Bob Chill Posted October 28, 2011 Share Posted October 28, 2011 About half of the Raleigh's ensemble members at hr 48 on the 18z GFS seem to have the 0c 850 line a bit further east than the OP http://raleighwx.ame...rs/18zf048.html Closer look -- http://raleighwx.ame...zthickf048.html what happened to #3? Link to comment Share on other sites More sharing options...
BethesdaWX Posted October 28, 2011 Share Posted October 28, 2011 About half of the Raleigh's ensemble members at hr 48 on the 18z GFS seem to have the 0c 850 line a bit further east than the OP http://raleighwx.ame...rs/18zf048.html Closer look -- http://raleighwx.ame...zthickf048.html All of the ensembles look warmer in NErn areas of the LWX CWA, most cooler to the SW. Not sure what that means as far as the final solution is concerned. Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 Take at own risk! Only one member shows less than 4" of snow along I-95: http://raleighwx.americanwx.com/models/gfsensemble/members/18zsnowf054.html Prob cut in half and good to go IMHO... but still wow Link to comment Share on other sites More sharing options...
TalcottWx Posted October 28, 2011 Share Posted October 28, 2011 I wasn't buying accums this time of year but it appears almost all of sne is accuming right now even on roads. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 It's hard to pick apart any of the models when they are all in such agreement. 85% rain 15% flakes. Best case will be a slight frosting on the trash can lid The temp profile is tricky. It favors elevation but a few degrees could be a world of difference in heavier precip (which could help cool the surface). Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 Take at own risk! Only one member shows less than 4" of snow along I-95: http://raleighwx.ame...8zsnowf054.html Prob cut in half and good to go IMHO... but still wow we really need a model thread... Link to comment Share on other sites More sharing options...
BethesdaWX Posted October 28, 2011 Share Posted October 28, 2011 Take at own risk! Only one member shows less than 4" of snow along I-95: http://raleighwx.ame...8zsnowf054.html Prob cut in half and good to go IMHO... but still wow Our ratios will be much lower. Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 we really need a model thread... Do we? Randy made this new thread... I made a weenie one.. I guess if need be. Make it so #1 Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 Our ratios will be much lower. Thats why I said cut in half. Would be 5:1 SRs... making the ensembles say that at least 2" is likely in DC and more to the N and W Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 Do we? Randy made this new thread... I made a weenie one.. I guess if need be. Make it so #1 We've already gone most of the way without.. Might as well finish that way Not in the future tho Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 I don't think you understand how to use model guidance in an event like this... Well I am open to learning... Link to comment Share on other sites More sharing options...
nj2va Posted October 28, 2011 Share Posted October 28, 2011 Prelim call for me is 0.75-1" of snow. Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 I just think you have to be more agile considering the circumstances....I think tomorrow we might be able to hone in better on where the boundary layers will be cold enough, but even then it is a bit of a guessing game and I think you need to lean on climo a bit more than normal.... True... I don't know climo well around here so I do need to lean a bit more on that Link to comment Share on other sites More sharing options...
nj2va Posted October 28, 2011 Share Posted October 28, 2011 I dont think there is really a reason to make a forecast amount at <400'........It is really just guesswork..... Better idea tomorrow but felt like making a first call. Do think I'll see flakes flying at least. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 I dont think there is really a reason to make a forecast amount at <400'........It is really just guesswork..... agreed tho 400' might even be a bit low (i honestly have no clue how much of the area lies below that). Link to comment Share on other sites More sharing options...
mattmfm Posted October 28, 2011 Share Posted October 28, 2011 SNE seems to be performing well tonight in a similarly marginal environment. Link to comment Share on other sites More sharing options...
WxUSAF Posted October 28, 2011 Share Posted October 28, 2011 About half of the Raleigh's ensemble members at hr 48 on the 18z GFS seem to have the 0c 850 line a bit further east than the OP http://raleighwx.ame...rs/18zf048.html Closer look -- http://raleighwx.ame...zthickf048.html I know that says 850mb T, but I think it's thickness, not temperature. I see 1320, 1310, and 1300 as some of the lines on there. The 850mb temp is on the other image you posted at the same time, and that seems to show the 850 0C line west of the Op for the most part. Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 It's fun to throw out numbers early but in reality even for the higher terrain it's tough in this case. I still like the nebulous working we have in the CWG piece though I'd be surprised if places above 1000 ft didn't see some accumulation. Nearer DC, wow, good luck with any forecasts. I don't think I'd trust the GEFS ensemble snow forecasts at all as the temperature is unlikely to get near freezing, especially at DCA near a still 60 degree Potomac. That said, earlier I saved this NAm sounding to post to show an unstable layer just northwest of Baltimore. Note the absolutely unstable layer at around 700 mb. For those who are familiar with sounding. Note the dashed curving lines (the moist adiabats and how the temp line tilts more the the left than they do. That's instability and would support convective snows. That may be part of the reason the NAM is so wet. The GFS does not have a similar layer but does have a layer with the temp line parallel to the moist adiabats so even it is close to having an unstable layer. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 SNE seems to be performing well tonight in a similarly marginal environment. i dont think that matters.. different type of setup anyway -- weak overrunning mainly Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 That said, earlier I saved this NAm sounding to post to show an unstable layer just northwest of Baltimore. Note the absolutely unstable layer at around 700 mb. For those who are familiar with sounding. Note the dashed curving lines (the moist adiabats and how the temp line tilts more the the left than they do. That's instability and would support convective snows. That may be part of the reason the NAM is so wet. The GFS does not have a similar layer but does have a layer with the temp line parallel to the moist adiabats so even it is close to having an unstable layer. I don't buy the NAM necessarily but I feel like it picks up on this stuff better than the globals. Am I just imagining that? It seems intuitive that it would given that it has better resolution. Link to comment Share on other sites More sharing options...
