After a somewhat chilly weekend and start of this week for some of us across the state, especially the northern portion of Illinois, there are growing indications and signals on medium range model guidance that a favorable pattern for warmer weather and above normal temperatures will develop by later this week. The entire week itself should be fairly quiet weather wise with near normal temperatures but things will improve by the end of this week as the large scale pattern changes to one that leads to a nice warm-up across the Midwest.
I dig into the details below, including what days will be warmest and how long will it last...
As we go through the majority of this week, our pattern will remain fairly stagnant and quiet but a slow moving upper level low will eventually be located across the western U.S. by Thursday and Friday and this will lead to a developing upper level ridge across the plains and eventually the Midwest. This upper level ridge is usually a good feature to look for when to expect warmer weather and above normal temperatures. By Friday afternoon (image below) the ridge axis (marked in red dashed lines) is centered off to our west. This will be the beginning of what looks to be a multiple day stretch of above normal temperatures across Illinois.
As we get into the afternoon on Saturday, we can see now that both the upper level low shifted east to over the Rockies and the ridge axis has also shifted west, now located nearly overhead of us here in Illinois. This is a favorable pattern as mentioned for a good bet of above normal temperatures across the Midwest.
As low pressure continues to inch closer across the plains, broad warm air advection (in red below) will commence and continue, especially during the second half of the weekend, which will help lead to that continued/multiple day stretch of warmth across our area.
Getting a first look at potential daytime highs during this period, model guidance is in fairly good agreement on the surface high being overhead or near Illinois by Friday which would mean a good deal of sunshine and widespread mid to upper 50's and some 60's.
By Saturday, the area of high pressure would move east, allowing for strengthening warm southerly winds to potentially boost temperatures into the 60's over a larger area.
We will not get into Sunday just yet but this looks like a several day period of warm weather and above normal temperatures across a large area, including Illinois from late this weekend and through the upcoming weekend. It is certainly possible it continues into the beginning of next week as well so stay tuned!