Aug 2, 2011: More Rain Tomorrow

Yesterday’s storms, while not widespread, resulted in damage in places that did get affected, especially in Westchester county and parts of Queens and Nassau county. As these storms stalled over the same areas for several hours, heavy rain resulted in flooding, and hail as large as 3 inches was observed in White Plains, New Hyde Park in Nassau, and 2.75 inch in Queens. Northern New Jersey was spared from the storms, and stayed dry the whole day other than an isolated pop-up thunderstorm in Bergen county.
With these storms out of the region, today was a warm but dry day, with high temperatures reaching the mid to upper 80s inland, upper 80s to lower 90s in the immediate NYC area, and the upper 80s to lower 90s as well in Long Island and southern Connecticut. A low pressure moving towards the region from the Great Lakes will bring much cooler temperatures for tomorrow, however, as it produces heavy rain from Pennsylvania into central New Jersey, potentially covering parts of the area as well.


Tomorrow’s Outlook:
Set Up: A low pressure currently near the Great Lakes will move ESE and then southeast, moving towards the region tomorrow. Due to an upper level low near New England, the low pressure will be forced to dive southeast, moving through Pennsylvania into northern Delaware. This will bring the axis of heavy rain from the NY/PA line into central New Jersey.
Due to the position of the low pressure and the New England cut off low, central/eastern Long Island and Connecticut should be spared from the rain, with a few light showers at most. The question is then how much rain falls from NYC and further west, ranging from almost none on the GFS/ECMWF, 1/2 inch on the GGEM, and nearly 1-2 inches on the NAM. The GFS is having difficulty handling this event, and the NAM seems to have a better handle on the storm itself. Despite having a better handle on the event, the NAM is still slightly changing the heavy rain axis with each run, ranging from central NJ in its morning run to SE NY in its evening run.
Forecast: It is unlikely that the heaviest rain falls as far north as SE NY, and when considering the location of the low pressure, the heaviest rain is expected to fall in central New Jersey. Northern NJ could still see locally heavy rain, but lighter amounts are expected, ranging from 1/4 inch to potentially as much as 1 inch near/south of the Interstate 80 corridor. There is still some uncertainty with this forecast, and these rain totals could still change slightly. Stay tuned for an update tomorrow morning regarding this storm.
Otherwise, tomorrow will start off with mostly cloudy to cloudy skies. High temperatures will peak early in the afternoon, reaching the upper 70s in NW NJ and Orange County, lower to mid 80s in the immediate NYC area, and upper 70s to lower 80s in Long Island and southern Connecticut. The rain will move into the western parts of the area around 12-2 PM, though the heaviest rain is expected in the late afternoon and evening hours.
Late Week – Weekend: Dry, Then Rainy Again

A high pressure will move towards the region and off the coast, which will bring an onshore wind for the rest of the week. Combined with a colder air mass, temperatures will stay seasonable across the area, reaching the lower to mid 80s from NYC and further west, and the upper 70s to lower 80s in Long Island and southern Connecticut.
By the weekend, a low pressure will approach the region. There is uncertainty with the exact timing and location of the low pressure, but widespread showers and thunderstorms are expected to affect the region, including the area, on Saturday night and Sunday. Due to this low pressure moving into the region and offshore, Tropical Storm Emily will be forced well offshore instead of moving up the coast (the Tropics page discusses Emily in more details). More information will be posted on the weekend rainstorm over the next few days.

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