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  • Tim McGill

Just Another Muggy Monday

Steamy & Stormy Pattern


It feels like the tropics descended upon Chicago. High humidity levels will linger through Thursday with dangerous heat index values tomorrow.

Cloud cover and occasional showers and thunderstorms will limit our heating today but not the mugginess on this Monday. The HRRR Model has our highs today in the lower to upper 80s. Average highs for today's date are around 83°.



Tuesday will see a lot more sunshine and that will heat us up into the lower 90s. Tomorrow will be one of the hottest days of the year so far in terms of temperature and humidity.

The heat index or apparent temperature values will be between 100° to 105°.



Dew points will stay in the lower to middle 70s through Tuesday and possibly all the way through Thursday this week. Gusty southwest winds continue to transport air rich with moisture from the Gulf Coast.


All this heat and humidity will fuel thunderstorms early and late today which could become severe. Another round of storms is possible late Tuesday into Tuesday night that could also turn severe. More on that below.



Tropical level dew points will be with us through Thursday and then those dew points drop dramatically. They fall into the 50s Friday and remain at more comfortable levels through next weekend into early next week.


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. Expect "sweltering" dew points the next few days then "delightful" dew points settle in on Friday.



Dew points aren't the only thing dropping late this week. Temperatures fall back to about average by Friday. The National Blend Of Models has highs near or above 90° Tuesday through Thursday before falling Friday and staying around average through early next week.



Any peaks of sun today will be through more haze. The HRRR Model vertically integrated smoke forecast suggests wildfire smoke from western fires and Canada will waft into our skies again today.



Here are some articles related to wildfire smoke that you may be interested in:



The long range temperature probability forecasts keep us warmer than average overall from this weekend through the following weekend.. The 6-10 day forecast has outlooked Chicago for above average temperatures from August 14th through August 18th. The longer range 8-14 day forecast favors us for above average temperatures overall from August 16th through August 22nd. Average highs are in the lower 80s for this part of August.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts start us out near normal and then flip us back to above average. The forecast for the week ending on August 27th has us outlooked for about average temperatures. The forecast for the week ending on September 3rd favors us for above average temperatures overall.





Wet Start To Week


We have seen just under a quarter of an inch of rain at O'Hare in the last ten days. August is now running .89" below average. Our best shot of rain this week will be early and late today and then late tomorrow.


Here is a recap from my post on Friday with the updated drought statistics for our northern suburbs:


Mostly good news from the latest US Drought Monitor analysis. The good news is that portions of Illinois in a moderate and severe drought have dropped slightly. 6% of the state is now in a moderate drought (level 1 out of 4 levels) down from 7.17% last week. 2.1% of the state is now in a severe drought (level 2 out of 4 levels) down from 2.31% last week. Northern Illinois is the only part of the state reporting drought conditions. The bad news is the portion of the state considered "abnormally dry" has increased to 10.99% from 9.74% last week.



The latest GFS model shows shots of rain in the form of scattered showers and thunderstorms late today into early Tuesday morning with more chances Wednesday and early Friday.



Some of the storms today into tonight might be strong to severe. Some of the storms late Tuesday may also become severe.


The Storm Prediction Center has us in the slight risk category for severe storms today into tonight. The biggest threat would be damaging winds and large hail but even an isolated tornado is possible.


A slight risk means "an area of organized severe storms, which is not widespread in coverage with varying levels of intensity."



The Storm Prediction Center has us in a slight risk category for late Tuesday and Tuesday night too.



Tuesday's main threat is also damaging winds with large hail. Slight risk means severe storms should be short-lived and/or not widespread with isolated intense storms possible.



The GFS model total rainfall forecast through this weekend squeezes out a range of rainfall from a quarter of an inch in our far northern suburbs to just over an inch south of the city. Locally heavy rainfall is possible today and tomorrow in particular and some spots could receive quite a bit more rain than is depicted by this model.



The Midwest region's drought news last week was discouraging overall. The good news is the area in a moderate drought fell from 27.33% to 26.26%. The area in a severe drought increased to 17.59% from last week's 16.74%. The area in an extreme drought nearly doubled to 6.72%, up from 3.73% last week.


The drought numbers for the west continue to stagger me. The area in the highest levels of drought (extreme and exceptional) diminished slightly but the area in the lower levels of drought (moderate and severe) increased at least slightly. Nearly two-thirds of the region is in an extreme drought and about a quarter of it is in an exceptional drought.


The longer range precipitation probability forecasts are discouraging for those of us in a drought. They keep us relatively dry from this weekend through the next. The latest 6-10 day forecast has the Chicago area favored for below average precipitation from August 14th through August 18th. The longer range 8-14 day forecast also favors us for below average precipitation from August 16th through August 22nd.



Here is my 7 day forecast:


Today: Mostly cloudy, periods of showers/t-storms (some strong) High: 84


Tuesday: Partly to mostly sunny, sct. showers/t-storms late (some strong) Low: 73 High: 93


Wednesday: Partly to mostly cloudy, sct. shower/t-storm possible Low: 74 High: 90


Thursday: Partly to mostly sunny, sct. shower/t-storm possible Low: 73 High: 91


Friday: Mostly sunny, cooler & less humid Low: 68 High: 82 (cooler lakeside)


Saturday: Mostly sunny Low: 64 High: 83 (cooler lakeside)


Sunday: Mostly sunny Low: 65 High: 85 (cooler lakeside)


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