SPC Nov 12, 2017 2000 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 12 Nov 14:41

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook RESENT 1 NWS Storm Prediction Center Norman OK 0137 PM CST Sun Nov 12 2017 Valid 122000Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Some thunderstorm activity is possible across coastal areas of Washington and northern Oregon by late tonight, but the risk for severe weather still appears negligible through 12Z Monday. ...20Z Outlook Update... Only very minor changes to the general (10 percent probability) thunder line have been made across parts of Southeast coastal areas, to account for ongoing convective/destabilization trends. Weak to moderate potential instability (for boundary layer parcels) now appears to exist across much of the southern Florida Peninsula. Pockets of locally stronger low-level convergence to support isolated thunderstorm development appear generally confined along Atlantic coastal areas. Deepening convective development emanating from the more strongly heated interior southern Peninsula is evident near southwestern Gulf coastal areas, but it is possible that lingering mid-level inhibition may remain suppressive inland of the coast. ..Kerr.. 11/12/2017 .PREV DISCUSSION... /ISSUED 1024 AM CST Sun Nov 12 2017/ ...Synopsis... A shortwave trough will move eastward from the mid MS and OH Valleys to the Mid-Atlantic through the period, as a separate upper low approaches the coast of the Pacific Northwest late tonight into early Monday morning. At the surface, several areas of high pressure along and east of the Rockies will maintain cool/stable conditions across much of the central/eastern CONUS. Rich low-level moisture and related isolated thunderstorm chances will likely remain confined to parts of coastal southeastern LA and the central/southern FL Peninsula this afternoon and tonight. Modestly enhanced low-level easterly flow across the FL Peninsula weakens quickly with height beneath mid-level sub-tropical ridging, suggesting severe thunderstorm potential remains low across this region. Although low-level moisture is present across parts of south TX, an inversion around 600 mb (see 12Z CRP sounding) should limit the potential for thunderstorms there. Late tonight both low and mid-level lapse rates will steepen across the eastern Pacific and coastal Pacific Northwest in advance of a pronounced mid/upper-level low and attendant speed maximum. While instability is forecast to remain quite modest, there will be some potential for isolated thunderstorms along parts of the WA/OR Coast late tonight and early Monday morning. Read more



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