a third of an inch for most of us. Well south of the city and northern Indiana would see nearly three quarters of an inch of rain if this model verifies.

Yesterday's long range rainfall forecast favored us for above average rainfall but the latest forecasts trend us towards a more dry pattern. The latest 6-10 day forecast has the Chicago area favored for about average precipitation from August 23rd through August 27th. The longer range 8-14 day forecast favors us for below average precipitation from August 25th through August 31st. This is bad news for our far northern suburbs.

Most of the Midwest is also favored for above average rainfall in the long range forecasts too. The Midwest region's drought news is mixed with the latest analysis. The good news is the area in both the moderate and severe drought levels dropped slightly. The bad news is the area in an extreme drought increased slightly and for the first time a portion of the region slipped into an exceptional drought, the highest level.

The west region saw a a slight decrease in their extreme and exceptional drought area, the two highest categories of drought. The area in the two lowest levels of drought, moderate and severe, increased slightly. More than 95% of the west is in some level of drought and just over a quarter of it is in the worst level of drought, the exceptional category.

Here is my 7 day forecast:

Today: Partly to mostly cloudy, isolated shower/t-storm? High: 86 (79 along lakefront)

Thursday: Partly to mostly sunny, isolated shower/t-storm? Low: 70 High: 87 (79 lakeside)

Friday: Partly to mostly sunny, sct. t-storm possible Low: 72 High: 88 (82 lakeside)

Saturday: Partly to mostly sunny, pm sct. showers/t-storms Low: 71 High: 88

Sunday: Mostly sunny Low: 68 High: 87 (cooler lakeside)

Monday: Mostly sunny Low: 68 High: 85 (cooler lakeside)

Tuesday: Partly to mostly sunny Low: 69 High: 87 (80 lakeside)


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