By CBS3 Staff

PHILADELPHIA (CBS) — Much of the area is under the risk of severe thunderstorms both this evening into tonight and again Thursday evening into tomorrow night. A cold front approaching from the west will serve as the trigger mechanism for thunderstorms during both time frames, as the front will approach tonight, slow and stall over the area tomorrow.

Thunderstorms are developing over Western Pennsylvania and will progress east toward the Delaware and Lehigh Valleys into tonight. Locations south and west of Philadelphia, including portions of Berks, Chester, Montgomery, Delaware and New Castle Counties are under a Slight Risk (level 2 out of 5) for severe weather into tonight, with the remainder of much of the area under a Marginal Risk (level 1 out of 5).

The main time frame looks to be from 8 p.m. until 1 a.m. overnight, from west to east. Gusty winds and heavy rain are the main threats tonight, though an isolated tornado cannot be ruled out, particularly in the Slight Risk area.

Thunderstorms will likely be scattered in coverage, so not everyone may see a storm, but prepare for the possibility regardless and stay weather aware.

Thursday will feature sunshine throughout much of the day, then as a surface low tracks and rides along the stalled frontal boundary, another round of thunderstorms will develop. The risk is more elevated tomorrow evening and night, and the storms may be more widespread in coverage.

Southern parts of the area, including southern interior New Jersey, the shore and the state of Delaware are under an Enhanced Risk (level 3 out of 5) during this time frame, with Philadelphia and surrounding counties under a Slight Risk (level 2 out of 5), and the Lehigh Valley and Poconos under a Marginal Risk (level 1 out of 5).

Threats include damaging winds, hail, frequent lightning, heavy rain and the potential for flash flooding and isolated tornadoes. The time frame of concern looks to be from 8 p.m. until 2 a.m.

Remember the difference between a watch and a warning. A watch means the ingredients are present for the possible development of severe weather and we need to stay alert to changing weather conditions. A warning means severe weather is occurring or imminent and action must be taken to seek safe shelter from the warned hazard.

National Weather Service

CBS3’s Lauren Casey and Matt Peterson contributed to this report.