Well this sounds a tad scary. Would be nice to not have trees falling on the house just as I prepare to leave the country for a much needed vacation.
Synoptically, this will be an impressive evolution as tropical and mid-latitude meteorology collide. The remnants of Ida are tracking steadily northeastward through the Tennessee Valley, and its cloud pattern remains well-defined on satellite. The most prominent feature of this setup is the strong (140 kt) upper jet streak which will build into northern New England on Wednesday. Ida`s remnants will track straight into its right entrance region, where large scale upper divergence is maximized. The system will begin to interact with the upper jet and the lingering frontal boundary currently over our area. After days of weakening over land as a tropical system, Ida`s remnants will reintensify as a highly dynamic, baroclinic low, but still with tropical moisture. Strong increases in low and mid level winds, frontogenetic forces, and low level convergence will allow a dramatic increase in the coverage and intensity of the rain shield as it moves in. Meanwhile, as the system takes on traditional frontal characteristics, an unstable warm sector will likely overspread southern portions of the area, contributing to severe weather potential. Overall, this continues to look like a high impact event. Details... First, a note on timing: The bulk of the impacts are expected to occur throughout the daytime Wednesday, Wednesday night, and early (mainly predawn) Thursday. This represents a slight earlier shift in timing. Severe weather concerns will peak from about mid afternoon to late evening Wednesday, around 2-10PM. Hydro concerns will focus more on the later afternoon through the overnight, with residual impacts into Thursday especially on slower responding rivers. Today`s guidance overall showed a small but definite trend northward with the highest QPF. However, that followed a small southward shift last night. So again, noise level changes. Our rainfall forecast was changed little, with a slight northward shift in the axis of heavier QPF and a slight trend upward overall in rainfall amounts as CAM guidance certainly supports the potential for a widespread swath of 4 to 6", with locally over 6" possible. This will be more than sufficient to bring both widespread flash/urban flooding and widespread main stem river flooding, discussed more in the hydrology section. One area where concern has increased today is severe weather potential. With the more amplified trend, wind fields are looking robust across the area from Wednesday afternoon into Wednesday night. As mentioned, the warm sector of the system will overspread approximately the southern half of the area, and that is where severe weather concerns are maximized. Southeasterly surface flow will veer to to southwest with height, with good speed shear and directional shear in the lowest levels especially strong. There are some very concerning 31.12z CAM runs such as the 3km NAM, ARW, and HRRR. Soundings from those models over southern New Jersey and Delmarva show long, clockwise curved hodographs reflective of 0-1km SRH in the 200-300 range and 0-3km SRH in the 300-400 range, and 40 to 50 kt southwesterly bulk shear vectors. These values on their own are not enough to produce severe weather, but it is looking like they will be paired with 1000 to 1500J of SB CAPE across our southern zones, providing the necessary instability for convection to grow vertically enough to be dangerous. The very high shear and sufficient instability, combined with high moisture and associated low LCLs, would create a highly favorable environment for tornadoes. If these trends hold, several tornadoes, including a chance for a strong tornado, would be possible especially over southern New Jersey and Delmarva, with the risk decreasing to the north. Some convectively enhanced damaging straight line wind gusts are also possible.