Per consult with the National Weather Service:

A cold front will move into the area today bringing an increased threat of heavy showers and thunderstorms. Storms that develop this afternoon and evening will bring an increased risk of severe weather and heavy rains. While the severe weather threat diminishes late this evening, an approaching area of low pressure will setup just southeast of the City stalling the front which is will cause showers to rain in the area through the weekend.

Precipitation and Timing
Today: This morning scattered showers are possible, they are expected to be pop-up in nature. Showers and thunderstorms will be more organized this afternoon and evening with an increased threat of severe weather. The storms associated with this system will be slow moving and bring the potential for heavy rains and flash flooding. The best chance of rain will be in the early afternoon through tonight. The chance of thunderstorms in the afternoon is 40-50% increasing to 60% in the evening. The risk of severe weather remains low.

A total of 1-1.5 inches of rain is expected with this system, with locally higher amounts possible. Rainfall rates of 2 inches per hour are possible in stronger storms, but are not expected to last for a full hour unless several storms line up together.

A low pressure system is expected to stall to the southeast of New York City will cause rain to linger through the weekend. Rain will be lighter and more scattered, with the chance of rain diminishing through the weekend. Dry conditions are expected for Memorial Day.

Severe weather brings the risk of strong wind gusts up to 58 MPH heavy rain, and the possibility of hail.

Temperatures (High/Low)
Thursday: 74/61
Friday: 68/49
Saturday: 62/51
Sunday: 63/63
Monday: 67/54

Winds
Thursday: Sustained winds of 10-15 MPH, with wind gusts up to 58MPH during severe weather.
Friday: Sustained winds 10-15 MPH.

Urban flooding is expected today in low lying and poorly drained areas with a risk of flash flooding with heavier periods of rain.

Products
Hazardous Weather Outlook: Locally heavy rainfall is possible today and tonight with rainfall rates of 1 to 2 inches per hour. Depending on the exact track of storms producing heavy rainfall. Flash Flooding is possible. The main threat though is minor flooding of poor drainage areas. Including urban areas and small streams.

The New York City Flash Flood plan has been activated, May 22, 2013 at 07:15 am.

(YWN Desk – NYC)