DAYS 1-5 (NOVEMBER 30-DECEMBER 4)
On this final day of November, a day which will feature weather similar to the next-to-last day of November (chilly, breezy, and dry), the fine-tuning continues regarding the storm threat that starts off our December. It’s a broad area of low pressure, the center of which will be a redevelopment of a mature / occluded storm system in the Plains, moving eastward and passing just south of New England on a west to east track, but also elongating and occluding itself as it does so due to the nature of the upper level pattern above it. This makes it a longer-duration storm, despite its eastward progression, with precipitation beginning as early as Sunday afternoon and ending as late as Tuesday afternoon. The details of what happens between the start and end window are the puzzle to figure out, and the reasoning for what follows is based on computer models often struggling with precipitation types, low centers, precipitation amounts, and surface temperatures in this “early-season” set-up. So instead of analyzing every piece of data, every model, and reading everybody else’s forecasts to find fault or agreement with them, I’ve resorted to just simple analysis and experience, whatever that’s worth – and I guess we’ll find out what it’s worth in this case. This is how I think it plays out for southeastern New England: Storm’s precip arrives west to east Sunday afternoon and evening as snow most locations, maybe rain or mix Cape Cod and South Coast as surface temperatures will be marginal there. Precipitation intensity picks up rather quickly Sunday evening, still as snow for a good part of the region, and this is when most of our accumulation will take place. Early numbers, maybe a coating South Coast and Cape Cod if it snows long enough, then it goes to rain, a solid coating (1/2 inch or so) up to 2 inches across the bulk of southern and central RI through southeastern MA and right up to Logan before going to rain during the night, 2-4 inches along the I-95 belt including south central MA and eastern CT in general before going to a sleet/ice mix and probably to rain eventually, 4-8 inches for the I-495 belt from its ending near the MA/NH border down to around I-90 and all points west of there before going to sleet/ice mix with potential pockets of plain rain for a while, with greater than 8 inch amounts possible in the highest elevations of north central MA and southwestern NH where it snows for the longest. Once we get into the day Monday, some drying aloft between the newer low and its older parent low still to the west will likely limit the precipitation somewhat, and any snow over the interior will struggle to accumulate. Monday night as the parent low in its dying stage also passes just to the south of the region, it will turn somewhat colder from northwest to southeast and we should see a switch back to snow, but also a gradual break up of the precipitation area into a more patchy or snow showery nature that will linger into Tuesday morning. Additional snow accumulation is possible from this back-end snow but at this time I don’t think it will amount to all that much. There is just enough uncertainty with this part of the system to keep a close eye on it in case it ends up being a little more organized here. Regardless, whatever is left on the ground will do an early December freeze-up as it gets cold later Tuesday and Tuesday night, along with a gusty wind, but it will also be clearing out at that time. Oh yes, I almost forgot, there will be life after “the storm” too so what will the weather do? Well in a fast-moving pattern we’ll already have another trough approaching on Wednesday so look for some additional cloudiness to arrive and perhaps some snow showers, although it already looks like the main energy with the initial system passes well to the north and a new low evolves too far offshore to have any significant impact.
The forecast details…
TODAY: Mostly sunny. Highs 36-43. Wind NW 10-20 MPH, higher gusts, diminishing gradually. Wind chill in the 20s in the morning.
TONIGHT: Mostly clear. Lows 18-25. Wind N under 10 MPH.
SUNDAY: Increasing clouds. Snow, except rain or mix South Coast, arriving mid to late afternoon west to east. Highs 33-40. Wind NE up to 10 MPH.
SUNDAY NIGHT: Overcast. Snow I-495 belt from about I-90 northward, snow to mix/rain elsewhere, rain most likely closer to the coastline. See above for snow accumulation info. Lows 28-33 interior, 34-39 coast. Wind NE to E increasing to 10-20 MPH, higher gusts near the coast.
MONDAY: Overcast. Mix/snow southwestern NH and north central MA, mix/rain elsewhere, diminishing but turning back to snow further east later in the day. Highs 32-37 interior, 38-43 coast. Wind E 10-20 MPH, higher gusts, shifting to NE.
MONDAY NIGHT: Cloudy. Periods of snow except mix near the coast and still some rain possible Cape Cod. Lows 26-31 interior, 32-37 coast. Wind NE to N 10-20 MPH.
TUESDAY: Mostly cloudy morning with passing snow showers. Partly cloudy afternoon. Highs 35-42. Wind N to NW 10-20 MPH, higher gusts.
TUESDAY NIGHT: Mostly clear. Icy areas on untreated surfaces. Lows 22-29. Wind NW 10-20 MPH, diminishing.
WEDNESDAY: Increasing clouds. Possible snow showers. Highs 33-40. Wind variable up to 10 MPH.
DAYS 6-10 (DECEMBER 5-9)
Low pressure offshore moves away, breezy and chilly December 5 but mainly dry. Trough pushes through later December 6 or early December 7 with a snow shower threat but no major storm, otherwise mainly dry and chilly through December 8 and warming up somewhat end of period.
DAYS 11-15 (DECEMBER 10-14)
Passing trough brings rain/snow showers December 10-11. Low pressure system brings snow/rain threat about December 13. Temperatures not too far from normal.