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  • Tim McGill

90° Days Adding Up Quickly

More Possible Today & Tomorrow

Our high hit 90° at O'Hare on Friday. That is the 8th time this year we have had a high of 90° or hotter. By this time of the year we normally see about three 90° days. On average we typically see 17 total 90° days per year. We are only a couple of weeks into summer and we have already seen nearly half the number of 90° days we see in an average year. From this point on through summer we average about 12 more 90° days.

The HRRR model has a high of 91° at O'Hare today. The model keeps it cooler along the lakefront with a breeze developing off the lake. Look for highs lakeside in the lower to middle 80s and temperatures possibly dropping into the 70s during the afternoon as the breeze off the lake strengthens.

Moderate levels of humidity today so the apparent temperatures or heat index values should be close to the actual air temperatures or a degree or two higher. We do crank up the humidity/dew points on Sunday to near 70°. Dew points are the preferred measurement of moisture for meteorologists. When the dew points/moisture level is at it's maximum the temperatures begin to fall a bit so the heat index values on Sunday should be just a few degrees higher than Saturday's. It may feel like the lower to middle 90s during the peak heat of the day Sunday.

Notice the wind shifting off the lake this afternoon on the hourly plot below. That will cool things down all the lakefront today.

The highest threat of rain between today and tomorrow is from about 1 pm Sunday through Sunday night into early Monday morning. There is a chance for an isolated shower or thunderstorm later today but mainly well south of the city and in northwest Indiana.

The National Blend Of Models has highs near 90° today and tomorrow. We slip back into the 70s for highs Monday an Tuesday. This cooler air will coincide with more comfortable levels of humidity too. We bounce back to near 90° by Thursday.

Today and tomorrow will be around 10° above average. The GFS model temperature anomaly forecast has us around 5° to 15° below average by Monday afternoon. That would mean temperatures in the middle to upper 60s.

The signal from the long range models is again calling for a cooler than average pattern to close out June and start July. The 6-10 day forecast has outlooked us for below average temperatures overall from June 24th through June 28th. The longer range 8-14 day forecast also favors us for below average temperatures overall from June 26th through July 2nd. Average highs for late June and early July are in the lower to middle 80s.

More Drought Relief Sunday

Here is a recap of my post from earlier this week with details on our drought:

Our ongoing drought in northern Illinois has both deepened and expanded according to the latest analysis from the US Drought Monitor. Almost 3% of the region is now in an extreme drought for the first time this year. That's the third of four levels of drought with "exceptional" being the fourth or worst level. 6.43% of Illinois is now in a severe drought (up from 4.58% last week). 9.18% of the state is in a moderate drought (up from 8.52% last week). The worst of the drought is centered in the northeast corner of the state and includes most of Lake County, all of McHenry county and portions of Cook, Kane, DeKalb and Boone counties. This does not take into consideration the rain that fell Thursday night into Friday morning.

O'Hare is now down about a .77" below average for rainfall in June and down nearly eight inches since March 1st.

The graphic below plots out the departure from average rainfall for the past thirty days ending yesterday. Most of the area north and northwest of Chicago and even some parts of the city itself have seen between 25% to 50% of average rainfall for the past 30 days. A few spots well west of the city have seen just 10% to 25% of average. This analysis includes the rain the fell Thursday night into Friday morning.

Friday's post also included a look at Wisconsin, the Midwest and where the drought is hitting hardest, the western states.

The GFS model has the highest threat of rain over the next ten days coming later Sunday into Monday morning and then again next Friday.

Father's Day may not be a washout with most of the rain falling late in the afternoon and into Sunday night. The thunderstorms that do develop may be strong to severe. The Storm Prediction Center has the Chicago area and all of northern Illinois in a slight risk area (level two out of five) for severe weather on Sunday.

The biggest risk from these Sunday's storms is damaging winds but even isolated tornadoes can't be ruled out. A slight risk means scattered severe storms are possible.

The latest GFS model total rainfall forecast through Monday morning squeezes out a wide rang of rainfall. This reflects the possibility of locally heavy rainfall later Sunday into Monday morning. Some spots well southwest of the city get just about a half inch of rain while in and around the city and some western suburbs possibly picking up nearly three inches of rain.

The long range precipitation probability forecasts remain encouraging and hint at a more active pattern that could help ease the drought. The latest 6-10 day forecast has us outlooked for above average precipitation overall from June 24th through June 28th with the Chicago area close to the bullseye of the highest probabilities. The longer range 8-14 day forecast also favors us for above average precipitation overall from June 26th through July 2nd.

Here is my 7 day forecast:

Today: Partly/mostly sunny, sct. shower/t-storm possible mainly south High: 92 (84 lakeside)

Sunday: Partly/mostly cloudy, pm sct. showers/t-storms Low: 66 High: 91 (84 lakeside)

Monday: Partly/mostly cloudy, sct. showers/t-storms early? Low: 67 High: 75

Tuesday: Mostly sunny Low: 55 High: 74 (cooler lakeside)

Wednesday: Mostly sunny Low: 58 High: 80 (cooler lakeside)

Thursday: Partly/mostly sunny, isolated shower/t-storm? Low: 63 High: 87 (cooler lakeside)

Friday: Partly to mostly sunny, sct. showers/t-storms Low: 69 High: 88 (cooler lakeside)



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