We’ve got a little bit of everything coming up in the next few days, but that’s actually fairly typical for autumn.
The weekend starts off on a stormy note as the remains of Zeta pull away tonight while a second system quickly follows. The heaviest rain is expected this evening and the first part of tonight from Zeta’s remains, but as it pulls away, it will draw some colder air into the region just as the second storm moves in. As that colder air moves in, we’ll see the rain mix with and change over to sleet and wet snow, first in the hills of southwestern New Hampshire and central Massachusetts early Friday morning, then across the rest of southern New Hampshire and eastern Massachusetts by daybreak or shortly thereafter. Everything should wind down by early afternoon, followed by rapid clearing and diminishing winds (more on this in a moment).
Since the National Weather Service has posted Winter Weather Advisories for the interior of the region, you must be expecting some decent snow, right? We don’t think so. Across the hills of Worcester County and the Monadnocks, a few inches may accumulate, possibly a little more on top of the hills. For Southern New Hampshire (Concord-Manchester-Nashua), you could see an inch or so, maybe two inches in a few spots, mainly on grassy surfaces. From the New Hampshire Seacoast into the Merrimack Valley of Massachusetts we’re looking at an inch or less, again mainly on grassy surfaces. For the rest of us, just a mix of rain or snow, maybe enough to coat the grass in some spots, mainly from Metro West to the North Shore.
Why is our forecast for less than most of the TV and NWS forecasts out there? Most of the forecast models are showing the potential for 1-3, possibly as much as 6 inches of snow. However, a lot of people seem to forget a few things. First, those maps assume a 10:1 ratio of snow to liquid (1 inch of rain equals 10 inches of snow). With temperatures near or just above freezing, the ratio won’t be 10:1, more like 7 or 8 to 1, so that trims to 20-30% off of the map totals. Second. the ground is still relatively mild. While this impact is minor, it just means that the snow won’t stick initially, as it will melt on contact until the ground cools a bit more. So that may take away another 10% of the model totals. Factor those into the model forecasts, and you arrive at the numbers we have.
Once the system pulls away, it will clear out as we mentioned before. Temperatures will drop quickly, likely bottoming out in the 20s across much of the region, maybe even upper teens in some spots. Any roads that are still wet during the evening may start to ice up, especially bridges, overpasses, and elevated roadways. Keep this in mind if you’ll be out Friday night or early Saturday morning. As for Saturday, it’ll be a rather chilly Halloween despite sunshine. High temperatures will only get up into the middle to upper 40s at best.
Saturday night probably won’t be quite as cold, as winds will shift into the southwest and clouds will start to move in. Sunday will be milder, but with a cold front approaching, a few showers are possible during the afternoon and evening. Much colder air settles in behind that front on Monday, when temperatures will struggle to reach 40 in some spots. We may even see a few flurries. The good news is, it looks like it will start to warm up again later next week, but we’ll have more details on this on our Weekly Outlook Monday morning.
Thursday night: Breezy with rain, possibly heavy at times, gradually mixing with and changing over to sleet and wet snow. Low 30-37, except 37-44 across Cape Cod and the Islands.
Friday: Snow or a wintry mix ending around midday, then skies start to clear out with diminishing winds. High 34-41, a little warmer across Cape Cod and the Islands.
Friday night: Clear and chilly. Low 18-25, 26-33 across Cape Cod and the Islands.
Saturday: Sunny and cool. High 40-47.
Saturday night: Clear during the evening, clouds start to move in after midnight. Low 25-32, but temperatures may start to rise a bit after midnight.
Sunday: Cloudy with a few late-day showers possible. High 54-61.
Sunday night: Mostly cloudy, any showers end during the evening. Low 30-37.
Monday: A mix of sun and clouds, slight chance for a snow flurry or a sprinkle. High 39-46.