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End of March, beginning of April "could it snow again" talk


HM

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HM and Matt both mentioned an April window. Is that going by the wayside?

 

Tho honestly April snow is fake.. #climo

 

If it wasn't for the time of year, I'd be hyping the crap out of 4/5-4/10 (Matt's window). The problem, besides it being April, will be the tendency for the Plains/W-C warmth to limit the cold air coming down. Otherwise, the NAO / Atlantic become favorable for another coastal storm threat then.

Here's the good news for you: typically, El Nino-type forcing promotes a ridge in the means over the Midwest-Northeast as we move deeper into spring. Eventually, that ridge is going to win; but, we have a few hiccups to get through, both with the tropical forcing itself and the NAO.

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If it wasn't for the time of year, I'd be hyping the crap out of 4/5-4/10 (Matt's window). The problem, besides it being April, will be the tendency for the Plains/W-C warmth to limit the cold air coming down. Otherwise, the NAO / Atlantic become favorable for another coastal storm threat then.

Here's the good news for you: typically, El Nino-type forcing promotes a ridge in the means over the Midwest-Northeast as we move deeper into spring. Eventually, that ridge is going to win; but, we have a few hiccups to get through, both with the tropical forcing itself and the NAO.

 

Huge GEFS support for this window. Everything is there for a threat, not using Analogs:

1. Retrograding helps boost ridge in West

2. NAO signal peaks early April and retrogrades with 50-50 low / cyclonic wave breaking in Atlantic.

3. Split stratosphere supports NAO and holds cold air source in Canada.

I love this potential, I just hate the date.

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Lol ggem.

The 4/4-4/5 system is a legit snow threat for the interior, especially if the NAO can remain more negative than today's 12z GEFS/GFS solutions. The NAO peaks in next 3-5 days and then from there models diverge significantly. Some erode the block quickly while others, like the GGEM, do not. This will make or break this threat.

Cyclonic wave breaking happens as the surf zone/background wind relaxes with sufficient gradient. This is exactly happening after this week and is a good way of ruining early spring around here. It is also a great way for seeing late season wet snow.

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The 4/4-4/5 system is a legit snow threat for the interior, especially if the NAO can remain more negative than today's 12z GEFS/GFS solutions. The NAO peaks in next 3-5 days and then from there models diverge significantly. Some erode the block quickly while others, like the GGEM, do not. This will make or break this threat.

Cyclonic wave breaking happens as the surf zone/background wind relaxes with sufficient gradient. This is exactly happening after this week and is a good way of ruining early spring around here. It is also a great way for seeing late season wet snow.

It's kinda funny this year that threats never stop appearing. In a simpleton view it's "just one of those years that wants to snow".

Probabilities of things coming together right for the 95 corridor are dropping off sharply now but defying odds seems to be our mantra this season.

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The 4/4-4/5 system is a legit snow threat for the interior, especially if the NAO can remain more negative than today's 12z GEFS/GFS solutions. The NAO peaks in next 3-5 days and then from there models diverge significantly. Some erode the block quickly while others, like the GGEM, do not. This will make or break this threat.

Cyclonic wave breaking happens as the surf zone/background wind relaxes with sufficient gradient. This is exactly happening after this week and is a good way of ruining early spring around here. It is also a great way for seeing late season wet snow.

Let me rephrase this bottom portion a little bit. When the phase speed of the wave matches the background flow, that's when breaking is likely. Surf zones are just averaged areas around the NH where anticyclones tend to break and cyclones tend to break. In this case, it's the wake of the big trough currently going on that will see the PV gradient weaken, flow speeds reduce and allow this to happen on residual baroclinicity.

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Huge GEFS support for this window. Everything is there for a threat, not using Analogs:

1. Retrograding helps boost ridge in West

2. NAO signal peaks early April and retrogrades with 50-50 low / cyclonic wave breaking in Atlantic.

3. Split stratosphere supports NAO and holds cold air source in Canada.

I love this potential, I just hate the date.

 

Canadian has the idea, for sure:

 

post-109-0-03657000-1395857255_thumb.gif

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It's kinda funny this year that threats never stop appearing. In a simpleton view it's "just one of those years that wants to snow".

Probabilities of things coming together right for the 95 corridor are dropping off sharply now but defying odds seems to be our mantra this season.

 

The coldest air in the NH remains on our side with a very impressive snow cover extent. This isn't the only factor for April snows but it is a "must-have" for them too, usually. In order for the coastal plain to see April snow, you have to either have a perfect set of synoptics, like 1982, or you have to have something extremely dynamical with good timing. I've seen both enough to know that this is one of those Aprils where you have to pay attention.

Rates are the only thing that ever matters, really. Yesterday was a good lesson in that across DELMARVA-SE NJ.

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The 4/4-4/5 system is a legit snow threat for the interior, especially if the NAO can remain more negative than today's 12z GEFS/GFS solutions. The NAO peaks in next 3-5 days and then from there models diverge significantly. Some erode the block quickly while others, like the GGEM, do not. This will make or break this threat.

Cyclonic wave breaking happens as the surf zone/background wind relaxes with sufficient gradient. This is exactly happening after this week and is a good way of ruining early spring around here. It is also a great way for seeing late season wet snow.

Thanks for the explaination. Would be interesting to get am april event in this region even though I'd rather have spring.

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Locally it needs to be at night and perfect. Getting a -30 daytime high is almost impossible.

 

Yeah this is big. Even earlier in the morning will work, too. I had a nasty, near-blizzard like, snow pasting back in 2000. You remember it well I'm sure. It came in early in the morning. By mid afternoon, it was in the 60s, pleasant with sunshine--all the snow gone.

http://www.raymondcmartinjr.com/weather/2000/09-Apr-00.html

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didnt we get almost get one yesterday?

-25 or so. It could happen and of course average in the morning might only need a -20 but getting a good April snow into the city would be the achievement of the winter IMO. It's basically gone extinct except for dustings. And I'm not talking hills etc Dulles does have a tiny April avg.
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Yeah this is big. Even earlier in the morning will work, too. I had a nasty, near-blizzard like, snow pasting back in 2000. You remember it well I'm sure. It came in early in the morning. By mid afternoon, it was in the 60s, pleasant with sunshine--all the snow gone.

http://www.raymondcmartinjr.com/weather/2000/09-Apr-00.html

Yes that was a great thumper. I think I got like 8-9". Bottom of our hill way less.
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It's 30 degrees right now at 2:15

Dulles avg low is still 39ish then.. so not impossible. The 5th over the 12th is pretty huge.. we are starting to gain climo numbers fast. Again, mostly focusing on the city.. because that's all I really care about.  

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Dulles avg low is still 39ish then.. so not impossible. The 5th over the 12th is pretty huge.. we are starting to gain climo numbers fast. Again, mostly focusing on the city.. because that's all I really care about.

Do you have a link or do you have information that puts DCA's April snowfall in a quick chart or something? I could do the digging but I was hoping someone else already did. ;) I could just go to LWX website, lol.

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