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Tuesday 1/7/20 Disco snow event


MountainGeek
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Our Tues storm and what to expect will probably come down to how 3 packets of energy/shortwaves are handled as they progress eastward through the CONUS. Using the overnight Euro to show you what I mean.

Probably somewhat hard to see with this map but what we have are 3 shortwaves embedded within the trough below.

shortwave.gif.3951cacf3efded3f6fd21a3691444193.gif

Looking at the vort map will give you a much clearer picture of where these shortwaves are located. Now what we see in our region will be dependent on how these three packets interact/don't interact as they progress eastward. What we saw with the overnight Euro run is that there was pretty good cooperation between the three. Though it wasn't the cleanest of phases we did see energy packet 2 drop down on top of #3 over Oklahoma. Packet (2+3) then progressed eastward to where we then saw #1 drop down (again not the cleanest of phases) into it over W Kentucky/W Virginia. This cooperation between the energy helped to create a deeper drop of the 500's into the shortwave as well as a quicker turning of the shortwave as to where we were seeing it reach neutral status in the mid-west going negative through our region.

phases.gif.abf41c74f2789ef602537cfc406063c1.gif

 

The repercussions of the changes in the 500's on the surface with our storm can be seen below. Note that we are seeing stronger low pressures that have been shifted northward over the previous 18z run which is to be expected given a more favorable 500s for storm intensification.

 

stronger.gif.37d71d46109f319dab7961e69cd268fe.gif

 

weaker.gif.2784cc3b1cd711b4fd1faf9a907d723a.gif

 

Now seeing a stronger system is a double edged sword. It gives better rates to help overcome the lower level warmth for those that can stay in the snow sector but it also will tend to pull a system farther north compared to a weaker low. And you can the results of this below. Note that we are not only seeing better snows to the N and W due to the better rates but we are also seeing a decent swath to our NE as the low intensifies quickly enough to pull it up the coast vs. the previous run with the weaker low which headed OTS.

 

currentsnow.gif.5aa2999005438a076b197338045ab29c.gif

 

18zsnow.gif.524c1ba6082189922b4efbb207554630.gif

 

Looking over other models we are seeing quite a variance with how they want to handle these 3 packets of energy. Pretty much goes to show that what to actually expect come Tuesday might very well be close to a game day call.

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14 minutes ago, Weather Will said:

NWS not impressed two days out with the potential

 

2 big problems with this event for decent accumulations- bad set up for getting the surface cold enough- outside of dynamics, which could happen given the latest trends- and it's a fast mover.

At this point there is a decent chance some places NW of the fall line will see a solid coating to a couple inches. The trend towards a deeper system could up that potential. I see no shot for the coastal plain unless there are some dramatic changes. Surface is simply too warm.

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3 minutes ago, C.A.P.E. said:

^6z Euro is a tad south and colder. Probably some good snow tv to a light coating along I-95 verbatim. Nearby mountains and the hills up near PA line are clearly in the best position to pick up a couple inches.

Exactly...even out here I can see how this plays out.  Without elevation any accumulation will be in the last hour or two of snow falling....= slushy inch or so on non paved surfaces.  Only chance lower elevations have is if this juices up some as we we approach game time.  .2" qpf only works if it's cold smoke...

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2 minutes ago, poolz1 said:

Exactly...even out here I can see how this plays out.  Without elevation any accumulation will be in the last hour or two of snow falling....= slushy inch or so on non paved surfaces.  Only chance lower elevations have is if this juices up some as we we approach game time.  .2" qpf only works if it's cold smoke...

At least you have a short drive up the mountain if it fails in your yard. I drove up to Washington Monument State Park back before Xmas and it was a winter wonderland above 1000 or so feet.

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3 minutes ago, C.A.P.E. said:

At least you have a short drive up the mountain if it fails in your yard. I drove up to Washington Monument State Park back before Xmas and it was a winter wonderland above 1000 or so feet.

I make that my back way to/from work in situations like this. lol  While the creak valley has a slushy inch there can be 2-3" up there.  A temporary soul soother.

It's too bad this didnt move in just before sunrise.  Euro has temps in the mid 20s at 7am but 40 by 10am.  Maybe a thick cloud deck at sunrise will play out and temps struggle to rise much...long shot imo.

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1 minute ago, poolz1 said:

I make that my back way to/from work in situations like this. lol  While the creak valley has a slushy inch there can be 2-3" up there.  A temporary soul soother.

It's too bad this didnt move in just before sunrise.  Euro has temps in the mid 20s at 7am but 40 by 10am.  Maybe a thick cloud deck at sunrise will play out and temps struggle to rise much...long shot imo.

Or the precip gets here 6 hours earlier

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^ Not sure that would help. The air mass in place ahead of the storm isn't very cold- the cold temps in the AM are a function of long night/radiational cooling. The only high pressure around is a weak ridge moving off the east coast- that is not good for cold air advection. Look up north - nothing but low pressure. So temps will warm as the storm approaches and starts to deepen along the coast. The low level 'cold' comes in behind with the deepening trough, but it is a relatively low qpf, short duration event, so its too late for the lowlands. Pretty textbook for some modest wet snow for inland/elevated areas as currently advertised.

1578391200-gB7bjBhNTcg.png

eta- if the low is a little deeper/slower, and tracks a bit more to the SE, there could be a better outcome, as showme discussed in his post earlier.

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