SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Thu Oct 07 2021 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST NEVADA TO SOUTHERN IDAHO AND NORTHERN UTAH... ...SUMMARY... A few strong storms with gusty winds and marginally severe hail will be possible later today into this evening from northeast Nevada into northern Utah and southeast Idaho. ...Northeast Nevada through southern Idaho and northern Utah... A series of low-amplitude impulses embedded within a southwesterly upper flow regime will move through the Great Basin area today. Low-level moisture is limited, but steep lapse rates will be present, and with diabatic warming of the surface layer, MLCAPE from 300-500 J/kg will be possible. Scattered showers and thunderstorms are expected to develop within this regime later this afternoon. Inverted-V boundary layers, steep mid-level lapse rates along with 30-40 kt effective bulk shear might promote some risk for a few strong wind gusts and marginally severe hail with the stronger storms. However, overall threat should remain marginal due to weak instability. ...Great lakes region... Upper low circulation likely to be centered near St. Louis MO by 12Z today will continue moving slowly northward, reaching northern IL by late Thursday night. A weak warm front currently situated over the OH Valley will reach the southern Great Lakes by early this afternoon. A moist warm sector with mid 60s F dewpoints will exist across this region, but widespread clouds and weak mid-level lapse rates should limit MLCAPE to generally 500-1000 J/kg. Areas of scattered showers and thunderstorms will persist during the day within the corridor of ascent in the eastern half of the upper low circulation from the OH Valley into the Great lakes region. Weak vertical shear and marginal instability will limit overall severe potential. Low-level veering of the winds will persist in vicinity of the warm front, especially across southern parts of the Great Lakes during the afternoon. However, 0-1 km storm relative helicity should remain less than 150 m2/s2 due to weak wind magnitudes. While it can't be ruled out that some of the convection might develop low-level rotation as it crosses the warm front, posing some risk for a brief tornado, threat appears too marginal to introduce categorical severe probabilities at this time. ..Dial/Bentley.. 10/07/2021 Read more LIVE: spc.noaa.gov
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