Severe Storm Risk - Mercersburg, PA

There is a Marginal Severe Storm Risk for your location. Continue reading for today's outlook from the National Weather Service's Storm Prediction Center. -------------------- National Severe Storm Outlook THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN GREAT LAKES INTO THE MID-ATLANTIC STATES SUMMARY A couple of organized clusters of thunderstorms may develop across the southern Great Lakes and mid/upper Ohio Valley today through tonight, accompanied by the risk for damaging wind gusts. More widely scattered strong thunderstorms east of the Blue Ridge may also pose potential for damaging wind gusts this afternoon and evening. Southern Great Lakes into Mid Atlantic Early-morning satellite imagery shows a deep cyclone over the Pacific Northwest and upper ridging covering the majority of the CONUS east of the Rockies. A belt of enhanced mid-level flow persists between these two features, arcing anticyclonically from southern CA through the central Rockies and northern Plains into the Upper Midwest/Upper Great Lakes and eventually through the Northeast. Recent surface analysis shows a reservoir of low-level moisture beneath the upper ridging, to the south and east of this belt of stronger mid-level flow. Much of this area is void of notable surface features, but a weak front does extend from southern New England through southern NY, central Lower MI, and central WI to a weak low over southern MN. A large cluster of showers and thunderstorms to the south of this front from southern WI into southern Lower MI. This cluster, which was initiated by warm-air advection across MN and WI is forecast to continue southeastward today, likely encountering a diurnally destabilized airmass. The steeper mid-level lapse rates will remain displaced west of this region, but ample low-level moisture (i.e. upper 60s/low 70s dewpoints) coupled with afternoon temperatures from the mid 80s to mid 90s will still support moderate to strong buoyancy. As such, reintensification and/or new development is anticipated as the ongoing cluster continues southeastward. Much of this region will be on the southern fringe of the stronger deep-layer shear, with bowing line segments as the predominant storm mode. The best overlap between buoyancy and shear is expected across central and eastern OH, where a corridor of greater potential for damaging gusts exists. The threat for damaging gusts will extend into the Mid-Atlantic this afternoon and evening amid a very warm and moist airmass. Vertical shear will be weak, but ample moisture (i.e. PW values from 1.8" to 2"), strong buoyancy, and steep low-level lapse rates will support the potential for strong outflow capable of wind damage. Bowing line segments will be the primary storm mode here as well. Central Plains Weak lee troughing could contribute to modest low-level convergence from western KS across western/central NE into southwest SD. Dewpoints will likely be in the low to mid 60s within this convergence zone, and steep mid-level lapse rates will contribute to moderate/strong buoyancy. Even so, warm mid-levels may prevent the airmass from completely destabilizing. The remaining convective inhibition, coupled with the presence of large-scale height rises across the region, casts doubt to whether successful convective initiation will occur. Any mature updrafts could result in strong downdraft, but uncertainty is too high to introduce any probabilities with this outlook.