By Lauren Casey

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PHILADELPHIA (CBS) — Heavy rain, snow, sleet, ice, wind, a flash freeze, and maybe even some thunder. An intense, moisture-laden storm system will impact the Delaware and Lehigh Valleys Saturday night and Sunday.

Precipitation is spreading over the area as we speak. For many in the form of snow, though as the rain/snow line lifts north through the evening, the flakes will transition to drops, lots of drops.

A flood watch is in effect for Philadelphia and the surrounding suburbs until 1 p.m. Sunday as the rain will become heavy at times overnight.

Expect one to two inches of rain, with locally higher amounts through midday Sunday.

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Thunderstorms, capable of producing gusty winds, are also possible as a low-level jet moves in overhead — though that won’t be the only wind threat.

After the cold front tears across the region Sunday morning, the winds will turn wicked.

Expect wind gusts up to 40 miles per hour across the area, and combine that with a 35 degree temperature drop in about 12 hours time.

Temperatures in the 50s Sunday morning will nosedive to sub-freezing by mid-afternoon for most, thereby initiating a flash freeze, in which any remaining precipitation will freeze over to create hazardous, icy conditions on roads and sidewalks.

Temperatures will continue to plummet into the teens by early evening, with dangerous cold by Monday morning with lows in the single digits and wind chills as cold as negative 10 degrees.