Severe Storm Risk - Orrstown, 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 OVER PORTIONS OF THE SOUTHERN GREAT LAKES INTO THE MID AND UPPER OHIO VALLEY SUMMARY Severe storms capable of scattered occurrences of damaging wind with gusts up to 70 mph are expected across the southern Great Lakes and mid/upper Ohio Valley overnight. More isolated severe storms capable of large hail and severe wind gusts may occur over portions of the northern Plains. Strong to severe storms with a risk for damaging wind gusts may persist for another couple of hours in the southern Mid-Atlantic. Great Lakes into the Ohio Valley Forcing for ascent attendant to a weak mid-level disturbance cresting the mid-level ridge is contributing to a couple of areas of thunderstorm activity this evening over portions of eastern IA and central WI. The 00Z DVN sounding is likely representative of the inflow air mass for these storms, featuring a moist boundary layer and relatively steep mid-level lapse rates with MLCAPE of around 4000 J/kg. It remains unclear whether a subset of the current storms will grow upscale into a cold-pool-driven MCS overnight, or whether additional storms will develop farther to the east across portions of southern Lake MI and southwest Lower MI in the next few hours. Either way, there is a consistent model signal for a bowing convective system to evolve across portions of northeast IN into OH, along the cool side of a composite surface boundary extending from central WI through central IN into eastern KY. Regional VWPs and 00Z soundings indicate the presence of 30-35 kt northwest winds in the mid levels along the axis of the prospective MCS track, which will contribute to sufficient deep-layer shear for cold-pool organization. As such, a corridor of more concentrated wind damage appears possible along with severe gusts up to 70 mph. Northern Plains A cluster of mainly elevated thunderstorms is ongoing this evening over north-central SD, with that activity likely rooted above a warm capping inversion observed by the 00Z ABR sounding. Additional storms are expected to develop overnight along a nocturnally strengthening low-level jet, where warm advection and moisture transport will be maximized. Mid-level flow and resultant vertical shear are forecast to weaken overnight owing to the proximity of the mid-level ridge. However, the presence of steep mid-level lapse rates and associated moderate to strong instability suggests the potential for isolated severe storms capable of large hail and severe wind gusts. As such, 5% wind and hail probabilities have been included in this forecast update. Southern Mid-Atlantic Clusters of strong to severe thunderstorms ongoing over portions of southeast VA into north-central and northeast NC will remain capable of mainly damaging wind gusts for the next hour or two. Thereafter, storms are expected to gradually weaken as the boundary layer stabilizes.