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  • Tim McGill

Cool Now But Chicago's New Normal Is Warmer

Jackets Needed For Weekend Weather

I still find it hard to believe that just last weekend we were basking in some sunshine and 80s. May started off feeling just like July. A cool pattern kicked in on Tuesday and began to wipe away the surplus warmth we had at the start of the month. We are now up 1.4° above average for May. After this weekend we should dip below average overall for the month. We will be at least 25° to 35° colder this weekend compared to last weekend.

We squeaked out a 60° high at O'Hare on Saturday. Today's highs will in the middle to upper 50s for most of us with just lower 50s along the lakefront. The average high for this date is 68°.

The culprit for the cool to cold couple of days coming up is a brisk breeze off the lake. The water temperature in southern Lake Michigan is in the 50s near the shore and 40s further into the middle of the lake. Today will be just a bit breezy but on Mother's Day the winds will gust to near 30 mph.

There will be a slow recovery into the 60s for highs by the middle of next week. There will be at least a component of the wind off the lake through Friday so each day should be cooler lakeside.

Make sure Mom has her jacket and umbrella for Mother's Day. Compared to average, Chicago will be one of the coldest spots in the country with afternoon temperatures more than 20° below average.

Next weekend should be much warmer than this weekend but not as warm as our first weekend of May. Highs a week from Sunday should be in the 60s and 70s.

Warmer Is The New Normal For Chicago

It might have felt more like March than May the past few days but climate data is showing that the new normal for Chicago and most of our country is warmer. NOAA updated their climate normals this week like they do every thirty years. Comparing our new normal period (1991-2020) with the previous one (1981-2010) shows widespread warming across the U.S., with the exception of the northern Great Plains (lower right map).

Our country is now nearly a half of a degree warmer that it was ten years ago. The 30-year average temperature for the 48 contiguous states has risen to a record high of 53.28° over the past thirty years. The warming is most striking when comparing the differences between the start of the 20th century and our most recent thirty years. The darkest two shades of red in the upper left map of the U.S. represents the biggest jumps in temperature. Those portions of the United States are between 2° to 4° warmer with a few smaller pockets as more than 4° warmer.

Chicago's new normal temperature jumped 1.5° in a decade. The effects of climate change are magnified even more when comparing the newest normals to data from the beginning of the 20th century (1901-1930). In Climate Central's study of 242 cities they found that 76% (183) of the cities analyzed reporting an increase of 1° or more.

Drought More Desperate Out West

I am repeating this portion of yesterday's blog post but updating the forecast graphics.

We are already down just under an inch of rain below average for May so far. We are down just over five inches below average since the start of spring on March 1st.

The update from the U.S. Drought Monitor for the Chicago area shows the drought here has deepened over the last week. Keep in mind that it doesn't consider Thursday's rainfall.

Nearly 98% of our region is at least abnormally dry. Nearly 60% of our area is now in a moderate drought which is up about 22% compared to last week.

The hardest hit areas have only seen about 25% to 50% of average rainfall during the last 90 days. Those more parched portions of northern Illinois are focused just west and northwest of the city.

The GFS model offers the most hope for putting a dent in the drought here on Sunday. Most of our rain this weekend will be early Sunday. Rain should at least taper off by midday. The rainfall next week looks to be lighter but we have at least three more chances for rain after tomorrow.

The GFS model precipitation accumulation forecast through the weekend suggests a range of rainfall from about a half of an inch in our northern suburbs to just over two inches south of the city. Most models keep the heavier rain south of I-80. Based on prior forecast tendencies, I think the GFS model might be too generous with the rainfall it expects through Sunday. Still, we will take anything we can get to help defeat this drought.

The drought is more dire in the western United States. Three out of the four drought categories saw an expansion in the last week. Nearly half of the west is in an extreme drought.

The two states in the worst shape out west include Arizona and Utah. Nearly 87% of Arizona is in an extreme drought and nearly 58% of the state is in an exceptional drought. Just over 90% of Utah is in an extreme drought and just over 57% is in an exceptional drought.

End To Cool Pattern In Sight

The longer range temperature probability forecasts are again suggesting we could break out of this cool pattern in a little over a week. The latest 6-10 day forecast still has us outlooked for cooler than average temperatures overall from May 13th through May 17th but the probabilities are low. The 8-14 day temperature probability forecast has us now flipped us in favor for returning to about average temperatures overall from May 15th through May 21st. Average highs for the middle of May are around 70°.

Help With Drought In Longer Range?

The longer range precipitation probability forecasts are now favoring us for a more active pattern that could help with our drought. Both forecasts have the Midwest and most of the middle of the country outlooked for above average precipitation for the middle of May. The latest 6-10 day forecast has Chicago favored for above average precipitation from May 13th through May 17th. The longer range 8-14 day forecast also has us favored for above average precipitation overall. It covers the period from May 15th through May 21st.

Here is my 7 day forecast:

Today: Partly to mostly sunny, a bit breezy High: 58 (53 lakeside)

Sunday: Cloudy, blustery & colder, rain mainly early Low: 38 High: 48 (cooler lakeside)

Monday: Partly to mostly sunny Low: 41 High: 56 (cooler lakeside)

Tuesday: Mostly sunny Low: 38 High: 60 (cooler lakeside)

Wednesday: Partly to mostly cloudy Low: 42 High: 63 (cooler lakeside)

Thursday: Partly to mostly cloudy, chance of rain Low: 44 High: 64 (cooler lakeside)

Friday: Partly to mostly cloudy, chance of rainy Low: 45 High: 66 (cooler lakeside)



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