Sept 13, 2011: Warmth Ends On Thursday

The NYC area observed partly cloudy skies today, with temperatures once again above average, peaking in the lower 80s inland, lower to mid 80s in the immediate NYC area, and in the upper 70s to lower 80s in Long Island and southern Connecticut.

The latest regional radar shows that there are thunderstorms in far northern and western NY associated with a cold front. This cold front will approach the area, but will fail to cross the area tomorrow. Instead, another low pressure on Thursday will push this front through the area with showers and thunderstorms. Behind this front, a dry and chilly pattern will develop across the region, as temperatures will drop into the 40s for overnight lows with dry conditions lasting through next week due to a high pressure which is expected to be stuck over the Northeast.

Tomorrow’s Outlook:

As previously mentioned, a cold front moving towards the region will fail to move through the area, and will instead remain stationary near the central Northeast, to the west of the area. This will keep a SW wind with above average temperatures in place for the area once again. Temperatures will be warmer than they were today, reaching the lower to potentially mid 80s inland, mid 80s in the immediate NYC area, and the upper 70s to mid 80s in Long Island and southern Connecticut. Parts of NE NJ may reach the upper 80s.

Thursday: Cold Front Brings Rain, Thunderstorms

An update early this evening mentioned that the latest models have trended stronger with a low pressure in southern Canada, which resulted in a stronger front moving through the region. This change in the expectation, combined with the models trending slower with the timing of the front, increases the risk of rain and thunderstorms during the day on Thursday. The NAM model is the most bullish with this potential, showing nearly 1 inch of rain in NYC, and although such amounts are possible in a few areas west of NYC, widespread heavy rain is not expected with this event at this time. The NAM may still be having some issues handling this event as it shows a very strong temperature gradient with this front, with some places dropping over 20 degrees in in just 1-2 hours, which is most likely too extreme. The front will bring light to moderate rain and thunderstorms throughout the day on Thursday, focusing on the second half of the day. By the time that the rain ends on Thursday evening, at least 1/4 to 3/4 inch of rain is expected, with locally higher amounts possible. Stay tuned for more information on Thursday’s rain event with tomorrow’s update.

Friday – Next Week: Dry And Chilly

Behind Thursday’s cold front, a strong high pressure will begin to move towards the region. A relatively tight pressure gradient is expected behind the front, which will produce windy conditions on Thursday night into Friday, with winds potentially gusting up to 30 mph on Thursday evening once the front moves through. Clearing skies are expected later into the overnight hours, and as a strong trough begins to move into the region, temperatures will quickly cool down, dropping into the lower 40s in NW NJ/SE NY, mid to upper 40s in the immediate north/west suburbs of NYC and southern CT, mid 40s to lower 50s in Long Island, and the lower 50s in NYC. While no frost is expected in the area, parts of the interior Northeast will experience the first frost of this fall.

Friday will bring mostly sunny skies as the high pressure moves into the Northeast, with temperatures colder than those of Thursday, only rising into the lower to mid 60s in NW NJ/SE NY and the mid to upper 60s across the rest of the area. With mostly clear skies on Friday night, low temperatures similar to those of Thursday night are expected. The cold air mass will begin to slightly weaken on Saturday, with temperatures slightly rising, peaking in the mid 60s inland and the upper 60s across the rest of the area.

From Sunday through about the middle of next week, the latest models are showing the strong high pressure settling over the region as a low pressure develops well offshore, keeping the area under dry conditions and chilly temperatures, in the upper 60s to mid 70s. Only one model, the DGEX, takes this low pressure and moves it right up the coast with heavy rain, and the DGEX typically isn’t reliable in its longer range. At this time, the next chance of rain appears to be towards the middle of next week, but there is uncertainty with the models regarding what happens with the high pressure by that time. Stay tuned for more information for next week’s outlook.

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