Update: Tornado watch issued for Lehigh Valley

BETHLEHEM, Pa. — A tornado watch has been issued for the Lehigh Valley and much of the Mid-Atlantic region by the National Weather Service.

The watch is in effect until 11 p.m. Monday and includes at least 17 Pennsylvania counties — including Lehigh and Northampton.

Earlier in the day, forecasters warned of an active severe weather setup and said the area was at risk of damaging winds, hail and a few tornadoes.

• A very active start to the weather week is anticipated, with the widespread threat for severe storms
• The Lehigh Valley is at an enhanced risk for severe weather
• Damaging winds are the main threat, with tornadoes also possible

The Storm Prediction Center has much of the eastern United States, including all of the Lehigh Valley, at an enhanced risk (3 out of 5) for severe storms.

Several instances of flooding are possible, according to the weather service, especially in urban and poor-drainage areas and near vulnerable small creeks and streams.

The setup

A warm front came through the region overnight, bringing heavier and steadier rain as it moved off to the north and east.

Behind the warm front, dew points crept toward and past 70 degrees, making for a noticeably muggier day than Sunday.

Temperatures were expected to run very close to Sunday, with highs mainly in the mid to upper 80s, with an unstable atmosphere expected to develop before a cold front comes crashing through.

Timing

“This is a late-day thing here,” EPAWA meteorologist Bobby Martrich said in his Monday video forecast.

“This is not something that’s going to be happening early for most areas,” he said, noting much of the region will be dry through the morning and into the afternoon.

The weather service said all indications are that the bulk of the storms and rainfall will occur in a single round or two, with these storms moving through rather quickly this evening, mainly 5 to 10 p.m. from west to east.

The threat

Martrich reminded his audience an enhanced risk means a 30% chance of severe weather within 25 miles of any given point.

While damaging winds will be the main risk Monday, forecasters are noting the threat for isolated tornadoes of the "QLCS" variety.

A QLCS is a weather acronym that stands for Quasi-Linear Convective System. It refers to a complex of thunderstorms that occur in squall lines and tend to be weaker and shorter-lived than those associated with supercell thunderstorms.

All storms are expected to end fairly quickly late this evening, the weather service said, certainly by midnight as they progress off the coast.