Very Active Pattern Favors Multiple Storm Threats Final Week of January: First Call for Monday
As a sign of an active regime that is replete with a consistent flow of Pacific energy, a storm system for Monday is already coming into focus here on the eve of the storm to begin the weekend later tonight an into tomorrow.
Synoptic Situation:
A consequence of the active Pacific jet frequently supplying energy onto the west coast is that it teleconnects to higher heights over the southeast. Thus while we have a very active storm track due to a Pacific assembly line of systems, there will be a tendency for them to de-amplify as they approach the east coast.
The system approaching on Monday is no different. Indeed, the consistent feed of energy spilling over the AK EPO ridge and onto the west coast pumps up heights over the southeastern US and attenuates the storm due to the compressed nature of the flow between the southeast ridge and the confluent flow over SE Canada.
While the lack of high latitude blocking and southeast ridge make it likely that a strong and phased system will track inland, the compressed nature of the flow in between render it less likely that a system will reach the coast without undergoing rather significant attenuation. The nuances of precisely how each system interacts with this pattern will determine the exact track and where the rain snow line will be, but what is more certain is that this does not initially appear to be a pattern favorable for major east coast snowstorms.
This same situation also applies for the follow up wave later in the week, which also attenuate on approach.
The bottom line is that the general theme will be moderate sized storms that will favor mixed precipitation and more snow inland, as well as to the north.
Expected storm evolution for Monday:
Precipitation should begin to break out late Monday evening over western New England, s potentially snow and sleet over the Berkshires and NW Connecticut hills with rain elsewhere.
Then by the predawn hours, snow and sleet become relegated to the northern Berkshires, as a rather mild antecedent airmass in conjunction with a southwest flow aloft cause the mid levels of the atmosphere to warm even further.
Ordinarily in mid January, mid level low pressure tracking just south of Boston would still mean significant snows for much of the area. But in this instance, the low is tracking close enough given the mild antecedent airmass as to induce enough warm air advection to ensure primarily rainfall for the bast majority of southern New England, save for the northern Berkshires.
However, as the low begins to pass by Nantucket islands, winds should begin to back more out of the north. This will slightly colder air to being working back to the south and a transition back to snowfall of any mixed precipitation will occur over the Berkshires around the time of the Monday AM commute.
And then the precipitation may potentially end as a period of snow showers across the rest of the region during the midday Monday period, however, the same northerly winds that are responsible for the colder air advection are also transporting drier air into the region.
What this entails is that backside snowfall is usually overdone on guidance, especially in the lower elevations, thus any appreciable light accumulations on the backside of the storm system during the day on Monday will be confined to the Worcester hills.
First Call:
Final Call will be issued on Sunday-