Severe Storm Risk - Collegeville, PA

There is a Slight 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...PORTIONS OF THE UPPER MIDWEST AND CENTRAL HIGH PLAINS...AND SOUTHERN ARIZONA SUMMARY Thunderstorms with severe wind gusts will be possible this afternoon and evening from northern Illinois eastward into Pennsylvania. Severe gusts and hail will also be possible from parts of the central and northern Plains into the Midwest, with scattered severe storms over southern Arizona. Synopsis Another highly uncertain and complex forecast with mesoscale convective dependencies apparent this forecast update. Water-vapor imagery implies a belt of west-northwest mid to high-level flow extending across the northern High Plains east through much of the Midwest, and to the north of a flattened mid-level ridge extending from the Four Corners to FL. Embedded within the flow, a convectively augmented disturbance over the southern Great Lakes will move east into PA by early this afternoon. Another minor perturbation over southwest MT this morning will quickly move into the Dakotas by early evening and probably influence the severe threat from SD into adjacent parts of IA/MN overnight. IL to the Mid-Atlantic Radar mosaic this morning shows an organized line segment moving east along the OH-Lake Erie shoreline and a couple of other thunderstorm clusters over western OH and south-central PA. The Detroit, MI WSR-88D VAD showed a mid-level speed max associated with the convectively augmented vorticity max moving east across the Lake Erie vicinity. Gradual intensification of storms is expected this morning as the boundary layer heats downstream across OH into PA and the Mid-Atlantic states (refer to MCD 1892 for short-term details regarding the northeast OH thunderstorms). Of particular note, the 12 UTC Pittsburgh, PA and Wilmington, OH raobs showed a moderate to very unstable airmass (1800-2700 J/kg MLCAPE, respectively) in place over the upper OH Valley. Severe gusts capable of scattered wind damage will be possible through the afternoon with any stronger thunderstorms and clusters of storms. Farther west, models show storm redevelopment perhaps centered over northern IN/IL later this afternoon/evening. Shear/buoyancy profiles will support organized storms, including supercells and linear clusters. Damaging wind and hail will be the primary hazards, though a tornado or two also could occur. Dakotas into MN/IA Similar to previous forecast thinking, southeasterly low-level flow will aid in the transport of seasonably rich moisture (mainly 60s F surface dewpoints) north and west into SD. Model forecast soundings show large buoyancy developing by mid afternoon within the aforementioned moist plume. The weak impulse implied by model guidance moving into western SD may enable at least isolated to potentially scattered storms developing towards early evening over western and central SD. The 00z ECMWF and 00z HREF consensus suggest a linear cluster evolves during the evening and grows upscale into an MCS during the overnight moving east-southeast along a residual frontal zone. Have included an intensity level-1 to denote this conditional but significant wind risk if this forecast scenario occurs. AZ Mid/upper easterly flow will persist today amid plentiful moisture and strong heating. This will support thunderstorm development once again across higher terrain. Scattered storms are forecast to eventually develop with their cold pools coalescing over the lower desert. Based on the latest CAM guidance and inverted-V profiles with marginally supportive shear for loose storm organization, have upgraded a part of the lower desert into higher severe-wind probabilities. Widely scattered to scattered severe gusts 60-75 mph are possible with this activity. NE/CO/KS Scattered thunderstorms are expected to develop near a surface trough across western NE/northeast CO by late afternoon/early evening. As the high-based storms mature into possibly a small linear cluster and move into richer moisture with east extent, steep low- to mid-level lapse rates will support severe gusts (60-75 mph) and perhaps hail with this activity.