Overnight Severe Weather Outlook for Sunday, August 9, 2009...

Discussion...
As mentioned, probabilities are capped at 30/15/2 for Damaging Wind, Large Hail, and Tornadoes, respectively.

Current thinking is that by Mid-morning, Western NY into Northwestern PA should begin to see some clearing from current cloudiness/precipitation moving thru. This should allow for ample enough destabilization to occur here by mid-Afternoon and support thunderstorm re-development by 18z. While at first, storms may be somewhat loosely organized, think we could see a quick transition into a more linear configuration, possibly a bow echo, that will track east-southeast from Western NY into north central PA, and points southeast. For this reason, cashed in previous D2 30% coverage probability for an enhanced 30% Damaging Wind probability that will span from Western NY to East Central PA. It should be noted that the 00z WRF shows what could be a powerful bow echo tracking over this 30% Damaging Wind corridor. So, bottomline, think Damaging straight-line winds will be the primary threat, with Large Hail a secondary threat.

Despite a somewhat favorable environment for a few isolated tornadoes, overall convective mode should feature more in the way of bows/segments/clusters and associated damaging wind threat. The tornado threat is somewhat conditional on the question as to whether any discrete supercells can develop aside from any organized lines/bows. As mentioned earlier, as the Afternoon progresses, feeling is that on-going convection, if it hasn't already, will transpire into an organized MCS of sorts that tracks into PA by Evening, before weakening as it reaches the Lower Susquehanna Valley.

I'll will surely re-analyze things later this Morning when the RUC becomes of relevent use. I don't plan on lowering any probabilities at this point, so biggest potential change, if there was any, would be to possibly leverage a corridor of 5% Tornado probability. Other than that, I have fairly good confidence in this current outlook verifying to my liking.

..EGAN.. 08/09/2009