Severe Thunderstorms Possible Thursday August 27
relevant SPC discussion:
...Northeast/Mid-Atlantic... Storms will probably be ongoing Thursday morning along/near a warm front in a low-level warm advection regime across parts of the Northeast, with a limited severe threat evident. Additional convective development appears likely by Thursday afternoon across this region along both the warm front and a pre-frontal trough. The airmass along/south of the warm front is expected to become at least moderately unstable, with MLCAPE of 1500-3000 J/kg possible. Strong deep-layer shear of 35-50 kt will be present across this region owing to enhanced west-northwesterly mid-level flow. Initial afternoon storm development will likely be supercellular, with both a large hail and damaging wind threat. Some of the large hail could be significant (2+ inches) given somewhat steepened mid-level lapse rates and very favorable thermodynamic/kinematic environment. Clustering and upscale growth appears possible later Thursday afternoon as storms approach NYC and southern New England. A more substantial severe/damaging wind threat will likely develop as this mode transition occurs.
drummerboy said:
foo
I do not need another power outage.
The generators! The noise!
Just a reminder that there is a potential for severe thunderstorms today, Thursday Aug 27th, most likely in the late afternoon and early evening hours. Unusually, storms in this system will be coming from the north, not the west, and could contain high winds and hail. A small tornado is possible but not likely. Please have the emergency alerts turned on on your phone for timely warnings.
That said, the worst of this is likely to be north and east of the MAPSO area.
Forecast remains on track from yesterday, with severe storms possible this afternoon across the area. The SPC has kept their risk areas consistent with yesterday's forecast. Damaging wind and large hail remain the most substantial threats with a tornado possible as well:
...Northeastern CONUS... Widely scattered to scattered thunderstorms are forecast to develop episodically near the low and frontal zone from midday through afternoon, where low-level lift will be relatively maximized amidst weak CINH. Activity should move east-southeastward to southeastward across the outlook area as the inflow/boundary layer to the south continues to destabilize diurnally. Some supercells are possible, and convection should pose a threat for all severe types. Diurnal heating and 60s F surface dew points along and south of the boundary will offset modest midlevel lapse rates enough to yield MLCAPE in the 1000-1500 J/kg range -- locally/briefly above 2000 J/kg. Elongated, somewhat curved low-level hodographs are expected in the warm sector before and as the low passes a given longitude, before the surface flow substantially veers. Effective-shear magnitudes of 50-60 kt may be common, in support of supercells and small bows. Some aggregation of early convection into fast-moving clusters with enhanced wind-damage potential is possible.
Most recent SPC outlook has pushed the threat of the most significant severe weather to the north. We are not out of the woods, but looking like things will be a little tamer down here than it appeared this morning.
Looks like the forecast did highlight the worst area - which is north of us.
jamie said:
Looks like the forecast did highlight the worst area - which is north of us.
Beat me to it. While there is still a threat to our area as those storms drift south, the longer they take to get here the lesser the threat will be.
From South Salem NY.
The video won't upload. My friend up there says pebble sized hail.
This is just the southern edge. The real action went by to our north.
Not to be lost in the (well deserved) attention being paid to Hurricane Laura, a fairly high-end severe weather setup appears increasingly likely for the area tomorrow, as the Storm Prediction Center has us under an enhanced risk for severe thunderstorms. While the higher probability threat appears to be largely driven by wind (SPC 30% hatched for significant wind gusts of 75+ mph), it is the threat for large hail that has my attention. The SPC has a 15% hatched for significant hail probability drawn for the entire area indicating the possibility of 2"+ hailstones. These hail probabilities are rare -- I'm not sure I remember the last time I've seen a hatched for sig hail contour drawn for this area. I think the main threat for a few tornadoes will be north of us, but we can't completely rule one out around here either.
Edited to add: To sum up how rarified this environment is, this is the first time the SPC has issued a day 2 enhanced risk for NYC since they started issuing the enhanced risk category in October of 2014. That having been said, the risk looks to be largely driven by supercell storm modes transitioning to a mixed/linear mode as it approaches us. As a result, while the whole region appears primed for a severe weather event, any one given area may not experience severe criteria thunderstorm impacts (hail greater than 1", 58+ mph wind, a tornado).