First Alert Weather Blog: Storms Moving In Overnight

A line of storms will arrive in the Delaware Valley, bringing the possibility of wind damage, localized flooding, and even small hail or an isolated tornado.

The threat of severe weather will continue progressing east across the country Monday. By early Tuesday morning, the line of storms arrived in the Delaware Valley, bringing the possibility of wind damage, localized flooding, and even small hail or an isolated tornado.

A cold front will pass the area early Tuesday morning. The cold front, combined with lingering warm air from Monday afternoon (highs in the 80s) and ample moisture, will fire off a line of thunderstorms as it passes the Tri-State area.

The Storm Prediction Center, an organization that analyses the threat of severe weather, has categorized our region under a mix of Enhanced and Slight threats.

That might not sound too bad, but it’s a bit deceiving. Why? Because we’re talking about the threat of SEVERE weather. Severe weather is worse than a run-of-the-mill thunderstorm with some rain and windy conditions. Severe storms can cause major damage. In fact, a severe thunderstorm is defined by the ability to produce hail one inch or larger in diameter and/or winds equal to or exceeding 58 miles per hour. 

Here’s a look at the Storm Prediction Center’s threat map for Monday:

Notice the western edge of our viewing area (Berks County) is under the Enhanced threat. That’s the 3rd highest threat level. Most of our region is under a Slight threat. Still, that’s about a 2/5 on the severe weather threat scale.

As for the timing, storms will pass overnight, which is actually a good thing. The strongest Spring storms gain part of their strength from the warm afternoon air. As we cool overnight, this may help weaken the storms a bit.
Still, the line of thunderstorms is expected to hold together enough to provide some wind damage and small hail threat. There is a very low threat of an isolated tornado mostly west and south of our viewing zone (where you see the brown shading on the above map).

Here’s one computer models’ projection for the line, which shows the thunderstorms entering the region around midnight near Berks Co. and the Lehigh Valley.

That line should move through the I-95 corridor around 4 a.m. and clear the shore by 6 a.m. The line will also likely weaken as it nears the shore (where there is cooler air).

As the line of storms continues to progress to the east through the day, the NBC10 First Alert Weather Team will get a better picture of the storm threat to our region. We’ll be updating this blog regularly, so keep checking in on air and online!

NBC10 First Alert Weather Blog: Rain u0026 Cooling Temps This Week

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