SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1132 AM CST Fri Nov 13 2020 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR NORTHEAST OK ACROSS NORTHWEST AR INTO SOUTHERN MO... ...SUMMARY... Isolated severe thunderstorms may occur across eastern Oklahoma and the Ozarks/Ark-La-Tex regions late Saturday afternoon and night. ...Synopsis... A deep shortwave trough is forecast to move quickly across the Plains and into the Upper/Middle MS Valley on Saturday. This shortwave will be accompanied by a strong (i.e. 100 kt at 500 mb) jet, which will likely extend from eastern KS through the middle MS and southern OH Valleys, and into the Lower Great Lakes region early Sunday morning. Surface cyclogenesis is anticipated ahead of this shortwave and attendant jet streak. The resulting low is forecast to develop over the mid MO Valley before then tracking quickly northeastward through the Upper Midwest. An associated cold front will sweep eastward/southeastward. By 00Z Sunday, this front will likely extend from the low over central IA southwestward through western MO and eastern OK. By 12Z Sunday, consensus of the guidance places the front from Lower MI south-southwestward into western TN and then back southwestward across the Lower MS Valley into the TX Hill Country. ...Eastern Oklahoma/Ozarks/ArkLaTex... Modest low-level moisture advection will be underway across the southern Plains at the beginning of the period. Southwesterly low-level flow will persist throughout the day from the southern Plains into the Mid MS Valley, contributing to continued moisture advection and the potential low 60s dewpoints into the Ozark Plateau ahead of the front. Current observations place the low 60s dewpoints in central TX, under north winds and weak cold advection. Early day showers and cloudiness are also expected from northeast OK into southern MO. As a result, there is some uncertainty whether low 60s dewpoints will actually be able to advect as far north as the models suggest. Whether or not this is enough low-level moisture to support severe thunderstorms will also depend on the amount of heating the area receives. Current consensus within the guidance is for overcast conditions to hamper daytime heating, keeping temperatures in the low 60s (perhaps even upper 50s across northwest AR and southern MO). Given the resulting convective inhibition associated with those surface temperatures, updrafts would likely struggle to maintain depth and consistency, limiting the overall severe potential. In contrast to the marginal thermodynamics, kinematic fields are very supportive of organized storm structures with notable low-level curvature and long hodographs. Any updrafts that are able to maintain depth and consistency would likely pose a risk for damaging wind gusts and tornadoes. The overall scenario is conditional on destabilization but the strength of the wind fields merit upgrading to a 5% tornado/15% wind Slight Risk. ..Mosier.. 11/13/2020
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