SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0101 PM CDT Wed Oct 21 2020 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE EASTERN IOWA VICINITY TO NORTHEASTERN OKLAHOMA... ...SUMMARY... A few strong to locally severe storms, capable of producing marginal hail and perhaps a strong wind gust or two, will be possible Thursday from the eastern Iowa vicinity south-southwestward to eastern Kansas, western Missouri, and the northeastern Oklahoma area. ...Synopsis... A short-wave upper trough digging southeastward across the Intermountain West is expected to gradually turn eastward Day 2, reaching the mid Missouri and upper Mississippi Valleys through the second half of the period. As the upper system advances, a surface wave over the western Kansas area -- along a pre-existing baroclinic zone extending from the central High Plains to southern New England -- will develop northeastward to the eastern Iowa area by early evening, and then to the northern Lower Michigan vicinity by Friday morning. In the wake of the progressing low, the cold front will surge southward, and should extend from Lake Michigan to northern and western Texas by the end of the period. ...Eastern Iowa and vicinity to the northeastern Oklahoma area... Early-day convection is expected across northern portions of the outlook area, but will gradually shift northeastward with time. This should permit some clearing -- and diurnal heating -- ahead of the evolving surface cold front and associated/digging upper system. Despite this heating, and low-level moistening/warm advection, capping will likely remain firm through the day, with the stronger ascent associated with the upper trough remaining to the cool side of the front. Eventually, near-frontal convective development may finally occur over the eastern Iowa vicinity by early evening as capping weakens. However, any surface-based storms will likely become quickly undercut by the front, while more widespread convective development is expected to the cool side of the boundary. Initial storms forming over the eastern Iowa area will evolve in an environment sufficient for sustained/rotating updrafts. As such, a very limited risk for surface-based severe weather -- including gusty winds and possibly a brief tornado -- may exist for a couple of hours during the early evening. Afterwards however, any lingering severe risk would likely be in the form of marginal hail. As primarily anafrontal convection develops southward overnight, some marginal hail risk may persist through the end of the period. ..Goss.. 10/21/2020
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