Tuesday, January 26, 2010

Jan 26: Uncertainty For Next Weekend

Verification For Monday Night: I expected Mostly Cloudy skies with a few showers ending early, with low temperatures in the lower to mid 30s north and west of NYC, and in the mid to upper 30s for NYC and closer to the coast. Except for a few showers after midnight, the forecast verified.
Score: 4/4

Verification For Today: I expected Partly Cloudy skies, with high temperatures in the upper 30s to lower 40s north and west of NYC, and in the lower to mid 40s for NYC and closer to the coast. The forecast verified.
Score: 4/4


Tonight: Partly Cloudy. Low temperatures will be in the lower to mid 20s north and west of NYC, and in the upper 20s to lower 30s for NYC and closer to the coast.

Tomorrow: Mostly Sunny. High temperatures will be in the lower to mid 40s for the area.

Tomorrow Night: Partly Cloudy. Low temperatures will be in the lower to mid 20s north and west of NYC, and in the upper 20s to lower 30s for NYC and closer to the coast.

Thursday: Mostly Cloudy. A few rain/snow showers possible. High temperatures will be in the upper 30s to lower 40s north and west of NYC, and in the lower to mid 40s for NYC and closer to the coast.

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Short Term Forecast (Tuesday Night to Thursday):

For tomorrow, high temperatures will be in the 40s except for Sussex and Orange counties, which should stay in the upper 30s. Overnight lows will be in the 20s to lower 30s for both tonight and tomorrow night. Scattered rain/snow showers are possible on Thursday, with high temperatures still in the 40s. Thursday night will then take a turn towards colder weather, with low temperatures back into the 10s for places north and west of NYC.

January 29-31 Storm Update:

The cool down from Thursday continues, with high temperatures on Friday only in the 20s to lower 30s. Then, there is a storm that approaches the Mid Atlantic region, however its impacts on the area, if any, are uncertain.

As I mentioned yesterday, the models have been trending north with this storm. However, we have seen an abrupt ending to this north trend, something not seen this winter where the previous coastal storms kept trending north, but instead the models took a significant trend to the south. For comparison, yesterday the GFS model showed New York City getting 5+ inches of snow, and today's runs of the GFS did not bring precipitation north of Philadelphia. The only model still showing any notable snowfall for the area is the DGEX.

So what we do know is that the models have reduced our probabilities of a snowstorm. And even if we do get a north trend, it will take a very big trend to put us in the heavy snow zone, which is unlikely in the 4 day range. But what we can do at this time is find a range of the possible storm track and snow area.

The southernmost model runs have been those of this afternoon, showing a snowstorm for the southern Mid Atlantic and no precipitation to the north of Philadelphia. The northernmost model runs were from yesterday evening, when snow was shown up to southern NY and Boston. So if we were to go according to the data above, the snow range would be from northern North Virginia to Boston.

However, there are some reasons why this most likely won't trend as far north as last night's model runs. We have suppression in place, with a strong cold air mass, meaning that even if it were to trend north, it wouldn't be a big trend. We also have a lack of phasing, meaning that the storm won't become intense, and what we get is a relatively weak storm going out to sea. So at this time, I will say that things are not looking favorable for us to get a snowstorm, but we still have to keep an eye on future trends in case we do see changes in the model solutions.

Whether we get snow or not, it will be cold. As I mentioned previously, the strong cold air mass is what's keeping the storm to our south. With all of this cold, high temperatures are going to be in the 20s for the area for next weekend. However, what depends on the storm is the overnight lows. If the storm does impact us, cloud cover will keep our temperatures in the 10s to 20s. But if the storm stays far enough to our south that we see at least partially clear skies, then radiational cooling will help cool down temperatures, with low temperatures being some of the coldest this winter.

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