Eastern pacific oscillation is a variation of the atmospheric flow across the eastern pacific.
Here is the epo index pattern in its +phase for h5 and surface temps (negative would be the opposite of map)
When in the + phase mild air flows onto the west coast and as it crosses the Rocky Mountains it dries out and becomes temperate and sinks. In the east we would rather the epo be negative, as would be the opposite of the above +phase depiction. A ridge would be in place over the east pacific off the west coast and high pressure would force the air up into Alaska and the artic. The ridge would displace the colder air down into the central and nothern US which would then modify our temperatures here in the northeast as well also indicated on the above index pattern.
The stronger the -epo the more cold that can be displaced, the longer the epo stays negative the longer the temperatures in the central and nothern reaches of the US will stay modified.
So no the hugely +epo upcoming is not good for snows in the east which makes the current model depictions of a snowstorm so difficult.
However bombogenesis can create its own dynamics as we well know. Fascinating to watch the battle on the models for this period.
Dewpoints are still rather high across the northern areas so I wouldnt be surprised if areas start off as some rain before the transition occurs but the primary SLP is looking to be reaching to the coast more so recently probably pop a LP by morning time which should help draw down the colder air into many areas. AS MD stated definitely elevation dependent this go around. Honestly really depends on precip rates what will happen in many areas. If it goes band band band type of deal it will be interesting cause it may not pile up as much but still be hazardous where if it becomes a solid shield with some meso bands mixed in then I could see some warnings being hoisted.
Some decent dry air aloft may help with the cooling process but also may have some virga issues initially where it can manage to stay all snow
925 low is in a good spot. BIG thermal gradient over NJ and the Atl
850 is improving, but just doesn't seem to be much cold air at this level yet. It is getting colder over PA and expanding out though.
Only one area of <32f for now (happens to be where my in-laws are by Belleayre). This has worsened through the day. Is expected to expand out over the next 6 hrs
Belleayre web cam showing 32.4f with either rain or nothing.