Good morning folks, after a very cold start below zero this morning, we will “warm” up into the low to mid 20s #Balmy
Clouds will be increasing through the day, with high clouds streaming in first, producing an obscured star with silvery snow sky as a result, which I love.
Low pressure now over Indiana will meander east and weaken. Its upper level low component will swing energy around its southern and southeastern flank and secondary low pressure will develop along the Virginia coastline by tonight.
As a result, clouds will thicken and lower tonight, with lows in the mid to upper teens, with a light wind.
NOR’EASTER SETUP
By Monday morning, our secondary low pressure system will be tracking northeast off of the DelMarVa coastline, east of New Jersey, and will be strengthening.
At the same time, we’ll classically have a cold, strong high pressure system north of us over Quebec Province which will help produce an increasing pressure gradient between the low to the south and the high to the north.
With clockwise circulation around the high and counterclockwise circulation around the low, we will generate our moist east and northeasterly winds off the Atlantic Ocean, giving rise to our Nor’easter by Monday afternoon.
A NOTE ON SNOW ONSET
The onset of snow looks to have sped up, which means that it could be snowing in the northern counties of CT by mid to late morning, and then spreading slowly northward into the early afternoon in the WMass and CMass region, with first flakes by mid afternoon-ish in SVT and SWNH.
Light snow accumulations are expected by sunset across much of if not all the region (some very light accums. are possible north of the MA/-VT-NH state line).
By Monday night a strong easterly and east-northeasterly low level jet streak (i.e. a faster river of air about a mile above our heads) will be helping to slam moist air off the ocean and into central MA and western MA, as well as northern CT.
This should help produce a heavy thump of snow over Worcester County, northern CT and southwest NH, as well as the western hilltowns and eastern Berkshires. The biggest snow impacts will be experienced by late afternoon and especially Monday evening and night until the early pre-dawn hours when a dry slot or area of drier air aloft entrains into our storm system, which will cause lighter snows and may change the crystal type from big, fluffy, stackable dendrites to snowflake types that don’t accumulate as well or as high, so that is something to watch for.
Also, in the CT River Valley some “shadowing” is possible, so for those who didn’t read the report last night, let’s take a detour into that for a minute (if you read it, you can scroll down).
SHADOWING
To start, rising air in a saturated-or-moist-enough atmosphere creates precipitation eventually, whereas sinking air tends to dry out precipitation shields, or the air below the downward-moving parcel, generally speaking.
In the valley of western MA (and northernmost CT and southeasternmost VT sometimes) if a Nor’easter passes to our south and produces a more easterly wind (traveling from east to west), we can get what’s called shadowing.
What happens is moist easterly flow slams into the Worcester hills and dumps heavier snows there, and this can also last into the hilltowns of eastern Franklin County and eastern Hampden County (and to a lesser extent, the towns of Pelham, Ware and Belchertown in eastern Hampshire County).
Then, as the air drops off and descends into the valley floor, that subsidence (which means sinking air) dries out the snow shield, and causes much lighter snow to fall, reducing accumulations, and this could happen with this storm system.
Finally, that same air keeps trucking and rises back up into the western hilltowns and eastern Berkshires and heavier snow picks back up, if the flow is strong enough.
NOTE: This phenomenon will likely be predicated on our coastal low meandering around off the NJ coast and prolonging an easterly or east-northeasterly wind. We have to see how that low tracks, stalls, or if it elongates and spins off another low to its east. It’s complicated, kinda like me!
PEAK OF STORM
Travel will go downhill as snow becomes steady and moderate to heavy by late afternoon and evening, so plan accordingly.
Snow will fall heavily at times Monday night at the rate of 1-2″ per hour at times, and by the pre-dawn hours of Tuesday sometime, snow may become light to moderate, and intermittent, and I will update on this tonight.
Snow may linger on Tuesday as the secondary low isn’t going to be in a hurry to get out of here given the fact that it will have atmospheric traffic to its east and northeast due to blocking high pressure.
BLIZZARD-ESQUE CONDITIONS POSSIBLE
While a blizzard is very likely not going to verify with this storm (that is 35mph wind or frequent gusts for 3 contiguous hours or more along with 1/4 mile or less visibility during that time), we could have some blizzard-like conditions at times in the Worcester County highlands, the Monadnock Region, northeast CT, and the western hilltowns/Berkshires/Litchfields, which would likely happen (if it did) Monday night into the very early pre-dawn hours of Tuesday morning.
Highest wind will be in the Worcester highlands and high terrain west of the I-91 corridor, where some outages are possible.
SNOW CONSISTENCY
This won’t be complete powder, but should be fairly dry, though heavier wet snow is possible east of I-91, especially in Worcester County where isolated outages are more likely to occur.
AMOUNTS
I think that assuming the low center doesn’t hug the coast and pass over Martha’s Vineyard or west of Nantucket (which we can’t rule out yet) Worcester County and northeast CT should get hammered by this storm, and some power outages will be possible there with accumulations of 10-15″. This may extend into easternmost Hampden County as well as the high terrain of eastern Franklin County.
I think the Pioneer Valley from Greenfield down to Hartford will see more like 5-10″ of snowfall, with the lower end of that range possible if the downsloping/shadowing effect really sets up.
I think the western hilltowns and Berkshires up into SVT and down into NW.CT will also see 10-15″ of snowfall, including Brattleboro. Southwest NH should fit into this range as well.
UNCERTAINTY AROUND MULTI-LOW OUTCOME
I am unsure about how this shadowing effect will setup exactly. I just don’t know, to be honest, and that will impact snow totals in the Pioneer Valley floor from Greenfield south to Hartford.
We also may see more than one low center develop south of New England, and these may meander or wobble around to our south Monday night and this may impact the dry slot, how fast it gets in here, where it does, and how it breaks up or keeps in tact the precipitation shield overhead.
All that said, I doubt these amounts would go up from here (though you never know), but this storm could bust LOWER for some, ESPECIALLY IN RIVER VALLEYS (Housatonic, Connecticut, southwest VT in Bennington, etc).
TUESDAY NIGHT THROUGH THROUGH THURSDAY
Snow showers should abate Tuesday night with lows in the low to mid 20s. This storm is not existing super fast, so lingering clouds will be around on Wednesday with highs in the upper 20s to low 30s and lows in the upper teens to low 20s.
Thursday looks like a sweet day with highs in the low to mid 30s under mostly sunny skies with low sin the 20s as clouds increase.
FRIDAY AND BEYOND
Several systems are possible during this timeframe, with mixed rain and snow possible Friday, but I need to focus on this storm in front of us, which will alter streamflows that will follow it, which will impact how those future systems track and develop.
So, as in life, we’ll put one foot in front of the other and deal with what’s in the present moment, breathe deep, and engage.
Have a great day, and please stay tuned for my evening report!! I will try to get it posted no later than 7pm!