SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0237 PM CDT Sun Aug 01 2021 Valid 012000Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON ACROSS PARTS OF THE CAROLINA COASTAL PLAIN... ...SUMMARY... Thunderstorm activity may continue to develop and organize across the North Carolina coastal plain late this afternoon and pose a risk for damaging wind gusts. ...20Z Outlook Update... Adjustments have been made to the categorical and probabilistic outlook lines, mostly to the account for the progression of a number of synoptic and sub-synoptic perturbations and associated surface boundaries. Seasonably modest low-level moisture and boundary-layer warming are limiting destabilization across the Northeast, as a vigorous short wave trough gradually begins to turn east of the lower Great Lakes region. However, there does still appear at least a window of opportunity for some intensification of ongoing convective development late this afternoon and evening, particularly across parts of southwestern into central Pennsylvania, as a 50 kt 500 mb jet streak propagates eastward out of central Ohio. Across Texas, vigorous thunderstorm development is ongoing along a weak southward advancing outflow boundary across the Edwards Plateau and Hill Country vicinity. However, this is far removed from even the weak to modest (10-20 kt) west-northwesterly mid-level flow on the southern fringe of upper troughing across the Ark-La-Tex vicinity into the Gulf Coast states. With thermodynamic profiles not much, if any, more conducive to downburst potential, severe weather probabilities appear comparatively weaker, and generally less than 5 percent. ..Kerr.. 08/01/2021 .PREV DISCUSSION... /ISSUED 1120 AM CDT Sun Aug 01 2021/ ...Carolinas... A few supercells have evolved into a small cluster along the surface front across northeast NC. Additional convective development is expected farther southwest near the surface cyclone across central NC. Air mass ahead of the front/cyclone continues to destabilize in the presence of mid to upper 70s surface dew points. While low-level SRH should remain modest, slightly backed surface winds across far eastern NC may support the threat for a tornado or two. The primary hazard will likely be scattered damaging winds as the upstream convection develops and evolves into an eastward-moving cluster across eastern NC through this afternoon. ...NY/PA... Lower-topped thunderstorms have developed along and just ahead of an eastward-progressing cold front in the lee of the Lower Great Lakes. More pronounced boundary-layer heating is underway across western to northeast PA into southeast/east-central NY, which should aid in some intensification of convection this afternoon. However, boundary-layer temperatures and dew points will be seasonally subpar with the bulk of destabilization occurring through steepening of mid-level lapse rates with approach of the shortwave trough. In addition, lower-level flow will remain relatively modest with faster mid-level flow largely confined to the upper portion of the weak buoyancy profile. As such, convection may struggle to become substantially deep and organized, which may result in only sporadic bouts of damaging winds and isolated marginally severe hail. ...Deep South... Scattered thunderstorms are expected along a trailing cold front that will slowly slide south across the region this afternoon. Weak deep-layer shear but large buoyancy will favor pulse to loosely organized multicells. Wet microbursts capable of producing locally damaging wind gusts will be the main hazard. ...West... In what is otherwise a weak meridional flow pattern across the West, a pair of MCVs, one over southeast NV and the other near the OR/ID/WA border area, may help focus weakly organized severe potential this afternoon. Relatively high PW values along with steep low-level lapse rates will support a threat for microbursts capable of isolated severe gusts.
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