Summer temperatures are back in the Chicago area.
Temps could move for an impressive 90 degrees on Friday with the storm outlook increasing late Friday and increasing Friday night.
Temps rose for the eighth time this year on Thursday and will do so again on Friday. For comparison, there were only 5 such days on this day a year ago.
Forecasting 85 degrees on Thursday, the Chicago high represents a 25-degree increase from Wednesday’s 60-degree maximum and puts this day’s temperature at July levels. Although higher than Wednesday, the humidity has yet to drop.
That comes on Friday amid strong SSW winds that, even without thunderstorms, are likely to whip above 40 mph in the afternoon. The outflow originates in the Gulf of Mexico – so Friday’s enhanced SSW puddles will act as a conduit for the northward transport of humid tropical air. Atmospheric humidity levels are also due to “take off” on Friday with dew point, a measure of moisture in the atmosphere, forecast to increase sharply in the 60s. By evening, nearly 2 inches of water will be present. in a column of air above Chicago. It’s all humidity and it sets the stage for showers and thunderstorms to erupt, especially on Friday night.
Interactive Radar: Watch Showers & Storms here
The “mantle” of the atmosphere – where a layer of warm air prevents floating air from creating storms – could play a role in preventing hurricane t from developing on Friday. Once a thunderstorm breaks out Friday night, we could pass peak heat and set the stage for some sporadic downpours rather than ferocious storms — but the warmth and humidity abound. atmospheric energy Friday afternoon and evening, and if the limit is breached, the result is storms that could exploit this energy supply and cause gusts and the potential to generate hail. So, the Hurricane Forecast Center continues its “MINUTE RISK” assessment for severe weather on Friday.
Big Rains Saturday
Far and away, the more interesting weather development late Friday night into the Saturday night time frame could hold potential for some downpours. Average over the precipitation estimates forecasted by the multitude of models we access these days for yields as we prepare forecasts for overall yields in the 0.85″ to 1 .80″ – although individual forecast models suggest a local amount of 2-3.50″ may occur in areas swept through a lot of downpour.
The atmosphere appears to be likely for a classic downpour to form between Friday night and Saturday night. One front is falling south across the surface windward from “NNE” Saturday. This introduces a layer of cooler air into the Chicago metro area. However, the modeling keeps a strong southerly wind blowing straight out of the bay running up and over the cool layer. Atmospheric humidity levels should run at 1.5 times normal, providing ample water vapor for a northerly wave that will move forward south to our south. This sets the stage for dramatic rains – and with storm surges accompanied by rain screens, the possibility of downpours is real.
It won’t be surprising to see rainfall and its intensity increase as we move into Saturday afternoon and night — so prepare your rain gear!
Full forecast details and more at WGN Weather Center blog
Everything is dry on Sunday
Fortunately, it continues to look like it’s going to be dry Sunday despite being fairly cool in season with daytime highs likely to stay low and into the mid-60s.