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  • Tim McGill

More 70s & More Sneezes

Warm Start To The Week

We will follow up the warmest weekend we have seen in nearly five months with a warm start to the week. O'Hare's high of 76° on Sunday tied with 1989 as the 8th warmest Easter on record for Chicago. It was also just 3° shy of a record for the date that goes back to both 1921 and 1929.

Today's highs will again be well above average. Gusty southwest winds along with at least partly sunny skies should push highs to near 80°.

Sneezing Season Expanding

I've got bad news for all of us seasonal pollen allergy sufferers. There are more than 25 million of us according to the Centers for Disease Control and Prevention. As climate change continues to warm our world it is stretching the allergy season out. Typical spring temperatures are coming sooner in the year and typical fall temperatures are lingering longer. Climate Central did a study of the changing lengths of growing seasons for over 200 locations across our country. 82% of the places they examined have seen their growing seasons lengthened. Chicago's has lengthened by nearly two weeks in the past 50 years. A longer growing season means a longer allergy season.

The consistent increase in carbon dioxide in our atmosphere can stimulate plant growth and contribute to higher pollen concentrations. Grass pollen levels could double if carbon dioxide levels increased from current levels (around 400 ppm) to 800 ppm according to one study. That jump could happen by the end of this century if the emission trends we are seeing continue without any new attempts to mitigate them.

In my case, the hay fever I experience every spring is only an annoyance since there are effective over the counter medications I can take to deal with the symptoms. However, seasonal allergies can be more serious for a lot of people because they can decrease their quality of life if they suffer from respiratory problems such as asthma.

Streak Of 70s Continues

The hourly temperature meteogram compares many different forecast models. Wednesday should be our fifth straight day with highs in the 70s. The last time that happened was back in early November of last year. Even though we fall to near 60° for a high by Friday, that is still above the average high of 55°.

The GFS model's temperature anomaly forecast has temperatures between 20° to 25° above average for most of the Midwest on Tuesday too. The only part of the country tomorrow afternoon that is below average is the northern and central Rockies.

More Active Pattern

The GFS model precipitation meteogram has several periods of rain over the next ten days. The best chance overall is late Wednesday into early Thursday. There is a chance both today and tomorrow for an isolated shower or thunderstorm but both days should be mainly dry.

We could actually use some rain around here. There has only been a trace of rain in total over the past ten days. Just 1.25" of rain has fallen since March 1st. The GFS model suggests around an inch to an inch and a quarter of rain could fall in total through Friday this week.

Mild Through Middle Of Month & Beyond

The warm weekend we just enjoyed may not be an anomaly for this April. The long range temperature probability forecasts have us outlooked to stay above average overall just past the middle of the month. The latest 6-10 day temperature probability forecast has us outlooked for above average temperatures overall from April 10th through April 14th. The longer range 8-14 day also has us favored for above average temperatures overall from April 12th through April 18th.

The even longer range Subseasonal Experiment (SubX) forecast is signaling a warmer than average end to April. The temperature anomaly forecast for the week ending April 23rd has us outlooked to be above average for the period. The forecast for the following week ending on April 23rd has us outlooked to stay above average overall. Average highs for the end of April are in the middle 60s.

Drying Out By Middle Of The Month?

The longer range precipitation probability forecasts suggest a drier pattern may develop after this week. The latest 6-10 day forecast has Chicago favored for about average precipitation from April 10th through April 14th. The longer range 8-14 day forecast has us outlooked for below average precipitation overall from April 12th through April 18th too. The risk for spring flooding is above average for many area rivers. More on that below.

Spring Flood Risk Forecast

The National Weather Service considers many risk factors for spring flooding. They include snow cover, soil moisture, and current river conditions.

"A significant snow cover with high water content can increase the chances of flooding once warmer weather melts the snow. Elevated soil moisture conditions reduce the amount of rainfall that is soaked up by the ground and increase the amount of water that then runs off into area streams. Above average river levels reduce the river rise required to reach flood stage, while below average river levels would require an increased amount of river rise to reach flood stage."

The map shows the locations where there is a greater than 50% chance of moderate or minor flooding during March through May 2021.

Their latest forecast suggests the flood risk is above average for many of our area rivers. The Des Plaines and Fox rivers in particular need to be watched closely.

Here is my 7 day forecast:

Today: Partly to mostly cloudy, isolated shower/t-storm possible, breezy High: 77 (cooler lakeside)

Tuesday: Partly to mostly cloudy Low: 55 High: 79 (cooler lakeside)

Wednesday: Partly sunny, sct. showers/t-storms early & late Low: 56 High: 67 (cooler lakeside)

Thursday: Showers mainly early, mostly cloudy, cooler Low: 53 High: 66 (cooler lakeside)

Friday: Partly to mostly sunny Low: 49 High: 62

Saturday: Partly to mostly sunny Low: 47 High: 63

Sunday: Partly to mostly sunny Low: 47 High: 66 (cooler lakeside)



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