SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1132 AM CDT Wed Jul 14 2021 Valid 141630Z - 151200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF IOWA...SOUTHEAST MINNESOTA...NORTHWEST ILLINOIS AND SOUTHERN WISCONSIN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF NEW ENGLAND... ...SUMMARY... Damaging winds, along with some hail threat, are expected with thunderstorms across the upper Midwest later this afternoon and evening. Isolated damaging winds are also possible across parts of the Northeast. ...IA/WI vicinity... Complex forecast scenario as ongoing MCS over eastern IA/southeast MN continues to result in substantial cloud cover/rain-cooled air across the area. Some uncertainty remains regarding whether this MCS will strengthen with time as downstream heating/moistening takes place. Current trends suggest at least some continued risk for strong/possibly severe winds and isolated severe hail will continue into early afternoon across southwest WI. In the wake of the morning MCS, redevelopment of severe thunderstorms later this afternoon/evening is still anticipated along and north of the residual outflow boundary as warm advection increases with a strengthening low-level jet. RAP forecast soundings and 12z HREF guidance depict a favorable parameter space for supercells with severe hail/wind, as well as some potential for a tornado or two. Upscale growth should occur within a few hours of initiation, resulting in damaging winds becoming a more prominent risk. Overall, no changes were made to the current risk areas and probabilities, although this may be necessary at 20z as the effects of morning convection and amount of air mass recovery become clearer. ...Northeast CO... An MCV was located over western CO this morning and will move slowly east today, providing modest large-scale ascent for afternoon thunderstorm development. A moist boundary layer beneath steep midlevel lapse rates will lead to sufficient instability for a risk of isolated severe storms, with damaging gusts and severe hail possible as storms move into the adjacent northeast CO plains through this evening. ...Northeast States... Isolated thunderstorms this afternoon may pose a risk for strong/locally damaging gusts as weak/pockets of moderate buoyancy develops within a weakly sheared environment. Ascent associated with a midlevel shortwave trough from eastern NY/northeast PA will contribute to scattered thunderstorm development, with a few stronger multicell storms capable of strong downburst winds. ...NV/UT... Strong heating will result in a deeply-mixed boundary layer again today, but generally weak vertical shear as the area remains south of the stronger midlevel flow. Thunderstorms developing this afternoon will have the potential to produce strong outflow winds, a scenario supported by 12z CAM guidance. Overall, only modest adjustments to the MRGL risk area were made with this outlook. ..Bunting/Karstens.. 07/14/2021 Read more LIVE: spc.noaa.gov
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