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  • Tim McGill

No Real Cool Fall Weather In Sight

Many Mild Days Ahead

Today will be the 10th day in a row with above average temperatures. So far October is running nearly 12° above average. I think this streak of above average days will stretch to at least 20 days in a row. There are signs that a relatively mild pattern will stick around into the start of next month. While there will be a couple of cooler days, overall, we should be above average for the next four weeks or so.

The average temperature for the day considers both the high and low. Our lows so far this October have been between 61° and 65°. Those temperatures are close to our average highs for this time of the year.

The GFS Model has our highs at least a couple of degrees above average today. The average high for today's date is 68°.

It should be a warm Chicago Marathon weekend. The GFS Model temperature anomaly forecast for Saturday afternoon has our temperatures between 15° to 20° above average. That translates into a high near 80° or even more on Saturday.

The start time for the marathon on Sunday is 7:30 AM. It will be a relatively warm start to the race with temperatures near 70°. The high on Sunday should also be near 80°.

Today and tomorrow won't be that warm but will be above average. Highs today should top out near 70° and into the lower to middle 70s on Wednesday.

Winds will gust over 20 mph today out of the east and northeast.

There will be a few spots of drizzle today or a few spotty sprinkles but the best chance of rain comes late tomorrow into Thursday.

Above Average Temps Keep Coming

The National Blend Of Models has our highs above average for the next eleven days in a row. They peak this weekend near 80°.

The consistent strong warm long range temperature outlook signal continues. The 6-10 day outlook has us favored for above average temperatures overall from October 10th through October 14th. We are in the 70% to 80% probability contour, the highest for this outlook. The longer range 8-14 day forecast also favors us for above average temperatures overall. It covers the period from October 12th through October 18th. We are in the 60% to 70% probability contour, the second highest for this outlook. Average highs for this period are in the middle 60s.

The relatively warm signal has also been consistent for the even longer range temperature forecast. The longer term 35 day temperature anomaly forecast still has all of the Midwest and most of the country outlooked for above average temperatures overall all the way through nearly the first week of November. We are outlooked to be between 4° to 6° above average overall for the period from October 2nd through November 6th. The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members The model tries to give an idea of the amount of uncertainty in a forecast by running an ensemble of multiple forecasts which are each tweaked a bit with their initial conditions.

More October Showers

The weekend rain put a small dent in the drought for a portion of northern Illinois. Another round of rain is coming Wednesday night and continuing during the day on Thursday. So far October is running about a third of an inch of rain below average and O'Hare is down 2.25" below average since the start of September.

The latest US Drought Monitor analysis from the U.S. Drought Monitor had our drought deepening compared to last week's analysis.

Here is a recap from Friday's post:

The areas in a severe drought (level 2 out of 4) and extreme drought (level 3 out of 4) areas have more than doubled compared to last week. The area in a moderate drought increased slightly. Northern Illinois is being hit the hardest by the drought.

A side-by-side comparison shows the change between September 28's drought conditions and the prior analysis back on September 21st.

Drought Conditions On 9/28 (Left Image) Vs. 9/21 (Right Image)

Here is a summary of the impacts the ongoing drought is having on northern Illinois from the National Weather Service:

Volunteer observers across far northern Illinois indicate much lower then typical stream flows on area creeks and rivers, particularly along Beaver Creek and the Kishwaukee River.

Reports also indicate that lawns have gone dormant and there has been some stress to the trees. Few impacts to agriculture have been received recently, though the dry conditions and stressed crops have resulted in an early start to the harvest season across northern Illinois. Data available from the Illinois State Water Survey, USGS, and NCEP indicate that soil moisture, groundwater, and surface water levels remain below normal.

The drought news was also discouraging for the Midwest as a region. The areas in a moderate, severe and extreme drought all expanded.

An analysis of the past 30 days of rainfall that includes are weekend rain shows just only slight improvements for portions of the area. North of the city in eastern Lake County and south of the city for southern Will County and most of Kankakee County benefitted from rainfall over the weekend. Most of our northern Illinois is still rather parched for the period, only receiving about 25% to 75% of average rainfall over the past four weeks.

The GFS model's meteogram for O'Hare has most of our rain falling on Thursday. There could also be some scattered showers on Friday, Saturday and late Sunday into Monday but there will be many more dry hours than wet ones.

The GFS model's total precipitation forecast through Friday still has a wide range of rainfall. The model suggest anywhere between about a third of an inch of rain to around nearly an inch of rain in total.

The latest longer range rainfall outlooks are nudging us back to above average precipitation for the middle of this month. The latest 6-10 day forecast has the Chicago area favored for above normal rainfall from September October 10th through October 14h. The longer range 8-14 day forecast has us outlooked for above average precipitation from October 12th through October 18th. We are among the lowest probabilities that favor above average rainfall but we'll take that as a positive.

Here is my 7 day forecast:

Today: Mostly cloudy, patchy drizzle or spotty sprinkles High: 70

Wednesday: Partly to mostly cloudy, mild, sct. showers possible late Low: 62 High: 73

Thursday: Mostly cloudy, scattered showers & thunderstorms Low: 63 High: 72

Friday: Partly to mostly cloudy, sct. shower possible Low: 63 High: 75

Saturday: Partly to mostly sunny Low: 64 High: 80

Sunday: Partly to mostly sunny, pm sct. showers possible Low: 66 High: 79

Monday: Partly to mostly cloudy, sct. showers possible Low: 60 High: 75


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