SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CST Tue Dec 29 2020 Valid 301200Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE TEXAS COASTAL PLAIN AND VICINITY... ...SUMMARY... Thunderstorms -- and limited severe potential -- will affect portions of the Texas Coastal Plain and Hill Country from late afternoon Wednesday into the overnight hours. ...Synopsis... A highly amplified, split flow pattern will prevail across the U.S. Wednesday. In the northern stream, a trough initially over the upper Midwest is forecast to move quickly east-northeastward across the Great Lakes, reaching New England late. Meanwhile, a second, eastern Pacific short-wave trough will move inland over the Pacific Northwest early, and dig southeastward toward the Great Basin through the period. Meanwhile in the southern stream, an upper low is forecast to move across northern Mexico. At the surface, a cold front will move eastward across the Great Lakes region and into New England, and southeastward across the Ohio/mid and lower Mississippi/Tennessee Valleys, and southern Plains. Meanwhile, in response to the Mexican upper low, cyclogenesis is expected to occur during the second half of the period near the lower/middle Texas coast, eventually becoming commingled with the southeastward-moving cold front. ...Texas Coastal Plain and portions of the Hill Country... Showers and embedded thunderstorms -- ongoing at the start of the period -- are forecast to spread southeastward across the southern Plains Wednesday, along and behind the advancing cold front. Meanwhile, pre-frontal shower activity is forecast to increase ahead of the front, with scattered thunderstorms evolving from within this activity by evening as warm advection increases ahead of the advancing upper system. Limited CAPE is expected in the vicinity of the front as it advances across Texas, with warm mid-level air/modest lapse rates limiting convective intensity. Still, given ample flow aloft that may aid in sustenance of a few stronger updrafts, a 5% risk for hail appears warranted. Later, as a surface low develops near the southeast Texas coast, an increase in convection just ahead of the advancing front is expected. With favorable low-level veering/shear, beneath amply strong mid-level flow, a few rotating storms may evolve overnight. As such, very limited potential for a tornado (2%) and locally gusty/damaging winds (5%) will be included in this outlook, centered over the middle Texas Coastal Plain. ..Goss.. 12/29/2020
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