Upstate New York Weather

Severe Thunderstorm Watch SEVERE THUNDERSTORM WATCH OUTLINE UPDATE FOR WS 456 NWS STORM PREDICTION CENTER NORMAN OK 250 PM EDT THU AUG 27 2020... SEVERE THUNDERSTORM WATCH 456 IS IN EFFECT UNTIL 800 PM EDT FOR THE FOLLOWING LOCATIONS NYC003-009-011-013-015-029-037-051-069-097-099-101-121-123- 280000- /O.NEW.KWNS.SV.A.0456.200827T1850Z-200828T0000Z/ NY . NEW YORK COUNTIES INCLUDED ARE ALLEGANY CATTARAUGUS CAYUGA CHAUTAUQUA CHEMUNG ERIE GENESEE LIVINGSTON ONTARIO SCHUYLER SENECA STEUBEN WYOMING YATES

Next round of storms on the way

Severe weather outbreak update. 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.

Newest update on the severe weather outbreak today there are a few changes. ...Northeast... A west-northwest mid-level flow pattern will be in place today across the Northeast as a 60 to 75 kt mid-level jet moves across the... region. At the surface, a low will move east-southeastward across New York as a cold front advances southward into the central Appalachians, to the west of the surface low. In the path of the surface low, surface temperatures will warm considerably allowing for the development of moderate instability by late morning. In response to surface heating and increasing low-level convergence, thunderstorm development should take place from western and central New York into southern New England by midday. Lift associated with the right entrance region of the mid-level jet will support convective development. In response, thunderstorm coverage will increase through the early afternoon as an east-to-west convective line organizes and moves south-southeastward across the region. NAM and RAP forecast soundings in southern New York in the early afternoon show veered winds at low levels with unidirectional west-northwesterly winds above 850 mb. The thermodynamic profile has very steep low-level lapse rates from 0-3 km with MLCAPE forecast to be in the 2000 to 3000 J/kg range. This combined with 40 to 50 kt of 0-6 km shear should be favorable for severe storms and possibly supercells. The more dominant supercells that form in proximity to strong instability may be able to produce hailstones 2 inches in diameter. In addition, bowing line segments may form in parts of the convective line. These faster moving bowing structures will likely produce wind damage along the leading edge of the line. A few gusts of greater than 65 kt will be possible. The severe threat is expected to move south-southeastward into northeast Pennsylvania and northern New Jersey during the late afternoon and early evening.

Newest update on the severe weather outbreak for tomorrow afternoon and evening please note the changes. ...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. See more