Wednesday, June 05, 2013

Risk For Heavy Rains Friday, Friday Night

Tropical enhanced rains remain a possibility for parts of the region late this week and into the weekend as the combination of a tropical disturbance in the Gulf of Mexico (Tropical Storm Andrea, which will make landfall in Florida at some point late tomorrow) and an approaching cold front will combine to bring a lot of rain to portions of the region.

We pointed out yesterday that this is not a traditional tropical storm for us -- it's remnant rainfall that will interact with an approaching cold front. We've been here, done that in Philadelphia before...but whenever you have this situation, the potential for excessive rainfall definitely exists.

The brunt of the event looks to be Friday PM -- generally midday through Friday night as the tropical piece of energy pushes up the coast.  Modeling varies a bit on timing but the GFS has been more consistent on suggesting that as the timeframe.  Euro and NAM are slower, with the Euro the middle ground in timing...but by and large it is generally looking like a Friday PM brunt for rains and thunder.

The question in terms of exactly how much is still to be determined -- and will depend largely on the interaction of the tropical disturbance with the cold front that approaches.  The disturbance itself will probably not be fully tropical in nature at this latitude but it will pull tropical moisture northward with it for the ride.  The question becomes how much rain ultimately falls -- a track relatively close to the coast (such as the Euro) suggests the potential for a more widespread one to three inches of rainfall around the whole of the region.  The GFS has been relatively consistent in placing some sort of a dryslot just west of the shield of rainfall.  The GFS track has waffled around a bit but has generally remained consistently east of the Euro's track up I-95.

Regardless of track, the risk for heavy rainfall in this timeframe does exist and with that comes the prospect for some flooding or flash flooding of the usual suspect streams around the region.  Also looks like Friday evening could be a rather craptastic commute around town as well if this heavier rainfall times itself for that timeframe.