The month of June has been very wet throughout the Mid-Atlantic region and it appears that the final days of the month, and the beginning of July, will very likely bring more substantial rainfall to the entire area - perhaps on the order of several inches. So far this month, the official rainfall totals for DC, Philly and NYC are already well above normal, and they are certain to climb substantially by the close of the month on Sunday:
6.59 inches at Reagan National Airport (3.57 inches above normal); 8.75 inches at Philly Intl Airport (6.00 inches above normal); 9.81 inches at Central Park, NY (6.17 inches above normal).
Yesterday featured scattered afternoon and evening showers and thunderstorms in the Mid-Atlantic region, some with torrential rainfall, and that same threat of heavy rain continues today and tomorrow. By Thursday, we’ll start to get under the influence of an approaching unusually strong upper level low pressure trough and its associated surface cold front. The central and eastern US have had multiple unusually strong upper level troughs to deal with during the past several weeks contributing to many severe weather and heavy rainfall events. By Friday, the surface cold front will reach the east coast and strong upper level low will become established in the upper atmosphere over the Great Lakes and Northeast US. As a result of this unfolding late week weather pattern, showers and thunderstorms will become even more numerous on Thursday and Friday with heavy rainfall and severe weather almost certain to be included in the mix. That strong upper level low will then tend to spin around for a few days over the Great Lakes and Northeast US as the surface cold frontal system remains stationary near the coastline; consequently, the threat for showers and thunderstorms will continue on Saturday as well, but that won’t be the end of the wet period. In fact, surface low pressure may form along the front later in the weekend enhancing the threat for showers and thunderstorms on Sunday and Monday with the possible outcome additional heavy rainfall and severe weather. By the way, at the same time strong upper low forms in over the Great Lakes and Northeast, an extensive and strong upper level ridge will develop over the interior western US leading to a major league heat wave for that region which will elevate the already high wildfire risks.
The bottom line, the next week to ten days look quite wet indeed in the Mid-Atlantic region and flooding may very well become a serious concern given the already saturated grounds. An even scarier scenario in terms of potential flooding for the region would be if a tropical system forms in the near future and affects the Mid-Atlantic region – not at all out of the realm of possibility as we discussed last week (Thursday, 6/20 blog).