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  • Tim McGill

Above Average Streak Stretches On

A Relatively Warm & Muggy Monday

This summer tied for the 8th warmest on record. We followed that up with the 5th warmest September on record. October is starting off warm too and there are indications this relatively mild pattern could stick around through at least the start of November. So far October is running nearly 13° above average.

Highs this week should be around 2° to 7° above average. Our lows will be between 10° and 15° above average. The average temperature for the day considers both the high and low. So this week it's primarily the lows that will be boosting those average daily temperatures.

The WRF Model has our highs climbing to near 70° today. The average high for today's date is 68°.

The GFS Model has similar highs for tomorrow.

Our highs climb back into the middle 70s by the end of the week and could approach 80° this weekend.

It looks like a warm weekend for the Chicago Marathon. The GFS temperature anomaly forecast for northern Illinois on October 10th still suggests it could be at least 10° to 15° above average. That would mean highs around 75° to 80° on race day.

Dew points will be in the lower to middle 60s the next few days. So it will be a bit muggy on this Monday and stay fairly humid much of this week.

Without our expected cloud cover and a wind off the lake we would probably be looking at 80° highs today and tomorrow.

Showers today will be more spotty in coverage compared to over the weekend. The best chance of rain will be during the middle of the day. I expect about 30% to 40% areal coverage.

Relatively Warm For A Relatively Long Time

Today will be the 9th straight day with above average temperatures. That streak could stretch to at least 19 straight days.

The National Blend Of Models has our highs at least a smidge above average for the next ten days after today. Today and tomorrow are the two coolest days with highs near 70° but then we warm into the middle 70s by the end of the week and near 80° by the weekend.

The past several runs of the longer range temperature outlooks have shown strong signals for a relatively warm pattern in Chicago. The latest are no different. The 6-10 day outlook has us favored for above average temperatures overall from October 9th through October 13th. The longer range 8-14 day forecast also favors us for above average temperatures overall. It covers the period from October 11th through October 17th. We are in some of the highest probability contours on both outlooks. Average highs for this period are in the middle 60s.

Looking even longer range shows more mild weather can be expected through the start of November. The even longer term 35 day temperature anomaly forecast still has a fairly strong warm signal for the Midwest and most of the country all the way through nearly the first week of November. We are outlooked to be between 4° to 8° above average overall for the period from October 1st through November 5th. 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.

Scattered To Spotty Showers

Our first weekend of October was wet at times. O'Hare saw .16" of rain this weekend and is running .18" below average. It is now just over 2" of rain below average since September 1st.

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.

The GFS model's meteogram for O'Hare shows spotty showers today with a better chance for scattered showers and maybe a few thunderstorms Thursday into Thursday night. It suggests a few showers later Sunday that would hopefully hold off until after the Chicago Marathon.

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

The longer range rainfall outlooks are fairy promising for a more active pattern during the middle of this month. The latest 6-10 day forecast has the Chicago area favored for above normal rainfall from September October 9th through October 13th. The longer range 8-14 day forecast has us outlooked for above average precipitation from October 11th through October 17th. While we need some rain here with our ongoing drought the west is in even more dire need of some precipitation. Both of these outlooks favor a good portion of that region for above average rainfall.

Here is my 7 day forecast:

Today: Mostly cloudy, scattered showers, breezy High: 70

Tuesday: Mostly cloudy, mild, breezy Low: 62 High: 70

Wednesday: Partly to mostly cloudy, pm showers Low: 62 High: 73

Thursday: Mostly cloudy, scattered showers & thunderstorms Low: 63 High: 73

Friday: Partly to mostly cloudy, sct. shower possible Low: 64 High: 75

Saturday: Partly to mostly sunny Low: 64 High: 77

Sunday: Partly to mostly sunny, pm sct. showers possible Low: 63 High: 78


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