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  • Tim McGill

Temps Tumble After Today But Bounce Back Big This Weekend

60s For Second Straight Day



Our spring rollercoaster temperature ride continues today as we peak the hill with more highs in the 60s. Prepare for a dramatic drop starting tomorrow. Like yesterday, some sunshine along with gusty southerly winds will push our highs to at least 10° above average.


Here are some of the stronger gusts reported on Monday:


51 mph at O'Hare

48 mph at Rockford

47 mph at Aurora

46 mph at Waukegan

45 mph At Wheeling


Look for highs today to top out in the middle to upper 60s with even a few spots south of the city hitting 70°.






Falling Fast Then Bouncing Back


The hourly temperature meteogram compares many different forecast models. The model consensus calls for colder air to sweep in tonight. The coldest part of this week will be Thursday morning when lows dip into the lower to middle 20s. Highs Thursday may fail to hit 40° but the recovery comes quickly after that. Highs by Easter Sunday should approach 70°.



We will jump nearly 50° between Thursday morning's lows and Sunday afternoon's highs. The GFS model's temperature anomaly forecast for Thursday morning has lows at least 10° below average for most of the Midwest. That means lows in the lower to middle 20s here.


By Sunday afternoon the temperature anomaly forecast has us nearly 20° above average. That means highs around 70°. Parts of the northern plains will be more than 30° above average. That would mean 80s as far north as South Dakota.




Quiet Pattern For Now


The GFS model precipitation meteogram doesn't call for any significant precipitation until next week. There is a chance for some spotty showers mainly south of the city this evening and tonight but the best chances for rain are early next Tuesday and then late the following Wednesday into Thursday.



Snow is still a possibility in northern Indiana early Thursday. Cold northerly winds will sweep over a relatively warm Lake Michigan and the result could be some light lake effect snow.


The GFS model snowfall accumulation forecast squeezes out some light accumulation in north central Indiana. It suggests a dusting to a third of an inch is possible. Yesterday's model run was squeezing out an inch or two. These numbers will no doubt be refined as we get closer to Thursday.







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%.









Strong Signal For Warm Start To April


The longer range temperature forecasts continue to signal a very mild start to next month. Average highs by the start of April are in the lower to middle 50s. Chicago is included in the highest probabilities of being above average in both of the longer range temperature forecasts. The latest 6-10 day temperature probability forecast has us outlooked for above average temperatures overall from April 4th through April 8th with at least an 80% probability. The longer range 8-14 day has us favored to stay above average overall from April 6th through April 12th with at least a 60% probability.




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.







Near Normal Precipitation

The longer range precipitation probability forecasts keep us around average for the first couple of weeks of April. The latest 6-10 day forecast has most of us favored for around average precipitation from April 4th through April 8th. South of the city and northern Indiana are favored for below average precipitation. The longer range 8-14 day forecast has most of the Chicago area outlooked for around average precipitation overall from April 6th through April 12th too. The exception is our far northwester suburbs which are favored for above average precipitation. 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 sunny, windy (gusts to 35 mph) High: 67


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


Thursday: Sunny skies Low: 26 High: 39


Friday: Mostly sunny Low: 28 High: 55


Saturday: Mostly sunny Low: 42 High: 67


Sunday: Partly to mostly sunny Low: 50 High: 71


Monday: Partly to mostly sunny Low: 52 High: 72


#ilwx


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