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  • Tim McGill

Might Be A Mild Winter But Cooler In The Short Term

La Nina Means More Moisture For Midwest

The National Oceanic and Atmospheric Administration issued their winter forecast for the United States and it has most of the hallmarks of a La Nina influenced season. That means a relatively dry and warm winter for our southern states. It also can mean a more snowy winter for the Midwest and the Pacific Northwest. A La Nina had developed prior to last winter and it had an impact on the season. Chicago had its 14th snowiest winter on record with 46.3" reported at O'Hare The average temperature last winter was 27.4° which was 1° above normal. It ranked as the 71st mildest winter out of 149 here.

NOAA'S official forecast has us "leaning" towards above average temperatures for the period of December through January. The strongest signal for a warmer than average winter is in the southeast.

NOAA's winter forecast has favored us for above average snowfall too. We are "leaning" towards a more snowy winter here. Most of the Midwest, Pacific Northwest and northern Rockies are also favored for more snow than average. This is a precipitation outlook so this might not all be snow during the months of December through January.

Keeping It Cool Through The Weekend

Thursday was the 41st day of the past 51 to have above average temperatures. There has only been one below average day this month. A cool change kicks in today followed by possibly the coldest night we have seen in just over five months.

Average highs for today's date are around 60°. The HRRR model has our temperatures topping out in the middle 50s this afternoon. Cloud cover and a northwest wind will combine to keep us about 5° below average.

Our first widespread frost of the season is likely tonight for areas northwest and west of Chicago. The GFS Model has our lows dropping into the lower to middle 30s from near Aurora to Antioch and further west. Lows in the lower to middle 40s are expected in and around the city.

The GFS Model keeps us cooler than average on Saturday too with highs only in the middle to upper 50s.

Clouds and rain on Sunday mean another cooler than average day to round out the weekend. Highs again expected to only reach the middle to upper 50s.

50s for highs today and tomorrow. The difference is that there will be more clouds than sun today with even a few spotty sprinkles possible along and southeast of I-55 but plenty of sunshine expected Saturday.

Clouds will build by Saturday evening with rain developing overnight into early Sunday.

Cool Pattern Settles In

We will be around or a bit below average for the next eleven days in a row. The National Blend Of Models has our highs holding in the middle to upper 50s through Tuesday before bouncing back to 60° on Wednesday. It then has hour highs falling back into the 50s from next Thursday through the following weekend.

The signal isn't as strong as previous forecasts but the longer range temperature outlooks still favor us 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 27th through October 31st. The longer range 8-14 day forecast favors us for above average temperatures from October 28th through November 4th. Average highs for this period are in the upper 50s.

The longer term 35 day temperature anomaly forecast favors us to be just a bit above average overall all the way through most of Thanksgiving week. We are outlooked to be between 1° to 3° above average overall for the period from October 20th through November 24th. 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.

Wet End To The Weekend

October started off soggy with over two inches of rain in the first two weeks. The pattern has been more dry lately with just .02" of rain over the past seven days. Officially the airport has seen 2.15" of rain so far this October which is .20" below average. A soaking rain Sunday into Monday could bring us back to about average. More on that below.

O'Hare is down just over 2.16" of rain below average since the start of fall on September 1st.

The most recent US Drought Monitor analysis was released Thursday. It was the second report in a row to bring mostly good news for Illinois.

The area in at least a moderate drought (level 1 our of 4) dropped dropped slightly compared to the previous analysis. The area in an at least severe drought (level 2 out of 4) did not change. The only big of discouraging news is the area consider "abnormally dry" jumped by almost 25%. That is the area most likely to slip into at least a moderate drought if conditions don't improve.

It's hard to see much change when looking at the side by side comparison of this week's Illinois drought map next to last week's. The only thing that stands out is the growing area of yellow or "abnormally dry" conditions.

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 Midwest receive more good news. Every drought category saw a reduction in area. The biggest drop was for portion of the region in an extreme drought. It was reduced by more than half compared to the last analysis.

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 a soaking rain starting later Sunday and lingering into early Monday. It also has another round of rain for us next Wednesday. This second round should be lighter that Sunday's rain.

The GFS model's total precipitation forecast through Monday morning shows northern Illinois getting soaked with a range of rainfall between an inch to nearly three and a half inches. The heavier amounts are expected near and south of the city with amounts tapering off north and northwest of there.

The longer range precipitation projections continue to trend towards less rainfall. The latest 6-10 day forecast has the Chicago area favored for about average rainfall from October 27th through October 31st. The longer range 8-14 day forecast has us outlooked for below average precipitation from October 29th through November 4th.

Here is my 7 day forecast:

Today: Mostly cloudy, cool, sprinkles possible south & southeast High: 56

Saturday: Mostly sunny Low: 39 High: 57

Sunday: Cloudy, rain likely, sct. t-storm possible south Low: 43 High: 56

Monday: Rain early, mostly cloud, chance of rain pm Low: 50 High: 56

Tuesday: Partly to mostly cloudy Low: 49 High: 59

Wednesday: Partly to mostly cloudy, sct. showers possible Low: 51 High: 61

Thursday: Partly to mostly cloudy, sct. showers possible Low: 47 High: 58


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