Dec 21: Discussion On Dec 25-27 Storm

Today was a mostly sunny and breezy day for the area, with high temperatures in the mid 30s to lower 40s across the area, which once again was warmer than expected. Tomorrow appears to be another mild day across the area as high temperatures will be similar to, if not warmer than today, in the mid to upper 30s inland and in the upper 30s to lower 40s for the rest of the area. These temperatures will continue through at least Saturday, with dry conditions until then, however by Sunday a storm is expected to reach the region and may affect the area with snow and wind.


December 25-27 Storm Discussion: Split Continues Between Big Snowstorm Or Nothing

When making yesterday's discussion for this storm, the majority of the models took the storm out to sea, and even though the pattern so far this month would favor that solution, I did mention that there were some factors that make this snow event potentially more likely to verify than the previous potentials which ended up being too far south/east. Today's models trended more west again, and also trended slower, meaning that the snow will not fall on Christmas, but on the day after Christmas. While there are still at least 5 days left until the storm begins, there is enough confidence for higher snow probabilities in the area. There is still a split between the models about the storm's track, which still gives us a range of either a big snowstorm or a suppressed storm to the south/east of the area.


Model Analysis: The ECMWF model, which was the most consistent with showing the big snowstorm potential, continues to show the big storm with today's runs, and even shows a powerful 966 mb low pressure sitting east of New Jersey in its 12z run. The ECMWF, however, seems to be too slow with the storm, not showing the storm starting until at least Sunday night. At this time, this solution is a slow outlier, and the track is also potentially too far west, as no other reliable model shows the storm just east of New Jersey. The 00z ECMWF run was also potentially a little too strong and too far west, however it is more reasonable than today's 12z run and was used for the forecast.

The GGEM model has trended towards the ECMWF today, with its 00z run showing a big snowstorm for the area with apparently over 10 inches for NYC, but the storm would be so far west that rain/sleet mixing with the snow becomes an issue for Long Island. At this time, the storm is unlikely to be west enough to lead to precipitation other than snow falling in the area, and the 12z GGEM, which is slightly further east, is a more reasonable solution and was also used for today's forecast. The GFS model has trended much more suppressed, however it is currently the least consistent of the models, and is still slowly trending slower, meaning that it is still trending and could return further north/west tomorrow. At this time, I am considering the 18z GFS run as a potential outlier, but if the GFS is consistent with this solution tomorrow and/or other models trend towards it, then it could be a sign that the storm could be suppressed.


Storm Scenario: The models are generally consistent with the storm track until at least Saturday, when the storm is likely to end up near south Carolina, but from there where it goes is uncertain and depends on the phasing of the storm.

It is possible that the storm starts to intensify early and comes up the coast like the ECMWF and GGEM models show, which is the track to the left in the image to the left. This tpye of track would support a major snowstorm from the Delmarva Peninsula into New York City/Long Island and much of New England. The second possibility is the one that the GFS model is showing, where the storm doesn't intensify until it's too late, and as a result ends up moving ENE to NE and out to sea, keeping any snow away from the region. At this time, the more reliable models show the western track and the less reliable models show the eastern track.

Looking at the set up, it is more favorable than it has been for the potential December 19-20 storm which ended up being too far east, including a more defined western ridge and a sharper East Coast trough, which gives the storm a better chance to intensify and move up the coast. With the above mentioned, I am currently going for a solution in between, leaning towards the first track, but keeping the second track in mind as it cannot be ruled out yet.


Potential Scenario In NYC Area: At this time, as previously mentioned, I am thinking that a solution in between the first and second track, leaning towards the first track, may be more reasonable at this time. If I was to follow this scenario, there would be the potential of significant snowfall in the eastern parts of the area, with lighter snowfall west of NYC.

At this time, though, due to this being 5 days away and with uncertainty on the models, I am going more conservative with this storm, and while the 5-Day Forecast was not updated tonight, it appears that the best time frame for snow to fall would be on Sunday night, with at least a 40-50% chance for the western parts of the area, 50-60% chance of snow for the immediate NYC area, and a 60-70% chance of snow for the eastern parts of the area. It is still possible that it does not snow in the area, however if tomorrow and on Thursday the GGEM/ECMWF models stay consistent and the other models, including the GFS and UKMET, start to trend west, then I will probably increase the precipitation chances. On the other hand, if the GFS remains consistent and the GGEM/ECMWF trend further east, probabilities could be decreased tomorrow.

The scenario mentioned above is just a possibility at this time, and it is possible that other solutions might verify. If the eastern solution verifies, the area would likely stay dry, but if the western scenario verifies, as much as a foot of snow, if not even more could be possible in the central and eastern parts of the area. Both of these solutions are currently extremes, and at this time they remain only possibilities.

There is still uncertainty with the storm, and the scenario mentioned above is subject to change with future updates. Stay tuned for more details on this storm and how it may affect the area.