SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1140 PM CST Fri Dec 11 2020 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY NEAR THE UPPER TEXAS COAST... ...SUMMARY... A couple of strong storms could impact upper Texas coastal areas Sunday afternoon, accompanied by some risk for severe weather. ...Synopsis... Models continue to indicate that a vigorous short wave trough digging out of the Arctic latitudes will be accompanied by a more substantive cold intrusion into the northern Great Plains and Upper Midwest by late Sunday night. However, a belt of westerlies emanating from the mid-latitude Pacific appears likely to maintain considerable influence across much of the U.S. through this period. Within the southern stream, one significant short wave trough is forecast to dig to the lee of the southern Rockies by 12Z Sunday, before turning eastward across the Red River Valley and Mid South, ahead of another significant upstream perturbation digging across the Pacific Northwest into the Great Basin by 12Z Monday. Models indicate little, if any, phasing of the lead perturbation with the northern stream impulse, but associated forcing for ascent may support modest surface wave development along an initially stalling frontal zone across the Gulf States/lower Mississippi Valley into the southern Great Plains. There remains meaningful spread evident within the various model output concerning these developments, which continues to contribute to somewhat uncertain convective potential. In general, though, it does appear that at least some further moistening will support more appreciable boundary-layer destabilization across the northwestern into parts of the northeastern Gulf of Mexico, as deep-layer wind fields and shear strengthen across much of the Gulf Coast states. Stronger mid-level cooling and mid/upper forcing for ascent associated with the progressive short wave trough likely will remain displaced well inland from the boundary-layer destabilization over the Gulf of Mexico. However, moistening on return flow above the cooler and more stable air mass inland of the coast will contribute to weak elevated destabilization. The latest NAM forecast soundings, in particular, appear more suggestive that thermodynamic profiles could become conducive to convection capable of producing lightning. Although probabilities may be relatively low, this could occur in a couple of swaths, including within the exit region of the mid-level jet streak, across the Red River Valley into the Ark-La-Miss vicinity, and perhaps in association with warm advection to the northeast of the surface low track, across the lower Mississippi Valley toward the southern Appalachians. ...Southeast Texas coastal vicinity... As the primary frontal wave begins to form inland of upper Texas coastal areas Sunday afternoon, there may be a window of opportunity for modest boundary-layer destabilization in the presence of strengthening deep-layer wind fields and shear. This could contribute to an environment favorable for scattered discrete storms, one or two of which may intensify into supercells, before associated forcing shifts northeastward by Sunday evening. ..Kerr.. 12/12/2020
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