**New feature to the site will be the dot in the above image. This is where I would place myself if I was chasing tornadoes (topography and road network not factored in). This is just another way to raise awareness and to try out new methods for tornado forecasting (not to scare anyone near these areas). The thoughts and opinions in this blog are mine and not an official forecast. For an official Severe Weather Outlook please visit www.spc.noaa.gov. ***
The threat is still going to be around for Friday but since my last post a few things have changed. The MCV in the south is not going to be as much of a factor further north as a s/w will come in from the west to increase the mid level winds and lift. The MCV will aid in height falls across much of the area keeping a good part of the area in the threat for isolated severe wx. The main s/w from the west is the feature that will keep the threat favorable for NE PA into SE NY/N NJ instead of all the way down into DCA. As a result the best chance for organized convection has diminished in coverage and focused in the red outlined area. Areas outside of this still have a shot at some isolated severe weather which could turn into a few line segments capable of heavy rainfall and strong gusty winds. The MCV will spread some energy this way across the southern areas from DCA on south providing enough ascent in an unstable environment for intiation. The lack of vertical shear should allow these storms to be multicell/pulse with only a slight chance of severe weather.
Isolated tornado potential cannot be ruled out given the sfc vorticity rich environment and favorable low level stretching. As a result marginally severe hail and damaging winds will accompany these storms and possible supercell structures in the red outlined area.
I decided to add another area of red outline to address an area of possible organized multicells with damaging winds being the main threat. The potential for supercell structures will be confined to the northern threat area with 30+Kts of vertical shear, but this area across S NJ into MD/DE has been sticking out to me the last few runs. It goes back to the MCV and the increasing low level and sfc convergence in an area of MLCAPE values approaching 2000J/Kg. Although vertical shear is weaker the increasing low level vertical shear combined with increasing forcing shoudl result in some organization of multicells. Main threat will be for heavy rain and strong gusty winds.
Another tough forecast exist over the Midwest where a sfc low will develop along the quasi-stationary front and increase convergence across SD for storm initiation along with subllte s/w energy passing through. The greatest isentropic lift along this boundary exist from SD into MN. But given the lifting and thunderstorm initiation likely to occur in SD and progress into IA/NE this will be the area best suitable for supercells and line segments capable of large hail and damging winds. Given the locally enhanced shear associated with the low pressure backing the winds at the sfc in a vorticity rich environment should support an isolated tornado threat. Lack of low level winds will limit any tornadic threat for tomorrow across this area. But if storms can initiate in the marginal instability north of the front in MN in the greatest but weak isentropic lift than a tornado threat will increase. But right now main threats are for winds and large hail.
Further South and East the threat will still exist for severe weather but will remain isolated with weaker vertical shear favoring storm modes to be multicell/pulse.
Dryline activity should fire up during the late afternoon and evening hours. Given the steep lapse rates and ample instability along with favorable vertical shear a few supercells are possible. High based supercells will not favor any tornadic potential as damaging winds should be the main threat followed by large hail.