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  • Tim McGill

Drought Becomes "Extreme"

Drought Moves To A New Level

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.

O'Hare is now down about a .84" below average for rainfall in June and down nearly nine inches since March 1st. These numbers do not include the rain that fell last night and early today. The latest drought analysis also does not reflect this most recent rainfall. Some of the most parched portions of our northern suburbs picked up around one to two inches overnight into early today.

The graphic below plots out the departure from average rainfall for the past thirty days ending yesterday. Some of our far northern suburbs had seen just 20% to 25% of average rainfall during this period. Chicago has seen about 25% to 50% of average rainfall over the past thirty days.

The GFS model is hinting at a more active pattern over the next ten days or so. Most of our rain today will fall during the early morning hours. A few scattered showers or thunderstorms may redevelop late today mainly south of the city. There is a slight chance for an isolated shower or thunderstorm Saturday afternoon but the best chance of rain this weekend will be late Sunday. Some of those storms could linger into early Monday.

Any thunderstorms that redevelop in the heat and humidity this afternoon could be strong to severe especially south of the city. The Storm Prediction Center has Chicago and areas south and southwest of the city in a marginal risk (level one out of five) area for severe weather with our far southern suburbs in a slight risk area (level two out of five).

The greatest risk from any afternoon or evening storms would be damaging winds and large hail. A marginal risk means isolated severe storms are possible while a slight risk means scattered sever storms are possible.

The latest GFS model total rainfall forecast includes any rainfall from today through about midday Monday. The range of rainfall expected varies from around a half inch to around an inch and a half of rain in total.

The long range precipitation probability forecasts are encouraging even if the latest drought analysis isn't. The latest 6-10 day forecast has us outlooked for above average precipitation overall from June 23rd through June 27th with the Chicago area in the bullseye of the highest probabilities. The longer range 8-14 day forecast also favors us for above average precipitation overall from June 25th through July 1st.

Our neighbors to the north in Wisconsin have also seen both a deepening and expansion of the drought mainly in the southern portion of the state along and just north of the Illinois border. Just under one percent of the state is now in an extreme drought. 8.84% of the badger state is now in a severe drought (up from 5.09% last week). More than half of the state (55.53%) is now in a moderate drought (up from 34.25% last week).

The Midwest as a region has seen increases in the moderate, severe and extreme levels of drought. The biggest jump is in the severe level. The area now in this category has nearly doubled compared to last week.

The West region is the most worrisome in terms of drought. There were slight increases in the moderate and extreme drought levels and a slight degrease in the severe drought level. Nearly three quarters of the region is in a severe drought with over half the region in an extreme drought. No change in the worst level of drought with 26.77% of the region still in an exceptional drought.

Steamiest Day Of The Year So Far?

The combination of heat and humidity today may make it feel like the hottest day of the year so far for some of us. Average highs for today's date are around 81°. We should be around 10° above average with highs in the lower 90s for most of us but upper 80s along the lakefront.

The HRRR model has hottest high temperatures today mainly south and southwest of the city.

Combining those expected high temperatures with our high humidity yields apparent temperatures or heat index values over 100° south and southwest of the city.

Cooler air is coming but not until Monday. Dew points are the preferred measurement of moisture for meteorologists. They will remain high through Saturday and then fall a bit Saturday night. The surge back well into the 60s and might tag 70° or a bit more on Sunday. The real relief in the form of cooler temperatures and more comfortable dew points arrives Sunday night into Monday as a cold front crosses through the area. Late Saturday there will be some relief from the mugginess along the lakefront as the winds turn in off the lake.

The National Blend Of Models has highs near 90° today through Sunday. We slip back into the 70s for highs Monday through Wednesday and then see more moderate heat build back for the end of next week.

Monday will feel 25° to nearly 30° cooler than today. The GFS model temperature anomaly forecast has us around 5° to 15° below average Monday afternoon.

The signal from the long range models is still fairly strong for a cooler than average end to June. This may be in part due to a more active rainfall pattern for the end of the month. The 6-10 day forecast has outlooked us for below average temperatures overall from June 23rd through June 27th. The longer range 8-14 day forecast also favors us for below average temperatures overall from June 25th through July 1st. Average highs for late June and early July 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.

Here is my 7 day forecast:

Today: Partly/mostly sunny, sct. shower/t-storm possible High: 92 (87 lakeside)

Saturday: Partly to mostly sunny Low: 69 High: 90 (83 lakeside)

Sunday: Partly/mostly sunny, sct. showers/t-storms late Low: 66 High: 90 (85 lakeside)

Monday: Partly/mostly cloudy, sct. showers/t-storms early? Low: 69 High: 77

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

Wednesday: Mostly sunny Low: 58 High: 77 (cooler lakeside)

Thursday: Partly to mostly sunny Low: 59 High: 83



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