SPC Nov 11, 2017 1730 UTC Day 2 Convective Outlook

By Newsroom America Feeds at 11 Nov 12:17

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CST Sat Nov 11 2017 Valid 121200Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S., Sunday through Sunday night. ...Discussion... Within larger-scale mid/upper troughing now evolving across the eastern Pacific, at least one significant embedded short wave trough is forecast to progress through its base, before pivoting toward Vancouver Island and the U.S. Pacific Northwest coast by late in the period, accompanied by a deepening surface cyclone. Downstream, broadly anticyclonic flow appears likely to prevail across the Intermountain West into the Rockies and Plains, to the north of a prominent subtropical high center encompassing the Baja of California, northern Mexico and the lower Rio Grande Valley. Models suggest some building of ridging within the southern branch of the split westerlies may occur, across the southern Rockies and adjacent high Plains, in the wake of one short wave trough expected to progress across and east/southeast of the middle Mississippi Valley, toward the middle and southern Atlantic Coast. This latter feature is expected to be accompanied by at least some reinforcement of generally dry and/or stable conditions with negligible convective potential, particularly from the Rockies through the Appalachians. ...Florida... Substantive low-level moistening appears probable on deep easterly low-level flow across at least the southern half of the peninsula. Models suggest that this will coincide with weak mid-level height falls and an erosion of relatively warm and capping lower/mid tropospheric air. Forcing to support convective development inland of coastal areas remains unclear, but isolated afternoon thunderstorms may be possible in response to insolation. Otherwise, any risk for thunderstorms seems likely to become maximized in areas of stronger low-level convergence near Atlantic coastal areas late Sunday into Sunday night. ...Southern Mid Atlantic Coast... Ahead of the approaching mid-level wave, modest low-level moisture return off the Atlantic appears possible, prior to the onset of strengthening large-scale ascent across eastern North Carolina and adjacent areas of southeast Virginia/northeastern South Carolina late Sunday night. However, the extent to which thermodynamic profiles become conducive to convection capable of producing lightning remains unclear, resulting in the maintenance of less than 10 percent thunderstorm probabilities. ...Pacific Northwest... Weak conditional instability may be present to the west of the Cascades through much of the period. However, forcing to support an appreciable risk for thunderstorms may be lacking until the exit region of a vigorous cyclonic mid/upper jet streak approaches coastal areas late Sunday night. ..Kerr.. 11/11/2017 Read more



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