Sept 22, 2011: Heavy Rain Tomorrow, Saturday

After a round of light rain last night, with rainfall amounts mostly falling up to 1/4 inch except for parts of NW NJ and SE NY, which saw up to 1/2 inch of rain, today brought drier conditions to the area with mostly cloudy skies. With the breaks in the cloud cover, temperatures were slightly warmer than expected, peaking in the upper 70s to lower 80s from NYC and further west and the mid to upper 70s in Long Island and southern Connecticut.

A surge of tropical moisture will move up the coast through tomorrow and Saturday, bringing heavy rain into the area from Friday afternoon through Saturday morning, with 1 to 3 inches of rain expected. Even though the heaviest rain of this time frame is expected to fall on Friday night, scattered showers are possible through the weekend, with occasional showers early-mid next week as the cut off low begins to exit the region. With the cut off low only slightly drifting out of the region, rain chances will continue well into next week.


Tomorrow's Outlook:

Tomorrow will bring cloudy skies to the area with a SE wind expected. Due to the cloud cover and rain, especially during the second half of the day, temperatures will be slightly cooler than those of today, peaking in the mid 70s across most of the area with a few upper 70s possible in parts of NE NJ in the warmer case scenario.

Looking at the regional radar in the Southeast US, rain and thunderstorms are covering a wide part of the region as a surge of tropical moisture is moving up the coast. This moisture will affect the area tomorrow into Saturday morning, with precipitable water values reaching 2 inches, easily capable of producing heavy rainfall. Cloudy skies with a few showers are expected for Friday morning, with steadier rain developing by the afternoon and evening hours. The rain will be occasionally heavy at times, especially in the immediate NYC area. Moderate to occasionally heavy rain will continue through Friday night and into Saturday morning before weakening by Saturday afternoon.

Rainfall amounts are expected to end up between 1.5 and 3 inches by Saturday afternoon across the area. Above, I posted a rain map showing my current thoughts on where the heavier rain will end up. It is a possibility that the 1-2" and the 2"+ inch zones may have to be moved further east than shown above. Stay tuned for storm updates which will be posted throughout the late afternoon and evening on Friday.


Weekend - Next Week: Rain Continues

The cut off low expected to form over the Ohio Valley will not be quick to leave. The main flow of storms will move through central Canada, and with no feature expected to drop far south enough to reach the cut off low until the middle of next week, the cut off low will remain stationary over the Ohio Valley through next Wednesday, keeping a risk of scattered showers in the forecast through Wednesday or Thursday. The rest of the weekend will bring an improvement in the conditions, however, as mostly cloudy skies are expected with scattered showers and temperatures peaking in the mid to upper 70s across the area, potentially reaching the 80 degree mark in parts of NE NJ if there is more sunshine than currently expected.

By early next week, another low pressure will form around the cut off low, and will produce more rain across the region. This time, the heavier rain is expected to fall to the west of the area, but occasional showers are still expected from Monday through Wednesday, with an additional 1/4 to 3/4 inch of rain expected through Wednesday. Should the storm end up further east or wetter than currently expected, amounts may pass 1 inch in parts of the area early-mid next week. Stay tuned for more information on the additional rainfall for early next week.

By the middle of next week, a storm in Canada is expected to finally pick up the cut off low, taking it away from the region. The models differ with the details regarding how the cut off low leaves, with solutions ranging from a cold air mass dropping into the region, bringing high temperatures down into the 60s, to the cold air mass leaving the region with warmer temperatures building back in, with highs staying in the mid-upper 70s. Stay tuned for more information on the longer range.