Active Weather Period Over the Next 96-Hours

We are in store for one helluva roller-coaster ride weather wise over the next 96-hours and that ride begins well as I speak.  A powerful Arctic cold front is set to push through southern New England later on this evening and as this front plows through temperatures will really bottom out as lows tonight will be in the single digits to around 0 and even maybe slightly below-zero in some spots and that's without the wind chill.  While it has been quite gusty today the core of the strongest winds have yet to arrive.  There are some differences within the NAM computer forecast model and GFS forecast model as to what the higher end of the wind spectrum may be, however, both models are very impressive with the maximum wind gust potential.  Looking at some bufkit soundings from the latest afternoon run of the 4km NAM model across some selected locations across southern New England (Windsor Locks, CT, Worcester, MA, and Chatham, MA) the 4km NAM is suggesting that the maximum wind gust potential could be as high as 70-80 mph late this evening.  With this range we are talking about minimal category one hurricane-force gusts.  The NAM also has the profile mixing nearly dry adiabatically up to about 9,000' (~700mb) which is incredibly impressive.  Given how this may be a tad overdone and we have to consider friction, the extend of these winds are possibly a bit too high, however, 65-75 mph wind gusts are certainly possible and this is what the GFS model indicates for highest gust potential:

(NOTE:  I only showed 18z NAM bufkit soundings...even though the winds atop mixing layer are probably overdone b/c this was latest data available as 18z GFS bufkit was not out)

With winds increasing further this will not only set the stage for the possibility of scattered to numerous wind damage (downed trees/limbs and power lines) but with temperatures dropping further we will be looking at very dangerous wind chill values which could be as low as -10F to -20F.  Values these low can lead to frostbite in a short amount of time for any exposed skin.

While high temperatures on Friday will be much colder than today (not getting out of the teens in many locations) the winds will not be as strong as today, however, gusts could still get into the 20 mph range and we will once again deal with near dangerous wind chill values (as low as -10F).

One other note of interest with this brutal Arctic airmass is how close to the ground the stratosphere will be.  This point-and-click forecast sounding for a location in western MA for about 10:00 PM tonight morning shows the tropopause (layer which separates the troposphere from the stratosphere) being only around 9,000'-10,000ft off the ground...very impressive for these parts:

This brutal Arctic cold blast will be quite short lived, however, as late Friday night into the early part of Saturday our next weather system begins to impact the region.  Like with last Sunday into Monday we will once again see a developing storm system track well off to our north and west and this means we will eventually warm things up (and actually quite substantially) but before that happens we will have to deal with quite the wintry mess.  We are looking at accumulating snows for pretty much everyone (with the further north you go into southern New England the higher the potential totals) before everyone eventually transitions over to some sleet, freezing rain, and then some rain and then temperatures begin spiking up all the way into the 40's, 50's, and maybe even near 60F in some spots before the cold front pushes through Sunday night and some much colder air filters back in.

Given the extent of the airmass we will have in place it will take some time to really get the surge of warmer air into the region, thus we will begin as snow.  As always with these setups, the biggest question is how quickly does the warm air move in and how much precipitation falls as snow?  By 7:00 AM EST Saturday morning some shortwave energy moving through the jet stream aloft will be just off to our west which will help enhance the degree of atmospheric lift.  At the same time we'll have the main surface low pressure well off to our west across the Ohio Valley region:

  Due to the fact there will be no amplification of the jet stream/short wave energy (the short wave energy is also not really consolidated and compact) the system isn't expected to strengthen all that much and most of it's strength will really be from the influx of warmer/moist air from the Atlantic Ocean and cold dry air working around the backside of the system (creating a good thermal gradient which helps these systems intensify) so we aren't really looking at a powerful system.  In fact, the system may begin to weaken which will ultimately shut down the influx of warmer/moist air into the storm and the precipitation will begin to "shut off" and the axis of heavier precipitation moves off the coast:

Region wide temperatures will be certainly cold enough for precipitation to begin as snow and the first flakes should begin to fall during the overnight hours of Friday into Saturday (between 1:00 AM and 4:00 AM).  There will be some dry air in place initially, however, the profile will begin to saturate rather quickly.  As we move through the early part of Saturday morning some stronger atmospheric lift will push into the region and with this we will see periods of moderate to perhaps even some heavy snows.  At the highest snowfall rates may approach 1'' per hour and given we are looking at snowfall rations perhaps as much as 15:1 the snow will be quite fluffy and will accumulate rather quickly.  Looking at some bufkit profiles for a few locations across southern New England, initially snow growth may not be the greatest but they quickly become better (you want the yellow contours to be right between about 12,000-18,000ft with the -15C isotherm running through it ).  This is great for developing those fluffy flakes.  The next thing you want is to be able to lift parcels/moisture into this region and for that we look for those thin red contours (omega) which indicate vertical lift.  The more contours (and negative the number) the greater the lift.  Looking at these soundings we do have some red contours intersecting this great snow growth zone, however, not a great deal of red contours.  While lift will not be extremely heavy (this will preclude rates exceeding 1'' per hour) it will be sufficient for a period of moderate to perhaps heavy snow:

By early afternoon, however, much warmer air begins to filter into the region and as this warming occurs we will see a transition from snow to sleet/freezing rain, then rain beginning from south to north:

With all this said this is what I am expecting for snow.  Keep in mind that mainly everyone south of the MA Pike (and even a bit north of the Pike) will eventually transition over from snow to rain.  While some areas will see some freezing rain this should be be a major concern as the stay will be brief:

We aren't done just yet!  As Saturday progresses, we will continue to see a very strong push of warm-air advection, both at the surface and in the lower-levels of the atmosphere.  In fact, overnight Saturday into Sunday temperatures about 5,000' off the ground will be approaching the 50F mark and we will feel this warmth at the surface as well with temperatures rising into the 40's/50's and maybe near 60F in spots by 7:00 AM EST Sunday morning:

This warmth arrives just ahead of another cold front which will push through sometime mid-to-late afternoon.  With the warmth, however, just ahead of the cold front we will deal with yet another period of moderate to perhaps even heavy rain and we can't even rule of a thunderstorm as well, especially if some low-level instability develops thanks to the surge of warmth/moisture in the lower-levels of the atmosphere.  Once the cold front passes through we are back towards cold temperatures with overnight lows Sunday into Monday back into the teens/20's and high's on Monday only into the 20's.  This is certainly going to be a roller-coaster of a ride and certainly some active and very interesting weather!