Potentially severe storms to hit Philadelphia area Sunday, flood watch in effect

PHILADELPHIA (CBS) -- A NEXT Weather Alert is in effect between 1-11 p.m. Sunday to help prepare and protect you from the threat of severe storms and flooding rains.

Several rounds of low-moving storms will produce heavy rainfall rates of up to 1-2" per hour. The storms will be scattered and not all of us will see storms at the same time. Parts of our area will experience more than one storm while other parts might possibly have no storms.

The National Weather Service issued a severe thunderstorm watch for the following counties in Delaware, New Jersey and Pennsylvania effective through 10 p.m.:

Delaware : New Castle and Kent

New Jersey : Atlantic, Burlington, Camden Cape May, Cumberland, Gloucester, Ocean, Salem and Mercer

Pennsylvania : Berks, Lehigh, Northampton, Monroe, Bucks, Chester, Delaware, Montgomery and Philadelphia

Severe thunderstorm warnings from the NWS are starting to roll through the Greater Philadelphia area.

A severe thunderstorm warning is in effect until 5:15 p.m. for the following Pennsylvania counties: Lehigh, Montgomery and Bucks. The warning set in Northampton County was extended to 5:30 p.m.

We are currently under a Slight Severe Risk (level 2 of 5) for severe storms. This risk has been elevated since yesterday to reflect the increased risk later today.

Here are the possible storm threats in order of concern:

1. Heavy rains of 1-2" per hour with flash flooding
2. Damaging wind gusts of 60+ mph could lead to downed trees and powerlines
3. Frequent lightning
4. Brief spin up tornadoes. Isolated if at all.
5. Hail 1" or larger

We are not alone. Today's risk of severe weather encompasses a large portion of the eastern U.S.  It actually forms a large smile shape extending from Philadelphia to the deep south and back up to the Midwest. This smile area is where a strong cold front and trough will drop through today and tonight triggering the severe storms.

Storm timing Sunday

Trying to avoid the rain and re-arrange any outdoor plans? Here is the timing for the start of today's storms so you can be prepared and protected.

• • 1 PM - 3 PM: The Lehigh Valley, Berks, Chester County, upper Montgomery and Bucks counties.
  • 2 PM - 5 PM: Lower Montgomery, lower Bucks, Delaware, New Castle and Philadelphia counties plus areas adjacent to I-95 in South Jersey.
  • 4 PM - 7 PM: South Jersey, Central and southern Delaware and the Shore.
  • The storms may linger along the Shore until Midnight.

Latest on Tropical Storm Ernesto

There is also a Coastal Flood Advisory in effect through Monday morning at 5 a.m. during the high tides for areas along the Delaware River, back bays and tidal waterways. Up to 1 foot of water inundation is possible with minor flooding expected.

Remember to use caution if driving during heavy rain. Do not risk driving through flooded roads, as it only takes a few inches of water to stall your vehicle, and a few inches more could float the entire thing. Remember, "turn around and don't drown."

Speaking of the coast, beach conditions will be dangerous along all of the Jersey Shore and Delaware Beaches through early Monday. The rip current risk is very high with high surf and nearshore waves reaching 5-10 feet.  Best to avoid swimming at the shore. Lifeguards are prepared to restrict swimmers to waist deep water or close the beaches to swimming altogether.

The high surf and rip current threat are being caused by Tropical Storm Ernesto. The storm is nearly 700 miles offshore but as it heads north in the Atlantic the giant swells it produces will reach the east coast creating the dangerous conditions.

Monday will be our weather transition day. Scattered showers are possible in the afternoon with highs in the low 80s.

By Tuesday a touch of Fall arrives with sunshine and highs in the low to mid-70s with overnight lows in the 50s.

7-day forecast

Sunday: High of 83, NEXT Weather Alert Day

Monday: High of 82, low of 70, scattered showers

Tuesday: High of 73, low of 63, much cooler

Wednesd ay: High of 76, low of 56, sunny and cool

Thursday: High of 79, low of 58, sunny and cool

Friday: High of 83, low of 59, mostly sunny

Saturday: High of 85, low of 64 mostly sunny