In spite of appreciable deep-layer shear afforded by a 50kt 500mb jet along the periphery of the upper-level shortwave, the low- centroid and marginal character of instability suggests thunderstorm intensity should be rather weak (by the standards of May, at least) with threats for only locally gusty winds and occasional lightning strikes. In fact, shallow low-level moisture advection ahead of the front may provide just enough low-level instability to support a thunderstorm or two as equilibrium levels nose toward -20C. However, the temporal intersection of the approaching upper-level shortwave and afternoon “daytime” heating should support an increase in shower coverage this afternoon primarily near and east of I-55. As the front drifts eastward slowly this morning, so should the ongoing scattered showers from eastern Iowa into northern Illinois while gradually decreasing in intensity and coverage given the aforementioned antecedent dry airmass in place. Low- to mid- level moisture ahead of the front is fairly scant with surface dew points only in the low to mid 50s and mean 700-300mb relative humidity values of only around 30-40% (re: 00Z DVN RAOB). SHORT TERM… Issued at 217 AM CDT Fri May 19 2023Ī recent hand surface analysis places a baggy trough axis along a weak cold front stretching from central Wisconsin to far northwestern Illinois and into the Southern Plains. National Weather Service Chicago/Romeoville, IL The southeasterly flow will keep locales west of the lake in the 60s today. However, with the pre-frontal warm advection, we`re still looking at middle to upper 70s this afternoon. In fact, actually knocked highs back a couple of degrees for today with the smoke sure to shield some of our solar radiation. Sunny skies today will once again be filtered by the plume of wildfire smoke moving overhead that originates from a plethora of wildfires occurring across parts of Canada. Hello mobile users! If you encounter a mobile “unfriendly” weather page, turn your phone sideways for a better view. Weather forecast for Friday, May 19, 2023.
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