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  • Tim McGill

From Sunshine To Severe Storm Risk

More Steamy & Eventually Stormy


After a couple of relatively cooler and more comfortable days we turn the heat and humidity up today and brace for some possibly strong storms tonight. More on the severe storm risk in my discussion below.


Sunshine and southwest winds will push highs today well above average again. The HRRR model has highs today near 90°. Average highs for today's date are around 81°.



The humidity will be rising along with the heat. Dew points are the preferred measurement of moisture for meteorologists. They have been very low the past few days, even bottoming out in the upper 30s. Today's dew points will be relatively dry as they start out in the 40s but jump into the 60s by tonight. Some gusty southwest winds today will be bringing us the heat and eventually the higher humidity. Other than a few isolated showers and thunderstorms today the best chance of rain will be between 10 pm tonight and 7 am tomorrow morning.



The National Blend Of Models has highs hovering near 90° today through Sunday. A cooler pattern kicks in early next week and highs slide back into the 70s for Tuesday and Wednesday.


A cooler pattern could be coming for the end of this month too. Above average rainfall (see below) for this period might be contributing to this cool change. The 6-10 day forecast has outlooked us for below average temperatures overall from June 22nd through June 26th. The longer range 8-14 day forecast also favors us for below average temperatures overall from June 24th through June 30th. Average highs for late June are in the lower to middle 80s.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecast contradicts these forecasts a bit. It favors us for a warmer than average end to June and start to July. The average highs for this period are in the lower to middle 80s. The temperature anomaly forecast for the week ending July 2nd has us outlooked for above average temperatures overall. The forecast for the following week ending on July 9th also has Chicago outlooked for above average temperatures overall too.




Hope For Help With The Drought


It's feast or famine with our rainfall. O'Hare is now down about a .75" below average for rainfall in June and down 8.74" since March 1st. I'll have the latest drought analysis from the US Drought Monitor on Friday. Tonight's rain could be heavy enough at times to produce some localized flooding.


Before I get to the rainfall forecast, here is a short recap of my drought update (before Saturday's rain) from last week:


The U.S. Drought Monitor says 8.52% of the state is in a moderate drought. That is an increase of 1.6% compared to last week's analysis. 20.89% of the state is considered "abnormally dry" which is an increase from 16.97% last week. "Abnormally dry" is just one level away from a moderate drought. The amount of Illinois in a severe drought remains unchanged at 4.58%. I'll have the latest analysis on the drought Friday from the U.S. Drought Monitor.


The GFS model is advertising a more active pattern starting tonight. We have a round of showers and thunderstorms this evening through early Friday with another coming later Sunday into Monday. Another unsettled period is forecast for late next Thursday into the following Saturday.


There will be a few isolated showers and thunderstorms today. Tonight's showers and thunderstorms could be strong and even severe. The greatest risk in terms of severe weather is damaging winds and large hail. The window for these seems to be between 10 pm tonight and around 3 am Friday. The Storm Prediction Center has most of the Chicago area in a marginal risk (level one out of five) area for severe weather with our far northwestern suburbs in a slight risk area (level two out of five).


The Storm Prediction Center has most of the Chicago area in a marginal risk (level one out of five) area for severe weather with our far northwestern suburbs in a slight risk area (level two out of five).



The latest GFS model total rainfall forecast through Monday morning includes two rounds of rain, tonight into early Friday and then later Sunday into Monday morning. The range of rainfall forecast is around a half inch well south of the city to about an inch or inch and a half for most of us to more than two inches well northwest of Chicago. This heavier rainfall is targeted to help some of the more parched parts of Illinois that are currently in a moderate to severe drought.


The long range precipitation probability forecasts favor us for a more active pattern that could lead to above average rainfall as we finish out June. The latest 6-10 day forecast has us outlooked for above average precipitation overall from June 22nd through June 26th. The longer range 8-14 day forecast also favors us for above average precipitation overall from June 24th through June 30th.




Here is my 7 day forecast:


Today: Partly/mostly sunny, isolated showers/t-storms High: 90


Friday: Partly/mostly cloudy, sct. showers/t-storms mainly early Low: 70 High: 91


Saturday: Sunny skies Low: 69 High: 88 (cooler lakeside)


Sunday: Partly to mostly sunny, sct. shower/t-storm mainly late Low: 68 High: 88


Monday: Partly/mostly cloudy, sct. showers/t-storms Low: 67 High: 78


Tuesday: Mostly sunny Low: 57 High: 74 (cooler lakeside)


Wednesday: Mostly sunny Low: 56 High: 78


#ilwx

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