DAYS 1-5 (MARCH 13-17)
Today’s a quiet but cloudy day, with our clouds a combination of broken low clouds from our adjacent ocean underneath a canopy of thickening high to middle clouds in advance of an approaching storm from the southwest. A little bit of rain may sneak into the region this afternoon in advance of the main storm system. A moderate to high impact, long-duration late winter storm is next up from later tonight to early Wednesday. This is going to come about when a low pressure area moving eastward from the Great Lakes combines with low pressure moving north northeastward from off the Mid Atlantic Coast to just south southeast of New England. During its life cycle, the resultant storm will take the form of a slightly elongated center that will eventually consolidate into a more symmetrical center, doing a fairly tight cyclonic loop as it’s captured by the upper level low pressure area associated with it. Where this all takes place and how it behaves is key to what we see across the area for rain vs. snow, and of course snowfall amounts. A system like this comes with a fairly high potential for the forecast for some areas to not work out well, and this can include both under-performing and over-performing snowfall production. Keep this in mind when you see my snowfall expectations posted below. However, snowfall is not the only aspect of this upcoming storm. Wind will be a factor too, as well as coastal flooding to some degree, though limited. Let’s break down each aspect of the storm…
Precipitation: Starts as mix/snow across southwestern NH and the higher terrain of Worcester County in MA, and starts as rain in all other locations, moving in from southwest to northeast during the late night Monday to early morning Tuesday. The rapid deepening of the low center will initiate dynamic cooling, bringing cold air down from above, most rapidly where precipitation is heaviest but also a tendency to happen from northwest to southeast. This combination can sometimes prevent a clear-cut rain/snow line, with the changeover happening in a more irregular fashion. The last places to see this changeover take place should be the South Coast and Cape Cod as well as the Islands. Unless an area is under a heavy snow band, some of the snowfall will have a difficult time accumulating, especially the closer to the coast you are, during the daylight hours of Tuesday, but as darkness falls, the accumulation ability will improve quickly and that is when I am expecting most it to take place. The snow should then taper off from west to east in the pre-dawn to mid morning hours of Wednesday, and as the precipitation becomes light and more spotty, the dynamic cooling process will stop, and some of the showers will be falling as rain or a rain/snow mix, though this will be insignificant precipitation anyway by that point.
Snowfall totals for the event: Slushy coating to 2 inches Cape Cod / Islands as well as the immediate South Coast westward through RI and CT, 2-4 inches interior southeastern CT through south central RI to just inland from the MA South Coast up through the MA South Shore, as well as the tip of Cape Ann MA, 4-8 inches northeastern CT and northern RI through the I-90 and I-95 belt including Providence to Boston’s Metro West including the city of Boston (except 2-4 inches Logan Airport) and up to the immediate NH Seacoast, 8-12 inches central MA and interior southern NH lower elevations eastward to the I-495 region north of I-90, and 12-16 inches in the higher terrain of central MA and interior southern NH. Caveats for snowfall include the potential for lower amounts with a closer low center loop and a dry slot working into some southeastern areas, but a low probability of this occurring, or a potentially higher swath of snowfall (greater than 4 inches in my 2-4 inch area) in southeastern MA with a low center loop slightly further east and stronger snowfall banding resulting in this region. Adjustments will be made in the comments section (and next blog post) if necessary.
Wind: No issue Monday evening with just light to moderate east to northeast wind. Increases steadily and quickly Tuesday, peaking during the afternoon and evening while backing from northeast to north. Peak wind gusts are expected to be 35-45 MPH inland, strongest in higher elevations, and 45-55 MPH in coastal areas with occasional gusts above 55 MPH possible. These winds will gradually diminish while blowing from the north and northwest during Wednesday as the low center pulls away from the area.
Power outage potential: With temperatures not far from freezing, and in some cases slightly above freezing where it snows, snow load can become a problem for trees and power lines, and combined with strong, gusty winds, this will likely lead to scattered power outages, especially where snow load / wind gust combo is maximized.
