Sept 23, 2013: Cooler Than Average Week Ahead

Forecast Highlights:

temp13Another strong cool air mass is present over the region, with temperatures today expected to be at least 10 degrees below average with frost possible for interior areas tonight. A slow warm up will take place this week, but with temperatures likely only warming up to seasonable to slightly above average at most as highs stay in the low to mid 70s through next Monday (image credit: PSU e-Wall).


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Sunday, September 22 Observations:

9.22.13Behind the cold front on Saturday night, a much cooler air mass returned into the region, with partly sunny skies and a breezy NW wind at 10-15 mph, gusting up to 20-30 mph at times. High temperatures were cooler as well, peaking in the mid 60s inland (NW NJ, interior SE NY), upper 60s in the north/west suburbs of NYC, and the low 70s from NYC and further east and into southern CT. The highest temperature was 73 degrees in Bridgeport, CT and New London, CT, and the coolest high temperature was 62 degrees in Port Jervis, NY.



This Week: Chilly Temperatures Continue

temp13The coolest air mass so far this fall is located over the region, with 850mb temperatures near 2-4C over the area. Chilly temperatures were observed this morning, falling into the 40s for most of the area with 39 degrees in Sussex, NJ; Central Park reached 50 degrees for the second time this month. Sunny skies are expected today with a NW wind at 6-12 mph and highs in the mid 60s, with the 6z run of the 4k NAM shown to the left depicting today’s modeled high temperatures (image credit: PSU e-Wall). Clear skies and lighter winds are expected tonight, with lows in the mid-upper 30s inland, upper 30s-low 40s in interior CT and the Long Island Pine Barrens, low-mid 40s in the north/west suburbs of NYC and coastal CT, mid-upper 40s in Long Island away from the coast, and upper 40s-low 50s in NYC. Areas of frost are possible towards NW NJ, interior SE NY and possibly the Pine Barrens.

A slight moderation in temperatures will occur on Tuesday and Wednesday, with highs rising into the low 70s across the area. A shortwave trough will slide underneath the ridging to the west, then diving southeast while staying south of the area, which will keep the cool air mass at the western end of a cutoff low in Atlantic Canada stuck over the region through the late week, and as a result, temperatures have been slightly lowered in the 7-day outlook for the rest of this week. Temperatures on Thursday are expected to reach the upper 60s to low 70s in eastern areas and low to mid 70s from NYC and further north/west, with slightly cooler temperatures on Friday in the upper 60s-low 70s east of NYC and the low 70s from NYC and further north/west.


Next Weekend – Next Week: Showers Possible

While the persistent troughing east of the area and a quickly approaching shortwave trough by the late weekend will prevent ridging from building in for more than a day, with 850mb temperatures struggling to warm up much above 10C, if at all, temperatures are likely to slightly warm up by the weekend ahead of the next trough. Highs at this time are likely to reach the low to mid 70s across the area for the weekend, perhaps rising over 75 degrees in NYC and northeast NJ on Saturday and/or Sunday. Dry conditions are expected to continue through the weekend as well.

The next cold front is likely to move through around Monday, with the timing subject to some changes, which at this time looks to produce some rain across the region but may not be a significant rain producer. Behind the cold front, another cool down is likely, but as yesterday’s pattern outlook noted, there may not be as much cold air in Canada to pull down into the region, and the resulting trough may not be as cold as the current chilly temperatures. Stay tuned for more information on the longer range outlook.

8 thoughts on “Sept 23, 2013: Cooler Than Average Week Ahead

  1. Anonymous Reply

    Do you know what was the cause of the morning low clouds and showers in New York City and on Long Island last Saturday (9/21)?

    • NYC Area Weather Post authorReply

      The clouds and scattered showers that morning were triggered by a weak shortwave that previously moved through the area on 9/18 without having produced any precipitation, which then stalled offshore for a few days before lifting north into NYC and western LI/CT early on 9/21 due to an intensifying southerly flow ahead of the approaching trough.

    • NYC Area Weather Post authorReply

      The shortwave was weak when moving through initially on the 18th, and the air mass in place was dry with subsidence due to a strong surface high pressure centered near the area. When it came back north on the 21st, the air mass was much more humid and scattered showers were triggered ahead of it.

  2. Anonymous Reply

    By the way, is there any chance for a similar setup to occur later this week, with a shortwave moving through and stalling east of the region, while returning ahead of the next cold front with clouds and showers?

    • NYC Area Weather Post authorReply

      The setup starts off in a somewhat similar way as a shortwave trough on Thursday stays south of the area while tracking SE and offshore into the Atlantic. Then it’s likely to stall off the coast south of where the last one did, but the outlook for Long Island would depend on where it stalls, should it do so, and where it gets picked up by the approaching trough. The possibility is there for a somewhat similar idea of clouds and showers for eastern parts of the area ahead of the front, but there’s still a bit of uncertainty as should be expected this far out, especially if the setup is more progressive and the shortwave simply moves offshore as the GFS depicts.

  3. Anonymous Reply

    Would the next shortwave most likely affect Long Island on Sunday, 3 days from when it will come offshore, like last week, when it came offshore on Wednesday and affected Long Island on Saturday?

    • NYC Area Weather Post authorReply

      There is still some uncertainty with the shortwave, but as it will end up further south than the last one and will be pulled up ahead of the incoming trough, any possible impact would likely be on Monday as opposed to Sunday.

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