Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1224 AM CDT Tue Aug 11 2020 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTH DAKOTA AND NEBRASKA... ...SUMMARY... Scattered strong/severe convection is expected across portions of the Plains from late afternoon into the overnight hours, especially across portions of South Dakota and Nebraska. Hail and wind are the primary threats. Marginally severe storms are also possible across parts of the mid-South and over northern Maine. ...South Dakota/Nebraska... Early-evening water-vapor imagery depicts a short-wave trough along the ID/WY border, shifting east in line with 00z model guidance. This feature is forecast to translate east across WY into western SD/NE Panhandle by mid-late afternoon. In response, boundary-layer moisture that has been shunted south into KS should be drawn northwest as lee trough becomes established from the western Black Hills into eastern CO. Strong boundary-layer heating is expected along the lee trough and forecast soundings suggest convective temperatures will be breached around 21-22z. 500mb flow on the order of 30-35kt will be maintained at this latitude, along the southern edge of the stronger westerlies. As a result, forecast shear appears at least somewhat supportive of supercell structures. Latest CAMs are reasonably consistent with scattered convection developing ahead of the short wave with eastward propagating storms across SD during the overnight hours, being maintained by a LLJ and warm advection. ...Mid-South... High-Plains convection that developed from western KS into the TX Panhandle is shifting east across south-central KS/central OK early this morning. Remnants of this activity should migrate into eastern OK by daybreak. It's possible a weak MCV could evolve along the northern extent of this convection, and this may encourage downstream convection from southeast OK into AR later in the day. Models also suggest a weakness in the mid-level height field will evolve over the Ozarks and drift south. This will also prove favorable for scattered storms as a reservoir of instability currently resides across this region that has not been overturned. ...Northern Maine... Remnants of Monday's Derecho have progressed across the OH Valley and mostly dissipated. However, MVC remains intact over northern lower MI and an associated short-wave trough is ejecting toward southern ON. This feature should translate north of the international border into southwestern QC by 18z. Scattered convection should evolve ahead of this short wave and the southern extent of this activity could spread across northern Maine. Locally strong winds would be the primary threat with these storms. ..Darrow/Squitieri.. 08/11/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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