Aug 13, 2011: 3+ Inches Of Rain Possible

NOTE: This is the last full update until Monday, August 22. Storm updates will be posted tomorrow morning with some last minute updates on the storm affecting the region.


Today started out as a nice day, with high temperatures peaking in the lower 80s inland, mid to upper 80s in the immediate NYC area, and the lower to mid 80 in Long Island/S CT, which was close to the forecast but a little cooler than expected in the western parts of the area. Since this morning, however, cloud cover has increased, and cloudy skies are now covering most of the area as thunderstorms in Pennsylvania are bringing rain into the western parts of the area. This is just the start of a stretch of wet weather, however, as a slow moving low pressure will bring anywhere from 1 to as much as 4-5 inches of rain across the area through Tuesday.

Sunday – Tuesday: Storm Brings Heavy Rain

Since last night’s update, there has been a trend in the models to shift the low pressure to the east of the area, making this a coastal low. As a result, the axis of heavy rain has shifted east as well, and the western and central parts of the area are now expected to be affected by the heaviest rain from this storm. This will be a slow moving low pressure, which combined with high precipitable water values and moisture, will produce heavy rainfall amounts across parts of the region including the area, which could be as high as 4 to 5 inches locally.

Sunday – Sunday Night: A broad low pressure over the Ohio Valley on Sunday morning will shift southeast, becoming a stronger coastal low near the coast of the southern Delmarva Peninsula by Sunday evening. Scattered thunderstorms are expected for tomorrow morning, locally heavy, but by the afternoon and evening, more widespread storms are expected to affect the area, especially from NYC and further west.

The precipitation tomorrow will fall in the form of occasional rain and some thunder, heavy at times, meaning that the rain will vary in intensity throughout the day, and some thunder is expected even though no severe weather is expected. At least 1-2 inches of rain are expected from NYC and further west with 1/2 to 1 inch in Long Island/S CT, but as previously mentioned, the rain will vary in intensity, and locally higher or lower amounts are possible.

Monday – Tuesday: The low pressure will move offshore on Monday, which is expected to keep the heaviest rain offshore. Despite this, heavy rain will still affect the area, especially the central and eastern parts of the area. Most of the rain is expected at this time to fall on Monday afternoon and evening, with some rain in the morning and the overnight hours. An additional 1-2 inches of rain are expected across most of the area on Monday. More information on Monday’s outlook will be posted tomorrow.

Occaisonal light rain will continue through Tuesday afternoon/evening as the low pressure will be slow to move out of the region. By the time that the storm ends on Tuesday evening, at least 2 to 4 inches of rain are expected from NYC and further west, and 3/4 to 2 inches in Long Island and southern Connecticut. Amounts could be locally lower or higher than currently expected.

Wednesday – Saturday: Slightly Warming Up

Behind the storm, temperatures will slightly warm up. While highs tomorrow and on Monday will be in the mid 70s to lower 80s across the area, Wednesday will bring partly sunny skies and highs in the upper 70s to mid 80s across the area. South/SE winds are expected for Thursday, Friday and Saturday, however, which will keep temperatures in the upper 70s to lower 80s across most of the area until the next storm arrives next weekend, bringing more rain into the area.

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