July 25, 2011 Morning Update

10 AM: Some Storms Today, Severe Weather Stays West

Yesterday, a cold front moved through the area, bringing scattered thunderstorms especially in northern New Jersey. This cold front brought an end to the heat wave which has brought record temperatures into the region, and the front is now to the south of the area, which will help keep temperatures below the 90 degree mark today. A weak low pressure will move towards the Northeast, bringing another cold front through with thunderstorms affecting the region, but the NYC area will likely be spared from the majority of the action today.

Today’s Set Up: The cold front is stuck to the south of the area as of this morning, and the warm front associated with the low pressure is currently near central Pennsylvania. The front will continue to move east for now, but there is a high pressure off the coast which will make it more difficult for the warm front to move east as it reaches the area. As a result, it is expected to remain near or just west of NYC through this evening, keeping an onshore SE wind in the area resulting in a stable air mass, while places further west become more unstable. Later tonight, the warm front is expected to move through, but it will be quickly followed by the cold front, keeping the area under a stable air mass.

We have seen this type of scenario happen several times throughout the spring. Not all cases were the same, but in most of them, we ended up seeing storms further west, towards Pennsylvania, weakening and later dissipating as they moved through NJ towards NYC. This is the same scenario that most of the models are showing for today as well, with most of the thunderstorms staying in Pennsylvania, and some models fail to bring any rain to NYC. This does not mean that the area will not see any rain, but the stable air mass will cause any storm that enters the area to begin weakening as it approaches NYC.

Today’s Outlook: Instability further west today will cause strong to locally severe thunderstorms to form to our west, towards central Pennsylvania, New York and Virginia. These storms will then move east towards the more stable air mass over the area. Some storms are expected to move into northern NJ this afternoon evening, but as they do so, they will lose their severe characteristics. Despite this, they will still be capable of producing heavy rainfall in northern NJ and interior SE NY. As these storms continue to move towards the coast, they should rapidly collapse by the time that they reach and pass NYC. As a result, the best risk of storms today is to the west of NYC, where locally heavy rainfall is possible, and Long Island/southern Connecticut are expected to stay mainly dry other than some isolated shower/thunderstorm activity tonight. Storm updates will be posted this afternoon and evening if necessary.

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