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January/February Medium/Long Range Disco


nj2va

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Just now, StantonParkHoya said:

Quick question for my own understanding: at what point does sun angle start making a difference in marginal events? Early Feb? Mid-Feb?

Oh boy. Sun angle doesn't really matter until March.. By that point, you need heavy rates to cave surfaces and the snow would melt a couple days later anyways depending on what time of march it is

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7 minutes ago, psuhoffman said:

dude a full CONUS trough with that kind of blocking is a great look.  A HUGE full lat PNA/EPO ridge is great if you want to hit -20 but not necessarily what we want to get a lot of snow if we have blocking.  Now in a progressive pattern without any NAO blocking...a PNA ridge is a must.  This is all a game of moving parts and different ways to get the longwave pattern right for us.  There are multiple ways to do it but the one that gives us by far the most wiggle room and leeway is a west based NAO block.  There are a LOT of ways to work with that.  

What is the advantage of a broad trough over a sharp one?  I would think a sharper one with greater amplitude would create stronger storms?

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Just now, JakkelWx said:

Oh boy. Sun angle doesn't really matter until March.. By that point, you need heavy rates to cave surfaces and the snow would melt a couple days later anyways depending on what time of march it is

I'm not sure that is true considering February sun angle is similar to that of late October, early November.

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Just now, StantonParkHoya said:

Quick question for my own understanding: at what point does sun angle start making a difference in marginal events? Early Feb? Mid-Feb?

Depends how marginal...it can start to matter in late February if we are talking a very light event with near freezing temperatures during the middle of the day.  Generally though if we are talking decent rates and surface temps around freezing or below...we are good through the first week of March.  But even after that... we have seen SO MANY examples of how it can work if we get the right pattern and a cold enough profile even after March 10th.  The issue is it becomes increasingly hard to get that as we move later in the year.  The much bigger problem is the dumb angle which seems to have a major impact 365 days a year!

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1 minute ago, JakkelWx said:

Oh boy. Sun angle doesn't really matter until March.. By that point, you need heavy rates to cave surfaces and the snow would melt a couple days later anyways depending on what time of march it is

Depends on rates.  I just watched 6 hours of light snow and snizzle melt on contact on hard surfaces at 29F on Sunday.  

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1 minute ago, EastCoast NPZ said:

What is the advantage of a broad trough over a sharp one?  I would think a sharper one with greater amplitude would create stronger storms?

Sharp trough can help spin up stronger storms but the tradeoff is a much narrower qpf field. Broad troughs allow storms to really draw in the moisture so a weaker lp system can dump more QPF over a wider area. Personally, I prefer a broad trough and more W-E trajectory vs a sharp trough with a S-N trajectory. The margin for error is typically a lot larger. 

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1 minute ago, EastCoast NPZ said:

What is the advantage of a broad trough over a sharp one?  I would think a sharper one with greater amplitude would create stronger storms?

If you have a monster ridge in the west along with blocking and a 50/50 low its going to create an extreme NW to SE flow into the east and just overwhelm the pattern with cold and likely push the baroclinic zone way off to our southeast.  A broad trough like that will allow systems to come at us from the west...without a block that would be bad but with a block they will generally be forced under us.  They might not be BIG HECS level storms but we could be talking waves every few days coming at us and lately just about anything seems to have a ton of QPF with it so...  Sometimes something that would be bad in one pattern is good in another.  

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16 minutes ago, psuhoffman said:

We had two accumulating snow events into DC last March.  One was a borderline warning level event on March 20th!  I am almost 100% certain that would have been a HECS level event had it been February and not March 20th.  Not sure what "didnt work" about the pattern last year except it came too late to reach full potential.  

Drive up I-5 in California to Washington state and tell me if you see any snow. 

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1 minute ago, Jandurin said:

doesn't matter and doesn't really matter are different things

obviously we'd snow a lot more here if the sun never came out at all

Just speaking for myself living near sea level, the reduced sun angle of Dec and Jan can overcome the challenges that folks at increased elevation don't have to worry about until late Feb and March. To make a blanket statement that sun angle isn't an issue until March goes entirely against what I see year in and year out. 

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1 minute ago, DCTeacherman said:

The cold front hasn’t passed yet so it makes sense to me. 

There's not even really a "cold front'. It's a cool front at best as there is no effective HP behind it. We're going to get a lot of looks on this one and there's plenty of time for things to change (in any direction). 

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12 minutes ago, Bob Chill said:

Euro holds the big trailing storm idea but there's no hp anywhere near where we need it for a cold feed. However, 6 days out and a lot can change. Track is good. Temps are not. 

is there anything dr no will ever not say no to?

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Just now, Ji said:

is there anything dr no will ever not say no to?

I have a hunch it's going to toss out a snowstorm solution before the weekend is over. Probably won't look anything like what we're seeing right now. The changes going on in the high latitudes are going to cause significant swings in model solutions until further notice. That's my theory and I'm sticking to it. 

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