Feb 24, 2011: Uncertainty With Tomorrow's Storm

As a strong storm is developing near Arkansas and is moving towards the region, cloudy skies have covered the area with some isolated showers, mixing with snow/sleet well north of NYC. Through today, there was generally good agreement with the models, which I used for my forecast discussion, however right now there are last minute changes going on with the models that if verify, will lead to a major bust with the forecast, preventing temperatures from rising above 40 degrees north/west of NYC with a cold rain during the entire day, instead of 45-55 degrees and thunderstorms. Below, I will discuss both scenarios in detail, as well as a light rain/snow event for Sunday and another rain/thunderstorm event for Monday.


Tonight - Tomorrow: Rain And Wind Expected

As previously mentioned, there are now two possible scenarios for tomorrow's storm. As I already worked on today's forecast and discussion earlier this afternoon focusing on the first scenario, this will be the one this discussion will focus on, however I will also mention what will happen should the colder scenario verify.

Warmer Case Scenario:

Rain is expected to begin falling tonight, and while generally light rain is expected until at least 2 AM, afterwards a more steady moderate to heavy rain will develop across the area. The heaviest rain will fall between the early to late morning hours, with windy conditions beginning to develop, especially in the southeastern parts of the area. Thunder is also possible with the rain as a line of heavy rain moves through before the main part of the storm ends around 2 PM.

During the day, the storm will track across Pennsylvania from SW to NE and end up near southeastern Maine. As the warm front moves through most of the area, temperatures surge well into the 40s except for the northwesternmost parts of the area, which should stay in the lower to mid 40s, with a strong south wind expected for Long Island and parts of the immediate NYC area and southern Connecticut, with gusts up to 50 mph possible, locally higher.

As the cold front approaches, a weak squall line of showers and thunderstorms may develop in the late afternoon to early evening and move through the area, producing gusty winds, which will be followed by the cold front and windy conditions spreading across the rest of the area, gusting up to 40 mph. The winds will begin to calm down after midnight.

By the time that the storm ends, at least 1 to 2 inches of rain are expected across the area, with the highest amounts generally from NYC and further north. This will lead to flooding especially in places that still have a deep snow pack. Windy conditions may also lead to damage, especially in the central and eastern parts of the area.

Colder Case Scenario:

The latest models have been coming in colder and further south, which if correct, would lead to major changes in the forecast. While it will not be anywhere near enough to make this a major snowstorm for any part of the area, it will prevent temperatures from surging well into the 40s and lower 50s for most of the area except for Long Island. In this scenario, the low pressure will take a track near New York City instead of northeastern Pennsylvania, meaning that the warm front does not move through most of the area. This will keep high temperatures in the mid 30s to lower 40s north and west of NYC, with high temperatures in the 40s for Long Island, NYC and southwest/south of there.

The precipitation outlook in this scenario would not be much different, with the main difference being shifting the heavy rain axis further south, so that the heaviest rain falls near the immediate NYC area, not north of the area. There will still be the heavy rain line in the late morning and the late afternoon squall line potential, especially from NYC and further south, and light snow will mix in the interior parts of the area and even potentially towards the north/west suburbs of NYC as the storm ends.

This scenario is closely being monitored right now in case this does become the actual outcome. At this time, the first scenario is the more likely one, however I will post an update tomorrow morning about which scenario will be the one to verify.


Saturday Night - Sunday: Light Rain/Snow

As a weak disturbance moves through the Northeast, it will produce widespread light precipitation. The NAM model earlier today suggested that this will track south enough to produce light accumulations for most of the area, however all of the other models are north of the NAM, and it also adjusted north with its latest run, bringing only light rain to the immediate NYC area and a light mix further north. Most of the precipitation from this weak storm will stay to the north of the area, though a light mix is expected north of NYC, with light rain for NYC potentially starting out with some light snow showers.


Monday: Another Major Storm Expected

Another major storm is expected for Monday as an intense storm moves into the Great Lakes. While it appears that surface temperatures may be cold enough initially for freezing rain in the interior parts of the area, temperatures quickly warm up into the 50s by the afternoon, with the cold front moving through, bringing rain and thunderstorms in the evening followed by colder temperatures. Stay tuned for more information on this storm.