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  • Tim McGill

Real Fall Will Finally Arrive Soon

Above Average Streak Stretches On

Today will be the 18th straight day with above average temperatures at O'Hare. So far the month is running just over 11° above average. If you are a fan of cooler fall weather, hang in there because it will arrive soon. Saturday could be the coolest day in over four months.

Average highs for today's date are around 64°. The GFS Model has our highs this afternoon in the upper 60s to lower 70s.

We should continue with at or above average temperatures Thursday and Friday. The GFS Model finally brings in some cool and crisp weather that we associate with more "real" fall weather by Saturday morning. Lows are forecast to dip into the lower to middle 40s. It will be the first time we have fallen into the 40s since late May.

Saturday's highs may fail to climb out of the 50s for some of us. It could be the coolest day in a little more than four months. The GFS Model has highs near 60°.

Temperatures bounce back on Sunday just in time for the Bears to host the Packers at Soldier Field. Not exactly "Bear Weather". The GFS Model temperature anomaly forecast for Sunday afternoon has our temperatures between 4° to 6° above average. The average high for Saturday is 62°. That would mean highs in the middle to upper 60s.

More mild weather before we cool things down for this weekend. Highs today should climb into the lower 70s. Our official high for Thursday may occur just after midnight tonight with a high near 70° but most of tomorrow afternoon will be in the middle to upper 60s.

Fairly strong south winds today will gust occasionally over 20 mph today.

A few rounds of rain are possible today with one coming during the midday and early afternoon hours and another later tonight into early Thursday morning. More rain possible late Thursday night into early Friday morning.

Cooler Air Coming But Overall Mild Pattern

A couple of cooler days coming but overall the longer range forecasts keep us mild for the remainder of October and even the start of November. The National Blend Of Models has our highs slipping to just 60° on Saturday but we warm back up to near 70° by Monday. Another shot of relatively cool air could be coming by the end of next week.

The overall mild pattern we have been in all this month could hang around towards the end of the month based on the longer range temperature outlooks. The 6-10 day outlook has us favored for above average temperatures overall from October 18th through October 22nd. The longer range 8-14 day forecast also favors us for above average temperatures overall. It covers the period from October 20th through October 26th. Average highs for this period are in the upper 50s to lower 60s.

The even longer range temperature anomaly forecast keeps the overall mild pattern going into next month. The longer term 30 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 the first week of November. We are outlooked to be between 4° to 6° above average overall for the period from October 11th through November 10th. 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 Rain

O'Hare now has a surplus of .27" of rain above average for the month of October after .12" of rain fell there yesterday. O'Hare is still down 1.69" of rain below average since the start of September.

Recent rain may have helped to put a dent in the ongoing drought across much of northern Illinois. The most recent US Drought Monitor analysis was released last Thursday.

The areas in a moderate drought (level 1 our of 4) and severe drought (level 2 out of 4) increased slightly from the previous week while the area in an extreme drought (level 3 out of 4) remained unchanged.

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 for the entire Midwest was mostly good. The areas in a moderate, severe and extreme drought all decreased at least slightly. The area considered abnormally dry increased slightly.

After a dry summer and start to fall we have received abundant rainfall over the past week or so. Most of northern Illinois has picked up between 150% to 500% of average rainfall during the seven day period ending on October 12th. This rain should help with the drought and will probably be reflected in the new US Drought Monitor analysis that I will post about on this Friday.

The GFS model's meteogram for O'Hare keeps us the pattern relatively active through Friday night. Most of the rain on Thursday is favored for areas southeast of the city but there are at least occasional chances for rain today, tomorrow and all the way into the early morning hours on Saturday. Most of the weekend and nearly all of next week should be dry.

The GFS model's total precipitation forecast through the weekend may be a bit overdone but it offers hope for help with the drought. The range of rainfall in the forecast is from a bit more than a half inch of rain to just over an inch and a half. Our northern and northwest suburbs that need the rain the most are favored to get the lower end of that range.

The Storm Prediction Center has removed us from the "marginal" risk area for severe weather today and tonight. The threat of severe weather here has diminished. The most unstable set up for severe weather has shifted to the west.

A marginal risk is level 1 out of 5 possible risk levels. It is the low end of the risk categories but means "an area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity".

The longer range precipitation outlooks dry us out for the second half of this month. The latest 6-10 day forecast has the Chicago area favored for below normal rainfall from September October 18th through October 22nd. The longer range 8-14 day forecast has us outlooked for below average precipitation from October 20th through October 26th.

Here is my 7 day forecast:

Today: Mostly cloudy, breezy, pm sct. showers & t-storms High: 72

Thursday: Spotty showers possible early & late, mostly cloudy Low: 60 High: 70

Friday: Mostly cloudy, scattered showers Low: 54 High: 64

Saturday: Mostly sunny, cooler Low: 45 High: 59

Sunday: Mostly sunny Low: 46 High: 67

Monday: Mostly sunny Low: 48 High: 69

Tuesday: Mostly sunny Low: 53 High: 69


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