SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1235 AM CDT Wed Sep 01 2021 Valid 011200Z - 021200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MIDDLE ATLANTIC... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IMMEDIATELY SURROUNDING THE ENHANCED RISK AND ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Several tornadoes and scattered damaging winds appear probable across parts of the Mid-Atlantic as the remnants of Ida move through the region later today. Isolated strong/severe storms may also occur across portions of the northern/central Plains. ...Middle Atlantic... Remnants of Ida are currently spreading northeast across the southern Appalachians early this morning. Surface low associated with this feature is forecast to track into southern WV by the start of the day1 period, then advance into northern VA by early afternoon. In response, warm front should advance north across NJ, ultimately orienting itself near Long Island during the evening. This boundary will serve as the northern demarcation of meaningful tornado potential. Have opted to extend 10% tornado probabilities a bit farther north across NJ due to the warm sector that should spread across much of the Garden State. Latest water-vapor imagery depicts a more open short-wave trough in association with the remnants of Ida. This feature will eject into WV by 18z, then east during the overnight hours as stronger 500mb flow translates into southern New England. Latest model guidance continues to suggest LLJ will strengthen across the Delmarva into NJ ahead of the low and strong vertical shear will prove sufficient for sustaining supercells. Additionally, while very moist air mass (PW values 2"+) will overspread this corridor, some boundary-layer heating is expected, especially across the Delmarva into southern NJ where surface temperatures could approach 80F. This should aid buoyancy and increase the likelihood for robust updrafts. Given the strength of the wind field, tornadoes appear possible with supercells until the surface low advances off the NJ coast later in the evening. ...Northern/Central Plains... Several weak embedded disturbances are rotating north, around the southern Plains anticyclone, across the Four Corners region. One of these features is forecast to eject across the Dakotas during the early evening with a substantial increase in 500mb flow expected. This feature will likely induce lee surface cyclone over northeast CO with an inverted surface trough forecast to extend north across the western Dakotas. Boundary-layer heating is not expected to be particularly strong but low-level warm advection, steep mid-level lapse rates, and weak large-scale support suggest a corridor of convection by evening. Hail is the primary risk, though some wind can not be ruled out. ..Darrow/Wendt.. 09/01/2021 Read more LIVE: spc.noaa.gov
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