Temperatures struggled to make it much above 50 degrees Tuesday afternoon, warming only to 51 degrees in Rockford. The average high temperature this time of year should be in the low 60s. We’ll gradually see those numbers climb by the end of the week, but it looks like highs will drop right back down into the weekend and beginning of May.
A ‘Greenland Block’ is responsible for the latest chill, buckling the jet stream to the south over the Midwest and Great Lakes. This pattern will ease a bit late week but build right back up for the weekend. This is caused by the negative phase of the Arctic and North Atlantic Oscillations. These are circulations in the mid-latitudes of the atmosphere near the Arctic and North Atlantic that consist of a positive and negative phase, both affecting the position of the jet stream. Forecasts through the beginning of May indicate we will remain in the ‘negative’ phase for both the Arctic and North Atlantic oscillations before transitioning into the positive phase after the first week. This transition could potentially increase in the risk for a little more of an active storm pattern as the jet stream shifts.
Until then, temperatures are expected to remain below average – although we will briefly see numbers climb Thursday and Friday. Another strong low-pressure system will move into the Great Lakes late Friday night and Saturday, holding strong into early next week. Several storm systems rotating around the main low will provide us with scattered rain showers throughout the day Saturday. Highs on Saturday will warm into the upper 50s, to near 60 degrees, but drop behind a cold front Saturday night. This will push temperatures back down into the low 50s Sunday and Monday of next week. As temperatures cool it is also likely we may see a few snow showers, or even some graupel, mixed in – similar to what occurred just this past weekend.