Dec 20: Christmas Storm, Too Far South?

Notes:

- The 5-Day Forecast was updated tonight.

- The poll for the Christmas storm impact on the area remains open until Thursday. So far, the majority of 7 votes is for heavy snow in NYC, with one vote for no snow in NYC, however it is not too late to vote yet!

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Today was a mostly sunny day across the area with high temperatures in the mid to upper 30s across most of the area, which was slightly warmer than expected. The storm that was just offshore yesterday ended up bringing a big snowstorm to Cape Cod today, which was not predicted very well by some of the models, as 2 nights ago, some models didn't even have more than a few flakes there. This storm is expected to stick around for a few days, affecting the Northeast with snow showers and bringing increased cloud cover to the area, and while the cloud cover will briefly clear afterwards, the attention then focuses to a storm in the western US, which may affect the area on December 25-26.


Tomorrow's Outlook:


**Map correction: The 35 degree line should be moved slightly more NW on the map.**

Tomorrow will be a partly sunny day across the area with increasing cloud cover by the late afternoon and a NW wind expected, with breezy conditions along the coast. High temperatures will be in the lower to mid 30s inland, in the mid to upper 30s in the immediate NYC area, and in the mid to upper 30s in Long Island and southern Connecticut.


Wednesday - Friday: Dry, Slightly Warmer

By Wednesday, the cold air mass over the area will weaken, leading to warmer temperatures returning to the area. As snow showers take place to the north and east of the area, related to the storm that passed east of the area yesterday, high temperatures will warm up into the mid to upper 30s across most of the area, with some lower 40s possible in the immediate NYC area and in Long Island.

For Thursday and Friday, as the storm's influence starts to decrease across the region, the cloud cover will clear with mostly sunny skies expected, however temperatures will remain milder than they have been recently, with temperatures very similar to, if not slightly cooler than those of Wednesday. By late Friday night, however, cloud cover will start to increase again due to a storm approaching from the west.


Christmas Storm: Big Snowstorm Or Too Far South?

Yesterday, it was mentioned in the discussion that the models had 3 separate solutions for this time frame, the first and the least likely one being the western solution bringing a wintry mix to the area, the second scenario bringing a big snowstorm to the Interstate 95 corridor including New York City, and the third track taking the storm well south of the area, keeping the snow in the central and southern Mid Atlantic, or from Washington DC and further south. The western solution is no longer appearing on the models, signalizing that it was likely an outlier solution, however the split is now between whether the storm can make it far north enough to bring a big snowstorm to the area, or if it will stay south enough that the area stays dry.


Latest Model Summary: The models today are still not very consistent, considering this is still in the medium range, however there are now solutions that the models are split between. The ECMWF and the GFS models continue to show a big snowstorm for the area, however there are some differences between the two models, as the ECMWF digs the storm well south, into the extreme northern Gulf of Mexico, before being pulled NNE along the coast and bringing a large coastal snowstorm. The GFS model has the storm moving west to east through the central US like showed in yesterday's map, however with most of the models showing a further south solution, it is likely that the storm will start at least slightly further south than yesterday's map showed it.

Looking at the other scenario, the UKMET and the GGEM models support a storm that goes out to sea. The storm also starts out in the far southern US like the ECMWF model shows, but from there they take the storm out to sea, with intensification taking place too late that by the time that the storm starts to move northeast, it's already away from land.

Both of these solutions are reasonable at this time, and based on the pattern we've seen so far this month, the southern scenario would seem to be more likely, however there are some differences from the previous storm that give this storm a better potential to produce snow for the area. There is a more defined ridge in the western United States and a deeper trough in the East than the previous storm, which is usually better for a storm to move northeast and up the coast instead of simply going out to sea. The models are also more consistent than they have been at any point with the previous storm with a big storm close enough to the coast to produce a big snowstorm near or east of the I-95 corridor, and with the storm's energy moving into California in 2 days, the models will likely start to reach a better agreement by then.


Current Thoughts For Area: As mentioned previously, based on the pattern we've seen so far this month I'd prefer to go with the suppressed storm solution and keep the snow to the south of the NYC area, however there is also evidence suggesting that the set up is better than it was so far this month. At this time, I am going in between, slightly learning towards the suppressed solution, with at least a 40-50% chance of snow for NYC out of this storm, however this is still subject to change over the next few days, and may increase if more models start showing the northern/western scenario. In addition, the latest models have delayed the timing of this storm so that it starts on Saturday night and lasts into Sunday, and considering that the models that usually have a fast bias also trended slower to show this solution, it appears that if any snow falls in the area, it should start to fall around Saturday evening, and in the 5-Day Forecast, at this time I went with mostly cloudy skies and a chance of snow showers west of NYC for Saturday.

There is still uncertainty with this storm, and the forecast above could change. Stay tuned for more information on this storm over the next few days.


Longer Range: Cold Returns

Regardless of the path that the storm takes, the latest models show another round of cold air dropping down into the region behind the storm for early next week. As this is in the longer range, there is uncertainty on how cold it gets, though the latest model runs have been suggesting high temperatures potentially returning into the 20s again for parts of, if not most of the area. Windy conditions are also possible along with the cold due to the storm offshore, resulting in cold wind chills if this scenario verifies. Stay tuned for more information on this time frame.