Long Duration Complications

By:  Lionel Hutz
December 9, 2014 5:53 am | Category: Weather

Last week I discussed complications. Nothing has changed since then, life is still complicated.

First, it is going to snow Tuesday into Wednesday. And the pieces are in place for it to keep snowing (in the mtns) at least Wednesday night into Thursday. And then likely Thursday into Friday. That’s all well and good and really awesome. In theory.
Well, the weather gods or the old gods or the whatever gods say fuck theory and give you the sloppy wack-a-do mess of a storm that is on our doorstep.

So lets break this down.

Today, a low pressure center is going to move north by northwest (already weird) and interact with a large trough dropping out of Canada.

In the current analysis you can see the large upper level trough and surface low very clearly.

500mb:
500mb

surface:
surface

Last week I thought this “phasing” would not occur until the trough (well the critical exit region of the jet associated with the apex of the trough) was offshore to our east. I expected the cold high pressure of today (Monday) to be a little less french and resist movement. Nope.

As the oceanic low pressure interacts with the trough today, upper level divergence will spark surface deepening and rapid strengthening. This will wrap the system up into a tight little ball that will track towards Long Island during the day Tuesday.

Tuesday into Wed. AM:
output_RpUGRP

The first signature of this storm will be a VERY strong wind anomaly drawing air and moisture in from the east and moving towards the west. This is typical in coastal low pressure systems as part of the triple jet structure, however in this case the west-flowing oceanic mid level jet will be very strong and draw an extraordinary amount of Atlantic moisture into the system.

The result is a very heavy slug of precipitation at the outset of the system. Given that temperatures will be cold enough through out the whole column of air for m the Northeast Mtns (Cats, Berks, So. VT, Nor. VT, Maine, NH) for this first round of moisture to be mostly all wet snow. So beginning Tuesday mid-day and progressing through Wednesday AM the N/E will see a period of heavy snowfall, 1-2″ an hour at times. By Wednesday am, a widespread 8-12″ is likely.

nam_namer_036_precip_p24

If the story ended there, we’d all be happy. There would be much rejoicing. I prob. also would have ranted at the outset of this post. (Ok, I might have). Our story gets weird from here.

Instead of tracking northeast as coastal lows are want to do, this one will occlude and be drawn in under the upper level (500mb) low center. THis is the second signature of this storm. As the low does this, it will moves westward in over Mass, NH and So. VT. This will push a nose of warm mid-level air into the Northeast on Wednesday.

gfs_namer_048_850_temp_mslp_precip

Areas to the east of the low pressure center will see temps move above freezing. Areas to the west (ADK) will likely see the column remain mostly cool. Where the boundary sets up between YEA! and Sad Trombone will be somewhere over VT.

Right now it looks like maybe that line wavers back and forth over the spine. My best guess though is that during the day Wednesday, that line sets up west of the spine. This isn’t a very moisture rich movement so the result will likely be generally light mixed precip. and drizzle over the “warm areas” and light snow back west of the ADK.

Once the surface and mid-level low pressure centers cut-off and stack under the upper level low, we say it has become “vertically stacked” and generally stagnant. From Wednesday night to Thursday our lil’ buddy will sit and spin as a stacked cut-off low over VT. Though it will be cut off under much cooler air as the strong flow of air from the east as been cut off.

output_jWu7t4

During this period, an impulse will interact with the low and spark a round of heavier precip. to the west of the low (likely the Northern ADK) and generally light snow showers will persist as the moist rotating low interacts with mountains and some minimal upward lift occurs. The best chance for this to happen will be Thursday night as the center of the low moves eastward and the prevailing flow turns North/Northwest and some real orographic signatures begin to show up.

The low will exit the region on Friday and clearing skies likely for the weekend.

So what does all this add up to?

Snow by Wednesday mid-day likely a widespread 8-12, with some pockets a little higher down by the Catskills, and maybe Western Maine, and along with the high elevation ADK.

Additional snow through Thursday mid-day – Mostly drizzle/snizzle with possibility for more (2-4″) in the Northern ADK.

Additional snow Thursday night – Friday AM – Likely a few more inches widespread in the ADK and Nor. VT with the most in orographic favored areas.

Mid-December Storm Prediction

Now, there is a somewhat reasonable historical analog to this storm. In late February/Early March 2010 two storms moved in off the coast like this one and just PASTED the Northeast. I use “pasted” because it was pure paste. Like 2.5″ of water resulting in 18″ of snow. The place that did the best, in that event? The Catskills and the ADK where enough northerly cold air was drawn in to allow the mess to remain a snowy mess. Will this play out the same way? Possibly.

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Related Stuff:

  1. Major Winter Storm “Fox” (REVISED FORECAST)
  2. Mid-Week Storm Complex to Bring Snow to Northeast (Wed Update)
  3. March of the Storms
  4. Long duration event set to affect Wasatch range (UPDATED Sat. 11/20)
  5. Upper Level Low putting the ULL in Ullr? (Update as of 1pm Tuesday)
  6. Complications

2 Comments

  1. elmoreman
    wrote on December 9th, 2014 at 2:01 pm  
    1

    looking good! Just bump out that blue circle to include the Worcester range north of Montpelier :-)

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  2. bushman
    wrote on December 18th, 2014 at 8:52 am  
    2

    JP wound up with 24-30″ when all done. First batch was heavier but end stuff light. Was able to taste it Sat & Sun. As temps dropped heavier stuff stiffened forming pretty good base for this early. The usual ice-sheeted trails were real nice–mashed-potatoes on grade that were carveable with a little on top. For pre-Christmas it was great. Looks like another system coming in this WE. Thanks Lionel

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