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Weekend Storm Discussion Part II, 2/18-2/19


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Gotta stay optimistic about temps here. Subtle shifts can really make us smile (or cry). Pretty much a lock we get some rain at the beginning. Can't really get around that. Once we hit nowcasting time we'll have a much better idea of how much we're going to lose before the changeover.

GFS showing 40's at onset. What if we are say.....38 or so?

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Gotta stay optimistic about temps here. Subtle shifts can really make us smile (or cry). Pretty much a lock we get some rain at the beginning. Can't really get around that. Once we hit nowcasting time we'll have a much better idea of how much we're going to lose before the changeover.

GFS showing 40's at onset. What if we are say.....38 or so?

my only concern is that realistically, there aren't many storms that i can think of where we do well with a rain to snow changover (last year was one of the better ones i can remember like that)...but given the way this winter has gone, it would be great to see a couple of inches...i'll take it and run with it.

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I could see it snowing a bit earlier than that, but it might be a 34F snow..or something like that. Once it flips, it should come down good..but surface temps will may be a slight issue at first, anyways. With any elevation...even 300'..it will make a difference.

Surface dews on the GFS are just plain ugly. Still around 35 at 15z. Would be great to have the GFS precip and NAM temps (/banter)

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If you take the GFS at face value, 18z seems like the changeover time, and DCA/BWI get about 0.3" after that. 2-3" snow considering the surface. If we go over instead by 15z or so, then there is 0.5" frozen and we end up with a nice little event.

I could see it snowing a bit earlier than that, but it might be a 34F snow..or something like that. Once it flips, it should come down good..but surface temps will may be a slight issue at first, anyways. With any elevation...even 300'..it will make a difference.

Just looked at soundings for DC and maybe hour 76-77 or so I think we flip....by 18Z we are solid snow and 33-34

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Ukie only goes out to 72 hrs, but here's 6 hr qpf ending at 72 hrs, which I know is early

http://vortex.plymou...t=h24&cu=latest

here's 700 mb RH at 72 hrs....she's flat!

http://vortex.plymou...t=h24&cu=latest

500mb looks like it should bring up qpf to us

http://vortex.plymouth.edu/cgi-bin/gen_grbcalc2.cgi?re=us&id=&zoom=.6&ti=0≥=1280x1024&mo=ukmet≤=500&va=hght&in=60&pl=cf&ft=h72&cu=latest&overlay=no&mo=≤=&va=&in=&pl=ln&ft=h24&cu=latest

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That's how I see it, on the GFS as well.

FWIW ukie imo wasn't as bad as the Canadian..just by looking at the H5 pattern.

I've never cared what the Canadian shows and I am not going to start now...hope the euro holds or improves....Looks like Leesburg flips by hour 74-75 or so...going to be tough by me...I'd love to see this air mass trend colder and I think it willl..I'lll take the under on a max of 54 on Saturday

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Yes, thanks for not just looking at QPF to determine if it's flat or not. It might not be as good as the GFS, but the H5 pattern would likely bring the moisture into DC.

Would the UKmet yield an all-snow event, or is the thermal profile the same or similar to the GFS? Trying to see the positives in any future model trends.

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If GFS and Euro are in sync I am not sure why we'd care about the UKMET and GGEM other than for laughs. I still think suppression is the bigger risk than inland runner, though.

That's my thought as well, although inland or wrapped up is still on the table. If anything, I'd rather be on the northern edge right now.

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Would the UKmet yield an all-snow event, or is the thermal profile the same or similar to the GFS? Trying to see the positives in any future model trends.

Well I only see through hr 72, but it probably would not be as good as the GFS since some are saying it only went ENE from hr 72 to hr 96. I couldn't say exactly what ptype would be. Probably a mix to snow I would assume.

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Based on the model runs so far this storm will most likely end up being like 10/29 or 12/8 for West Virginia and the Shenandoah Valley on up into Maryland. There are many of the same issues, especially poor surface temps and the models are handling it in a similar fashion.

