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  • Tim McGill

Mini-Heatwave Hits This Weekend

Wildfire Smoke Still Here

O'Hare's high of 88° on Tuesday was the warmest we have seen in two weeks. A cold front swept south of the city last night so we'll drop back below average today. Highs this afternoon will be around 10° or more cooler than yesterday. The HRRR Model has highs today in the middle to upper 70s for most areas. A wind off the lake will keep it cooler lakeside with highs there in the lower 70s. The average high for today is 85°. Today will be the coolest day we see for the next several days. We could see a streak of four days in row with a high of 90° or more starting on Saturday.

We will see some peeks of hazy sunshine today. That haze is being caused by wildfire smoke from out west and in Canada wafting all the way east to Chicago. It has been mainly elevated the past few days (around at least three to five thousand feet) but some of the smoke may make it to the surface. The HRRR Model vertically integrated smoke forecast has smoke spreading all the way from the west coast to the east coast today.

Our wind shifted off the lake late Tuesday and will continue off the lake through Thursday morning. Winds begin to shift back to the south on Thursday as we jump back into the 80s for highs. This southerly wind will pump up not only more heat but more humidity as well with dew points climbing tomorrow.

The wind off the lake continues to cool us down on Wednesday as highs slip back into the 70s.

There may be a spotty sprinkle or shower today but the best chance of rain over the next two days is late tomorrow afternoon into tomorrow night. That is when we could see some scattered showers and thunderstorms.

The National Blend Of Models has our highs bouncing back quickly from today's 70s to the middle 80s Thursday and near 90° Friday and into the lower 90s this weekend.

Both heat and humidity will be building. Dew points are the preferred measurement of moisture for meteorologists. Dew points may fall briefly into the 50s today and then soar to near 70° by late Thursday. Dew points in the 50s will almost make it feel like fall but dew points near 70° will make it feel almost tropical. Dew points should stay high through the weekend into early next week.

The combination of heat and humidity will make it feel like 100° or more this weekend for most of the Chicago area. The GFS model shows widespread heat index values hitting those levels on Sunday.

The longer range temperature probability forecasts have an even stronger signal today for a warmer than average end to July and start to August. The vast majority of the country is favored for a toasty period. The 6-10 day forecast has outlooked us for above average temperatures overall from July 26th through July 30th. The longer range 8-14 day forecast also favors us for above average temperatures overall from July 28th through August 3rd. Average highs are in the lower to middle 80s for the end of July and start to August..

The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts hint a cooler pattern may be coming for the first half of August. The temperature anomaly forecast for the week ending August 6th has us outlooked below average temperatures overall. The forecast for the following week ending on August 13th keeps us cooler than average overall but not quite as cool as the first week of the month.

No Real Drought Relief In Sight

Tuesday was our fourth dry day in a row. July is now running .89" of rain below average at O'Hare and nearly 6" below average for the year. The worst drought conditions are across our far northern suburbs. I'll have the updated drought analysis from the US Drought Monitor on Friday.

Here is my recap from last Friday's post:

The area of Illinois in a moderate drought (level 1 out of 4) has dropped slightly from 7.40% last week to 7.32% this week. The area of the state in a severe drought (level 2 out of 4) has increased slightly from 2.22% a week ago to 2.40% this week. The area experiencing an exceptional drought (level 3 out of 4) remains unchanged at .96". All in all, very little change in our drought status from last week.

The latest GFS model doesn't offer any hope for real drought relief over the next ten days. The best we can hope for is some scattered showers and thunderstorms at times beginning late Thursday and into Friday with more possible over the weekend. Scattered is the key word though since we really need a more widespread soaking rain to make a difference in this drought.

The GFS model total rainfall forecast through the weekend suggests a range of rainfall from around three quarters of an inch to just over an inch of rain is possible. This model has been overdoing it with rainfall so take these numbers with a grain of salt. If this verifies, it would be welcome rain but much more is needed to put a real dent in our drought.

While the long range precipitation probability forecasts have a generally dry outlook for most of the country it does hint at some hope for parts of the Rockies. Any rain there at all is welcome and could help bring some relief to drought stricken areas out west. The drought will drag on here into the start of August. The 6-10 day forecast has the Chicago area favored for below average precipitation overall from July 26th through July 30th. The longer range 8-14 day forecast also has us favored for below average precipitation overall from July 28th through August 3rd.

Here is my 7 day forecast:

Today: Partly to mostly cloudy, breezy & cooler High: 78 (73 lakeside)

Thursday: Partly to mostly cloudy, spotty shower/isolated t-storm late? Low: 66 High: 85

Friday: Partly to mostly sunny, sct. shower/t-storm possible Low: 71 High: 89

Saturday: Partly to mostly cloudy, sct. showers/t-storms Low: 73 High: 91

Sunday: Partly to mostly sunny Low: 72 High: 92

Monday: Mostly sunny Low: 72 High: 91 (cooler lakeside)

Tuesday: Mostly sunny Low: 73 High: 90 (cooler lakeside)


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