DAYS 1-5 (JANUARY 1-5)
Happy New Year to all! We start 2021 with an active weather pattern bringing 2 bouts of unsettled weather during its first 5 days. Today starts bright and cold with sun & high clouds as high pressure sits over the region. We’ll see cloudiness advance during the day as the high pressure area starts a northeastward retreat and low pressure approaches from the southwest. This low pressure area will be heading for the eastern Great Lakes, but along its warm front we’ll see a secondary low pressure area develop, near Long Island, then track northeastward across southeastern New England Saturday morning. This will be a progressive system with precipitation arriving as snow for most areas tonight, except rain along the South Coast, then transitioning to sleet & rain from south to north as warmer air comes in aloft, but surface cold will probably allow a period of freezing rain and some glazing of ice to take place across Worcester County, adjacent northeastern CT, and along the I-495 belt from near I-90 northward into southern NH, so be aware that any untreated surfaces may become very slippery. Temperatures should make it above freezing in all areas as the rain moves out from southwest to northeast by late morning or midday Saturday, and clouds will break as the secondary low exits via the Gulf of Maine, pulling drier air back in behind it. Similar to today, high pressure will then build in for Saturday night and early Sunday with dry/colder air. Watch for the formation of black ice Saturday night on surfaces that don’t dry off. Another low pressure area will make a run at us from the southwest later Sunday, and the slower movement of this one will allow it to hang around offshore Monday and even into Tuesday. This one should again begin as snow for most of the region except possibly mixed precipitation or rain for the South Coast, and drier air may eat away at the precipitation area for a time on Sunday night, but Monday’s situation may become more complex as the low center gets a shot of energy and intensifies, making for heavier precipitation at the same time colder air is drawn closer to the storm center. This would mean a better chance of accumulating snow for more of the region, including Boston. We’ll have to see how far south and east it can get from there, as temperatures will probably still be marginal or just too mild for all snow for at least a while. At this time, I do think while the low will be close enough to potentially bring snow and rain showers to at least eastern coastal areas, especially Cape Cod, on Tuesday, it should be far enough offshore to not bring any steady precipitation to the region.
TODAY: Sunny start, cloudy finish. Highs 32-39. Wind N up to 10 MPH.
TONIGHT: Cloudy. Snow, except rain South Coast, arriving southwest to northeast by late evening, may mix with sleet before changing to rain except freezing rain over northeastern CT, interior MA, and southern NH. Snow accumulation of a coating to 2 inches away from the coast, highest amounts in the higher elevation of southwestern NH and central MA. Lows 29-36 evening, rising slowly overnight. Wind N to NE up to 10 MPH inland and 10-20 MPH coast.
SATURDAY: Cloudy with areas of fog and a chance of rain in the morning. Breaking clouds in the afternoon. Highs 45-52. Wind NE to variable 5-15 MPH becoming W.
SATURDAY NIGHT: Clearing. Lows 23-30. Watch for black ice formation. Wind W up to 10 MPH.
SUNDAY: Increasing clouds. Snow, except mix/rain South Coast, arriving by the end of the day. Highs 35-42. Wind N up to 10 MPH.
SUNDAY NIGHT: Cloudy. Periods of snow except mix/rain in coastal areas. Lows 30-37. Wind NE 5-15 MPH.
MONDAY: Cloudy. Rain (mostly coast) & snow (mostly interior) may get heavier and rain may change to snow in all areas by later in the day. Highs 32-39. Wind NE to N 10-20 MPH, higher gusts.
MONDAY NIGHT: Cloudy. Snow/mix/rain tapering off. Lows 23-30. Wind N to NW 10-20 MPH, higher gusts.
TUESDAY: Variably cloudy. Snow and/or rain showers possible. Highs 32-39. Wind N to NW 10-20 MPH, higher gusts.
DAYS 6-10 (JANUARY 6-10)
Transition to a blocking pattern. Seasonably cold & dry weather will flank one storm threat that comes around January 8.
DAYS 11-15 (JANUARY 11-15)
Indications are for stronger blocking. Storm threat in the January 12-14 window.