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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.

Tuesday, July 5, 2022

SPC Jul 5, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Tue Jul 05 2022 Valid 052000Z - 061200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST SOUTH DAKOTA INTO SOUTHWEST MINNESOTA AND NORTHWEST IOWA... ...SUMMARY... A derecho with embedded gusts over 80 mph will spread across southeast South Dakota, parts of southwest Minnesota and northern Iowa through evening. Severe winds may persist tonight as far east as southern Wisconsin. ...SD/MN/IA region... A derecho is currently producing gusts over 90 mph as it moves across southeast SD, and the threat of particularly damaging winds should impact the I-29 corridor by 21Z. A zone of very strong instability exists along a stationary front, with MLCAPE of 3000-4000 J/kg from southeast SD all the way into northern IL. GPS precipitable water measurements are averaging 1.75 to 2.00" across the length of the front, confirming boundary layer moisture quality. As such, the derecho, or at least a severe MCS, is expected to impact the corridor extending well east across southern MN, northern IA, and southern WI. ..Jewell.. 07/05/2022 .PREV DISCUSSION... /ISSUED 1151 AM CDT Tue Jul 05 2022/ ...SD to IA and southern MN... An intense cluster over central SD will likely persist east-southeast across southeast SD. This should evolve into a forward-propagating linear MCS, expanding in latitudinal extent as MLCIN further diminishes ahead of it. A large MLCAPE reservoir in excess of 3000 J/kg across southern SD/MN and northern IA will support potential for embedded significant severe wind gusts exceeding 75 kts. While the majority of CAM guidance appears to be egregiously poor (especially the HRW-FV3) with handling the conceptual model for this event, the 12Z HRW-ARW and NSSL are in the ballpark and suggest bowing linear segments will be maintained into southern MN and northern IA before weakening this evening. ...Central/eastern MT to western ND... Air mass recovery is underway across central to eastern MT in the wake of the intense MCS over northwest SD. Residual 50s to low 60s surface dew points in conjunction with pockets of pronounced boundary-layer heating will yield MLCAPE of 1000-1500 J/kg. With 45-55 kt effective bulk shear, at least a few supercells are expected from central to northeast MT during the late afternoon and evening with large hail and isolated severe wind gusts as the primary threats. Some of these cells should consolidate into a cluster that spreads into western ND during the evening. Overall intensity should decrease as activity impinges on the more stable air mass left in the wake of the SD MCS. ...Mid-Atlantic to Midwest... Poor mid-level lapse rates were evident in 12Z observed soundings east of the Appalachians and this will be the main limiting factor to more intense convective development. An MCV over western PA will move east towards the NJ coast, with scattered thunderstorms near and to its south. With 30-40 kt 700-mb westerlies impinging on the region attendant to this MCV and the boundary-layer destabilizing from south to north, an increase in strong gust potential should occur from VA into the Lower DE Valley. Arcing convective bands extend west of the lead MCV across WV and OH/IN. This activity will likely persist through the rest of the afternoon into this evening, building south-southwest in time towards large buoyancy centered on the Lower OH Valley. Moderate deep-layer shear will be further offset as this process occurs, suggesting that loosely organized clusters will dominate with strong to isolated severe gusts as the primary threat. Additional multicell clusters will probably form northwest along the baroclinic zone near the IA/IL/WI border area during the late afternoon into the evening. These will similarly pose a threat for scattered damaging winds and isolated severe hail, although the spatial extent of this threat will likely be limited by this morning's stabilization in OH. Read more CHECK UPDATE ZOOM GRAPHIC
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