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  • Tim McGill

Summer To Surge Back By The Weekend

A Cool To Almost Chilly Morning


The low at Aurora fell to an almost chilly 47° this morning. O'Hare's low of 58° was the coolest in over two months. We will bounce back quickly and by Saturday it will feel just like July with highs near 90°.


Today will be a bit below average. HRRR Model has our highs today in the lower to middle 70s. The lower end of that range will be along the lakefront with a breeze off of Lake Michigan keeping it coolest there. The average high for today's date is 78°.


Summer surges back on Saturday. The temperature anomaly forecast has a big portion of the country from the southwest through the Rockies and northward into the Midwest with temperatures as much as 10° to 25° above average. Here in Chicago we should be about 10° above average with a high near 90°.


Today's wind will be lighter out of the northwest compared to yesterday. It will continue to bring in relatively cooler air from Canada. Low dew points mean a mild and pleasant day in terms of humidity.


Our winds shift to the southwest around midnight and will start to pump more heat and eventually humidity our way just in time for the weekend.


There is little to no chance of rain through Friday. The weekend should remain dry too. The exception is northern and north central Indiana which woke up to some lake effect showers. They should dry up early this afternoon.


The thicker wildfire smoke aloft will remain to our west today but it is building in our direction. The HRRR Model vertically integrated smoke forecast has the highest concentrations from the source of the fires in California and the Pacific Northwest and over the northern Rockies spilling into portions of the plains.


The National Blend Of Models has our highs still in the 70s today. There may be a streak of five straight days with highs in the 80s beginning on Friday. The hottest day during that streak would be Saturday with a high near 90°.


The signal is strong again for a warmer than average period overall for the middle and latter part of September. We aren't alone with most of the country outlooked for a warm pattern during this time. The 6-10 day forecast has outlooked Chicago for above average temperatures overall from September 14th through September 18th. The longer range 8-14 day forecast also favors us for above average temperatures overall from September 16th through September 22nd. Average highs for this period are in the middle to upper 70s.



The Climate Forecast System or coupled forecast system (both names abbreviated CFS) is a medium to long range numerical weather prediction and a climate model run by the National Centers for Environmental Prediction (NCEP). The signal for the next 30 days isn't strong but it is indicating it will be warmer than average overall from now through the beginning of October.






Straight Line Wind Damage In Minooka


The National Weather Service had 74 local storm reports on Tuesday that included hail as big as 2 inches in diameter in Dixon and a wind gust to 68 mph in Bull Valley. The strongest wind reports came from Minooka where there was an initial report of a tornado by spotters.



The National Weather Service sent a survey crew to the Minooka, Lisbon and Channahon area Wednesday to determine the cause of damage from strong winds on Tuesday.


Here are their findings:


Thunderstorms produced widespread damaging straight line winds across southern Kendall, northern Grundy, and eastward into western Will County. This includes the communities of Lisbon, Minooka, and Channahon. Much of the damage was consistent with winds of 60 to 70 mph, however, there were pockets of more intense damage consistent with 70 to locally greater than 80 mph winds. Numerous trees were downed, including some into homes, and there was also some mostly minor structural damage. Extensive ground surveying did not reveal any conclusive evidence of tornadic damage, though we will continue to evaluate any additional information that becomes available.


The tornado warning that was issued for that area Tuesday was one of 37 so far in northeast Illinois. That ties for third place with 2008 as the most tornado warnings in our area for a year.







Dry Through The Weekend


O'Hare has seen less than a third of an inch of rain in the past two weeks. The rainfall deficit is higher north of there where all of Lake and McHenry county are in a moderate to severe drought. I will update our drought status on Friday.


Here is a recap from Monday's post with more on our drought status:


More mixed news from the latest analysis from the US Drought Monitor. The past two weeks of rainfall (ending on September 8th) has been either feast or famine in northern Illinois. Much of the Lake and McHenry County saw between 10% to 50% of average rainfall in the past two weeks while some spots south of the city have seen 150% to 300% of average.



The US Drought Monitor analysis reports an increase in the area seeing a moderate drought compared to the previous analysis. The area in a moderate (level 1 out of 4 levels) drought in Illinois has jumped to 9.96% from 7.93%. The areas in a severe drought (level 2 out of four levels) did not change and remains at .79%.


The Midwest region's drought news though is much better. Every drought level saw a decrease in coverage area. The biggest drop was seen in the area in a severe drought (level 2 out of 4). It dropped from 18.95% in the previous analysis to 12.68% in the most recent.


The latest GFS model keeps us dry through Sunday. A more active pattern may develop next week with the highest chances for rain coming later Tuesday through Thursday.



The forecast for rainfall through this weekend from the GFS model shows little to no rain expected here.

Running out the forecast through next Thursday offers more hope for help with the drought. The model squeezes out about one to three inches of rain in total. This forecast will evolve as we get closer to next week so stay tuned.



Weak signals for the longer range rainfall forecasts but they favor us dropping from above normal rainfall to below average. The latest 6-10 day forecast has the Chicago area favored for above average rainfall from September 14th through September 18th. The longer range 8-14 day forecast favors us for below average precipitation from September 16th through September 22nd.






Here is my 7 day forecast:


Today: Partly to mostly sunny, mild & pleasant High: 76 (72 lakeside)


Friday: Sunny skies, warmer Low: 58 High: 80


Saturday: Mostly sunny, breezy & warmer Low: 64 High: 89


Sunday: Partly to mostly sunny Low: 68 High: 84 (cooler lakeside)


Monday: Partly to mostly sunny Low: 65 High: 85


Tuesday: Partly to mostly sunny, sct. showers/t-storms Low: 66 High: 85


Wednesday: Partly/mostly cloudy, sct. showers/t-storms Low: 65 High: 77


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