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  • Tim McGill

A Jump From Wintry Weather To Almost Summer

Some Snow Today Followed By Frost Tonight


Hard to believe that just two weeks ago we were enjoying an early taste of summer with highs in the 80s. Yesterday felt more like February with Tuesday's high of just 43° making it the second coldest day of April. Snow fell in spots with a trace officially at O'Hare and as much as 1.1" in Downers Grove. More wintry weather today with a variety of precipitation possible. More on that below.


Highs today will again be around 20° below average. Average highs for today are around 61°. Look for highs today only in the lower 40s. Freeze warnings are in effect tonight as lows could dip into the middle to upper 20s in our colder spots.





Plenty Of Precipitation Types


There is a variety of potential precipitation types in today's forecast. We could see anything from rain and snow showers to graupel and even a few isolated thunderstorms. Graupel is the Dippin' Dots of frozen precipitation. It is also known as "soft hail" or "snow pellets". Graupel forms when when supercooled water droplets freeze onto a snow crystal. The supercooled water coats snowflakes and the result is small soft pellets of ice.


The GFS model suggests rain and snow showers for today into early tonight. Rain is possible also late Friday into Saturday. We then enjoy a few dry days before some scattered showers and thunderstorms possible at times late Wednesday into Friday.



The accumulated snowfall meteogram for O'Hare shows a range of snowfall for today into tonight. The model range is from a dusting to around a third of an inch. Most of us will not see any accumulation. The areas favored for any minor accumulation is along the lakefront and in northern Indiana.



The GFS model suggests a dusting to around four tenths of an inch possible south of the city and into northern Indiana.





A Swing Of 50° Or More Coming


The hourly temperature meteogram compares many different forecast models. After just 40s for highs today our temperatures tumble into the middle to upper 20s tonight. By Tuesday we could be seeing highs near 80°. We will warm at least 50° between early Thursday morning and Tuesday.



A freeze warning is in effect tonight from midnight until 9 am Thursday morning. We will fall to near freezing in the city but as cold as the middle to upper 20s in outlying areas.



After feeling like February today and tonight we can look forward to feeling just like June by Tuesday. Highs Tuesday afternoon should soar well into the 70s and possibly tag 80° in a few spots.


The temperature anomaly forecast might be the best way to visualize this upcoming weather whiplash. Tomorrow morning's temperatures will be around 10° to 15° below average (lower left image) but by next Tuesday afternoon our temperatures will be around 15° to nearly 20° above average (lower right image).





Mild End To Month?


The longer range temperature probability forecasts have us favored for a milder than average end to the month then temperatures trend back to about average for the start of May. The latest 6-10 day forecast has us outlooked for above average temperatures overall from April 26th through April 30th. The 8-14 day temperature probability forecast has us favored for about average temperatures overall from April 28th through May 4th. Average highs in Chicago for late April into early May are in the lower to middle 60s.





The even longer range Subseasonal Experiment (SubX) temperature anomaly forecast is signaling a cooler than average pattern continuing into the middle of May. The temperature anomaly forecast for the week ending May 7th has us outlooked to be a around or a bit below average overall. The forecast for the following week ending on May 14th has Chicago below average overall. Average highs for this period are in the middle to upper 60s.







More Active Precip Pattern?

The long range precipitation probability forecasts suggests a more active pattern for the end of April spilling over into the start of May. The signal isn't that strong though. The latest 6-10 day forecast still has Chicago favored slightly for above average precipitation from April 26th through April 30th. The longer range 8-14 day forecast has us favored slightly for above average precipitation overall from April 28th through May 4th too.












Here is my 7 day forecast:


FREEZE WARNING FROM MIDNIGHT TO 9 AM THURSDAY


Today: Mostly cloudy, scattered rain/snow showers, isolated t-storm possible High: 44


Thursday: Mostly sunny Low: 30 High: 56


Friday: Partly to mostly cloudy, rain possible late Low: 40 High: 59


Saturday: Mostly cloudy, light rain at times Low: 43 High: 57 (cooler lakeside)


Sunday: Partly to mostly sunny Low: 40 High: 56 (cooler lakeside)


Monday: Partly to mostly sunny Low: 43 High: 71 (cooler lakeside)


Tuesday: Partly to mostly cloudy Low: 58 High: 79


#ilwx

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