Tuesday, August 14, 2012

Slight Risk of Severe Weather Today

This morning's thunderstorms continue to move slowly east and northeast through parts of the Delaware Valley.  They have been efficient at dropping a lot of rain in a quick amount of time -- some spots have picked up a quick inch of rain in about an hour's time and doppler radar estimates suggest an inch to two inches of rain are possible with this line as it lifts northeast and east.  In addition to heavy rainfall, lightning is possible in/close to the line of storms.  It's not a widespread array of lightning but there is enough of it in the line to throw that out there given the amount of people struck by lightning in the past couple of weeks.  This line should cross through the course of the morning hours, along and northwest of I-95, but it probably will not be the only line of storms that is discussed through the course of the day.

The region is under a slight risk of severe weather today as a disturbance and cool front begin to push in from the west.  It is, like the last frontal boundary to cross, a slow mover of sorts and will take until tomorrow to fully push through the region.   The showers and storms that are out this morning are an appetizer of sorts as the atmosphere begins to get primed for more thunderstorm activity late this afternoon and this evening.

The chief threats today with the severe storms that do fire are wind...and with a very slight possibility of a tornado or two around as wind shear is present. The SPC projects the highest odds (5%) across Northern Maryland and across South Central PA as of early this morning. I wouldn't be surprised if a spin up tornado or two occur in PA late this afternoon or this evening.

Most of the focus for thunderstorm development today will be to our west. Some storms may fire across Jersey and Delaware (the 2 AM run of the NAM suggests that possibility) but the bulk of thunderstorm activity looks to set up across Pennsylvania this afternoon and evening.  Whether that activity is more focused across Central Pennsylvania or closer to the city (the NAM last night, see above, shows storms much closer to Philadelphia) remains to be seen but points to the west of the city will probably be more at risk for more widespread thunderstorm activity later on this afternoon and into this evening.  In terms of "late this afternoon", think after 4 or 5 PM out towards Harrisburg.

Threats for this afternoon (besides the wind and isolated tornado) also include heavy rainfall (again). The locations within the "axis of thunder" later on today could pick up an additional couple of inches of rain.  Some localized flooding issues can't be ruled out later on.

You can track the radar throughout the day on our current weather page.