Severe Storm Outlook Narrative (AC)
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Issued by NWS
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558 ACUS01 KWNS 170543 SWODY1 SPC AC 170541 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1241 AM CDT Mon Jun 17 2024 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL AND NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Scattered strong to severe storms are possible across the central and northern Plains into the upper Mississippi Valley. ...Central/Northern Plains-upper MS Valley... Strong upper trough is currently located over the Pacific Northwest. This feature is forecast to shift into the northern inter mountain region by mid day, then into the northern Rockies by 18/00z, as an 80kt 500mb speed max rotates through the trough to near the ID/WY border. This is a very dynamic trough and latest model guidance suggests a surface low will be well identifiable over central WY by mid day. As the upper trough approaches the northern Plains late in the period, surface low should reposition itself downstream and track from the NE Panhandle into southeast ND by sunrise Tuesday. This evolution will encourage a warm front to advance north across the upper MS Valley during the latter half of the period, though warm-advection precipitation may slow its northward advance a bit. Early this morning, a notable uptick in warm-advection convection is observed across the central Plains from western NE into southeast SD. This activity should spread/develop northeast along/north of the warm front across southern MN into the upper Great Lakes region. Elevated convection may pose a risk for hail. While the primary concern for thunderstorms will be along the cool side of the boundary, strong heating south of the front will allow surface parcels to approach their convective temperatures. Forecast soundings suggest negligible CINH will be noted across southeast MN into central WI along the boundary. If thunderstorms can evolve, deep-layer shear may support supercell development. Have adjusted SLGT risk along the warm front to account for both elevated and potentially warm sector storms. Upstream across the High Plains, strong boundary-layer heating is expected across the central High Plains of eastern CO into southwest NE. As temperatures warm into the lower 90s convective temperatures will be breached and isolated supercells should develop. Forecast soundings exhibit substantial SBCAPE (>3000 J/kg) and steep lapse rates, along with favorable shear for sustained rotating updrafts. Very large hail may accompany this activity. Some tornado threat will also be noted with these storms. Strong dynamic forcing will encourage convection to develop across the High Plains of northeast WY/southeast MT immediately ahead of the surging cold front. This activity will spread northeast ahead of the short wave into the Dakotas during the overnight hours. After sunset, marked increase in the LLJ is expected across the Plains from eastern NE into western MN. Severe threat will shift into the upper Red River Valley by the end of the period. ..Darrow/Thornton.. 06/17/2024 $$