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Feb Long Range Discussion (Day 3 and beyond) - MERGED


WinterWxLuvr
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Nice discussion(as usual) from Mount Holly-

Thursday: A rather nice (if you like wintry weather) sfc configuration will be in place over our area on Thursday with a robust cold high positioned north of the area, with the resulting NE flow creating a nice CAD setup. However, the upper-lvls will be a bit less favorable, with the the H5 trough-ridge configuration being shifted a bit west of the "textbook" positioning. This results in a slightly more westward track of the surface/850 lows, with the consensus track of the sfc. low being just offshore of the NJ coast on Thursday night, while the 850 wave would pass overhead. All that being said, the trend over the last couple days has definitely been colder with this system with the east coast ridge trending flatter and the northern High trending stronger with each guidance cycle. Consequently this setup would likely result in a general thump of snow Thursday morning into early Thursday afternoon, before warmer air arrives aloft and we see ptypes transition from S-N to sleet/freezing ran/rain Thursday afternoon into Thursday night. The main questions now are how long-lasting and powerful that initial "thump" of snow is, and also how quickly the column warms . Given a solid 600-700mb FGEN signature in the warm advection regime, along with increasing UL divergence in the right entrance region of the northern jet, would not be surprised if the initial snow-thump packs a punch, and many locations could pick up several inches of snow fairly rapidly on Thursday. Given the robust CAD setup would also not be surprised if many locations NW of I-95 never get above freezing and thus see only frozen precipitation during the entirety of the event. This scenario would also largely alleviate any hydro concerns as the warm temperatures/rain would not fall on the areas with the healthiest snowpack. The one real dissident solution to the general evolution described above is the NAM, which has the system more amplified and further west, and as a result has a howling (70+kt) SWrly 700mb jet moving through the area early Thursday. This results in rapid warm advection aloft, with a very quick transition to sleet and thus limited snow accumulations, with also a fairly pronounced dry slot. The NAM can certainly act as the "canary in the coal mine" for warm nose potential in these setups so it can`t be discounted off hand. However, at the same time feel it is sufficiently at odds with the consensus synoptic evolution that it was largely ignored in this package.

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25 minutes ago, high risk said:

      I think that we should be all be spooked at least a little, but it's just so darned different from pretty much everything else that I'm still going with "synoptic outlier".  

Careful apparently letting the NAM spook you wrt mid level warmth qualifies as “going off the rails” to some ( @leesburg 04 ) around here.  
 

I agree is probably just an outlier.  It’s not stringing out the energy like the globals and that allows the primary to amplify and push everything to our NW.  Its so different from everything else (except the SREF which like that idea too). If I HAD to bet I would favor the globals but I don’t feel great with the NAM showing that. Given all the recent let downs I’d like to have it on board before letting myself get overly optimistic about the big snow totals being indicated by everything else. 

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8 minutes ago, Warm Nose said:

Any other year we would say the NAM is out to lunch and toss.

But this is the one year where it's caught on to things before the others. It's been alone before this year but the others have caved. Will that repeat this time or is it simply mishandling some piece of data that the others don't?

This is just my rule of thumb and anecdotal. When meso's have 2 events in their range to deal with, it's always best to wait until the first one is out of the picture before fretting solutions that are vastly different than the globals beyond that. The whole time/compounding error thing can often go haywire with mesos. Also, meso's biggest value is short range and not mid. Still a day or more away from being in the short range. 

Not saying the NAM wont nail it. Just that if you're trying to actually forcast and not weenie out, a blend of guidance and much less weight on outliers helps keep your job

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5 minutes ago, psuhoffman said:

Careful apparently letting the NAM spook you wrt mid level warmth qualifies as “going off the rails” to some ( @leesburg 04 ) around here.  
 

I agree is probably just an outlier.  It’s not stringing out the energy like the globals and that allows the primary to amplify and push everything to our NW.  Its so different from everything else (except the SREF which like that idea too). If I HAD to bet I would favor the globals but I don’t feel great with the NAM showing that. Given all the recent let downs I’d like to have it on board before letting myself get overly optimistic about the big snow totals being indicated by everything else. 

You're welcome for pointing out your flaws, hopefully you become a better poster for it because now you at least admit that it spooked you and you weren't "just" interpreting the model

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I see two camps. One wants to be reasonable and chuck the NAM. The other is ready to jump. I'm going to put this out there before the rest of 18z starts rolling in because I don't want to seem like I'm just rolling with the waves. 

When the mesos start trying to pull the globals back to reality, the writing is on the wall. I like where we're at right now considering where we were at two days ago, but to underestimate the NAM at this point--which I've tried to mention many times this winter is a good model--would be foolish. This just isn't a setup that's very conducive for us. We're lucky to have this shunting mechanism but it can only do so much. We're still threading the needle. 

Maybe I'm playing my own sublimation game and overcompensating to protect myself, but I think it's a pretty big stretch to hope for WSW criteria at this point. For me, I'm just happy if we get a storm that produces water in frozen form to any extent. Anything more than that is icing. 

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7 minutes ago, stormtracker said:

RGEM a bit warmer on the front end but basically remains the same in terms of trajectory.  Nothing like the NAM.  Hell of a sleet bomb after the changeover.

It can still eat it though.

The rgem is acceptable. But it was a baby step towards the NAM. That’s not something I want to see. Frankly I don’t want signs they will “compromise”.   A compromise is a minor snow to ice event. No thanks. I signed up for the euro/para/uk 6-12” of snow package. I’m not settling for some pathetic run of the mill 2-4” to mix event.  

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