Coastal flooding threat: Fortunately, this aspect of the storm will be limited due to astronomically low tides and strongest winds more from the north than directly onshore over a larger portion of the coastline. However, northeast-facing and north-facing shores most vulnerable will likely see minor to moderate flooding during high tide times Tuesday to early Wednesday.
Commute impacts: No issues Monday evening. Wet roads all coastal areas and metro Boston for Tuesday morning commute. Slushy roads at least partially snowcovered unless plowed in higher elevations of the interior. Tuesday evening commute most likely to see snow on road issues, most extensively away from the shores with more of a tendency for slushy or just wet roads right along the coastline unless snowing heavily at any given time. Just wet roads expected for the Wednesday morning commute and no issues for the evening one.
After the storm leaves us, improvement is expected for later Wednesday, and especially Thursday as high pressure builds in for a nice mid March Day, favorable for cleanup and recovery efforts in hardest-hit locations. Friday, a trough will approach from the west, and while surface high pressure tries to hang on, a warm front will head up from the southwest and across the region with some cloudiness, though precipitation chances seem to be rather low with this boundary based on current medium range guidance. Will reassess this potential during the week. One thing looks pretty certain, and that is a push of milder air arriving to end the week. By that time, the vast majority of the snow that will have fallen from our upcoming storm will be gone.
TODAY: Cloudy. Highs 39-46. Wind E up to 10 MPH.
TONIGHT: Overcast. Rain arrives except starting as mix/snow interior highest elevations of southwestern NH and north central MA. Lows 33-40. Wind E-NE 5-15 MPH, higher gusts in coastal areas.
TUESDAY: Overcast. Snow well inland and higher elevations. Rain changing to snow elsewhere. Snow will become heavy at times. Temperatures fall slightly to 30-37. Wind NE-N 15-25 MPH inland and 25-35 MPH coast, with gusts above 30 MPH inland and above 50 MPH coast.
TUESDAY NIGHT: Overcast. Snow tapers off gradually but still can be heavy at times in the evening. See above discussion for total accumulation expectations. Lows 28-35. Wind N 15-35 MPH, higher gusts especially in coastal areas.
WEDNESDAY: Mostly cloudy with snow and rain showers likely, becoming more isolated with time. Highs 35-42. Wind N-NW 15-30 MPH, higher gusts.
WEDNESDAY NIGHT: Mostly cloudy early, then clearing. Lows 25-32. Wind NW 5-15 MPH.
THURSDAY: Mostly sunny. Highs 41-48. Wind NW 5-15 MPH.
THURSDAY NIGHT: Clear. Lows 26-33. Wind variable up to 10 MPH.
FRIDAY: Variably cloudy. Highs 43-50. Wind SW 5-15 MPH.
DAYS 6-10 (MARCH 18-22)
Watch for a frontal boundary to pass through with a possible wave of low pressure on it bringing the good chance of precipitation – likely rain as it will be on the mild side for Saturday March 18. Breezy, dry, colder weather arrives for Sunday March 19. The early to middle part of next week looks mostly dry to start but there may be a storm threat before the end of the period with the potential for some precipitation.
DAYS 11-15 (MARCH 23-27)
One or two low pressure systems can impact the region with unsettled weather. Temperatures mostly below normal.
First, a warm front will cross the region today, parented by low pressure passing through the Great Lakes. A lot of clouds will accompany this feature, but it will be a rain-free day for the most part, with only a few light rain showers possible late in the day in areas north and west of Boston, and then a few more of those possible later tonight as a cold front swings through, passing offshore early Saturday morning. The air behind the cold front is not really that cold, so despite a developing gusty wind and dry weather on Saturday, it will be on the milder side. It won’t be until a secondary cold front comes through the region Saturday night or very early Sunday, possibly accompanied by a snow shower in northwestern reaches of the WHW forecast area, that we will be introduced to a little blast of cold air for the final full day of winter, fittingly, on Sunday, which will be chilly and windy, but dry. But we’re going to have a moderation in temperature just in time to welcome spring with the vernal equinox on Monday, and the first full day of the new season on Tuesday as high pressure sinks to the south of the region. After a cold start early Monday, a warm-up will commence, with continued fair weather.