5-1-17 will be a stormy day for the Lehigh Valley although most of the storms are not going to be present until later this evening.
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1233 AM CDT Mon May 01 2017 ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THE EVENING ACROSS MUCH OF THE LOWER GREAT LAKES REGION...THE UPPER OHIO VALLEY AND THE CENTRAL APPALACHIANS INTO MID ATLANTIC COAST....
...SUMMARY... Thunderstorms are expected to develop and overspread much of the lower Great Lakes region, the upper Ohio Valley and central Appalachians into the Mid Atlantic region today, accompanied by potentially damaging wind gusts and the risk for a few tornadoes.
...Eastern states... Models indicate strengthening of warm sector 850-500 mb wind fields to 40-70+ kt during the day today, particularly across the lower Great Lakes region, the upper Ohio Valley and the central Appalachians into the northern Mid Atlantic Coast region. This should prove more than favorable for organized severe thunderstorm development, given at least weak boundary layer destabilization, and surface dew points in the 60s probably will contribute to this with daytime heating, despite relatively warm and initially capping mid-level layers. Beneath increasingly difluent flow aloft, frontal and orographic forcing for ascent are expected to aid initiation of thunderstorm s near/east of Lake Erie, southward along the western slopes of central into southern Appalachians by 18-21Z. This activity seems likely to eventually consolidate and grow upscale into an organizing squall line as it crosses the Allegheny mountains and plateau, and to the lee of the Blue Ridge, by early evening. As it does, it probably will be accompanied by increasing potential for damaging surface gusts, given the strength of the ambient wind fields, with damaging straight line winds becoming the predominant severe threat. However, supercell structures, within and perhaps ahead of the line as it evolves, may be accompanied by a risk for tornadoes, one or two of which could be strong. Strong/severe storms may reach the Champlain/Hudson Valleys and Mid Atlantic coastal areas by this evening, before weakening within a more stable environment.