BOX unenthused this morning, for both snow and fzra threats.
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights...
* Rain changes to sleet/snow Friday - minor accumulations most
likely with slippery travel possible
* Dry and cold over the weekend
Main concern revolves around potential for rain changing to sleet
and snow late Thu night and Friday as colder air works into region
behind cold front. Plenty of large scale lift in place courtesy of
right rear quad of upper jet and mid level short wave rotating
through New England, along with plentiful moisture with PWATs
climbing to around 1" courtesy of broad SW flow aloft.
Challenge for this forecast is how quickly and how deep cold air
gets into SNE which has a direct impact on precipitation type and
resultant snow/ice amounts. Majority of models present an overall
warmer solution with slower transition to sleet and snow during day
Friday, while GFS remains the cold outlier and has a much faster
transition taking place Thu night and Fri morning, even down to the
South Coast. In fact, models have quite the temperature difference
Friday morning with NAM showing temps in 40s and 50s near coast
while GFS has temperatures below freezing! This colder solution
seems to be result of GFS having a much stronger surface high (1044
mb) over southern Canada as opposed to NAM, ECMWF, and Canadian
which have a weaker high (1030-1035 mb). Looking at individual
ensemble members, they all support their operational runs but some
of the Canadian members do have the stronger surface high.
At this point it is premature to jump on to the colder and more
aggressive solution, since it can be considered a low chance at this
point, but we can`t rule out this outlier solution completely
either. Leaning more toward NBM guidance, which gives a reasonable
compromise, suggests transition from rain to sleet and snow from
north to south Friday starting near VT/NH border before daybreak
reaching Hartford-Worcester-Boston Fri morning, and progressing to
Cape Cod Canal early Fri afternoon before reaching outer Cape and
Nantucket later in day.
Low level cold air should deepen quickly, such that threat of
freezing rain is minimal during transition. However we do think
there will be some impact to travel as temperatures drop below
freezing and transition to sleet and snow results in slippery
travel. It`s possible that Winter Weather Advisories will be needed.
Best chance of seeing minor snow accumulation is along and north of
Mass Pike, where a couple of inches is possible, with little if any
accumulation farther south.
Keep in mind snowfall totals are highly dependent upon the
changeover timing. Although we have a good idea on trends right now,
we probably won`t have a better handle on exact timing until we get
into window of high resolution models Wednesday night or even
Thursday.
Beyond Friday, it does appear that cold and dry weather will
dominate this weekend as high pressure builds over New England. A
weak low passing SE of region may bring some light snow Monday, or
rain/snow near South Coast.
