SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1109 AM CST Mon Nov 16 2020 Valid 171200Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few thunderstorms are possible to the west of the Washington and Oregon Cascades Tuesday afternoon and evening. Otherwise, the risk for thunderstorms appears negligible across much of the U.S. ...Synopsis... Much of the U.S. will remain under the influence of an amplified branch of westerlies emanating from the mid-latitude Pacific through this period. While lead large-scale mid/upper troughing continues to gradually shift east of the Atlantic Seaboard, large-scale ridging appears likely to prevail and expand eastward across the remainder of the interior U.S., ahead of large-scale troughing across the eastern Pacific into the Pacific Coast states. One short wave perturbation emanating from the western troughing may progress toward the crest of the downstream ridging and contribute to significant cyclogenesis to the lee of the Canadian Rockies late Tuesday through Tuesday night. Deepening surface troughing appears likely as far south as the Texas and Oklahoma Panhandle region. However, the southwestern flank of cold surface ridging shifting across and east of the lower Great Plains and Mississippi Valley will remain prominent across the northwestern Gulf of Mexico and Gulf Coast region. The will preclude substantive Gulf boundary-layer recovery and southerly inland return flow in the wake of the recent cold intrusion. ...South Florida... The boundary layer may remain seasonably moist across southeastern portions of the peninsula and Florida Keys through much of the day Tuesday, possibly contributing to weak to moderate CAPE with daytime heating. However, a remnant mid-level cyclonic shear axis progressing across the region may be in the process of weakening. Coupled with inhibition associated with relatively warm mid-level temperatures, probabilities for thunderstorms appear generally low and mostly confined to areas offshore of southeastern coastal areas/ southeast of the Keys. ...Pacific Northwest... The extent to which thermodynamic profiles will become conducive to charge separation remain unclear, with the mid-level cold core of the larger-scale troughing remaining mostly offshore through this period. However, models do indicate a swath of mid-level cooling (including 500 mb temps of -24 to -26 C) across coastal areas into the southern Washington/northern Oregon Cascades late Tuesday afternoon and evening, coincident with a belt of modest southwesterly onshore/upslope low-level flow. This seems to offer the best potential for scattered thunderstorm activity, and could become focused around the Greater Portland OR area. ..Kerr.. 11/16/2020
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