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February Medium/Long Range Thread


stormtracker
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20 minutes ago, brooklynwx99 said:

Next week's system has become increasingly ominous and holds potential for significant to major impacts from DC - NYC and even BOS. There are a few features that make this such a favorable setup, mirroring past major and even historic storms:

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  1. The most important feature of this setup is the retrograding and decaying west-based -NAO that migrates into central Canada. This is perhaps the most important feature for major EC snowstorms, and it is a huge factor here, as it slows the pattern down and locks in confluence. It also leads to the "banana" HP that often develops in these setups due to NVA downstream of the block.
  2. This is a lobe of the polar vortex (PV) that is the impetus for the storm threat. This lobe becomes trapped under the block and will be forced to pivot under it, leading to a potential phase with the southern stream vort (x) over TX/OK. This kind of slow-moving, amplified ULL is also a main feature of major storm threats.
  3. As is common in these setups, a disturbance, either coastal or otherwise, amplifies into the northern Atlantic and becomes trapped by the block, leading to a 50/50 ULL that departs. This is crucial for establishing confluence, which keeps heights in check downstream of the amplifying trough. Note how heights are zonal over ME and Atlantic Canada.
  4. Last but not least, there is a transient spike in heights over the Pacific NW that links up with the blocking. This is a crucial piece of the puzzle... if that disturbance offshore destructively interferes with the blossoming +PNA, you get a weaker solution. However, the trend has been for constructive interference, which helps lead to downstream amplification.

It's also worth noting that this setup very closely mirrors past setups that delivered historic snowfall to the northern Mid-Atlantic. Yes, it's for NYC, but you guys generally want the same pattern, and there is a lot of overlap between HECS for NYC and BWI/DC. Notice the 500mb composite that has all four main features... the retrograding and decaying block, the amplifying trough over the MS River Valley, departing confluence, and a brief PNA spike as the storm is getting its act together.

1468332707_Screenshot2025-02-14145159.png.2ba7336f1f3a14a1d591eb03f9f77645.png

Suffice it to say, this is probably the best synoptic setup that we have seen enter the medium range since February 2021 (I'd run that one back down there if I were you guys) and it does hold the potential to be just as impactful. The GFS not being on board is pretty common in these setups. However, we will want to see this amplification signal enter the 96 hour window, so if we see this signal last into Monday, talks about a legitimate major snowstorm will hold more weight. Right now, it's worth being cautious, but the pattern has been screaming this kind of outcome for a week now, and it is bolstered by past outcomes.

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Just now, Miss Pixee said:

Knickerbocker storm was 28".

That was almost 100 years ago and measured at the Arboretum I think... not a runway on an island in the patomac river.  lol

They probably won't ever challenge that so long as they keep the official records at DCA.  

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1 hour ago, Ralph Wiggum said:

@Scraff SBI was reading high so ran out to stock the fridge. If all else fails, the cellar is loaded with stouts and imperial stouts. And if the storm falls apart, well, I won't remember it anyway

Fiddlehead, eh?  My recent favorite.  The brewery is 3 miles from my house here in VT.  I know where I am stopping on the way home tonight!

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12 minutes ago, dailylurker said:

On board? This is his storm. He started telling us about it about 6 weeks ago. Unbelievable, and if it happens will definitely trip me out lol

Yeah no kidding… many of us north of 70 hardly remember what a 6”+ storm (let alone double digits) even looks like or feels like to experience, or what it’s like to get many straight hours of +SN (ski trips notwithstanding)

I’m still a little cautious since it’s 5 days out and the GFS is a little doubtful, but seeing the upper level setup, plus PSU and possibly Millville going all in, makes me think this could be the big one we’ve all been waiting for years to see.

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5 minutes ago, psuhoffman said:

That was almost 100 years ago and measured at the Arboretum I think... not a runway on an island in the patomac river.  lol

They probably won't ever challenge that so long as they keep the official records at DCA.  

I think I read somewhere, can't recall exactly, but the location that would have been DCA measured around 20-21 inches in the knickerbocker storm. On the other side of DC, Rock Creek Park measured 33"

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Just now, Terpeast said:

I think I read somewhere, can't recall exactly, but the location that would have been DCA measured around 20-21 inches in the knickerbocker storm.

I thought it was 17.8".  Seems that specific location cannot measure more than that even if a short distance away gets well over 20"!!! :lol: (OK, I think DCA did record around 19" for the PD-I storm but all the other big ones since, seem to have been stuck at literally 17.8!!!)

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