Light showers and isolated thunderstorms are possible Saturday morning as both a warm front and low pressure system near northwest Illinois and southwest Wisconsin.
Radar Saturday morning showed thunderstorms developing across northeast Iowa ahead of the warm front, as the low level jet increased through the night. The limited instability in the atmosphere will keep the majority of shower and storm activity isolated, and below severe limits, but showers moving across southwest Wisconsin will continue to dive southeast into northwest Illinois. The rain should remain light and continue mostly west of I-39 through mid to late morning.
Mostly cloudy to partly sunny skies are then expected for the remainder of the afternoon, although a few isolated on/off showers can’t be ruled out throughout the day. Temperatures starting off in the low to mid 60s will warm into the upper 70s and low 80s. Both moisture and humidity will increase following the warm front, which will pass through the Stateline during the afternoon, causing the overall ‘muggy’ feel to increase.
Following the showers/isolated thunderstorms Saturday morning, the risk for additional thunderstorms will be possible as a cold front moves through Saturday evening. The degree to just how strong thunderstorms *could* get will be heavily dependent on the amount of sunshine we are able to generate during the afternoon. A marginal risk for severe thunderstorms (isolated severe) remains in place for all of northern Illinois and southern Wisconsin. Storm threats include both wind and hail, but a low end risk for an isolated tornado is also present.
As low pressure moves further east into northwest Illinois, instability (amount of energy in the atmosphere) will slowly increase. That instability could increase quite a bit if we see a few hours worth of sunshine. Isolated thunderstorms may redevelop ahead of the advancing cold front after 5pm/6pm Saturday, shifting east/southeast through the evening. Given the location of the surface low, warm front and cold front a few of the storms could turn severe posing a risk for wind and hail, but also an isolated risk for a tornado. While the threat for severe weather isn’t high, it is there. Make sure you stay up to date on the weather, especially going into late Saturday afternoon and evening. Any storms that do form would be done by midnight.