430PM
The changeable La Nina weather pattern continues, and shows no signs of breaking down. Nothing is locked in. Temperatures go up and down, frequent weather systems visit, but nothing hangs around for very long. At the moment I suppose this is a good thing, because we’re still not seeing prolonged rain events which would lead to major flooding. Our heavier rains have been brief and have not had a chance to really kick off significant problems.
A cold but sunny Thursday is winding down, but a very cold night is ahead. As winds drop off and high pressure moves overhead, a mostly clear sky will provide excellent radiational cooling conditions, and the temperature will plunge. For anyone unfamiliar with the term “radiational cooling”, it refers to the warmth at the ground radiating upward back up, since warmer air rises. This takes place easily on clear, calm, dry nights, and even more efficiently when snowcover is present.
The next weather change will already be underway as Friday dawns. It will still be a chilly day, though not as cold as today was. But clouds will advance after some sunshine to start the day. This will be ahead of warmer air moving in, which will do so above us first. Before it makes it in at the surface, a period of snow or snow showers may occur on Friday night. Clouds will dominate Saturday, but precipitation is expected to be hard to find, other than perhaps a rain or snow shower early in the day. Warmer air will move in during the day. A mild Saturday night is expected, and a very mild day on Sunday will start dry but end wet, as a slow-moving cold front approaches from the west, with a couple waves of low pressure on it. This front will move across the region Sunday night into Monday, and one final wave of low pressure on Monday will likely cause a period of significant rain. I do not expect major flooding from this, as the heaviest rain should last only several hours in any one location, and may occur in the areas where there is less snow on the ground (southeastern MA & RI). I’ll fine-tune this as it gets closer. With colder air coming in at that time, we also have to watch for a possible switch to mix or snow before the Monday storm is over.
Looking ahead…
Dry & chilly weather is expected to return Tuesday into Wednesday of next week, with the next storm system due about Thursday. Early indications are that this will be a mild storm, with rain.
Boston Area Forecast…
TONIGHT: Mostly clear and very cold. Low ranging from around 5 over inland valleys to near 15 in the urban centers and along the immediate coast. A few deeper valleys may approach zero! Wind NW diminishing to under 10 mph then becoming calm.
FRIDAY: Increasing clouds. High 33 to 38. Wind light southeast.
FRIDAY NIGHT: Cloudy. A period of light snow is possible but little accumulation is expected. Low 27 to 32 but temperatures may rise back through the 30s overnight. Wind light south shifting to southwest.
SATURDAY: Mostly cloudy. High 45 to 50. Wind southwest 5 to 15 mph.
SATURDAY NIGHT: Mostly cloudy. Low 35 to 40. Wind southwest 5 to 15 mph.
SUNDAY: Cloudy. Rain developing from west to east during the afternoon. High 50 to 55. Wind south southwest increasing to 10 to 20 mph.
SUNDAY NIGHT: Cloudy. Rain likely. Low 40 to 45.
MONDAY: Cloudy. Rain likely, may mix with or turn to sleet/snow by late in the day. Temperature falling into the 30s.
TUESDAY: Partly cloudy & windy. High in the upper 30s.
WEDNESDAY: Mostly sunny. High in the lower 40s.
THURSDAY: Mostly cloudy. Chance of rain showers. High in the upper 40s.