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  • Tim McGill

Are The Drought's Days Numbered?

Drought Already Easing


It took a few months to develop but it may be over in a few weeks. Another example of weather whiplash in Chicago. There are encouraging signs that the drought that has targeted northern Illinois will see a significant reduction in the next several days. It's quite possible at least some of northern Illinois will see the drought come to an end.


The first sings of trouble showed up in March. We ended up 1.25" of rain below average. By the end of April, we were down 4.29" below average since March 1st or the start of meteorological spring. By the end of May we were down 6.99" below average for spring. We only received .01" of rain for the first eleven days of June. On June 11th we hit our low point officially for O'Hare down 8.54" below average. We have picked up 4.08" of rain since than and are now showing a surplus for June.


We are now up .75" above average for June rainfall but the rainfall deficit since March 1st is still over 6 inches below average. The more active and unsettled pattern that began yesterday should last through the weekend. This means several periods of showers and thunderstorms with locally heavy rainfall possible. A flash flood watch is in effect for most of the area until 7 am Friday.


According to the latest analysis from the US Drought Monitor there was no change in the area under a moderate drought but both the severe and extreme drought areas have decreased my more than half. Like last week, 9.8% of the state is still in a moderate drought (level 1 out of 4). The portion of Illinois in a severe drought (level 2 out of 4) has dropped from 6.43% last week to 3.12% this week. The portion of Illinois in an extreme drought (level 3 out of 4) has dropped to .96% this week compared to 2.84% last week.


This latest drought analysis does not any include rainfall since Wednesday.


The graphic below plots out the departure from average rainfall for the past sixty days ending yesterday. Some of our far northern suburbs had seen just 25% to 50% of average rainfall during this period. Chicago has seen about 50% to 75% of average rainfall over the past sixty days.



The GFS model keeps this active pattern coming through most of this weekend. There is a bit of a lull early Monday before more rounds of rain late in the day through early Wednesday. Another round arrives Wednesday night and continues into early Friday morning.



Some of the storms could be strong to severe. The Storm Prediction Center has northern Illinois in a marginal risk (level one out of five) area for severe weather for today and tonight.


Our threat of severe weather continues tomorrow. We are in a marginal risk area for severe storms Friday and Friday night.


A marginal risk means isolated severe thunderstorms possible that would be limited in duration and/or coverage and/or intensity. The greatest risk from from any severe storms would be damaging winds and large hail.


The HRRR model total rainfall forecast through this evening shows the potential for pockets of locally heavy rain. Some spots could pick up to two inches of rain just today with some torrential downpours.


The GFS model total rainfall forecast through the weekend and into Monday morning shows a range of rainfall from around an inch northwest of Chicago to two to four inches from the city south and westward.


The European model is even more generous with its rainfall forecast. It shows most of northern Illinois getting over three inches and some spots picking up almost twice that.


The long range precipitation probability forecasts shows a slight trend towards near normal precipitation for the start of July. The latest 6-10 day forecast has most of the Chicago area outlooked for above average precipitation overall from June 30th through July 4th. The longer range 8-14 day forecast splits the area with southern suburbs and northwest Indiana favored for above average precipitation overall from July 2nd through July 8th but the city and areas north and west favored for about average precipitation.



While Illinois has seen a serious dent put in the drought this past week, it is more of a mixed bag of news for the Midwest as a whole. The are of the region in a moderate drought has increased by almost 3% since last week. The area in a severe drought has decreased slightly (by .16%) and the area in an extreme drought has dropped by more than half (from .41% to .20%) compared to last week.



The West region is still in serious trouble. Three out of four categories of drought have shown increases over the past week. The areas in a moderate, severe and extreme drought all increased slightly but the area in an exceptional drought did not change. More than 78% of the region is in a severe drought, more than 55% is in an extreme drought and more than 26% is in an exceptional drought.




Muggy With Seasonable Warmth

The HRRR model has our highs today topping out near 80°. Cloud cover and occasional rain should keep most areas in the upper 70s. Average highs for today's date are 83°.



Dew points remain high for the next several days. Dew points are the preferred measurement of moisture for meteorologists. They should well stay in the upper 60s to lower 70s. This abundant moisture will provide the fuel for our showers and thunderstorms.


It will be breezy through at least Saturday. West and southwest winds will gust to near 25 mph the next couple of days.


Rain should taper off late this morning with more scattered showers and thunderstorms redeveloping during the afternoon. Rain chances ramp back up overnight and stay high through a soggy Saturday.


The National Blend Of Models has highs around or a bit above average (83°) with lower to middle 80s through Wednesday next week before cooler air arrives by the end of next week.


A cooler pattern could be coming for the start of July according to the long range temperature probability forecasts. The 6-10 day forecast has outlooked us for below average temperatures overall from June 30th through July 4th. The longer range 8-14 day forecast also favors us for below average temperatures overall from July 2nd through July 8th.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecast favors us for above average temperatures overall for the first half of July. The average highs for this period are in the lower to middle 80s. The temperature anomaly forecast for the week ending July 9th has us outlooked for above average temperatures overall. The forecast for the following week ending on July 16th also has Chicago outlooked for above average temperatures overall too. It takes a close look at this second map to see we are the exception for Illinois. Most of the state is outlooked for about average or below average temperatures.




Here is my 7 day forecast:


Flash flood watch through 7 am Saturday morning.


Today: Cloudy, breezy, sct. showers & t-storms (locally heavy rain possible) High: 78

Saturday: Periods of showers & thunderstorms, heavy rain possible Low: 68 High: 83


Sunday: Partly/mostly cloudy, sct. showers & t-storms Low: 70 High: 83


Monday: Partly to mostly sunny, sct. showers/t-storms Low: 68 High: 82


Tuesday: Partly to mostly sunny, sct. shower/t-storm possible Low: 68 High: 85


Wednesday: Partly/mostly cloudy, sct. shower/t-storm possible Low: 68 High: 85


Thursday: Partly to mostly sunny, sct. shower/t-storm possible Low: 64 High: 78 (cooler lakeside)


#ilwx

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