DAYS 1-5 (DECEMBER 31 – JANUARY 4)
On this final day of 2020, we won’t see much sun, but after morning rainfall exits the South Coast region, it will be a dry day. High pressure building across eastern Canada and pushing down into New England will bring some clearing tonight and 2021’s first day will dawn with sunshine, but clouds will advance steadily as the day goes on and another low pressure area approaches from the southwest. This system will have colder air to work with so snow & sleet are likely to be at the leading edge of the precipitation shield of this low pressure area when it arrives on Friday evening, but warmer air aloft will change that to rain during the night and into Saturday morning. However some colder air trapped at the surface may result in some pocket of freezing rain mainly over interior valley locations before temperatures rise sufficiently to eliminate that issue. By Saturday afternoon, low pressure will have crossed the region and drier air will be moving in behind it. But this dry interlude will also be short-lived, as a follow-up low will pass by the region Sunday night into Monday with another period of precipitation, the details of which still need to be worked out.
TODAY: Mostly cloudy. Rain South Coast region this morning. Highs 42-49 this morning, then slowly falling temperatures during the afternoon hours. Wind W 5-15 MPH with higher gusts.
TONIGHT (NEW YEAR’S EVE): Clearing. Lows 18-25. Wind N 5-15 MPH evening, diminishing overnight.
FRIDAY: Sunshine fading behind increasing high cloudiness. Highs 32-39. Wind N up to 10 MPH.
FRIDAY NIGHT: Thickening overcast with snow/sleet northwestern areas and mix/rain southeastern areas arriving from southwest to northeast, changing to rain except possible freezing rain interior valley locations. Lows 30-37. 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 25-32. Watch for black ice formation. Wind W up to 10 MPH.
SUNDAY: Increasing clouds. Chance of rain/mix/snow by late in the day. Highs 36-43. Wind N up to 10 MPH.
SUNDAY NIGHT & MONDAY: Cloudy with rain/mix/snow possible. Temperatures 35-45. Wind NE to variable 10-20 MPH shifting to N.
DAYS 6-10 (JANUARY 5-9)
High pressure builds in with fair weather January 5. Weak system may bring a few rain/snow showers, milder on January 6. High pressure builds back in with fair weather January 7. Next threat of unsettled weather comes from passing low pressure about January 8 before dry/cold weather ends the period.
DAYS 11-15 (JANUARY 10-14)
Stronger indications of a blocking pattern setting up during this period. Will have to watch one or two low pressure areas, strongest chance for unsettled weather around January 12-13.