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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.

Thursday, April 21, 2022

SPC Apr 21, 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 Thu Apr 21 2022 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST OKLAHOMA AND SOUTH-CENTRAL KANSAS AND NORTHERN KANSAS INTO FAR SOUTHEAST NEBRASKA... ...SUMMARY... Large, damaging hail, severe gusts, and perhaps a tornado are possible with any thunderstorms that can develop over parts of northwestern Oklahoma to south-central Kansas. Large hail is also possible across parts of north-central Kansas into far southeast Nebraska this evening into tonight. ...20Z Update... Surface analysis reveals a sharp warm front extending from southeast KS across southwest MO. Thunderstorms have initiated to the north of this boundary and these isolated thunderstorms may pose a threat for mainly hail over the next couple of hours. Hail probabilities were extending southeastward to cover this threat. Otherwise, the forecast remains on track with afternoon/evening initiation possible near the triple point over the central OK/KS border vicinity. Additional elevated thunderstorm development is still expected tonight across northern KS and southeast NE, with some hail possible. ..Mosier.. 04/21/2022 .PREV DISCUSSION... /ISSUED 1129 AM CDT Thu Apr 21 2022/ ...Synopsis... Latest water-vapor imagery continues to show an upper-level trough beginning to deepen across the eastern Pacific off the West Coast. Broad height rises are noted across the central CONUS, leading to a general amplification of the synoptic upper-level regime. At the surface, a weakening low is analyzed over the TX Panhandle with a warm front draped to the east/northeast across northern OK into northwest AR. This warm front is expected to lift to the north into the central Plains by 12 UTC Friday in response to a deepening low over the northern Rockies. A dryline currently draped southward from the TX Panhandle low will largely remain in place this afternoon before retreating west overnight as moisture advection continues. Thunderstorm chances this afternoon and overnight will primarily be focused along the dryline and warm front. ...Northwest OK/southern KS... Despite clearing across western OK, the inversion noted in the 12 UTC OUN sounding remains apparent in visible imagery across the region. This inhibition is expected to linger through the late afternoon as the warm front lifts north. The dryline across western OK and the eastern TX Panhandle will likely extend northward into the afternoon in tandem with the weakening surface low. Convective initiation is possible late this afternoon in the vicinity of the surface low and the dryline/warm front intersection where lift will be locally maximized. The probability of initiation remains somewhat low given the lack of stronger synoptic ascent (which is supported by recent CAM solutions), but if convection can occur it will mature in a favorable supercell environment. Storms will initially support a large hail/damaging wind threat with an increasing tornado threat after 00 UTC as the nocturnal low-level jet strengthens. Open warm-sector convection and/or surface-based convection along the warm front appears possible given weak capping by late afternoon and would develop in a similar supercell environment, but this threat is highly conditional and probability appears low. ...Northern KS/southeast NE... Isentropic ascent over the warm frontal boundary is expected to intensify through the day and into the overnight hours in response to the deepening low across the northern Rockies/northern High Plains. Elevated thunderstorms developing within the warm frontal zone this evening/tonight will become increasingly displaced to the cool side of the boundary overnight given storm motions to the northeast. However, strong shear within the MUCAPE layer will maintain the potential for organized cells with an attendant hail threat. This threat appears most likely across northern KS into southern NE where the potential for discrete storm modes is highest. Read more CHECK UPDATE ZOOM GRAPHIC
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