Looking over things this morning shows me that things are generally on track with what is expected from the upcoming storm. We’ve had snow falling over alot of MA, but it’s not really from the main storm system. There was an old storm and energy moving through the Ohio Valley on Christmas Day, north of the energy that is forming the new storm. That first batch is over us now, but looking at the radar loops, you can pick out snow moving over us from west to east, and also another plume of snow moving from east to west. That tells me we’re seeing a combination of the old energy along with some ocean-effect snow. That’s responsible for the coating of snow we’ve already seen, but is not part of the main storm. That storm is now redeveloping off the South Carolina Coast. Thunderstorms down there are clear evidence of the birth of the new low pressure area.

From here, the key will be the exact track of that low pressure center. It will be coming northward obviously, but when it gets closer to here, the placement of it will determine exactly who gets what, and how much. So far my thoughts of yesterday remain pretty much intact. There will be a good deal of rain over Cape Cod, and mixing over southeastern MA, but how close that mix area gets to  Boston will be determined by the placement of a coastal front. This is a boundary you often see set up during these kinds of storms where just to the east the temperature is milder (near 32 or even higher, for example), and snow will be very wet there and often mix with or turn to sleet and rain). Just to the west of this coastal front you will see a very sharp drop off in temperature, a wind out of the northeast to north, much drier snow, which can fall very heavily. This boundary can move, and usually does. But it can be erratic, so watching it is really all you can do, with radar and surface observations. I’m pretty sure we’ll be dealing with this type of boundary tonight, during the height of the storm.

So for now, I’ll go with a 12 to 20 inch storm snowfall anywhere this boundary stays east of, with amounts dropping off as you go east and especially southeast to a 6-12 inch area closer to and just south of Boston, 3-6 inches over alot of southeastern MA, and 1-3 inches over Cape Cod.

I’ll send another update sometime this afternoon, sooner if needed.

Have a great Sunday & stay safe!