2 chances of severe weather this weekend; NEXT Weather Alert Sunday

PHILADELPHIA (CBS) -- Your weekend has arrived and so has hot weather, humidity and threat of severe storms. Because of the heat and storms, we have issued a NEXT Weather Alert from Saturday night through Sunday night to help you prepare and plan.

Saturday will be a seasonable summer day with highs in the upper 80s and a noticeable increase in humidity. Skies will be mostly cloudy with a breezy south wind. An isolated pop-up shower is possible this afternoon but for the most part, we are dry.

A flash flood warning was issued in southwestern Chester County by the National Weather Service until 2:30 a.m. Sunday.

The National Weather Service Storm Prediction Center issued a severe thunderstorm watch for the Philadelphia region until 11 p.m.

The severe thunderstorm watch includes the following counties: Berks, Northampton, Lehigh, Carbon, Monroe, Bucks, Chester, Delaware, Montgomery and Philadelphia.

According to the local storm report from NWS , around 9:15 p.m., there were reports of power poles down near Slatington in Lehigh County from the 911 call center and a little after 9 p.m., there was a report of a tree down on a house in Longswamp Township in Berks County.

There were also many reports of trees and wires down in parts of Berks County.

NWS officials located severe thunderstorms a little after 6 p.m. Saturday moving east at 45 mph from Marshallton in Chester County to near Donaldson in Schuylkill County to Dehart Dam near Dauphin County.

The first of three threats in our NEXT Weather Alert arrives later Saturday with scattered showers and storms.

What is the severe weather risk in the Philadelphia area on Saturday?

A line of severe storms will form in western Pennsylvania this evening and arrive between 8 p.m. to 10 p.m. in the Poconos, Lehigh Valley and Berks County.

These storms will move through Philadelphia between 10 p.m. and midnight and exit the Jersey Shore between 4 a.m. and 7 a.m. Sunday.

From Philadelphia and the I-95 corridor north and west, there is a marginal risk for severe weather on Saturday, or Level 1 on a five-point scale. There is a higher Level 2, or slight, risk to the far northwest in the Poconos, Berks County, Lancaster County and Lehigh County.

The main threats tonight will be damaging winds with gusts 60 mph or more, and heavy rain with localized flash flooding.

Heat advisory and fog kick off Sunday weather forecast

Sunday morning there will be patchy fog in the area, especially along the Jersey Shore, where the warmer air will cross the much cooler ocean water which is in the 50s and 60s. Skies will be mostly cloudy with afternoon breaks of sun and highs in the 90's accompanied by a feels-like temperature over 100 degrees.

That intense heat will trigger the second part of our NEXT Weather Alert, for the heat. A Heat Advisory is in effect from 11 a.m. to 7 p.m. for all areas adjacent to the I-95 corridor including Philadelphia; Wilmington, Delaware and Trenton, New Jersey.

What is the severe storm risk in the Philadelphia area on Sunday?

Our third and final threat in this NEXT Weather Alert comes Sunday afternoon and evening as a line as strong to severe storms crosses the Delaware Valley ahead of a cold front. Our entire area is under a slight risk of severe weather, Level 2 on a five-point scale.

The main threats are damaging winds and heavy rain, with possible flash flooding and an isolated tornado. Here's when storms could arrive depending on where you're located:

• Lehigh Valley, Pennsylvania - storms arrive between 2 p.m. and 5 p.m.
• Philadelphia and Pennsylvania suburbs - 4 p.m. and 7 p.m.
• South Jersey - between 6 p.m. and 10 p.m.

Following Sunday's storms, cooler and more comfortable conditions arrive on Monday and Tuesday. We'll see sunshine and high temperatures will be in the low 80s.

Wednesday, we warm up again to near 90 with partly sunny skies.

And on Thursday, July 4, it will be muggy and hot with highs in the low 90s and a feels-like temperature again nearing 100.

Another Heat Advisory and NEXT Weather Alert may be needed for Thursday. Showers and storms are also possible Thursday afternoon and evening that could potentially disrupt Independence Day fireworks celebrations near you.

Here's your 7-day forecast:

Saturday : Mostly cloudy, night storms. High 87

Sunday : Heat storms. High 92, Low 76

Monday : Sunny and cooler. High 82, Low 65

Tuesday : Sunny and nice. High 86, Low 65

Wednesday : Mostly sunny. High 90, Low 72

Thursday : Chance storms. High 93, Low 75

Friday : Chance storms. High 92, Low 73

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