WinterFire

2 hours ago, psuhoffman said:

I totally get the frustration in DC. Thing is it’s been a failure of boundary temps not pattern. I don’t know what to say. This has been the pattern since Dec 1 and the last month!   This looks like a match to every big DC snow period.

 

And we’ve had perfect track after perfect track SWs this winter. I count about 5 storms that frankly everything went EXACTLY right for a DC snowstorm and DC got a 37 degree rain or mix event. I don’t know what to say and frankly I don’t even know what DC needs to get snow anymore. Colder is the obvious answer but if a storm takes the perfect track colder would have  suppressed it. If the amount of suppression it takes to get cold enough is so much so that it squashed any wave that’s a problem. And don’t bring up Dallas. They aren’t near the coast east of mountains. Totally different climate. 

If I had to guess, I'd say part of it is sea surface temperatures--if the Atlantic is warming, it would make it much more difficult to get cold and stay cold in the costal plain. Unfortunately since that's global warming-driven, there's not much we can do about that. But would a northern-stream dominant flow also have an impact? I.e., are systems required to dig more without drying out too much (which seems to have been happening with nearly every storm inside 72 hours), which makes any set up pretty precarious? Maybe it's grasping at straws, but that is something that (hopefully) doesn't stick around forever, and wouldn't necessarily imply that even moderate snow in the DC-Baltimore area is just shy of a lost cause...

1 minute ago, jaydreb said:

I thought so too but apparently everyone else has no problem with them.  

I don't know if you were following them up to the Snowquester...debacle...but people were really upset about CWG's forecast bust. Back then they were describing the forecasts the way you suggested (they had DC at 5-10" and low-medium confidence). Their post-analysis is here: https://www.washingtonpost.com/blogs/capital-weather-gang/post/snowquester-when-forecast-information-fails/2013/03/07/5d0d77ae-873b-11e2-9d71-f0feafdd1394_blog.html

I think after this "storm", they changed their approach to try to be clearer about what a busted forecast might look like. I think the bigger issue is that the public isn't interested in trying to understand the forecast but then will take it out on the mets if the forecast they internalized was wrong...

Just now, DCTeacherman said:

I also really don’t like the boom/bust thing.  I understand why they think they should do it but IMO it’s overcomplicating it. 90% of people outside of weather boards aren’t going to look at the boom/bust and understand it anyway.  Just give us the range you think is most likely.   

But isn't that what they're doing? They say in their text forecast and their graphic that they expect 4-8" in DC. Then they add information about uncertainty which is an important thing to do in public communication, no?

I saw a couple of things from Twitter mets this morning: 

It seems like there's a couple of features that are still moving around (although the trend isn't really our friend for the CCB snows), so maybe all is not said and done? But this storm does remind me of the Jan 2005 storm in DC--we were supposed to get a major winter storm, and got pretty decent WAA snows, but then the phase/capture happened too late and PHL north got a good storm but our WSW was downgraded to a blowing snow advisory. But as others have said, it's our first snow of any kind in years, so I'll take what we can get...

15 minutes ago, nj2va said:

To my weenie eyes, one of the key differences is the strength of the vort as it crosses the country.  Euro holds/strengthens as it nears our area which combined with a coastal transfer near OBX + backside energy to capture/slow it down.  GFS is initially closed off over the Midwest but then just opens/shears as it heads east.  GFS then transfers too far north/pops a coastal low at/north our latitude and the backside UL low swings through and closes off with the SLP too far offshore/north of our latitude.  

15 minutes ago, MN Transplant said:

The good thing is that this isn't some crazy setup.  We have a nice big trough crossing the country and there will be a traditional transfer from a dying OH valley surface low to an East Coast low.  The GFS keeps the trough more positively tilted as the axis gets towards 95, which is more of a large-scale pattern issue.  The backside vort may help there, but it isn't the whole story (it is never one thing, of course).

Thanks! I'm trying to learn more how to parse the upstream differences in model runs, so this is very helpful. I guess one question is would a faster movement of the backside vort prompt a negative tilt in the GFS progression or help it to slow down and close off south of our latitude? 

Though of course "it is never one thing" could really be the motto of this hobby, so I'm probably trying to oversimplify here haha

1 hour ago, MN Transplant said:

Two other things on the backside vort.  The GFS has it, but like the 00z Euro run, it is too late to help slow/wrap up the UL low over us.

And, the vort energy appears to be over Japan right now, so we are going to be waiting to see how the models handle it the rest of the week.

Thanks for pointing this feature out. I've seen a few Twitter mets mention it as well, so I'm wondering if that accounts for all or most of the GFS/Euro divide, and not necessarily the strength of the main low or it's position? In other words, is it fair to say there is reasonable (maybe not complete) agreement across guidance for the main UL low until it gets off the coast, but that guidance diverges when handling whether/how the backside vort interacts with the UL low?

FWIW during last October's ice storm in Oklahoma City, the temperature never got below 27, and that was a pretty massive storm (I think almost an inch of accretion?). Not saying that will happen here, but the temperatures don't need to be quite as low as some posters have suggested. 

Anyway, not a new poster (been lurking for years) but figured if I could add some Southern Plains ice knowledge, why not make that my first post!