Beyond The Forecast

Another Winter Storm will impact the Northeast and we are now about 24 hours from the first flakes.  Remarkably, there has been very little change in the overall picture since I last wrote yesterday morning.  I still feel the polar vortex is the most important player with this storm and it's track has wobbled a little from run to run of the models.  That slight shift has made a huge difference in QPF production as all of you know.  Despite the shifts over the last 24 hours we are pretty much in the same spot as yesterday with the max amounts in SE Mass...8-12"+!  At the moment, I'd make the 6" line from Boston to Worcester...north and west of that line there will be a sharp drop off in amounts down to just and inch or two in parts of Southern New Hampshire.  There really is a huge question on whether or not Boston gets into that the heavier banding caused by a 70kt low level jet at 3000 feet.  My initial gut feeling is that as the storm stacks up and bombs out off of the Cape it will have an opportunity (maybe brief) to slow and grow just large enough so that the better dynamics and moisture DO get into Boston...but probably no further...again a really close call. 

Timing:  We will luck out for tomorrow mornings commute, light snow and flurries will hold off until mid to late morning.  The snow will pick up in intensity during the afternoon with the height of the storm coming in the evening.  All the snow will taper off around midnight or shortly after so there will be plenty of time to recover for Thursday morning's commute.

Precip Type:  Expect it to be all snow just about everywhere except over the Cape and Islands and possibly along the South Shore Coast too.  Wind trajectories will be coming in off the water...out of the NE...most buoys are reporting temps in the mid to upper 30s, so the boundary layer will warm up more in those areas than across the interior.  Surface temps will be flirting with 32 if not 34 degrees so there may be some rain mixed in for a time holding amounts down.  However, as the storm consolidates and bombs out, ageostrophic flow will take over and winds should have more of a northerly component so any rain would be gone by early evening as the coldest air source will be tapped from Northern New England.

Snowfall Rates:  During the height of the storm, tomorrow evening, rates will likely be between 1 and 2 inches per hour.  There is very good lift being generated within the best snow growth layer which will be occurring as the winds go more ageostropic...so the air will be colder...thus not only will there be some heavy snow but it will be a drier snowflake...good for accumulating.

12Z stuff is coming in now...it's important to remember that the slightest shift either way will make a huge difference between very little and a whole lot!  Also, because there is such a fine line between really good dynamics and really bad dynamics models will continue to do this dance.

Get ready for our first big snowfall in over a month! It's been since the first few days of the new decade that we saw more than 6" of snow...our time has come. Unless there is a dramatic shift in the current path, which as we always know is possible, it looks like a wide swath of 6-12" of new snow will fall starting mid-morning Wednesday and Wednesday night. Along with the increasingly heavy snow will come increasing northeasterly winds of up to 40 mph in the Boston area  and possibly over 50 mph across the Cape and Islands. Things haven't changed much from Todd's explanation of the synoptics and dynamics involved with this storm (see below)...there will be a sharp cut-off line to the north between the 3-6" mark and nearly nothing up around Concord, NH. On the other hand it appears that some spots in Bristol, Norfolk and/or Plymouth Counties could see more than a foot by the time things wind down Thursday morning.

We narrowly missed that historic blizzard that buried the Mid-Atlantic over the weekend but the next storm in the pipeline looks much more promising!

The set-up:  A polar vortex will dive down from the Dakotas and link up with the southern branch inducing surface low cyclogenisis over the Deep South.  Out ahead of the powerful polar vortex PVA will spin up multiple surface low pressure centers as the entire system works into the Mid-Atlantic Wednesday morning.  The system will become vertically stacked from the surface to the upper troposphere by late Wednesday and Wednesday night in our coastal waters allowing the storm to grow very large and slow down.  The storm will drift toward the Canadian Maritimes by Thursday morning with wind and cold to follow.

Much of the computer guidance points to a track close enough for a sizeable storm for the Mid-Atlantic to here in Southern New England.  At this point I'd say that places south of the Mass Pike have the greatest chance for the most snow out of this one.  But that could easily shift a bit north.  Most should see a plowable snow with 6+"...topping out to around a foot.

Some thoughts:  There will be a fine line between a lot of snow and not so much snow and Southern New England is going to be right on that line.  There will be two snow producing lifting mechanisms at work with this storm and we need to get into both to get large amounts of snow.  One is the lift from the polar vortex the other is the lift from the warm air advection circulation.  So the way I see it, the track of the polar vortex is really critical here, out ahead of it lots of lift will be generated, leading to several inches on the front end of the storm.  If that vortex tracks too far south of us then we will be on the periphery of the significant lift and thus be on the low end of snowtotals compared to the Mid-Atlantic.  But if it tracks closer to us, such as is depicted in the NAM 6Z run, then the surface and 850mb low will track closer to us and not only will we see lift from the polar vortex but lift from the warm air advection as well and thus we'll get into the teeth of this thing and a widespread foot would be likely.

