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Posted: (August 04, 2008 01:46 pm)
Western-Central PA and NY (Most likely to see severe weather)
The threat will run for most of the day across these areas as several lines of storms are expected to form and push eastward at a quick pace with strong flow aloft. Despite weak mid level winds early in the threaten period the low level winds will be strong enough to warrant a tornado threat across Western PA. The stronger winds moving into the low levels will boost 0-2km shear to 26kts. The slight veering wind profiles from sfc to low levels will also help with rotation. Cloud bases being below 500m AGL highlight the ample moisture in lower levels and this will increase tornadic threat. The threat will be in the afternoon and evening hours as a low level s/w will be the reasoing for the backing winds at the sfc. Then towards the nighttime the winds will become uni-directional and lead to a few bowing segments possible. I think NY will be the winner in terms of most reports of wind damage and hail.
Philadelphia may dodge another bullet...
The forecast for tomorrow for philly is looking good for a few thunderstorms but not the storms areas across Western PA/OH. The better forcing and stronger flow aloft will push several lines of storms thru Western PA/NY/WV/OH but as they progress eastward they will weaken and probably will not make it to the PHL metro in the form of thunderstorms. A few reasons why I think this....
1) A sfc trough and associated vort lobe push thru during the afternoon to early evening hours allowing cloud cover and a few storms to develop. The convection that forms earlier could possibily cut down on diurnal heating and further destabilization.
2) Some of these storms could get strong but looking at forecast soundings it appears the CAPE will be under a 1000j/kg. These poor CAPE values will be in responce to the poor mid level lapse rates. Another factor that hurts the chances of a nighttime MCS (Mesoscale Convective System). These storms due form out ahead of the strongest winds aloft. The areas further North and West will have an upper level jet to 100+kts pushing these storms leading to the possibility of widespread damaging winds.
3) PHL soundings show a low level inversion becoming well defined towards midnight and this will limit any thunderstorm threat. And if any storms due form they will be elevated and will not reach severe limits.
**Things can change but I do not see Philadelphia metro southward to DC metro seeing much of anything severe tomorrow and tomorrow night.
We will continue to update on this event tonight into tomorrow.
The threat will run for most of the day across these areas as several lines of storms are expected to form and push eastward at a quick pace with strong flow aloft. Despite weak mid level winds early in the threaten period the low level winds will be strong enough to warrant a tornado threat across Western PA. The stronger winds moving into the low levels will boost 0-2km shear to 26kts. The slight veering wind profiles from sfc to low levels will also help with rotation. Cloud bases being below 500m AGL highlight the ample moisture in lower levels and this will increase tornadic threat. The threat will be in the afternoon and evening hours as a low level s/w will be the reasoing for the backing winds at the sfc. Then towards the nighttime the winds will become uni-directional and lead to a few bowing segments possible. I think NY will be the winner in terms of most reports of wind damage and hail.
Philadelphia may dodge another bullet...
The forecast for tomorrow for philly is looking good for a few thunderstorms but not the storms areas across Western PA/OH. The better forcing and stronger flow aloft will push several lines of storms thru Western PA/NY/WV/OH but as they progress eastward they will weaken and probably will not make it to the PHL metro in the form of thunderstorms. A few reasons why I think this....
1) A sfc trough and associated vort lobe push thru during the afternoon to early evening hours allowing cloud cover and a few storms to develop. The convection that forms earlier could possibily cut down on diurnal heating and further destabilization.
2) Some of these storms could get strong but looking at forecast soundings it appears the CAPE will be under a 1000j/kg. These poor CAPE values will be in responce to the poor mid level lapse rates. Another factor that hurts the chances of a nighttime MCS (Mesoscale Convective System). These storms due form out ahead of the strongest winds aloft. The areas further North and West will have an upper level jet to 100+kts pushing these storms leading to the possibility of widespread damaging winds.
3) PHL soundings show a low level inversion becoming well defined towards midnight and this will limit any thunderstorm threat. And if any storms due form they will be elevated and will not reach severe limits.
**Things can change but I do not see Philadelphia metro southward to DC metro seeing much of anything severe tomorrow and tomorrow night.
We will continue to update on this event tonight into tomorrow.