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I've never cared what the Canadian shows and I am not going to start now...hope the euro holds or improves....Looks like Leesburg flips by hour 74-75 or so...going to be tough by me...I'd love to see this air mass trend colder and I think it willl..I'lll take the under on a max of 54 on Saturday

Yea i thnk it will too matt, aside from the dynamic cooling via deform, beforehand were seeing runs trend colder, and that frontrunning northern stream is just finally being ironed out, expect the cold air and confluence to balance out pretty well for us, and theres not a warm layer which is a bonus leaving no doubt about dynamical cooling during the event. I say 51 on SAT.

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I've never cared what the Canadian shows and I am not going to start now...hope the euro holds or improves....Looks like Leesburg flips by hour 74-75 or so...going to be tough by me...I'd love to see this air mass trend colder and I think it willl..I'lll take the under on a max of 54 on Saturday

I'm not a big Canadian or Ukie person, other than to see what it shows. I've seen too many hiccups to actually have confidence in them, at this stage. I actually would not be shocked if you guys touched the low 50s Saturday. It's later that night, that the cold air builds in with the high.

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I'm not a big Canadian or Ukie person, other than to see what it shows. I've seen too many hiccups to actually have confidence in them, at this stage. I actually would not be shocked if you guys touched the low 50s Saturday. It's later that night, that the cold air builds in with the high.

In fairness I beilieve ukie outscores GFS and is second only to Euro....it's a pretty good model. Completely agreed with Canadian.

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since a few people asked, here's the Ukie 850 temps at 72 hrs

probably one of the cooler models, but it is likely further south so that makes sense

http://vortex.plymouth.edu/cgi-bin/gen_grbcalc2.cgi?re=us&id=&zoom=.6&ti=0≥=1280x1024&mo=ukmet≤=850&va=temp&in=5&pl=cf&ft=h72&cu=latest&overlay=no&mo=≤=&va=&in=&pl=ln&ft=h24&cu=latest

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In fairness I beilieve ukie outscores GFS and is second only to Euro....it's a pretty good model. Completely agreed with Canadian.

It does jump around quite a bit, and also..we don't have the data available to us, like we do with the GFS and others. I look at it as "guidance", but I wouldn't change a forecast based on what it shows.

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since a few people asked, here's the Ukie 850 temps at 72 hrs

probably one of the cooler models, but it is likely further south so that makes sense

http://vortex.plymou...t=h24&cu=latest

It appears to be slightly cooler than the GFS, perhaps a flatter solution would not yield a colder thermal profile. I think it's interesting that the NAM is almost an all-snow event for DC and Baltimore and the synoptic setup is similar to the GFS. Mabye the global models are not picking up on the dynamics associate with the deepening low pressure system.

prec.png

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It appears to be slightly cooler than the GFS, perhaps a flatter solution would not yield a colder thermal profile. I think it's interesting that the NAM is almost an all-snow event for DC and Baltimore and the synoptic setup is similar to the GFS. Mabye the global models are not picking up on the dynamics associate with the deepening low pressure system.

prec.png

those things aren't useful....use soundings and climo and model bias....

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If GFS and Euro are in sync I am not sure why we'd care about the UKMET and GGEM other than for laughs. I still think suppression is the bigger risk than inland runner, though.

I've never cared what the Canadian shows and I am not going to start now...hope the euro holds or improves....Looks like Leesburg flips by hour 74-75 or so...going to be tough by me...I'd love to see this air mass trend colder and I think it willl..I'lll take the under on a max of 54 on Saturday

That's my thought as well, although inland or wrapped up is still on the table. If anything, I'd rather be on the northern edge right now.

I'm not a big Canadian or Ukie person, other than to see what it shows. I've seen too many hiccups to actually have confidence in them, at this stage. I actually would not be shocked if you guys touched the low 50s Saturday. It's later that night, that the cold air builds in with the high.

I think its absolutely important to regard the GGEM and UKMET, at least with respect to their 500 hPa evolution. In terms of anomaly correlation scores, the ECMWF, UKMET, GFS, and GGEM are clustered very closely together. In fact the GFS is in third place with both the UKMET and ECWMF having significantly highly AC scores. The GGEM is just marginally worse than the GFS.

2hg8iec.png

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