7:36AM

DAYS 1-5 (DECEMBER 1-5)
The final month of 2019 has arrived, and the first winter storm of the 2019-2020 season is about to arrive! There has been no significant change to the discussion posted here just over 24 hours before this one, but let’s try to add a little fine-tuning. We’re still looking at a broad low pressure area with a couple centers to affect the region. There will be about a 1 to 2 hour delay of the precipitation onset due to its need to overcome a lot of dry air at lower levels. This will keep most of the region precipitation-free until dusk or evening, but snow may be making it to the ground in eastern CT, central MA, and possibly southwestern NH while it is still daylight. This may still start as a mix/rain across Cape Cod and parts of the South Coast, but conditions will be borderline there. As things get going tonight, that’s when most of the guaranteed snow accumulation takes place, and I’m still leaning toward a rather quick warming of the lower atmosphere on an east wind for eastern MA and RI, eventually into eastern CT and possibly parts of at least south central MA. And as this happens, the track of the initial low pressure area should be close enough to the South Coast to allow warming aloft to push northward. These conditions should combine to produce a change to rain in southern and eastern areas, but a change to sleet and some freezing rain across interior areas from perhaps northeastern CT through central MA, and at least a mix with sleet in north central MA and interior southern NH. The last 2 areas mentioned will likely stay mostly snow before there is some diminishment in precipitation coverage and intensity during Monday morning. This will occur as the initial low center moves away to the east and a bit of drying is introduced at mid levels, where most of the precipitation is generated. And what as always been the most uncertain part of the system remains so. Colder air will start to nudge back south and east as a second low center, the remains of the original low, head eastward just south of the South Coast. This will probably help trigger yet another redevelopment of some kind offshore which may intensify fairly quickly and track a little further northward, probably doing a cyclonic loop east of New England. The re-organization of precipitation and its coverage and movement in response to this final low pressure area will determine how much additional snow falls on the back side of the system Monday night and early Tuesday as it gets set to depart. Yesterday, and today as well, I’m leaning toward limited coverage for any heavier snow banding, and probably a fight with some drier air being pulled into the system at the same time it’s organizing and moving away. This will hold me back from adding too much in the way of accumulation to the forecast of the back-end portion of the storm, and result in similar numbers for the front-end portion of the snow, which I posted yesterday, and a small additional amount for the back end added to that for a total, resulting in amounts that should break down this way.
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Cape Cod / South Coast of MA: Coating to 2 inches.
RI and remainder of southeastern MA up the coastline to Cape Ann: 2-4 inches.
I-95 belt and NH Seacoast: 4-6 inches.
I-495 belt from near I-90 westward and northward including interior southeastern NH: 6-9 inches.
North central MA to southwestern and south central NH: 9-12 inches.
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Can that snow forecast still blow up in my face? Absolutely. If I feel there is a need to tweak it or make even more drastic changes, I’ll re-post it in the comments section of the blog and include it on the next full blog post of course. There are no changes in the thinking of how things run after the storm gets out of here. Breezy, colder weather arrives Tuesday. The next trough swings through with a snow shower threat later Wednesday to early Thursday with additional storminess occurring too far offshore for any direct impact, and cold air is just reinforced as that takes place.
The forecast details…
TODAY: 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.
TONIGHT: Overcast. Snow I-495 belt from about I-90 northward, snow to mix/rain elsewhere, rain most likely closer to the coastline. Lows 27-32 interior, 33-38 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/rain coastal areas turning to snow. Lows 26-31 interior, 32-37 coast. Wind NE to N 10-20 MPH.
TUESDAY: Cloudy start with snow showers likely and a chance of steadier snow for a while mainly NH Seacoast, eastern MA, and RI, then variably cloudy with scattered to isolated snow showers. Highs 33-40. Wind N to NW 10-20 MPH with 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.
WEDNESDAY NIGHT: Mostly cloudy. Possible snow showers. Lows 25-32. Wind variable up to 10 MPH.
THURSDAY: Partly sunny. Chance of snow showers early. Highs 33-40. Wind N 10-20 MPH.

DAYS 6-10 (DECEMBER 6-10)
A progressive trough and accompanying cold front will push through with a few snow showers late December 6 to early December 7, which turns out windy and cold. High pressure builds in with dry and chilly weather December 8 and still dry but milder weather for December 9. Next system at the end of the period should be a rain shower threat.

DAYS 11-15 (DECEMBER 11-15)
Fair and chilly weather returns early in the period. Low pressure trough may bring precipitation threat mid period before fair and seasonably chilly weather follows.