On Sunday night and Monday, this initial low pressure system over the Ohio Valley should weaken and give way to a developing storm near the Mid-Atlantic coastline and it is this secondary system that will become the dominant player. The exact timing of the transfer of energy from the initial low to the secondary system will play an important role as to how much snow (and/or rain/ice) can fall in the DC-to-Philly-to-NYC corridor as will the speed at which the coastal storm intensifies and its ultimate track. Shortly after the second storm starts a move from near the Mid-Atlantic coastline, it will encounter a strong blocking pattern in the upper part of the atmosphere over eastern Canada and this will impede its movement to the north and east. As a result, we are likely to be dealing with a long duration event in the Mid-Atlantic/NE US early next week.
It does appear increasingly likely that accumulating snow is a real threat in the Mid-Atlantic region during the initial “warm air advection” phase of the storm from Sunday into Sunday night. The second phase of the storm will be associated with “coastal storm generated” precipitation and this can be for an extended period of time from Monday into Tuesday. “Wrap around” snow or snow showers are possible in the I-95 corridor in the Monday/Tuesday time period as the storm stalls out and perhaps even retrogrades a bit back towards the coast. There is certainly a chance that some areas in the I-95 corridor see a changeover from snow to a wintry mix during this event and this is something that would have an influence on total snow accumulations. An influx of colder air on the back side of the coastal storm could result in a changeover back to snow in those areas that do indeed turnover to a wintry mix earlier in the event.
Stay tuned…lots of details to be ironed out in coming days for this complex and potentially significant winter storm for the Mid-Atlantic/NE US.
Meteorologist Paul Dorian