Since the start of the new year, New England has been under the influence of a large storm system centered to the northeast of the region. This system became cutoff as a strong Greenland Block set up. This has led to a backup of weather systems across the country, placing New England in between the low pressure to the northeast and a high pressure system to the southwest. This has led to very stagnant weather involving cold temperatures, high winds and persistent mountain snow showers.
Below: Pressure and flow Thursday afternoon, showing the very large size of the storm system to the northeast with ridging and high pressure across much of the rest of the country:
The pressure difference between the very large storm system and the high pressure is around 70 millibars, with New England caught right in the middle. The size of the trough is nearly 3,000 miles at its widest point. This has led to a persistently strong wind across the region. This wind will continue through Thursday with gusts of 35-50mph across the region. Wind advisories have been posted for a wide swath of the region.
The persistent northwest flow has created deep cold air advection, leading to persistently cold temperatures to accompany the winds. Wind chills will remain in the 0s to the north and west and teens elsewhere for Thursday. With New England caught on the edge of the trough, it has led to broad cyclonic flow, resulting in scattered, but persistent snow showers across the north. A few snow showers may work into central and southern New England today as well. These scattered snow showers will continue through the day, but gradually wind down in coverage through the afternoon.
Below: WRF-ARW showing potential weather this afternoon:
These three main weather components (wind, cold and snow showers) have been around for about a week now, but the overall blocking pattern is beginning to weaken. Thursday will be the final day in this current stretch. The blocking high that has been over Greenland is now gradually weakening, allowing an eastward progression of the large-scale pattern.
The large low pressure system will very slowly begin to chug eastward, away from New England, for the final time tonight and into Friday. This will allow the ridge of high pressure to slide eastward, allowing (most of) New England to get into weak ridging for Friday. Eastern Maine will remain under the influence of the trough for one more day as the system slowly moves east.
Below: 500mb height anomaly for Friday afternoon showing the trough now to New England's east with (very) weak ridging building in:
Blocking patterns are stubborn and slow to break down, and this one is no exception. The improvements will be gradual. The wind will lessen on Friday, but still remain breezy. Temperatures will climb a notch higher as well, likely back to seasonal averages. The ridging will also bring an end to the mountain snow showers, albeit very temporarily.
The weak ridging New England gets into for Friday will be very temporary as the unblocking of the pattern will also allow the next low pressure system to scoot through the region. A northern stream system will push through the region from west to east Friday night through Saturday. This will bring a period of light snow showers to the region. A stronger southern stream system will remain well south of New England, but it is still poised to inject some energy into the northern system, allowing it to overcome dry air and weaker forcing.
Most of New England will be under the gun for snow showers at some point Saturday morning. A wide swath of New England stands the chance to pick up a dusting to 3 inches of snow. Current probabilities are not enthusiastic about much by way of accumulating snow.
With that said, high snow ratios on the order of 15-20:1 will allow for very light and fluffy snow that accumulates quickly and easily. The cold temperatures will allow the snow to stick immediately. This may allow some areas to "overachieve" by picking up an inch or two. Eastern Maine will likely pick up the least.
Below: Current probabilities of at least an inch of snow Saturday. It wouldn't be surprising to see some areas overachieve on these percentages, which may increase over the 24 hours:
The weakening of the blocking pattern is helping to steer the southern stream system out to sea. Without blocking downstream, the storm cannot amplify and get pulled in a more northeast direction. Blocking highs in the North Atlantic/Greenland favor nor'easter development for New England. This one never really had a chance with the timing of the blocking pattern along with the stalled system to the northeast that will be just moving away by this weekend.
While this potential storm created plenty of buzz, the chances of just a glancing blow were always higher than a direct hit. While operational models hinted at a major storm a couple times, when looking at all resources (mainly all ensemble members), the chances of this storm coming together were always on the low end. This is a good reminder not to put all emphasis on just one (or two) resources, but instead to keep an eye on the bigger picture, especially in the longer term.
The break in the colder-than-average temperatures will likely last through the weekend and into Monday. Temperatures during this time will be seasonal rather than above average. Another weak northern system is likely to scoot by northern New England around Monday night to Tuesday with some snow showers. In the wake of this system, the cold air will be refreshed with a drop in temperatures once again for the rest of next week.
Looking ahead, January will likely continue to pan out as expected with generally cold temperatures expected to persist. While signals for below average temperatures aren't as strong as they have been in recent weeks, any major warm-up remains out of the picture. Overall, the weakening of the block for the rest of this week may be more of a temporary pause than a full-on pattern change.
