SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Tue Oct 27 2020 Valid 271200Z - 281200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the contiguous United States on Tuesday. ...Discussion... Early-morning water-vapor imagery depicts a well-defined upper low moving south toward the AZ/Mexico border. This feature is forecast to begin advancing east along the international border later this morning, then into extreme southwest NM by late afternoon. Very cold continental surface high has settled into the central Plains with the leading edge of this air mass now to the coastal plain of TX. Latest model guidance continues to suggest low-level warm advection will focus along a corridor from the Edwards Plateau-northwest TX-central OK. This zone will be the primary area of concern for elevated convection through the period. Currently, the leading edge of large-scale forcing for ascent appears to be spreading across the southern Rockies into far west TX, per moistening observed at mid levels in water vapor imagery. Scattered showers are now developing across the southern High Plains in response, and these showers should eventually deepen sufficiently for lightning. Much of this activity will develop atop sub-freezing boundary-layer temperatures and significant icing may ultimately be noted along the aforementioned corridor. Farther southeast across the Gulf Coast region, a strong mid-level Bermuda high will forcing deep southerly trajectories across the Gulf Basin ahead of Hurricane Zeta. While Zeta will not reach the central Gulf Coast during the day1 period, moisture will begin to spread inland such that isolated thunderstorms will be possible, despite the poor low-level lapse rates and overall weak buoyancy. ..Darrow.. 10/27/2020
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