Updated at 130AM

The Week That Was…

Monday…The warm Valentines Day! A spring preview with temperatures in the 50s to around 60 despite some cloudiness.

Tuesday… Back to reality and then some. Arctic cold, 20s, and gusty winds making it feel colder!

Wednesday… Still chilly, but not as cold as the day before, but fairly tranquil.

Thursday & Friday… Spring preview, part 2! Highs in the 50s to low 60s with clouds & sun both days. Lots of melting snow! Thunderstorms Friday night with vivid lightning, loud thunder (see below), & strong winds, rain, some snow north of Boston, & even some hail.

Saturday… Powerful northwest winds causing damage in some areas, lots of clouds, a few snow flurries, and colder temperatures.

Sunday… Still breezy, but bright & dry, though a cold day!

Why was the thunder so loud Friday night? There are 3 answers. 1) Leafless trees do not absorb sound waves nearly as much as ones with full foliage. 2) Snow, which often muffles the sound of thunder when it’s falling or freshly soft in the ground, does just the opposite when it’s hard & crusty. It acts more like a cement floor, reflecting the sound waves, or allowing them to bounce along. 3) Most of the lightning bolts were of positive polarity. What does that mean? About 90% of lightning is of negative polarity, and to simplify this, let’s just look at cloud-to-ground lightning strikes. Negative strikes are occurring between negative charges near the base of the clouds and positive charges on the ground. Positive lightning, which accounts for about 10% of lightning, is much more powerful, as it is discharging between positive charges near the top of the clouds and negative charges around the edges and outside of the storm on the ground below. The distance between the charges is greater, resulting in a more powerful spark, or bolt of lightning. These kinds of lightning discharges cause the thunder that often rolls across the sky, rumbles for several seconds, even up to half a minute or more, and sometimes produces a bottom-out sound so low it shakes the ground & the house you are in.

The Week Ahead…

For some of you, the weekend continues tomorrow, as it is the Presidents Day holiday, but whether it’s the start of a new week for you or the end of your weekend has no influence on the weather. It’s going to snow, but not much. We’ve been advertising a snow threat for Monday for several days now, and it is going to verify. It will not be a big storm, however, as a relatively weak wave of low pressure will be sliding rapidly eastward, passing just south of New England. The snow in the Boston area will begin around 2AM or 3AM and last until around or shortly after noon. Expect a slightly earlier start time to the snow in areas to the west of the city. Impact from this system will be minimal, even thought its peak will be during the Monday commute, as many people will not be on the roads due to the holiday.  Snow amounts should range from less than 1 inch in southern New Hampshire to around 1 inch to locally 2 inches in most of eastern MA. Similar amounts are expected to the south and west, though a few amounts locally over 3 inches are possible anywhere south and west of Worcester. Isolated 4 or 5 inch amounts are about as high as we can see out of this storm, and that would most likely occur in CT or southwestern MA.

High pressure from the north will build into the region late Monday and continue to dominate into midweek. This will shunt a second wave of low pressure south of New England on Tuesday, which will be a bright but very windy & cold day. Temperatures will moderate and winds will be lighter on Wednesday, a splendid but chilly late winter day.

As high pressure slips off to the east on Thursday, milder temperatures are expected, but you’ll notice clouds on the approach in the afternoon as the next storm system gets ready to move in from the west. There are some uncertainties with how this system, and another potential follow up storm over the weekend will play out, because the tracks of both storms remain uncertain. My current feeling is that the Friday system will track over or just northwest of the Boston area, which is a mild scenario, making me lean in the rain direction. After a break on Saturday, the next system is due on Sunday. It’s a week out, but early indications are that this storm may be a colder one, with at least some snow/mix involved. We’ll fine tune the late week situation as it gets a little closer.

A detailed forecast for the Boston area follows below. Have a great week everybody!

Boston Area Forecast…

MONDAY: Cloudy with snow in the morning, average accumulation under 1 inch in southern NH, around 1 inch north of the Mass Pike, 1 to 3 inches south of the Mass Pike, with the greatest chance of the 3 inch amounts south of Worcester.  Breaking clouds the first half of the afternoon & becoming mostly sunny during the second half of the afternoon. High near 30. Wind north up to 10 mph.

MONDAY NIGHT: Mostly clear. Low 10 to 15. Wind northwest 15 to 25 mph. Wind chill near zero.

TUESDAY: Mostly sunny. High 25 to 30. Wind northwest 15 to 25 mph. Wind chill in the teens.

TUESDAY NIGHT: Clear. Low 10 to 15 except  5 to 10 inland valleys. Wind northwest diminishing to under 10 mph.

WEDNESDAY: Sunny. High 33 to 38. Wind variable around 10 mph.

THURSDAY: AM sunshine. PM clouds. Low 25. High 40.

FRIDAY: AM rain/mix. PM clearing. Low 35. High 50.

SATURDAY: Partly cloudy. Low 25. High 35.

SUNDAY: Chance of snow/mix. Low 25. High 35.