Nov 20, 2010: Uncertainty With Long Range

**Notes: The 5-Day Forecast was also updated for the interior tonight, with updates in the 5-Day Forecast in Long Island/S CT to be resumed soon.

The winter outlook is currently being made revisions to, and is expected to be posted tomorrow instead of the regular daily discussion.

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Today was a partly cloudy and breezy day with warmer temperatures, reaching the mid 50s inland, mid to upper 50s in the immediate NYC area and in the lower to mid 50s in Long Island/S CT. A weak cold front moved through earlier today, and a colder air mass is now entering the area. While the coming week should start off mild, a storm is expected for Thanksgiving day, with a cold and windy weekend to follow.

Tomorrow’s Outlook:

Tomorrow will be a partly sunny day, with high temperatures colder than those of Friday, in the lower to mid 40s for most of the area, except for the immediate coast and the immediate NYC area which should be in the mid to potentially upper 40s. A NE turning SE wind is expected during the day.

Monday – Tuesday: Very Mild

A low pressure in the Midwest on Sunday night is expected to start pushing out the cold air mass, leading to a ridge building in the East on Monday. High temperatures are expected to reach the mid 50s to lower 60s across the area, with the warmest temperatures in the warmer spots in the immediate NYC area.

Overnight, as another low pressure organizes itself over the Midwest, a cold front should move through the Ohio Valley producing rain and thunderstorms, with a mild air mass persisting over the area leading to mild overnight lows, in the mid to upper 40s inland and upper 40s to lower 50s in the immediate NYC area. The cold front will weaken by the time that it moves through the area on Tuesday evening/night, though it will still be capable of producing light rain showers, with high temperatures on Tuesday in the lower to mid 60s for most of the area and mid to upper 60s in the immediate NYC area, making it the second warmest, if not the warmest day of the month.

Wednesday – Friday: Thanksgiving Storm, But Uncertainty Continues

On Wednesday, as the cold front from the earlier storm moves through the area, temperatures will cool down into the upper 40s to mid 50s across the area, but the cold air mass will not be able to advance much further southeast due to another developing storm.

Model Trends: As yesterday’s discussion mentioned, the GFS model was too progressive with the storm, already bringing rain to the area by Wednesday afternoon, which is a typical bias of the GFS, and it developed the wrong low pressure, leading to a mess of weak, disorganized and suppressed low pressures. The GFS is now backing away from these errors, and is developing a low pressure further west and has the whole storm slower, taking it into the Great Lakes like the other models have been doing for the last few days. Afterwards, however, it has significant differences with what to do next with the low, with some runs absorbing it into a larger low near Newfoundland to forming a Miller B low pressure off the New England/northern Mid Atlantic coast leading to a larger storm in the Northeast. The ECMWF and GGEM continue to be even more west, even putting the storm in the Midwest. This could be too far west, and I would expect these models to trend back east over the next few days.

Forecast: While there is uncertainty on the development of the storm, some things are likely, such as rain falling in the area from Thursday in the morning/early afternoon hours into Friday, the general storm track being in the Great Lakes/Ohio Valley moving east/ENE, not NE like a typical storm in that area, and there is also the potential for Miller B, or coastal redevelopment off the New England coast. As there is too much uncertainty at this time and given that this is still in the medium range, I am not going to go into more details into the specifics of the storm, but I am expecing rain for Thursday into Friday with potentially moderate rainfall amounts. Stay tuned for more details on this storm and how it may affect the area.

Saturday/Sunday: Cold, Windy

Despite differences with the storm, there is higher confidence for the weekend. It will get colder behind the storm, but the models have backed off from the intensity of the cold. The previous GFS runs from yesterday were way too cold, and showed what would be well below average temperatures, with highs in the lower to mid 30s and highs in the upper 10s to mid 20s. The GFS model has trended more conservative, showing high temperatures in the mid 30s to lower 40s and lows in the lower to upper 20s. While there is uncertainty on how cold it gets, below average temperatures are expected.

Windy conditions are likely on Saturday and potentially Sunday given the stronger storm to the NE of the region, and if the GFS solution was to verify, strong winds could be possible, however there is still too much uncertainty to know for sure what happens, as some models are still showing the coastal solution with snow to its north, the ECMWF barely shows a cold spell, and the GFS simply has cold moving into the region. This time frame will be discussed in more details once the scenario becomes clearer.

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