Oct 15, 2011: Chilly And Dry Weekend

After a strong cold front moved through the region today, a trough moved into the region, bringing an end to the cloudy skies and occasional rain observed during the second half of last week. Partly cloudy skies were obserbed today with high temperatures reaching the lower 60s in NW NJ/SE NY and the mid to upper 60s across the rest of the area. Windy conditions were observed as well, with gusts reaching the 30-40 mph range across most of the area. A peak gust of 40 mph was observed in Newark.

The seasonable temperatures will continue through Monday, with high temperatures slightly warming up, though the risk of an isolated shower will continue. By Tuesday night into Wednesday, however, a stronger low pressure will develop near the region with an intensifying low pressure moving up the East Coast, bringing a heavy rain potential for Wednesday, followed by a stronger cold spell which may be capable of bringing a widespread frost across the area.

Tomorrow’s Outlook:

Tomorrow will bring partly cloudy skies to the area again with a SW wind expected, but the wind will be weaker than it was today, with gusts between 20-30 mph across the area. With 850 mb temperatures around 4-5 degrees celsius again, high temperatures will reach the lower to potentially mid 60s inland, and the mid to upper 60s across the rest of the area. Places to the west and SW of NYC may reach the 70 degree mark.

Monday – Wednesday: Storm Brings Heavy Rain Potential

With yesterday’s low pressure stalling near the Hudson Bay in Canada, the cold air mass will remain stuck over southern Canada and the Northeast. The NYC area will be near the boundary between the colder temperatures to the north and the warmer temperatures to the south, and with a weak cold front moving through the region, Sunday night and Monday will bring mostly cloudy skies across the area with scattered showers, especially on Sunday night. Temperatures on Monday will slightly warm up, reaching the mid to potentially upper 60s inland, upper 60s to 70 degrees in the immediate NYC area, and the mid to upper 60s in Long Island and southern Connecticut.
The dry conditions won’t last for long again, as unsettled conditions will return into the area by Tuesday and Wednesday. A weak low pressure will move towards West Virginia and Pennsylvania on Tuesday, with the warm front moving to the north of the area. This will bring a slightly warmer air mass into the area along with a south wind, bringing temperatures into the mid to upper 60s across the area, potentially reaching 70 degrees in parts of NE NJ.
On Tuesday night, the primary low pressure will weaken as a stronger secondary low pressure develops near southeastern Virginia and begins to move NNE while intensifying. There is uncertainty with the location of this low pressure, but since yesterday’s models, when the storm was shown to be weak and stay mostly offshore, today’s models have trended stronger and further west as expected. The westernmost model run is currently the 18z GFS, taking the storm near western New Jersey, and considering that the models are still changing with each run, I went slightly to the west of the GFS, expecting the low pressure to move through eastern Pennsylvania, though it is possible that the storm ends up slightly further west, over central PA. Such a track would place the NYC area in the warm sector of the storm.

Should the scenario mentioned above verify, rain is expected on Tuesday night, with periods of moderate to heavy rain and potentially thunderstorms through Wednesday afternoon, when the cold front should move through. Tropical moisture is expected to be involved as well, enhancing the risk of heavy rainfall. By the time that the storm ends on Wednesday evening, the potential is there for 1 to 2 inches of rain to fall across the area, potentially up to 3 inches in the wetter case scenario. Stay tuned for more information on Wednesday’s storm.

Thursday – Saturday: Cold Returns, Widespread Frost Possible?

The Polar Vortex keeping the cold air stuck over southern Canada early this coming week will bring a widespread cold air mass into the United States. Wednesday’s storm will have plenty of cold air to pull into the US, and while the intensity of the cold is not very strong, with 850 mb temperatures failing to drop below -10 degrees celsius, the cold will be widespread, with sub-freezing 850 mb temperatures getting almost as far south as the Gulf of Mexico coast on Wednesday. The cold air mass will then move into the region between Thursday and Saturday, and while it is expected to slightly weaken by then, it will still provide below average temperatures.

High temperatures on Thursday are expected to drop into the upper 50s to lower 60s across most of the area, possibly a bit lower or higher, but the colder temperatures are expected for Friday and Saturday. Should there be no major change in the expected set up, high temperatures are likely to end up in the lower to mid 50s inland and the mid to upper 50s across the area, potentially getting up to 60 degrees in the immediate NYC area in the warmer case scenario. Low temperature potential is more uncertain due to cloud cover, but lows are expected to drop into the 30s and 40s across the area. In the colder case scenario, if there are mainly clear skies, temperatures may drop into the 30s across a large part of the area, bringing the potential for a more widespread frost. Stay tuned for more information on this cold spell.

By next weekend, temperatures will begin to moderate as the trough weakens and begins to lift out of the region. During that time period, however, cold air is expected to become more established over central Canada, and even though a weak warm spell may be possible around that time frame into the early week, the latest models continue to indicate the potential for below average temperatures for the last week of October, with the GFS operational run and ensemble runs bringing a strong cold spell by that time frame. More information on the longer range will be posted over the next several days.

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