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March 2-3 Storm Disco, Part II


stormtracker

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HM just posted this in the old thread... transferred it to the new one

 

Matt, it seems to me that the immediate DC area is over to snow around 10z. The line is JUST to your NW at 9z. Around 9z, it seems there is a transition period there where some ZR/IP is possible, as you indicated (9z 2m <0c).
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HM, the hardest thing for me to figure out is how much of the .3 falls after the changeover. It looks like the main slug is approaching through 7am so the majority of the .30+/- could be snow between the 5-7am range? I'm envisioning a lull between the front wave and the main slug. 

 

Of course dissecting to this level of detail is silly in many ways because we're going to have a new look every 6-12 hours to do the same exercise with. But it's what we do...lol

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HM just posted this in the old thread... transferred it to the new one

Thanks...my guess for DC on the Euro is that 2-3am, rain/zr to zr. Then, 3-5am is zr/ip and mixing with snow toward end of window. After 5 am you are all snow just before the thump hits. So a few hours of ice overnight before the snow happens. Yikes...

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Thanks...my guess for DC on the Euro is that 2-3am, rain/zr to zr. Then, 3-5am is zr/ip and mixing with snow toward end of window. After 5 am you are all snow just before the thump hits. So a few hours of ice overnight before the snow happens. Yikes...

 

great thanks...and I'd imagine of that 0.25" that falls in the 1am-7am window, 75% of it is after 5am...good run...

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HM, the hardest thing for me to figure out is how much of the .3 falls after the changeover. It looks like the main slug is approaching through 7am so the majority of the .30+/- could be snow between the 5-7am range? I'm envisioning a lull between the front wave and the main slug. 

 

Of course dissecting to this level of detail is silly in many ways because we're going to have a new look every 6-12 hours to do the same exercise with. But it's what we do...lol

I know that this may be useless in the end but it is fun. Yeah I think it is safe to assume that the slug is most if not all snow. You would see a very light glaze/crunch on the bottom with dropping temperatures and transitional precip types. The sig ice potential has significantly reduced with today's solutions. And again, with the stronger Quebec punch, it ends the stream of precip quickly and keeps the deformation zones pushing south.

To be honest, I'm not sure which way we shift tomorrow. If eastern Canada keeps trending more assertive, before you know it, this thing is suppressed (and to be honest I never thought that was a possibility based on how strong this Pacific wave is). If the Pacific wave can remain stronger, it is possible it comes back north and/or if Quebec influence reduces. Nightmare...

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great thanks...and I'd imagine of that 0.25" that falls in the 1am-7am window, 75% of it is after 5am...good run...

100% agreement from me. Most QPF is snow and possibly a small crunch underneath. The switchover timing being overnight and heaviest precip being during daylight hours means this will easily stick on all surfaces. Pretty crazy run for DC!

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I know that this may be useless in the end but it is fun. Yeah I think it is safe to assume that the slug is most if not all snow. You would see a very light glaze/crunch on the bottom with dropping temperatures and transitional precip types. The sig ice potential has significantly reduced with today's solutions. And again, with the stronger Quebec punch, it ends the stream of precip quickly and keeps the deformation zones pushing south.

To be honest, I'm not sure which way we shift tomorrow. If eastern Canada keeps trending more assertive, before you know it, this thing is suppressed (and to be honest I never thought that was a possibility based on how strong this Pacific wave is). If the Pacific wave can remain stronger, it is possible it comes back north and/or if Quebec influence reduces. Nightmare...

 

I've been concerned about suppression as well. Even several days ago when we were warm on the models. It's not like the precip field is expansive like other storms coming from the south this year. It's relatively narrow in the big picture. It doesn't take much to be a winner or a loser. Waves along boundaries are only good for those in the bullseye. And boundaries tend to move. It's what they do. haha

 

Otoh, we could end up with a juicier and more expansive system overall. Pretty nice storm off the pac and no prob tapping the gulf as it makes it's trip. I have more questions than answers. But that's normal for weenies.  

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The bolded is my favorite part of his discussion:

 

 

Latest from JB with the 12z runs

 

"There is a two fold problem with the storm that renders the model snow amounts questionable at best. That does not mean they cant be right. But what we are seeing here is the model jumping on a front impulse and pushing more cold air, and by doing so pushing the snow south.

This could be the start of a trend, or perhaps not, a glich so to speak. I really cant tell at this time, and have to watch it. The feedback of the front running system could be an error. For one, the GFS loves to do that. For 2 the ECWMF is weak on systems moving out of the southwest. What may be happening is both errors are at play here. The modeling 2-3 days away tends to have problems. What is interesting is the 2 models most far south yesterday, the Canadian and WRF have shifted north. So the reduction of liquid is problem one ( actually the push south)

Problem 2 is the ratios This will turn into a very cold storm and 20 to 30 to 1 ratios could occur where less than .5 liquid occurs. I am puzzled by the southward shift, suspect its an error, yet I can not be sure. The noon runs yesterday trended south, only to come back north again last night. Until the system is on the "playing field" so to speak, no run is etched in stone. The again there is alot of competition here and its complex. Complex and competition are not great for big storms.

However its too early FOR ME, maybe not for others brighter than I, ( side bar.. When someone says its too early to tell, they should speak for themselves. I someone right now says, the precip will be further south and nails it then its not too early for them. I always assume someone will have the right answer, it just may not be me. But when you hear someone say that, you should say, you mean for you) But right now I am staying with the idea that the GFS/ECMWF had for accumulations, but the reason I thought they were good was that in the northern part of that area, we did not need the 10 to 1 to get to the amounts. The model of course is using 10 to 1 all over, but I thought, well near the mason dixon line 10 to 1 gives a foot, but up in the I-80 corridor using 20 to 1 would give it.

Then again the best model on the storm a couple of weeks ago, the JMA remains wet

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As has been discussed this is not our typical setup where we have cold air and hope it holds on. We don't have it and it comes charging in. Thundersnow is possible. Sleet is probable but little if any freezing rain as this is not the set up for it. These are a lot of fun as temp can be 40+ for late day and early night and you wonder whay we are talking snow and then it drops 10 degrees in 45 minutes and it's game on.

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We should get a WSW with the 3 PM product update

 

      maybe, but I see no reason to pull the trigger this early for an event that is still over 54 hours from starting.

  As has been noted, while it's certainly looking like good chances of a major event, there are still some ways in

  which it can go wrong.   If I were LWX, I would hold off until the 00z model suite arrives.

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I used to expect that too, but IDK NAM looks much better so far. 

 

SREFS were way north..I don't expect it to be good

 

            I am completelyt baffled by the SREF.     It has consistently been way warm in the mid-Atlantic.

       By 12z Monday, pretty much all of the deterministic guidance has the 2-m  freezing line south, and

       in some cases well south, of DC.    The 15z SREF has the line up in central PA, and its probability of the 2-m temperature being below freezing in DC is under 20%.   I can't recall ever seeing it behave like this.

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