First Significant Winter Storm Threat Next Weekend
Significant Differences Amongst Guidance
Winter 2023-2024 has undoubtedly featured a slightly slower start than anticipated, as the end of what was a very mild month of December approaches on the eve of January 2024. And it looks as though winter may finally be preparing to make a grande entrance just one week into the new calendar year.
Guidance is in early strong agreement that a lead system on Thursday will remain to the south of the region.
However, the plot then thickens, as there is understandably much less of a consensus with respect to the follow up system next Sunday.
Two Main camps
The European ensemble suite:
And the Canadien ensemble are both slightly faster to deepen the Western US trough, which results in an increase in Southeast heights down stream.
This allows the wave to exit the coast at a higher latitude, which increases the threat of a winter storm for the southern New England forecast area. However, the European guidance depicts a slightly more amplified shortwave passing to the south of Long Island upon exiting the coast, which would result a major storm. Whereas the Canadien suite, while far enough north to impact the area, would suggest potentially more of a moderate winter storm. But the important note at this stage as that both pieces of guidance agree on a storm for the area next weekend, which in contrast to the GEFS, which suggests a near miss.
The GFS ensemble suite is slower to amplify the western trough and thus has a delayed response with respect to increasing downstream heights over the southeastern US.
This does not allow the system to gain as much latitude and results in a snowstorm for the mid Atlantic, but not much in the way of snowfall for most of southern New England. While it may ostensibly appear that the GFS suite is the outlier here, there is reason for pause before endorsing the snowier EURO/Canadien compromise.
Tropical Nod to the GFS
There is a strong consensus that the MJO will be entering phase 3 late this coming week and into next weekend.
And progression of the MJO into phase 3 offers support for a slower amplification of the west coast trough more in line with the GFS suite.
Although the ECMWF rapidly weakens the MJO wave in phase 3, it does still spend 3+ days in this area in the lead up to the period of interest on the 7th.
The prudent course of action at this stage is to stay tuned throughout the week and plan on at least some snowfall next Sunday, especially to the south of the Mass pike and through Connecticutt and Rhode Island.