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  • Tim McGill

From Steamy & Stormy To Spectacular

Storms Today Then Just Sunshine Sunday

The Blue Angels practice their routine on Friday for the abbreviated version of the Chicago Air & Water Show this weekend. They may have to dodge some scattered showers and thunderstorms today but Sunday should feature plenty of sunshine.

Friday's high of 91° at O'Hare was the warmest in ten days. It was the 17th time this year O'Hare has reached 90°. We average 17 90° days for an entire year. We still have more summer to go and the chance to add to that total next week.

If it wasn't for some cloud cover today we probably would have another 90° day on this Saturday. The HRRR Model has our highs topping out near 90° again. I think the clouds though will keep us just shy of 90° but it will be close. No break from the heat at the beaches today with gusty southwest winds bringing the heat right up to and through the lakefront.

Those highs combined with high dew points means it will feel like the lower to middle 90s today but a brief break from the humidity is on the way for Sunday.

Thicker wildfire smoke from western fires will remain to our north and northeast today. The HRRR Model vertically integrated smoke forecast has the thicker smoke (depicted in orange) near the source of the wildfires out west and across the eastern portion of the Great Lakes region.

The heat index or apparent temperature values today will be similar to Friday. The heat index will climb into the lower to middle 90s today.

It will be a bit breezy with gusty winds out of the southwest. Those winds shift to the northwest early tonight with the arrival of a cold front that will flush out the high humidity and set us up for a spectacular Sunday. Dew points drop significantly later tonight into Sunday.

The best chance for rain is from the midday hours through this evening. No washout but some scattered showers and thunderstorms. Some spots may escape with no rain at all. Other spots might get some strong, gusty winds with some thunderstorms. No widespread severe weather is expected.

Today's dew points will be around 70° but they drop into the lower 60s by Sunday morning. As I mentioned, it will be a brief break from the steamy conditions we have seen the past few days. Dew points climb quickly back to 70° or above early next week and remain high through the middle of the 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. We will go from "sticky" to "uncomfortable" dew point levels today to "pleasant" levels Sunday.

We flirt with 90° today before cooling off almost ten degrees for Sunday. We bounce back to near 90° for Monday, Tuesday and Wednesday next week. The National Blend Of Models then drops our highs back to average or around average from Thursday through next weekend.

We might not only end this month with a warmer than average pattern but it continue right into the start of September. The 6-10 day forecast has outlooked Chicago for above average temperatures overall from August 26th through August 30th. The longer range 8-14 day forecast also favors us average temperatures overall from August 28th through September 4th. 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.

Still Looking For Significant Rain

Friday was the 9th straight day without measurable rainfall at O'Hare. 1.33" of rain has fallen there so far this month which is down 1.47" from average. O'Hare is now .60" below average since June 1st. The rainfall shortage is more acute across our norther suburbs where a stubborn drought persists.

Here is a recap from Friday's post that includes the latest analysis from the US Drought Monitor:

Most of northern Illinois didn't see any measurable rain during the seven day period from August 13th through the 19th. Zero to 5% of average rainfall fell during the period.

So it is no surprise we got mostly discouraging news from the latest US Drought Monitor analysis. The only good news is the portion of Illinois in a severe drought (level 2 out of 4 levels) dropped from 1.19% last week to .79% this week. The bad news is 7.33% of the state is now in a moderate drought (level 1 out of 4 levels) up from 6.05% last week. Northern Illinois is the only part of the state reporting drought conditions. More bad news. The portion of the state considered "abnormally dry" has increased to 15.42% from 15.20% last week.

The latest GFS model suggests scattered showers and thunderstorms today followed by a dry Sunday and Monday. The pattern becomes more active starting Tuesday. This meteogram is showing periods of showers and thunderstorms Tuesday into Wednesday with a few additional showers and thunderstorms possible on Thursday.

The total precipitation forecast through Sunday afternoon from the GFS model isn't promising for significant rainfall. There could be some locally heavier amounts with thunderstorms but the range of rainfall is from nearly nothing to about a quarter of an inch.

The longer range precipitation forecasts are calling for near normal rainfall through the end of August and into the start of September. The latest 6-10 day forecast has the Chicago area favored for about average precipitation from August 26th through August 30th. The longer range 8-14 day forecast also favors us for about average precipitation also from August 28th through September 3rd.

Most of the Midwest is also favored for below average rainfall in the long range forecasts. The Midwest region's drought news is all bad with the latest analysis. There was at least a small increase in every level of drought for the region.

The west region some minor good news with this latest analysis. The areas in a moderate, severe and extreme drought all saw at least a small decrease. Unfortunately the area in the most dire drought category saw an increase. 25.71% of the region is in an exceptional drought. That is up from 25.35% last week. More than 95% of the west is in some level of drought.

Here is my 7 day forecast:

Today: Partly to mostly cloudy, sct. showers & thunderstorms, breezy High: 89

Sunday: Mostly sunny, less humid Low: 68 High: 82 (76 lakeside)

Monday: Partly to mostly sunny Low: 66 High: 89

Tuesday: Partly/mostly sunny, sct. shwr/t-storm possible Low: 71 High: 89

Wednesday: Partly/mostly sunny, sct. shwrs/t-storms Low: 72 High: 89

Thursday: Partly/mostly sunny, sct. shwr/t-storm possible Low: 69 High: 83 (cooler lakeside)

Friday: Partly to mostly sunny Low: 68 High: 82 (cooler lakeside)


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