SPC Aug 17, 2017 Day 4-8 Severe Weather Outlook

By Newsroom America Feeds at 17 Aug 2017

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0155 AM CDT Thu Aug 17 2017 Valid 201200Z - 251200Z ...DISCUSSION... Northwesterly flow should relax and become more zonal across the northern Plains during the day4 period as westerlies retreat to near the international border. Latest medium-range guidance is in general agreement regarding this evolution and a potentially meaningful short-wave trough is expected to progress across the northern Plains Sunday. Higher PW plume should advance northward across the Plains prior to this short wave and significant instability is expected to develop along southern fringe of westerlies where strong buoyancy should aid strong/severe thunderstorm development. Models suggest thunderstorms will develop during the late afternoon along a frontal zone draped across SD. This activity would then propagate toward the upper MS Valley during the overnight hours as the short wave progresses toward MN. Beyond day4, strong/severe convection may also develop across portions of the upper MS Valley into the upper Great Lakes Monday but uncertainty increases due to possible extensive convective event the prior day and the potential for boundary-layer air mass disruptions. Read more



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