SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1102 PM CST Sun Jan 10 2021 Valid 111200Z - 121200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across much of the nation today through tonight. ...Discussion... Short waves will continue to emerge from a strong, generally zonal mid-latitude Pacific jet, before progressing into and through modestly amplified branching downstream westerlies. To the southeast of the center of an initially broad and deep cyclone near Kodiak Island, models indicate that one of these perturbations may contribute to modest surface cyclogenesis across the northeastern Pacific. Coinciding strengthening of southwesterly lower/mid tropospheric wind fields into the Pacific Northwest is also forecast, including to 50-80 kts in the 850-700 mb layer, accompanied by a plume of moisture emanating from the lower latitudes of the western and central Pacific. While this may contribute to the development of very weak CAPE, primarily to the west of the Cascades, it appears that colder mid-level air with steeper lapse rates more supportive of convection capable of producing lightning will generally remain to the northwest of the region. Downstream, generally stable conditions will be maintained across much of the nation. An influx of moisture off a still modifying boundary layer over the Gulf of Mexico does appear likely to overspread much of the Southeast, as a short wave impulse emerges from larger-scale troughing to the lee of the southern Rockies. However, this perturbation will undergo considerable deformation as it accelerates into increasingly confluent mid-level flow across and east of the Mississippi Valley. And associated surface wave development along a frontal zone across the northeastern Gulf of Mexico and northern Florida into the western Atlantic is forecast to remain weak. Warming temperatures aloft, to the south of the perturbation, should maintain weak mid-level lapse rates across and inland of the northeastern Gulf coast. And models indicate that boundary-layer moistening will only become supportive of very weak CAPE across the coastal waters and immediate coastal areas. While a categorical risk for thunderstorms is being maintained across this region, probabilities may be near the minimum 10 percent threshold. ..Kerr.. 01/11/2021
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