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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.

Monday, June 20, 2022

SPC Jun 20, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Mon Jun 20 2022 Valid 202000Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SD...SOUTHEAST ND...AND NORTHWEST/WEST-CENTRAL MN... ...SUMMARY... Scattered to numerous severe thunderstorms are likely across the northern Great Plains through this evening. Destructive wind gusts, very large hail, and a couple tornadoes are possible. ...20z Update... The ongoing outlook remains on track and no changes have been made with the 20z update. A cluster of severe thunderstorms within Severe Thunderstorm Watch 393 is currently moving into the Nebraska Panhandle. This activity is showing some characteristics toward upscale development recently. With time, this activity may develop into a bow capable of producing a swath of intense, damaging gusts as it tracks northeast into central SD. Additional thunderstorm development is expected over the next few hours across parts of the eastern Dakotas/northwest MN within the baroclinic zone and ahead of a stalled front. This activity also will pose a threat for intense gusts and large hail. For additional information on short term severe potential, reference MCD 1233. More forecast details can be found in the previous outlook discussion below. ..Leitman.. 06/20/2022 .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Jun 20 2022/ ...Northern Great Plains... A vigorous shortwave trough near the UT/ID/WY border area will eject northeast into ND tonight, around the northwest periphery of a closed high over the Mid-South. Attendant mid-level jet will strengthen as it spreads from the central Rockies towards the Red River Valley. A wavy surface front extending southwest from a primary cyclone over northwest Ontario will move little today, and then begin to accelerate eastward tonight in response to the ejecting mid-level trough and convective outflows. A plume of upper 60s to lower 70s boundary-layer dewpoints will be maintained along the front from north-central/northeast SD and ahead of it across MN. The dryline should effectively mix into south-central SD through central NE where mid to upper 90s surface temperatures become common. Beneath steep mid-level lapse rates, the largest MLCAPE of 2500-4000 J/kg should become established across MN into the eastern Dakotas, with a bent-back plume of moderate buoyancy extending southwest along and to the cool side of the surface front into the NE Panhandle. Scattered thunderstorms are expected to develop by mid afternoon in advance of the ejecting mid-level trough, within the post-frontal environment from eastern WY into the NE Panhandle. Convection will subsequently spread northeast across the Dakotas, as well as likely develop separately along the baroclinic zone over the Red River Valley through early evening. Vertical shear will be strongest along and west of the stalled front, especially within the strengthening 500-mb southwesterly jet. Thus, the best chance for long-track supercells with significant severe hail amid highly elongated and nearly straight-line hodographs should be across northwest NE to central SD. As this activity approaches larger buoyancy during the evening, and likely impinges on downshear convection along the front, multiple MCSs with sustained bowing segments will probably develop, increasing the threat for severe wind gusts, some of which may reach 80-90 mph. Greater tornado potential is more nebulous, but a focused corridor for a couple tornadoes is apparent across north-central SD and southeast ND into northwest MN with any supercells/bows along this portion of the initially stalled front. Overall severe potential should diminish overnight through a combination of extensive convective overturning and increasing warm-sector MLCIN. ...Central/south FL... Scattered pulse thunderstorms will again develop along sea breezes this afternoon within a large buoyancy environment characterized by near 3000 J/kg of MLCAPE. Weak vertical shear will limit potential for more organized convection, but localized damaging downbursts will be possible in the strongest cells. Read more CHECK UPDATE ZOOM GRAPHIC
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