SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1057 AM CDT Thu Sep 16 2021 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF MN SOUTHWARD INTO EASTERN SD AND NORTHERN NE... ...SUMMARY... Severe storms will be possible late this afternoon and evening particularly across Minnesota into southeast South Dakota and parts of Nebraska. ...MN... Relatively fast zonal flow extends from the northern Rockies across the northern Plains today, with multiple fast-moving shortwave troughs embedded in this flow. A surface low over SD will migrate eastward into MN later today, with an associated cold front providing the focus for scattered thunderstorms. Activity will begin by mid/late afternoon over northern and central MN, where strong heating is occurring. Forecast soundings show relatively steep mid-level lapse rates and MLCAPE values of 1500-2000 J/kg in this area. Vertical shear profiles are also quite strong, supportive of supercells capable of large hail, damaging winds, and a few tornadoes. Initial storms may be discrete for a few hours before linear forcing mechanism and merging cold pools result in a squall line. Storms are expected to weaken this evening after dark as instability diminishes over northeast MN. ...SD/NE... Full sunshine is present today over most of SD/NE, leading to rapid heating and destabilization. A cold front will sag into this region this evening, providing the focus for scattered thunderstorms. Model guidance suggests that most of the storms will be behind the surface front and somewhat elevated. Nevertheless, hail and gusty winds may occur in the stronger cells for a few hours. ..Hart/Goss.. 09/16/2021 Read more LIVE: spc.noaa.gov
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