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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.


Wednesday, August 24, 2022

SPC Aug 24, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Wed Aug 24 2022 Valid 242000Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN ROCKIES TO UPPER THE MISSISSIPPI VALLEY... ...SUMMARY... Marginally severe gusts and/or hail will be possible in a corridor from portions of the northern Rockies to the upper Mississippi Valley. ...Discussion... No change was made to the previous convective outlook. ...Lower CO River Valley and for northeast NV and adjacent portions of northwest UT... The 18z 1Y7 raob in southwest AZ showed a 2 inch PW with weak flow below 500 mb. A few strong thunderstorms with gusty winds are probable in the lower CO Valley and northeast NV/northwest UT. Evolution of yet-to-be generated outflow casts large enough uncertainty to preclude the introduction of low-severe probabilities at this time. ..Smith.. 08/24/2022 .PREV DISCUSSION... /ISSUED 1121 AM CDT Wed Aug 24 2022/ ...Northern Rockies to upper Mississippi Valley... Modest west-northwest mid-level flow will prevail from the Northern Rockies into the upper Great Lakes through tonight. An upper low over WA will drift east, while a low-amplitude impulse over western MN moves slowly southeast. A surface front, extending from the MI Upper Peninsula west/southwest through western NE and southern MT, will serve as a focus for isolated severe potential as thunderstorms develop/intensify this afternoon. Two areas with potentially greater thunderstorm coverage remain evident, over portions of southeast MN/northern IA/southern WI associated with a weak surface low along the front over southern MN, and over western MT in association with the eastward-migrating upper low. Relatively greater boundary-layer moisture exists over IA/southern MN late this morning (surface dew points mid 60s), and this will contribute to pockets of moderate MLCAPE where heating can be maximized. Generally weak low/mid-level wind fields will result in effective shear below 30 kts, though this may support organized multicell structures capable of isolated damaging gusts and hail late this afternoon through early evening. Across western MT, steeper mid-level lapse rates will contribute moderate buoyancy, and effective shear values will average 30-40 kts. Scattered thunderstorms should develop this afternoon, aided by post-frontal upslope flow and ascent with the approaching upper low. A mix of multicell and transient supercell storm modes is possible with a risk for isolated severe wind and hail with the strongest storms. A focused Slight Risk was considered over portions of western MT, however with existing cloud cover some uncertainty remains regarding the degree of destabilization and spatial extent of any greater severe threat. Elsewhere along the front, storm coverage is expected to be more isolated overall, though with perhaps slightly greater coverage in the upslope region of the Black Hills in western SD. A well-mixed boundary layer and marginal low-level moisture will support at least some risk for strong wind gusts. Read more CHECK UPDATE ZOOM GRAPHIC
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