TalcottWx Posted October 28, 2011 Share Posted October 28, 2011 i dont think that matters.. different type of setup anyway -- weak overrunning mainly I think its a good sign simply because that storm up there lacks any really intense dynamics like a deformation. (There has been some thunder snows however) This storm looks to feature a CCB on Saturday. I think the point is the ease of accumulation is surprising and I doubted it would show much more than 1-3" in elevations tonight. Link to comment Share on other sites More sharing options...
snowfan Posted October 28, 2011 Share Posted October 28, 2011 I'd focus on the far reaches of MoCo, Howard, Carroll, and Northern Baltimore (Hereford Zone) counties. I'd be shocked if there were accumulating snows in Baltimore and DC proper or even around either beltway. Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 I don't buy the NAM necessarily but I feel like it picks up on this stuff better than the globals. Am I just imagining that? It seems intuitive that it would given that it has better resolution. It does providing it has the other fields right. That's why I'd watch it for the next couple of runs. If it still has the unstable layer and the colder temps on tomorrow afternoon run, then I'd be worried that we are underplaying the event. Until then, I'd still wait before goign overboard. Still the unstable layer makes this a tricky event because any convection would guarantee some accumulation. Link to comment Share on other sites More sharing options...
Avdave Posted October 28, 2011 Share Posted October 28, 2011 it is I think...not sure where the threshold is...I mentioned 800-1000' earlier...Wes and Jason have both used the 1000' demarcation.....We might be able to get more specific tomorrow but I don't think we can be precise....based on recall some of the places in upper MOCO at 600' I believe have done pretty well in events when others have gotten shut out....but I don't really know where the cutoff will be from some accumulation to perhaps just some flakes or mangled mix Matt, do you see this being similar to the 12/5/09 event where the snow was 6 inches at Bluemount at 900' down to a trace just outside the beltway say Annadale, va?? Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 it is I think...not sure where the threshold is...I mentioned 800-1000' earlier...Wes and Jason have both used the 1000' demarcation.....We might be able to get more specific tomorrow but I don't think we can be precise....based on recall some of the places in upper MOCO at 600' I believe have done pretty well in events when others have gotten shut out....but I don't really know where the cutoff will be from some accumulation to perhaps just some flakes or mangled mix I think we just mentioned 1000 ft as an example. if there is convection 500 feet will do great and some places much lower might see decent accumulations but that's assuming the NAM is on the right track which still is very much up in the air. Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 Matt, do you see this being similar to the 12/5/09 event where the snow was 6 inches at Bluemount at 900' down to a trace just outside the beltway say Annadale, va?? Dave, I'm not Matt and think this has more dynamics than that storm if I remember correctly. That means the precip rates could be higher with this storm. Still the idea of more west and at elevation is probably the way to go. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 It does providing it has the other fields right. That's why I'd watch it for the next couple of runs. If it still has the unstable layer and the colder temps on tomorrow afternoon run, then I'd be worried that we are underplaying the event. Until then, I'd still wait before goign overboard. Still the unstable layer makes this a tricky event because any convection would guarantee some accumulation. Yeah, that's why I'd lean heavily toward the up to a trace DCA but then on the other end (15%?) not really scale much till you get to like 2" or so as you can get that in a short period with convection even in marginal temps. Link to comment Share on other sites More sharing options...
Ian Posted October 28, 2011 Share Posted October 28, 2011 Dave, I'm not Matt and think this has more dynamics than that storm if I remember correctly. That means the precip rates could be higher with this storm. Still the idea of more west and at elevation is probably the way to go. http://www.meteo.psu...09/us1205j5.php it has more qpf to work with for sure this go around if the models are right-- that was a relatively quick hitter Link to comment Share on other sites More sharing options...
yoda Posted October 28, 2011 Share Posted October 28, 2011 Are the SREFs useful in this kind of situation? Link to comment Share on other sites More sharing options...
usedtobe Posted October 28, 2011 Share Posted October 28, 2011 Are the SREFs useful in this kind of situation? I'd for sure look at them. This is the time range when they should be more useful than the GEFS Link to comment Share on other sites More sharing options...
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