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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.

Saturday, May 7, 2022

SPC May 7, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Sat May 07 2022 Valid 072000Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF SOUTH DAKOTA AND NEBRASKA... ...SUMMARY... Scattered strong thunderstorm development is possible late this afternoon and evening, particularly across parts of the northern Great Plains, where a few may become severe and capable of producing large hail and potentially damaging wind gusts. ...20Z Update... Based on the progression of synoptic and sub-synoptic features, and ongoing trends concerning instability, the risk for thunderstorms through the remainder of this period appears increasingly negligible in a number of areas. Some adjustments to the categorical thunderstorm lines have been made to account for this (reducing thunderstorm probabilities below 10 percent). Some initial attempts at deep convective development are evident across parts of the Texas Hill Country/Edwards Plateau vicinity. However, due to the presence of warm and capping elevated mixed-layer air beneath mid-level ridging, the risk for sustained thunderstorm development near the sharpening dryline is also appearing increasingly questionable. Even so, with potential instability becoming quite large across this region in the presence of modest shear, if a storm can initiate and be maintained, the evolution of a supercell or two does still appear possible. Given little change to the degree of the conditional severe threat, the previous outlook across this area will be maintained. ..Kerr.. 05/07/2022 .PREV DISCUSSION... /ISSUED 1136 AM CDT Sat May 07 2022/ ...Nebraska/Dakotas... Increasingly prevalent/strengthening cyclonic upper-level flow will influence the region through tonight. Initial strong/severe thunderstorm development is expected across central portions of South Dakota/North Dakota near the eastward-shifting boundary, with a bit later (hour or two) development expected southward into west-central/north-central Nebraska by evening. Large hail will be possible with this initial supercellular development, prior to an upscale transition which will likely include an increasing potential for severe-caliber wind gusts during the evening. Low-level moisture will be limited in both magnitude and lateral extent, with a narrow corridor of mainly 50s F surface dew points extending from central Kansas to the central Dakotas, east of the dryline and cold front. Still, this and insolation will foster enough late-afternoon/early evening mixing/drying of the boundary layer to boost DCAPE and weaken MLCINH substantially, supporting the gust potential beneath 500-1500 J/kg MLCAPE values. Veering and strengthening of flow with height, from surface through midlevels, will support 45-55-kt effective-shear vectors aligned nearly orthogonal to the front in South Dakota, with initial discrete/semi-discrete modes until some mergers and cold-pool processes occur. Activity should transition from a hail-dominant to wind-dominant threat before shifting east and weakening in greater stability this evening. Farther south, scattered thunderstorms also are forecast to develop over portions of western into central Nebraska -- but this evening, generally as the front overtakes the dryline, and a combination of height falls and shots of DCVA occur in midlevels. Supported by the southerly LLJ, and its associated combination of increasing moisture and favorable storm-relative winds above the surface, elevated supercells and organized multicellular clusters are expected to offer a large-hail threat. Isolated severe gusts may occur as well, where sufficient downward momentum and cold-pool forcing from mesobeta-scale upscale growth can allow downdrafts to penetrate a near-surface stable layer locally. Continued eastward movement of activity atop progressively more-stable boundary-layer conditions should reduce storm intensity overnight. ...Central/south Florida... Scattered thunderstorms will continue near a west-east front across the Florida Peninsula, with outflow/sea breeze being additional developmental influences. A moist air mass and moderate buoyancy, with upwards of 2000-2500 J/kg MLCAPE, will yield some strong/sustained multicells in the presence of 25-35 kt effective shear. A few instances of locally damaging winds and/or hail are possible this afternoon. ...Portions of central/north-central Texas... Some potential will exist for isolated but intense thunderstorm development near the dryline late this afternoon. The region will be influenced the near-crest portion of the southern/central upper ridge, with most available short-term guidance suggestive of limited prospects for deep convective development. However, robust heating/mixing in the post-dryline environment and sufficient near-dryline convergence in the presence of upper 60s/near 70F surface dewpoints could result in isolated storm development. If/where storms develop, a storm or two capable of localized large hail and/or severe-caliber wind gusts would be possible in the presence of 3500+ J/kg MLCAPE and low/mid-tropospheric that is weak but veers with height. Any such severe risk would likely gradually diminish shortly after sunset. Read more CHECK UPDATE ZOOM GRAPHIC
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