SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CDT Wed Sep 01 2021 Valid 011630Z - 021200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PARTS OF THE MID-ATLANTIC STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NE PANHANDLE TO WESTERN/CENTRAL SD... ...SUMMARY... Several tornadoes and scattered damaging winds appear probable across parts of the Mid-Atlantic States as the remnants of Ida move through the region into this evening. The greatest tornado threat is expected from central Maryland to southern New Jersey. ...Mid-Atlantic States... The remnants of TC Ida will move east-northeast from southeast WV across northern VA through the afternoon to the southern New England coast overnight. Mid 70s boundary-layer dewpoints are prevalent across eastern VA to southern NJ to the south of a northward drifting warm front. Here to, surface temperatures have warmed into the 80s amid scattered to broken cloudiness which is already supporting a plume of MLCAPE from 500-1500 J/kg. Low to mid-level vertical shear will increase into this evening as the remnants of Ida become further absorbed into the deepening longwave trough emanating south from QC. An initial arc of low-topped showers has developed across parts of north to southeast VA, largely ahead of schedule compared to much of the CAM guidance. As large-scale ascent and instability continue to further increase, it seems probable that this arc will eventually deepen into a broken band/cluster with several embedded supercells that will spread east-northeast towards the Atlantic coast into this evening. The relatively greatest tornado threat should exist along the baroclinic zone from central MD into south NJ with several tornadoes and occasional damaging gusts probable. See MCD 1668 for further near-term discussion. Low-level static stability and the exact cyclone track will determine the extent of the tornado threat this evening into tonight across Long Island and the immediate southern New England coast. Otherwise, damaging winds will be possible given the rather strong low to mid-level wind fields. Vertical shear will also be progressively weaker farther to the south of the warm front. Still, it should be adequate given the buoyancy for some threat of an isolated tornado or two into eastern NC, as well as the potential for a few damaging gusts with scattered storms along and just ahead of the primary wind shift trailing southward from the Ida remnant cyclone. ...NE Panhandle into western/central SD... Lee cyclogenesis is expected this afternoon across northeast CO, on the southern fringe of southwest mid-level flow. An inverted trough will extend north of the lee cyclone, across the NE Panhandle into western SD, and a slow-moving northwest/southeast-oriented warm front will intersect the trough across the NE Panhandle. With daytime heating/mixing, convergence and low-level ascent should be sufficient to weaken convective inhibition and allow at least isolated thunderstorm development late this afternoon across the NE Panhandle. The storm environment will favor cluster with a couple embedded supercells moving north-northeast along the trough, with an attendant threat for large hail and severe gusts into early tonight. ..Grams/Lyons.. 09/01/2021 Read more LIVE: spc.noaa.gov
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