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  • Tim McGill

Heavy Spring Showers Coming But So Are 60s

Reasons For Hope


Monday looked and felt more like February than the middle of March. 1.8" of snow fell officially at O'Hare. Most of us saw between 1" to 3" of spring snow.


How about some good news? The sun begins setting at 7 pm or later starting today. We are now enjoying nearly three more hours (2 hours and 50 minutes) of daylight compared to the darkest days of December. We will be seeing highs near 60° by Sunday! Starting a week from today our average highs hit 50°.


Highs today will be a bit below average. Most of us should top out in the lower 40s but highs along the lakeshore will be a few degrees colder with a north or northeast wind off of Lake Michigan. The average high for today's date is 47°.




Weekend Warm Up


Yesterday was only the third day this month with temperatures below average so far. We are now running nearly 8° above average this month. Highs should hold in the lower to middle 40s through the end of the week but a warm up is on the way for the weekend. Highs should reach to near 60° both Sunday and Monday.


The GFS model's temperature anomaly forecast for Sunday afternoon shows the extent of our weekend warm up. Temperatures by then should be nearly 10° to 15° above average. Most of the Midwest, Great Lakes region and the northeast will be at least that much above average or even more.





Spring Soaker Thursday?


The GFS model is suggesting some moderate to possibly heavy rain late Wednesday night into Thursday. There could be a wintry mix in areas well northwest of the city Thursday morning and again Thursday evening. More on that below. Another round of at least moderate rain is possible next Tuesday.



The GFS model squeezes out the heaviest rain Thursday south of the city. The range of rainfall is as little as a quarter of an inch north of the city to more than an inch and a half south of Chicago in total Wednesday night and through Thursday.



It may be cold enough Thursday morning and possibly briefly Thursday evening to see some of the rain mix with and change over to some snow. Most of the models are suggesting a dusting or less but a few models are showing a range from about a third of an inch to just over two inches in total. I'm expecting the lower end of that range. We could possibly see a dusting to a half inch in some spots mainly north and northwest of the city.



The latest GFS model snowfall accumulation forecast through early Friday does show nearly an inch of snow well northwest of the city. It keeps heavier snowfall amounts well west of here along the Iowa border where up to four inches could fall.








Strong Winds & Big Waves


Strong winds later this week could whip up big waves along the southern end of Lake Michigan. Strong northeast winds Thursday could build waves to nearly ten feet by late in the day and into the night. A lakeshore flood advisory may need to be issued for the period.





March May End Mild


Strong signals for a milder than average end to March continue to show up in the longer range temperature probability forecasts. The latest 6-10 day temperature probability forecast has us outlooked for above average temperatures overall from March 21st through March 25th. The probabilities are highest from here north through the Great Lakes and east to the New England area. The longer range 8-14 day has us favored for above average temperatures overall from March 23rd through March 29th too.




The even longer range Subseasonal Experiment (SubX) forecast is signaling a mild end to March and above average start to April. The temperature anomaly forecast for the week ending April 2nd has us outlooked to be above average for the period. The forecast for the following week ending on April 9th keeps us above average overall. It suggests the temperatures will be even more above average compared to the forecast for the previous week. Both forecasts have the majority of the country milder than average overall.







Above Average Precip Pattern

The longer range precipitation probability forecasts keep us outlooked for above average precipitation overall through nearly the end of the month. The latest 6-10 day forecast has us favored for above average precipitation from March 21st through March 25th. The longer range 8-14 day forecast has northern Illinois outlooked for above average average precipitation overall from March 23rd through March 29th but at the lowest end of the probability range. The risk for spring flooding is above average for many area rivers. More on that below.






Springing Forward


The Climate Prediction Center's seasonal forecast for spring suggests a mild and moist pattern overall here. The temperature probability forecast for the months of March, April and May have us outlooked for above average temperatures overall. The precipitation probability forecast for the same period has us outlooked for above average precipitation overall.






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."


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: A.M. fog, mostly cloudy, not as blustery High: 44

Wednesday: Partly to mostly cloudy Low: 32 High: 47 (colder near the lake)


Thursday: Cloudy, windy, rain likely (possibly mixed with snow early) Low: 37 High: 44


Friday: Partly to mostly sunny Low: 31 High: 47 (colder near the lake)


Saturday: Mostly sunny Low: 30 High: 54 (cooler near the lake)


Sunday: Partly to mostly sunny Low: 36 High: 59


Monday: Mostly cloudy Low: 43 High: 62


#ilwx

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