Tuesday, July 31, 2012

Tomorrow's Downpours Could Be More Widespread

With a trough/weak surface front approaching the region from the west tomorrow, the potential for more afternoon and evening thunderstorms exists in the forecast. The NAM and other computer models hint strongly that a line of thunderstorms will develop during the afternoon hours.  Like Monday, movement may be minimal.

Atmospheric moisture indicators (below) show the potential for heavy rainfall -- the NAM hints that the PWAT index could reach as high as two inches in Delaware and Maryland, with PWAT's over 1.50" across all of Eastern Pennsylvania  and the vast majority of New Jersey in the blue shaded regions.  Thunderstorms tomorrow could bring localized one to two inch rainfall amounts in any one spot in the highest rainfall totals...others will see less.   Those who get those one to two inch rainfalls, especially in a short period of time, could see some ponding of water on roads and isolated flooding...especially if they were popped this past Saturday or yesterday with heavy rainfall.  

Dynamics support more of the "gusty downpour" type of thunderstorm and less of a hailer/gust front type of storm.  While severe weather isn't likely through the region, one or two storms could produce a gusty downpour that could reach severe limits -- similar in respects to what happened on Saturday around the region.

Timing-wise, modeling suggests we could see showers into the region as early as the pre-dawn hours tomorrow, with more numerous showers and storms around the region in the afternoon and evening hours.  Around Philadelphia, the best chances for heavier showers and storms could be between 2 and 9 PM.