SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 AM CDT Fri Aug 06 2021 Valid 061300Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN/CENTRAL ROCKIES AND NORTHERN PLAINS AND OVER THE MIDWEST... ...SUMMARY... Isolated severe storms are possible over parts of the central and northern Rockies into the northern High Plains this afternoon/evening. A few strong to severe storms may also develop later today over parts of the Midwest. ...Northern/Central Rockies and Northern Plains... Early morning water vapor imagery features a readily apparent upper trough centered over the northern Intermountain region near the Oregon/Idaho border vicinity. Notable height falls will develop ahead of this feature as it progresses toward western Wyoming by early evening. This will be accompanied by a 50+ kt mid-level jet, which will coincide with focused large-scale forcing for ascent with the exit region of this speed max. Above-normal Precipitable Water values over intermountain areas/interior Wyoming combined with strong surface heating will contribute to destabilization with high-based thunderstorms developing and increasing through mid/late afternoon. With cloud bases expected near 3 km AGL, gusty winds with some potential for severe-caliber downbursts can be expected. As the upper trough approaches the High Plains, the low-level jet should strengthen across western Kansas into extreme south-central South Dakota tonight. This may contribute to longevity of thunderstorm activity as it propagates east along a warm advection corridor. Portions of the region will continue to be reevaluated for a possible Slight Risk upgrade in subsequent outlooks. ...Midwest/Upper Mississippi Valley... Late-night convection over the Upper Midwest has tended to further weaken/diminish overnight with multiple/scattered weak MCVs persisting this morning. As clouds thin/scatter today, diurnal boundary-layer heating is expected to aid destabilization such that new updrafts, and possible thunderstorm clusters, will redevelop/intensify later this afternoon. This should particularly be the case across northern Illinois/southern Wisconsin into northern Indiana/Lower Michigan. Gusty winds and perhaps some threat for hail can be expected with this activity. ..Guyer/Mosier.. 08/06/2021 Read more LIVE: spc.noaa.gov
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