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  • Tim McGill

Cooler Pattern Kicking In Soon

So Long To 90s For Now


Tuesday was the 11th 90° day of the year so far. O'Hare hit 91° yesterday. We have nearly doubled the average number of 90° days we typically see by the end of the first week of July. There may be a few spots that come close to 90° today but for most of us it is safe to say so long to the 90s at least through the weekend. The HRRR model has our highs today topping out in the upper 80s for most areas but only in the middle 70s along the lakefront. Average highs for today's date are 85°.



The dew points have yet to drop so it will still be very muggy today. Dew points are the preferred measurement of moisture for meteorologists. Dew points will stay in the middle to upper 60s through today but then fall into the 50s Thursday afternoon.


Winds will continue to be a bit breezy out of the southwest today. We will have some gusty winds tomorrow too but the difference will be the direction of the wind. Winds will shift off the lake late this afternoon to bring in cooler and more comfortable air for the end of the week and weekend.


The best chance of rain over the next two days will be late this afternoon through late tonight. Scattered showers and thunderstorms could squeeze out some locally heavy rainfall.


The National Blend Of Models has highs in the 80s today and then sliding into the 70s for the next five days in a row. We then warm back to more seasonably warm temperatures by Tuesday next week.


We will experience an almost 20° swing in temperatures from Tuesday's highs to Thursday's. After lower 90s yesterday we will only reach the lower 70s tomorrow. The temperature anomaly forecast for Thursday drops our afternoon temperatures to around to around 15° below average.


The longer range temperature probability forecasts are now favoring the Chicago area for an above average middle of the month. Average highs are in the middle 80s. The 6-10 day forecast has outlooked us for above average temperatures overall from July 12th through July 16th. The longer range 8-14 day forecast also favors us for above average temperatures overall from July 14th through July 20th.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts doesn't have a very strong signal for the last two weeks of July. The average highs for this period are in the middle 80s. The temperature anomaly forecast for the week ending July 23rd has us outlooked for temperatures slightly above average. It takes a keen eye to see the pixel representing the Chicago area is shaded in light yellow. A stronger signal for a warmer end of the month is found just north of here and out in the western US. The forecast for the following week ending on July 30th also has Chicago outlooked for about average temperatures. We remain between the stronger warm signal north and west of here and a strong cool signal south of Chicago.



Dry Streak Stretches To Day Six

Tuesday was the 6th straight dry day at O'Hare. We are now a .65" of rain below average for July and down nearly four inches below average since the start of meteorological spring back on March 1st. I will have an update on our drought when I review the latest US Drought Monitor analysis on Friday.


Here is a recap of our drought status that I posted last Friday:


June really helped turned the tide in terms of rainfall. The period of March through May saw the rainfall deficit grow at O'Hare to nearly 7 inches below average. June ended up seeing 6.78" of rain. The month ended up with 2.68" of rain above average. According the the latest analysis from the US Drought Monitor, our recent rains helped put a slight dent in the drought.


Comparing this week's analysis to last week's shows some improvement. The portions of Illinois in a moderate and severe drought have diminished. The moderate drought (level 1 of 4) area has dropped from 9.18% to 7.55%. The severe drought area (level 2 of 4) has dropped from 3.12% to 2.22%. The extreme drought area (level 3 of 4) is unchanged at .96%.


A more active pattern could be coming starting day that would mean many more chances for drought relief. The GFS model has several potential rounds of rain in the forecast over the next ten days beginning with this afternoon and tonight.



The GFS model total rainfall forecast through this Friday morning squeezes out around a couple tenths of an inch to around four tenths of an inch of rain. There could be some locally heavier rainfall amounts with some thunderstorms.


I ran the model out through the Sunday afternoon to include any weekend rainfall. The additional rainfall this week brings the range of rainfall with this forecast to between about a half inch to nearly an inch of rain in total.


The longer range precipitation probability forecasts continue to favor us for a more active pattern for the middle of the month. The latest 6-10 day forecast has the Chicago area favored for above average precipitation overall from July 12th through July 16th. The longer range 8-14 day forecast also has us favored for above average precipitation overall from July 14th through July 20th.







Review Of Our Warm & Wet June


June ended up being a warmer than average and wetter than average month. The average temperature of 74.3° tied as the 4th warmest June on record. The nearly 7 inches of rain that fell tied for the 13th wettest June on record.



June had a rather moist end to the month with some spots picking up nearly nine inches of rain. 3.75" of rain fell at O'Hare. That means 77% of the rainfall we get on average for the entire month fell in just one week.



So far this year was feast or famine. We feasted on nearly 7 inches of rain during a 19 day stretch between June 11th through the 30th. Prior to that it took more than 5 months to get almost the same amount of rainfall. During this drier stretch we had only 2 days with thunderstorms but during the soggy end of June there were more than five times that amount of thunderstorm days.




Here is my 7 day forecast:


Today: Mostly cloudy, mainly pm showers & thunderstorms High: 86 (76 lakeside)


Thursday: Spotty AM showers, partly to mostly cloudy Low: 64 High: 73 (68 lakeside)


Friday: Partly to mostly sunny, spotty pm shower/t-storm Low: 60 High: 78 (72 lakeside)


Saturday: Mostly cloudy, sct. showers (isolated t-storm?) Low: 63 High: 74 (cooler lakeside)


Sunday: Mostly cloudy, sct. showers/t-storms Low: 64 High: 78 (cooler lakeside)


Monday: Partly to mostly cloudy, sct. showers/t-storms Low: 68 High: 79


Tuesday: Partly to mostly sunny, sct. shower or t-storm possible Low: 68 High: 83


#ilwx

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