SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0154 AM CST Fri Dec 11 2020 Valid 131200Z - 141200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S., Sunday through Sunday night. ...Discussion... A vigorous short wave trough digging out of the Arctic latitudes may be accompanied by a more substantive cold intrusion into portions of the northern Great Plains and Upper Midwest. Otherwise, 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. One significant embedded short wave trough, likely digging to the lee of the southern Rockies by 12Z Sunday, may support renewed surface wave development along a frontal zone, initially stalling across the lower Mississippi Valley into southern Great Plains. With the latest ECMWF (11/00Z) a bit slower than prior runs (and other model output) with the eastward progression of this feature through 12Z Monday, there is meaningful spread among the guidance that contributes to uncertain convective potential across parts of the northwestern Gulf coast vicinity into the Southeast. This mostly appears to impact the placement of the 10 percent probability of thunderstorm line for Sunday through Sunday night, as the rather modest amplitude of the surface wave forecast by most guidance is not particularly suggestive of appreciable severe weather potential. Furthermore, it appears that stronger mid/upper forcing for ascent will remain well inland of coastal areas, as boundary-layer moistening over the northwestern Gulf of Mexico becomes more supportive of appreciable destabilization. However, given the strengthening lower/mid tropospheric wind fields forecast across coastal areas, if storms can form within the destabilizing offshore waters, it might not be out of the question that some could advect into coastal areas and pose some risk for severe weather. Due to the conditional, in addition to apparent marginal, nature of this potential, severe weather probabilities are currently being maintained at less than 5 percent, but trends will continue to be monitored. ..Kerr.. 12/11/2020
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