Tuesday, December 29, 2009

Dec 29: Very cold times ahead

For my forecast verification from yesterday, I expected highs to be in the upper 30s to low 40s. The result highs were in the low 40s for the NYC metro including NE NJ, and further inland towards Orange County, NY and Passaic County, NJ, highs were in the upper 30s, so my forecast was correct. Scattered rain/snow showers were also reported to the north of NYC.

For the overnight verification, I expected lows overnight to be in the mid-upper 10s northwest of NYC, and upper 10s to low 20s for NYC and closer to the coast. The actual lows also followed the forecast, with the airports in NYC reporting lows in the low 20s, and airports further inland reporting lows in the mid to upper 10s.


Today: Mostly Sunny skies and windy. Very cold. High temperatures will be in the low 20s north and west of NYC, and in the mid 20s for NYC and closer to the coast. Wind chills will be in the single digits to lower 10s all day.

Tonight: Mostly Clear skies. Low temperatures will be in the upper single digits to lower 10s north and west of NYC, and in the mid to upper 10s for NYC and closer to the coast.

Tomorrow: Mostly Sunny skies. High temperatures will be in the upper 20s to lower 30s north and west of NYC, and in the lower to mid 30s for NYC and closer to the coast.

Tomorrow Night: Increasing Clouds. Low temperatures will be in the lower 20s north and west of NYC, and in the mid to upper 20s for NYC and closer to the coast.

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New Year's Day Storm:

This is where things get interesting again. Yesterday, I made a scenario map and said how this does not look like a mainly snow event for NYC. In fact, the forecast weather models still remain with a rain to snow solution for the area, however the coastal low has trended slightly further east than previous runs but still intensifies at about the same latitude, meaning we would get light rain to snow showers with light QPF amounts, with the storm intensifying at a location that would blast northern New England with the highest amounts of snow. It would be easy to say that this will be the final solution for this storm, however that would be following exactly what the models show, which is not very good considering how frequently they change. For that we have to look at the trends and the pattern, and what this might tell about this storm.

What we do know at this time is that there will be a storm, it will rapidly intensify and stall at some point, and there is also going to be a weak area of low pressure in southern Canada that will prevent the cold air from taking over at first. We have seen the forecast track by the models anywhere between along the immediate coast line to way offshore, giving us a wide range of possibilities. However, there is a general agreement that the storm will only begin to rapidly intensify after it passes the area, which would be too late for us to receive any significant precipitation. This is also when the cold is drawn in once the storm intensifies, meaning that with this solution, we would see scattered snow showers with very cold temperatures after this storm.

It is too early to know specific details at this time due to the uncertainty, however what we do know at this time is that the NYC tri-state area is likely to see both rain and snow, starting out as rain and then changing over to frozen precipitation. Once the strength of the storm and its location become clearer, it will then be easier to find out how much rain and snow we will get and the amount of time spent before the changeover to frozen precipitation.

For now, I continue with the expectation that NYC starts out with rain on Thursday afternoon, changes over to snow sometime on Friday, and then sees scattered snow showers into Saturday. Coastal areas will see mainly rain with snow showers at the end of the storm, and areas further inland (Orange NY/Passaic NJ counties and further north/west) will see a period of rain/mix changing over to mainly snow. The entire area could see windy conditions on Saturday and Sunday.

Long Range Update: Regardless of the storm and which scenario happens, it's going to get cold afterwards. Sunday will be the coldest day with highs in the 20s again, and combined with the possible windy conditions, wind chills could go back into the single digits. Temperatures then moderate into the 30s to start next week.

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