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  • Tim McGill

So Long 70s

Mild Pattern Nice While It Lasted

Wednesday's high of 72° was the third straight day with a high in the 70s. Wednesday was also the 19th above average day of the past 20 and the 40th of the past 50 days with temperatures above average. October is now running nearly 9° above average. Our mild fall pattern comes to a close today. While we will cool off, we are only expected to drop to just a bit below average the next few days. No signs of any extreme cold in sight.

Our official high for today occurred just after midnight as we started the morning in the lower 60s. Average highs for today's date are around 61°. The HRRR model has our temperatures tumbling into the lower to middle 50s this afternoon and possibly falling into the upper 40s north and northwest of the city.

So after 70s on Wednesday we face the possibility of frost Friday morning. It would be patchy light frost. The GFS Model has our lows dropping into the middle to upper 30s well north, northwest and west of Chicago. There is a chance of a more widespread frost Saturday morning.

The GFS Model keeps us rather cool on Friday. Highs tomorrow should only reach the middle to upper 50s. Much cooler than the 70s we enjoyed to start this week but still only a few degrees below average. By Sunday our average highs fall below 60° for the first time this fall.

We spend the next two afternoons in the middle to upper 50s. Gusty west and eventually northwest winds will add insult to injury today.

We have about a 20% chance of rain through most of this Thursday. Any showers would be spotty and light. There is also a chance tomorrow for some lake effect showers in northern Indiana but most of us should be dry on Friday.

Less Of A Rollercoaster Ride

After 70s early this week we fall into the 50s for highs through Monday. The National Blend Of Models has our highs bouncing back to 60° or warmer during the middle of next week. This is a change from earlier forecasts that were hinting at a 70° high next week. This latest forecast has flattened out the range of highs for the next eleven days.

The signal stays fairly strong for a mild overall pattern through the end of this month and into the start of November. The 6-10 day outlook has us favored for above average temperatures overall from October 26th through October 30th. The longer range 8-14 day forecast favors us for above average temperatures from October 28th through November 3rd. Average highs for this period are in the upper 50s.

There are still signs this mild pattern could continue well into November. The longer term 35 day temperature anomaly forecast has us in an overall mild pattern through the first three weeks of November. We are outlooked to be between 2° to 4° above average overall for the period from October 19th through November 23rd. 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.

A Sunday Soaker?

After a soggy start to the month it has turned a bit drier. We have only picked up a trace of rain in the last five days at O'Hare. Officially the airport has seen 2.15" of rain so far this October which is .09" below average. Only spotty and light rain possible today but a more substantial rain could be coming Sunday. More on that below.

O'Hare is still down just over 2" of rain since the start of fall on September 1st.

The most recent US Drought Monitor analysis was released last Thursday. It reflects the benefit of our recent rainfall. Here is a recap of that report:

The ongoing drought in northern Illinois was dealt a blow over the past week or so. Some serious rain put a significant dent in the drought. I have more details on the status of the drought further down in my post. The drought started back in the middle of April and arguably had two peaks. One was in the middle of June when nearly 3% of the state was in at least an extreme drought (level 3 out of 4). The second peak occurred just last week when the worst level of drought actually decreased but nearly 16% of the state was in at least a moderate drought, the highest point so far this year.

The areas in at least a moderate drought (level 1 our of 4) dropped nearly 28% while the area in an at least a severe drought (level 2 out of 4) decreased a whopping 86% from last week's analysis. We no longer have any part of the state in an extreme or exceptional drought (levels 3 and 4 out of 4).

The side by side comparison of this week's Illinois drought map next to last week's helps to visualize the improvement we have seen in just seven days time.

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 good too. The areas in every level of drought decreased since the last update.

Most of northern Illinois has benefitted from a moist start to the month. Most of the Chicago area has received between 110% to 300% of average rainfall so far this month.

The GFS model's meteogram for O'Hare suggests some spotty showers today but a more soaking rain Sunday into Monday.

The HRRR model has total precipitation forecast through today only squeezes out a few hundredths of an inch of rain with most of that falling north of the city.

The GFS model's total precipitation forecast run out through Monday morning has some substantial rain falling here, especially south of the city. The model shows a range of rainfall from nearly an inch for most of the area but increasing to two to three inches south of the city.

The longer range precipitation projections are trending towards less rainfall. The latest 6-10 day forecast has the Chicago area favored for above average rainfall from October 26th through October 30th but the longer range 8-14 day forecast has us outlooked for near normal precipitation from October 28th through November 3rd.

Here is my 7 day forecast:

Today: Mostly cloudy, breezy, spotty showers Afternoon High: 57

Friday: Partly to mostly cloudy Low: 40 High: 56

Saturday: Mostly sunny Low: 39 High: 58

Sunday: Cloudy, showers likely Low: 43 High: 58

Monday: Mostly cloudy, scattered showers Low: 47 High: 59

Tuesday: Partly to mostly sunny Low: 49 High: 61

Wednesday: Partly to mostly cloudy, sct. showers possible Low: 50 High: 63


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