The last three days were highlighted by two consecutive major winter storms that affected the area, the first with heavy wet snowfall, and the second with heavy snow changing over to ice and rain. While the snowiest time frame has passed, the cold pattern remains in place with additional snow potentials coming up over the next week but likely to a less significant magnitude than the early week storms.
Tonight – Sunday: Cold Returns, Snow Possible This Weekend
A chilly air mass has returned into the region behind yesterday’s winter storm; while the air mass is not nearly as cold as the arctic cold outbreaks of January, it is sufficient enough to sustain a week-long period of below average temperatures. Mostly sunny skies are expected to continue into Friday with highs peaking in the mid 20s-low 30s across the area.
The next weather highlight is from Saturday evening to Sunday afternoon, when the next storm system approaches the region, driven by two shortwave troughs just off the western US coast which will move onshore tonight, and a third shortwave a little further upstream over the Pacific. Based on the latest model guidance, this system would come in two parts; the southern shortwave entering California races ENE towards the Mid Atlantic, with a weak coastal low developing offshore producing rain up to North Carolina and/or Virginia, followed by the northern shortwave moving through the region reflecting to a weak, clipper-type system in the surface producing snow showers mostly north of the area before intensifying offshore, enhancing snowfall near eastern New England.
A few days ago, some of the medium to long range model guidance suggested a major snow event with a very intense low pressure near the coast producing major snowfall, and about a week ago this storm was also the subject of a viral spread of a 30+ inch snowstorm depicted on the ECMWF control model. While model guidance often tends to lose storm potentials in the medium range, depicting them as too weak and too suppressed, before trending back stronger and more amplified in the shorter range, this storm is no longer anticipated to turn into a major storm nearly close to the magnitude of what was modeled a few days ago, especially considering that the current upper level pattern over North America is noticeably different than what the models depicted for today while supporting the major snowstorm scenario, notably with a much weaker upper level low south of Alaska which promoted more significant height rises in the NE Pacific than currently observed; the main shortwave for this event was placed noticeably to the west of where it is currently placed; the polar vortex over Canada exited the region more quickly than currently anticipated, and the shortwave was ultimately significantly more amplified by the time it was modeled to depart the NW US by Friday.
Even with the major snowstorm scenario being considered as unlikely to verify, a recurring bias this year has been for the model guidance to underestimate mid level shortwaves over the US, which typically led to stronger, wetter and further northwest storms than modeled in the medium range. Following today’s model runs, while the coastal low on Saturday has trended slightly northwest, there are currently no signs of a significant northwest trend underway. At this time, I am siding towards a relatively minor event for the region, with scattered snow showers possible on Saturday evening and with additional snow showers into Sunday with minor accumulations, generally below 1-2 inches, although the potential for a slightly snowier outcome than currently forecast will continue to be monitored.