Skip to main content

UPDATE 2 1146PM ET: The line had 78 MPH winds as it came through northern Maryland and did quite a bit of tree/power line damage, but it quickly lost its punch and is no longer severe.

UPDATE 1 1000PM ET: The line is coming into Maryland and Amish country in Pennsylvania with 60 MPH winds.


A line of severe thunderstorms (not a derecho) is moving through Pennsylvania right now with winds of 60-70 MPH possible along its leading edge, prompting severe thunderstorm watches and warnings to be issued for the I-95 corridor between Washington DC and Philadelphia.

Here's the new watch, in effect until the storms pass through later this evening:

Here's the line of storms as of around 915PM EDT as it moves into southeastern Pennsylvania. Provided the line is able to sustain itself on what's left of the instability in the I-95 corridor, it should stay severe as it impacts the metro areas.

The storms have a pretty good chance of staying together, I think, so long as the cold pool doesn't jog too far ahead of the storms. If that happens, it's game over and the line dies. That's always a possibility. However, there's plenty of moisture in the area, as shown by the dewpoint map as of 900PM EDT:

...and the temperatures are still pretty warm...

...and the most unstable convective available potential energy (CAPE; essentially, the fuel storms use to generate updrafts and get strong) is between 2000 and 3000 joules per kilogram, which is more than enough to support thunderstorm development... it's very possible that the line of storms will maintain itself or even strengthen as it moves into this soupy tinder box that is the I-95 corridor.

If you live in the area or know anyone who does, please let them know to prepare for a potent line of storms.


National Weather Service Main Page
National Weather Service -- Washington DC/Baltimore
National Weather Service -- Philadelphia/New Jersey
National Weather Service -- Central Pennsylvania
National Weather Service -- New York City area

Storm Prediction Center Main Page
Storm Prediction Center -- Current Severe Weather Watches
Storm Prediction Center -- Convective (Severe Weather) Outlooks
Storm Prediction Center -- Mesoscale Discussions
Storm Prediction Center -- Storm Reports
Storm Prediction Center -- Mesoscale Analysis Pages

Wunderground's Detailed Radar (click the + nearest to you to see your local radar)

NOAA Weather Models's excellent GFS/NAM/RAP model website.

I'll continuously post updates to my Facebook page on this and most other major severe weather outbreaks.

Your Email has been sent.
You must add at least one tag to this diary before publishing it.

Add keywords that describe this diary. Separate multiple keywords with commas.
Tagging tips - Search For Tags - Browse For Tags


More Tagging tips:

A tag is a way to search for this diary. If someone is searching for "Barack Obama," is this a diary they'd be trying to find?

Use a person's full name, without any title. Senator Obama may become President Obama, and Michelle Obama might run for office.

If your diary covers an election or elected official, use election tags, which are generally the state abbreviation followed by the office. CA-01 is the first district House seat. CA-Sen covers both senate races. NY-GOV covers the New York governor's race.

Tags do not compound: that is, "education reform" is a completely different tag from "education". A tag like "reform" alone is probably not meaningful.

Consider if one or more of these tags fits your diary: Civil Rights, Community, Congress, Culture, Economy, Education, Elections, Energy, Environment, Health Care, International, Labor, Law, Media, Meta, National Security, Science, Transportation, or White House. If your diary is specific to a state, consider adding the state (California, Texas, etc). Keep in mind, though, that there are many wonderful and important diaries that don't fit in any of these tags. Don't worry if yours doesn't.

You can add a private note to this diary when hotlisting it:
Are you sure you want to remove this diary from your hotlist?
Are you sure you want to remove your recommendation? You can only recommend a diary once, so you will not be able to re-recommend it afterwards.
Rescue this diary, and add a note:
Are you sure you want to remove this diary from Rescue?
Choose where to republish this diary. The diary will be added to the queue for that group. Publish it from the queue to make it appear.

You must be a member of a group to use this feature.

Add a quick update to your diary without changing the diary itself:
Are you sure you want to remove this diary?
(The diary will be removed from the site and returned to your drafts for further editing.)
(The diary will be removed.)
Are you sure you want to save these changes to the published diary?

Comment Preferences

Subscribe or Donate to support Daily Kos.

Click here for the mobile view of the site