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Weather conditions on bar directly above are near Lakefront. Tabs under Moon Phases refer to O'Hare (official).

Archives for SPC Convective outlook are updated daily with a live map a the beginning of the article. Touch or click map to get possible update, and follow link at end of article for referral to NOAA/NWS Storm Prediction Center. Archives for Chicago's hourly weather data were updated 24-48 hours after end of each day prior to Dec. 2020.

Wednesday, May 4, 2022

SPC May 4, 2022 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0356 AM CDT Wed May 04 2022 Valid 071200Z - 121200Z ...DISCUSSION... ...Saturday/Day 4 to Monday/Day 6... A low amplitude progressive upper-level trough is forecast to move across the western U.S. on Saturday, as moisture advection takes place across the Great Plains. By afternoon, an axis of moderate instability is forecast across the southern and central Plains. Thunderstorms will likely develop at the northern end of the instability corridor across the Dakotas and Nebraska. The best combination of instability and shear is currently forecast over Nebraska, where a severe threat would develop near the exit region of a broad mid-level jet. Large hail and wind damage would be the primary threats. A 15 percent contour is added across parts of the central Plains for Saturday afternoon and evening. On Sunday, the models maintain southwesterly mid-level flow across the central U.S. and continue moisture advection across eastern parts of the Great Plains into the Ozarks and Arklatex. The northern end of this unstable airmass is forecast across eastern parts of the central Plains into the lower Missouri Valley. Even though forcing could be minimal, thunderstorms would develop in areas where low-level convergence becomes locally maximized. Strong deep-layer shear should exist along the instability axis creating favorable conditions for severe storms. Any severe threat would remain isolated, but a 15 percent contour seems warranted due to the forecast quality of low-level moisture and instability. For Monday, southwest mid-level flow is likely across the north-central states. This will enable low-level moisture advection to continue across eastern parts of the Great Plains and over the western Mississippi Valley. Surface dewpoints could reach the 70s across parts of the Upper Midwest. Thunderstorm development would be possible Monday afternoon along an axis of moderate to strong instability from the mid Missouri Valley northward into the upper Mississippi Valley. Again, considering the quality of low-level moisture, a 15 percent contour seems warranted, in spite of the uncertainties. ...Tuesday/Day 7 and Wednesday/Day 8... On Tuesday and Wednesday, model forecasts develop a belt of strong southwest mid-level flow across the western and northern states. A moist and unstable airmass is forecast to remain over the eastern Great Plains and western Mississippi Valley. Mid-level flow is forecast to become more meridional on Wednesday as an upper-level low develops across the southwestern U.S. As a result, the stronger flow is forecast to shift westward into the High Plains. Although thunderstorms may develop along the corridor of low-level moisture further to the east, uncertainty is substantial concerning the magnitude of deep-layer shear that will be in place. Also, a lack of large-scale ascent will be problematic. These factors are too great to warrant adding a severe threat area at this time. Read more CHECK UPDATE ZOOM GRAPHIC
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