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Possible snow->rain->snow? event, Tuesday-Thursday 3/3-5/2015


famartin

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Those wxbell maps are overdone.  Especially for the second part. 

... not saying you're wrong but why do you say that? I see all levels below freezing as the main precip moves in, and .5-.75 precip in those areas with all areas below freezing. the second map includes the first part of the storm so I don't really think they are that overdone.. again please correct me where I'm missing something.

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... not saying you're wrong but why do you say that? I see all levels below freezing as the main precip moves in, and .5-.75 precip in those areas with all areas below freezing. the second map includes the first part of the storm so I don't really think they are that overdone.. again please correct me where I'm missing something.

 

Well, its NOT cold at all levels as the precip moves in.  At 0Z as the next wave is starting to move in, its still warm. 

 

So, lets take PHL:

Still warm at 0Z.

Cools off by 6Z.  0.25" has fallen since 0Z, but lets assume its evenly distributed, which means half of it wasn't snow, so we're down to, say 0.13". 

6Z-12Z another 0.32".  0.45" total as snow.

Just 0.05" after that.  So, best guess is about a half inch liquid falls as snow.

 

Now, lets take, say, MIV:

It just cools to 0C through the column at 6Z, so we'll assume everything before then is sleet or rain.  So, after that point, MIV gets 0.61" liquid.

 

Now, here's the problem:  WxBell maps show about 10" on a 10:1 ratio.  In other words, its algorithm is assuming an inch falls as snow.  Which is not the case. What it means is that the algorithm assumed the 0.38" that fell from 0Z to 6Z at MIV was snow because the column just barely cooled to 0C or less at 6Z.  So, that's just not right.

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I am sure we can lock this in very early on Monday morning...the main event is Wednesday night and Thursday what can go wrong? Haven't we learned this year?....However I'm optimistic we have not had a system since November where cold air is actually filtering in instead of leaving...although we play all cards Tuesday to Thursday interesting week indeed...

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For our next "event" Wxsim has snow arriving by 4pm tomorrow temp 31.4 mixing pretty quickly with IP with about 1 or 2" falling as solid then ZR with a total of 0.59" w.e. with temps below freezing then rain 0.20" with temps topping out at 41.4

 

It of course does not see the post frontal wave to follow....wait for next couple runs for it to catch on. Only a coating to an inch at this point

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Wow that would be epic. Small chance of verifying imo. Unless the gfs starts trending towards it.

 

If you ask me the NAM has does as well this winter as the other models which isn't saying much.  I will concede that it is usually the model with the highest qpf but that's nothing new.

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I really like PHL for this storm. Even the toasty Ukie shows a flip to snow at the last panel with likely more precip to follow, I'd have to believe it would have shown at least 4-6" for the city. I almost don't think we have to worry if this trends, since NW means more juice, and everyone will flip to snow regardless of where this tracks.

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