SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Thu Jul 01 2021 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF EASTERN VIRGINIA...SOUTHERN MARYLAND....DELAWARE AND SOUTHERN NEW JERSEY... ...SUMMARY... Clusters of thunderstorms posing a risk for damaging wind gusts are possible across the northern Mid Atlantic Coast region this afternoon into this evening. ...Synopsis... Models suggest that the prominent mid/upper high center emerging from the Pacific Northwest/British Columbia vicinity may maintain considerable strength through this period. However, it appears that it will be gradually forced east-southeast of the Canadian Prairies, toward the central Canadian/U.S. border area, while downstream troughing undergoes amplification across southeastern Canada and east of the Mississippi Valley. The most prominent embedded perturbation, including a mid-level low, is forecast to dig across the lower Great Lakes region, preceded by a weakening perturbation to the south and southeast of the lower Great Lakes, and at least a couple of convectively generated or enhanced smaller-scale perturbations across the Ohio Valley into northern Mid Atlantic Coast region. By 12Z this morning, the leading edge of somewhat cooler/drier air, associated with the larger-scale mid-level troughing, may extend off southern New England into northern Mid Atlantic coastal areas, the lower Ohio Valley and central Great Plains, before advancing southward into southern Mid Atlantic coastal areas, the northern Gulf States and southern Great Plains by 12Z Friday. This likely will be followed by more substantive lower/mid-level cooling and drying across much of the Great Lakes, Northeast and Ohio Valley. It appears that the reinforcing front might provide a focus for modest cyclogenesis this evening through tonight, near/south of Long Island and the southern New England coast. Within slowly deepening surface troughing southward across the Delmarva Peninsula into the lee of the Blue Ridge Mountains, daytime heating of a seasonably moist boundary layer may become supportive of moderate to large CAPE in excess of 2000 J/kg. Coinciding with increasing forcing for ascent, downstream of the primary digging short wave impulse, and possibly in association with one of the convectively generated perturbations, considerable vigorous thunderstorm development appears possible late this afternoon and evening. ...Mid Atlantic... Mid/upper flow and deep-layer shear along the axis of stronger destabilization within the surface troughing may be fairly modest to weak, at least initially. However, strengthening of southwesterly winds to 30-40 kt in the 850-700 mb layer may be sufficient to contribute to one or two organizing clusters of storms by late this afternoon. Given the magnitude of the forecast CAPE, coupled with relatively steep low-level lapse rates, it appears that the environment will be conducive to potentially damaging surface gusts. This may be associated with locally strong downbursts initially, then with strengthening cold pools in upscale growing, northeastward and eastward propagating convection into this evening. ..Kerr/Lyons.. 07/01/2021 Read more LIVE: spc.noaa.gov
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