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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.

Friday, July 9, 2021

SPC Jul 9, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1207 AM CDT Fri Jul 09 2021 Valid 091200Z - 101200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LOWER MISSOURI VALLEY... ...SUMMARY... Thunderstorms, some with potentially significant severe weather, are expected this afternoon into tonight across parts of the lower Missouri Valley westward into the parts of the north-central High Plains. ...Lower Missouri Valley... A cluster of strong thunderstorms may be ongoing this morning near the nose of a LLJ over IA. Warm air advection is forecast to weaken during the morning with thunderstorm outflow and differential heating providing a focus for additional thunderstorm development during the afternoon. As a mid-level speed max moves from SD to the IA/MO border by late afternoon, initial storms will likely develop on the cool side of a warm frontal zone draped over the region. Surface-based storms will likely develop farther west over southern IA/northern MO during the late afternoon/early evening within a very unstable airmass (3000+ J/kg MLCAPE). A strongly veering and strengthening flow with height will favor supercells with the stronger and more discrete updrafts. Upscale growth into a cluster of high-precipitation supercells and subsequently into a squall line will favor swaths of severe gusts over the lower MO Valley during the evening. Some of the stronger gusts may be hurricane force in localized areas. As this activity moves east into less-buoyant air over IL, a weakening and/or lessening in severe coverage is expected. Storms may develop over southeast NE/northeast KS during the evening as a LLJ intensifies over the central Great Plains. Hail/wind will be the primary severe hazards with this activity during the evening. ...Central Plains... Upslope flow regime is expected to evolve north of stalled front across the central plains. Models are consistent in showing a corridor of mid 50s to near 60 F dewpoints beneath steep lapse rates and contributing to moderate instability with up to 2000 J/kg MLCAPE as the boundary layer destabilizes. A mid-level shortwave trough initially over eastern ID will move into the north-central High Plains by late afternoon and contribute to 50+ kt effective shear. Supercells will be the preferred storm type before one or more clusters evolves during the evening. Large to very large hail and severe gusts will accompany the stronger storms. ...Southern New England to the Delmarva... T.C. Elsa will continue to progress northeast moving beyond the coast of southern New England by the early afternoon. A conditional risk for a weak/brief tornado may exist near the immediate coast in association with an environment characterized as weak buoyancy and enlarging hodographs. During the afternoon, isolated to scattered storms are likely to develop. A few of the stronger storms may yield a localized wind-damage risk. ..Smith/Wendt.. 07/09/2021 Read more LIVE: