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  • Tim McGill

Strap In For Spring Rollercoaster Ride

Southerly Winds & Sunshine = 60s


The spring temperature rollercoaster ride began on Saturday when highs reached into the 60s. That was followed by a dramatic drop on Sunday. Most of us saw highs near 50° right around midnight but most of the daylight hours yesterday were spent in the 40s and gusty northwest winds made if feel more like the 30s.


Sunshine today and gusty southerly winds means highs in the lower 60s which is at least 10° above average.






Fire Weather Danger


The combination of dry conditions and gusty winds today will lead to an elevated to critical fire weather danger for parts of the area today. Burning is strongly discouraged.


Red flag warnings have been issued well west of Chicago.


The National Weather Service warns of the impacts for Winnebago, Boone, Ogle and Lee county:


The combination of strong winds, very low relative humidity, mild temperatures, and exceptionally dry fuels will likely promote extremely dangerous behavior of any fires. Any

fires that develop outdoors will likely spread rapidly. Any planned outdoor burning should be postponed today.





Another Dramatic Drop Coming


The hourly temperature meteogram probably best shows the rollercoaster temperature ride this week. 60° or warmer highs today and tomorrow then we fall back into the 40s for highs Tuesday and struggle to get to 40° on Thursday. We warm back up for the weekend with highs near 70° by Easter Sunday.



The GFS model's temperature anomaly forecast for this afternoon has highs here around 10° to nearly 15° above average (lower left image). By Wednesday afternoon our highs fall to around 5° to 10° below average (lower right image).





Mostly Dry Week


The GFS model has only two real chances for precipitation over the next ten days. The first is late Tuesday night into early Wednesday morning. A few wet snowflakes can't be ruled out early Wednesday as the the precipitation comes to an end. The next round of rain wouldn't be until a week from Wednesday.


While it may feel more lake May than March today it could feel more like winter within a few short days.


The GFS model snowfall accumulation forecast actually squeezes out some lake effect snow early Thursday morning in north central Indiana. Some spots could get an inch or two. Still early and subject to change so stay tuned.







Revised Spring Forecast


NOAA recently revised their spring forecast which covers the period from March through May. More of the country is now favored for above average temperatures overall for this spring. Our probabilities jumped to between 40% and 50% for seeing a relatively mild season. The only part of the country favored to be below average with temperatures overall is the northwest portion of Washington state.


We are still favored for above average precipitation this spring but our probabilities dropped from 40% to 50% down to between 30% and 40%.









Mild Start To Next Month


The longer range temperature forecasts have us starting off April above average overall. Average highs by the start of next month are in the lower to middle 50s. The latest 6-10 day temperature probability forecast has us outlooked for above average temperatures overall from April 3rd through April 7th. The longer range 8-14 day has us favored to stay above average overall from April 5th through April 11th.






The even longer range Subseasonal Experiment (SubX) forecast is signaling a mild middle to April and then a flip to a cooler than average pattern towards the end of the month. The temperature anomaly forecast for the week ending April 16th has us outlooked to be above average for the period. The forecast for the following week ending on April 23rd has us outlooked to dip back below average overall. It's a fairly dramatic forecast flip.








A Dry Start To April

The longer range precipitation probability forecasts continue the dry pattern that develops this week all the way into nearly the middle of next month. The latest 6-10 day forecast has us favored for below average precipitation from April 3rd through April 7th. The longer range 8-14 day forecast has northern Illinois outlooked for below average precipitation overall from April 5th through April 11th 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: Becoming sunny, windy (gusts over 40 mph) High: 63


Tuesday: Becoming mostly cloudy, shower possible late, windy Low: 47 High: 61


Wednesday: Partly to mostly sunny Low: 34 High: 45


Thursday: Sunny skies Low: 25 High: 40


Friday: Mostly sunny Low: 28 High: 54


Saturday: Mostly sunny Low: 41 High: 65


Sunday: Mostly sunny Low: 48 High: 68


#ilwx


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