Oct 24, 2011: Cold, Stormy End To Week

As last night brought less cloud cover than expected, the low temperature forecast busted once again but this time on the warm side, as temperatures dropped into the upper 30s in the interior parts of the area. High temperatures today also busted on the warm side, reaching the lower 60s inland and the lower to mid 60s across the rest of the area, with temperatures aloft not ending up as warm as I expected.

Today and tomorrow will be the warmest days in the area until early November, as a wave of low pressure on Wednesday will bring light rain followed by colder temperatures. There is more uncertainty on the forecast for Thursday with another wave of low pressure and the weekend with a potential nor’easter, but with stronger cold air in the region as well, the region will experience an early taste of winter for the end of this week, with not one, but two snow potentials in parts of the region.

Tomorrow’s Outlook:

After a weak cold front moves through tonight, bringing isolated showers in parts of the area, tomorrow will bring more sunshine but colder temperatures aloft, resulting in temperatures similar to those of today. High temperatures tomorrow are expected to reach the lower 60s inland and the lower to mid 60s across the rest of the area. A northwest wind is expected.

Storm #1: Wednesday – Friday

The first storm will affect the region between Wednesday and Friday. A weak low pressure will move through the southern Great Lakes on Wednesday, but will weaken into a broad area of low pressure by the time that it reaches the region on Wednesday afternoon. This will bring widespread light showers with high temperatures reaching the upper 50s to lower 60s across most of the area. During this time, a stronger wave of low pressure will organize near the southern Ohio Valley, with cold air slowly dropping further south.

The second wave of low pressure will organize itself on Thursday, bringing a more widespread precipitation event across the region. There is some uncertainty with the track of this storm, but at this time, I am leaning slightly towards the northern solutions, expecting the storm to track from West Virginia to central NJ and then offshore, just south of New England. The NYC area is expected to see light rain developing on Wednesday night, with steady light to moderate rain on Thursday into Thursday night until at least 12 AM. Due to the rain and chilly air mass, colder temperatures are expected, likely reaching the upper 40s to lower 50s inland, lower to mid 50s in the immediate north/west suburbs of NYC, and in the mid to upper 50s from NYC and further east. By the time that the storm ends, at least 1/2 to 1 inch of rain is expected.

With the cold air entering the storm’s northern parts, however, not only rain is expected out of this storm. Temperatures aloft are expected to drop below freezing by Friday afternoon over New England, which will produce an area of a wintry mix in parts of New York and central New England, with rain for the lower elevations and rain/snow for the higher elevations. As the storm moves out on Thursday night, the colder air will continue to push southwards, resulting in a more widespread rain/snow mix for the lower elevations of New England and accumulating snowfall for the higher elevations, with several inches of snow possible. For the NYC area, the precipitation type is expected to be rain, but if the storm is at least near where my map shows it or further south, flakes may mix in with the rain in parts of Sussex and Orange counties. Stay tuned for more information on this storm and its impact on the area and the region.
Storm #2: Saturday – Sunday
Last night’s update did not mention any storm risk for Saturday, as the model guidance was consistent in showing a strong high pressure over the region. Last night’s 18z GFS model run, however, began showing signs of a weak low pressure offshore, and trended closer to a phase until today’s runs, which showed a stronger storm in some cases. The 00z/12z ECMWF, 12z GFS and 12z CMC runs showed the low pressure near the coast, with the ECM producing a significant snowstorm for the Northeast and even accumulating snowfall north and west of NYC. Meanwhile, the latest GFS run fails to show anything significant, with only a weak low pressure well offshore.

At this time, there is still a lot of uncertainty with the location and the phasing of the storm, as the storm only recently started to show up on the models, and it may not be until the middle of this week when the models start to get a better handle on this storm. Until then, two main solutions are possible, the first where we see a weak storm staying offshore with mostly sunny skies and chilly temperatures across the area; the second scenario would bring a stronger nor’easter up the coast, producing widespread rain for the coast and potentially snow for interior areas. For now, I went with a solution in between, slightly leaning towards the second scenario, where the area sees potential rain, but the forecast is still uncertain and is subject to change. Stay tuned for more information on this weekend’s outlook.

Brief Longer Range Outlook: Regardless of the storm, cold temperatures are expected across the area during the weekend, with Saturday night in the 1st storm scenario and Sunday night in the 2nd scenario bringing cold overnight temperatures across the area with widespread 30s, bringing the first widespread frost potential of this fall across the area. The cold won’t last for long, however, as the teleconnections point to moderating temperatures in the East, with a warm up likely for the region around the start of November. This warm up won’t last through much of November, however, as indications show that a colder pattern may set up for November than we had most of this month.

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