So, over the next several model runs that's what one of my eyes will be on...the most important part of this storm...the track of the polar vortex.  Your thoughts????

Like last night at this time, my confidence has again been rattled by the latest output of the models. The consensus shifts the action southward sufficiently to negate a walloping on Wednesday. It will not be a miss but the question remains just how much of a hit happens here. Since the new guidance from the Euro model is unavailable until about 1:30am, I have an uneasy feeling about bailing out of potential blizzard conditions over southeastern Massachusetts and parts of Cape Cod. The expectation of two storm centers forming over the Atlantic complicates the picture and adding the progressive feature of this upper air pattern yields a scenario unfavorable for a blockbuster. In conclusion, I will just say that the highest risk for a plowable event exists near and south of the Mass Pike. This uncertainty should be resolved late tomorrow.

Good Night and THINK SNOW my friends! 

1AM Thursday Map

Where will Mother Nature strike next? The atmosphere will become tightly coiled and the spring will release somewhere over the Northeast at midweek. Late last evening, I became less confident of a major smacking as much guidance received through 11pm tilted toward a non-event for our region. However, the latest model output from the more reliable Euro was not available until about 1:30am. Its succeeding daytime run depicts an amazingly consistent prognostication of a rapidly intensifying storm along the New Jersey coast Wednesday morning. With a very potent closed upper air low pressure system strengthening on the approach to the coastline, I am convinced that this scenario has bombogenesis written all over it. I suspect that a swath of heavy snow will develop and pinwheel into southern New England during the day and I feel that there is a reasonably high risk of blizzard conditions at times during the afternoon into the evening. Please keep in mind that this is not etched in stone presently. The stakes are high and there are many factors to consider. Any slight variations can produce a significantly different result for parts of the area. The upper air pattern is quite progressive. Consequently, I do not anticipate that this storm will decelerate. Instead, it should move steadily out south of Long Island and Cape Cod and out over the open Atlantic. As a result, I am not anticipating mammoth amounts of snow similar to what accumulated over Pennsylvania, Virginia, Maryland, Delaware and New Jersey yesterday. Nevertheless, a plowable event is probable especially over southern New England where totals could easily reach minimums of 6-12 inches. Northeasterly winds may exceed 50 mph particularly over southeastern Massachusetts and Cape Cod. We're still more than 60 hours away from this weathermaker so some revisions may indeed be necessary.

In the meantime, a cold brisk northwesterly wind will continue tonight and become gusty to 25 mph or so tomorrow. Temperatures will fall to the middle to upper teens tonight then rise up to the lower 30s tomorrow as sunshine may be interrupted by some passing stratocumulus clouds at times. On Tuesday, the wind will be lighter and it will warm up to the middle 30s as sunshine yields to some increasing high cloudiness in the afternoon. Jumping ahead, the storm will exit early Thursday with returning sunshine and a lingering gusty wind. There is no sight of any mild weather for at least 10 days.

Following a study of fresh guidance this evening, I will post an update near or after 11pm if conditions warrant any change in the current thinking.

Make it a good week!

Super Sunday is looking good! We will have sunny skies to kick-off the day with more clouds diving from the north this afternoon/evening.  Highs will still be a handful of degrees below normal today.  The work week starts on a quiet note, but models are flirting with a midweek storm that looks like it willl affect us in some way, shape or form.  This is where the models diverge.  The GFS phases the low from the north and the piece of energy (hook) from the south in a different locale and keeps it farther to our south which would affect areas like D.C., Philly, RI, Connecticut, and our South Coast/SE Mass and the Cape/Islands.  On the other hand, the EURO phases these 2 systems together in a different fashion and delivers more snow to southern New England as it pulls the system farther north.  Snow lovers should keep their fingers crossed that the EURO has it right this time.  Once again, we are watching this develop from model run to model run.

Super Bowl XLIV....New Orleans Saints v. Indianapolis Colts...6:35pm ET right here on WBZ.  Who do you want to win?

Happy Super Sunday!

Melissa :)

Could the Mid-Atlantic States get smacked again? Upon studying new guidance during the evening, I am becoming less confident of a snow event here on Wednesday. It is becoming more apparent that blocking in eastern Canada may remain sufficiently strong to force a potent vortex to shift farther south perhaps producing another period of heavy snow over parts of Pennsylvania, New Jersey, Delaware and Maryland. It is clearly too premature to forecast any snow amounts for this area yet. Consequently, I withdraw my earlier discussion that it seemed safe to predict the potential for a plowable event in parts of the area. I don't think that we can rule it out just yet but I'm now leaning more toward a non-event thanks to this persistent pattern. Watch for zigs and zags over the next few days.

Over and out.