SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0436 PM CDT Sun Jul 25 2021 Valid 271200Z - 281200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS UPPER MISSISSIPPI VALLEY... AMENDED FOR ADDITION OF THUNDER IN THE NORTHWEST ...SUMMARY... Thunderstorms associated with hail and strong gusty winds will be possible on Tuesday across parts of the upper Mississippi Valley. ...Upper Mississippi Valley... A large area of high pressure is forecast across the western and central U.S. on Tuesday. At the surface, a frontal boundary is forecast to become quasi-stationary across the north-central states. A moist airmass will likely be in place to the south of the front from the eastern part of the northern Plains into the mid to upper Mississippi Valley. With surface dewpoints from 65 to 70 F, moderate instability should develop across much of this area by afternoon. Although large-scale ascent should be relatively weak, low-level convergence along the boundary will likely result in isolated to scattered convective initiation during the mid to late afternoon. From this convection, a few thunderstorms are expected to form and move southeastward across the region. NAM forecast soundings for Minneapolis at 21Z on Tuesday have MLCAPE near 4000 J/kg with 0-6 km shear near 45 kt and steep low to mid-level lapse rates. This should be favorable for cell rotation and isolated supercells will be possible. Any rotating storm that can organize should have a potential for hail and strong gusty winds. However, mid-level temperatures are expected to warm during the day with 700 mb temperatures increasing to near 12C. This could make it harder for updrafts to become established. For this reason, will keep the threat at marginal for this outlook. ..Broyles.. 07/25/2021 Read more LIVE: spc.noaa.gov
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