usedtobe Posted February 17, 2018 Share Posted February 17, 2018 6 minutes ago, high risk said: yes, and in the post of mine that you quoted, I mentioned the snow depth maps (I should have used the full "accumulated snow depth" term). They sometimes run a bit low, so I don't treat them as gospel, but I always view them in conjunction with the 10:1 maps. When they're radically different, the model is trying to tell us that it's not nearly as favorable for big accumulations as the 10:1 maps show. In the "no doubters", they'll be in the same ballpark. I'm not sure some of the snow maps use algorithms that look at the full depth fo the soundings. The WxBell ones are usualy way overdone in my region unless I've got an arctic airmass in place. This is a case where the accumulated snow depth shoulld be way better than the WxBell produce though it could fail in an S+ band with temps at the surface a tad above freezing. Link to comment Share on other sites More sharing options...
MD Snow Posted February 17, 2018 Share Posted February 17, 2018 1 minute ago, high risk said: 12z GFS is noticeably lighter than the 12z NAMs with QPF and is therefore warmer. Looks slightly better than it's 6z run with 850's. Keeps N/W of cities below for the whole event. Link to comment Share on other sites More sharing options...
RDM Posted February 17, 2018 Share Posted February 17, 2018 Interesting how the WWA surrounds Leesburg on 3 sides. Is that the heat island effect, or just plain ole bad luck. Don't often if ever see Leesburg excised out like that. Link to comment Share on other sites More sharing options...
H2O Posted February 17, 2018 Share Posted February 17, 2018 42.7/29. Temps already above forecast Link to comment Share on other sites More sharing options...
Bob Chill Posted February 17, 2018 Author Share Posted February 17, 2018 4 minutes ago, RDM said: Interesting how the WWA surrounds Leesburg on 3 sides. Is that the heat island effect, or just plain ole bad luck. Don't often if ever see Leesburg excised out like that. LWX browses this sub and Ji got on their nerves. Link to comment Share on other sites More sharing options...
high risk Posted February 17, 2018 Share Posted February 17, 2018 1 minute ago, usedtobe said: I'm not sure some of the snow maps use algorithms that look at the full depth fo the soundings. The WxBell ones are usualy way overdone in my region unless I've got an arctic airmass in place. This is a case where the accumulated snow depth shoulld be way better than the WxBell produce though it could fail in an S+ band with temps at the surface a tad above freezing. Wes, none of the snow maps use the soundings. Any snow map for NAM and GFS (other than the accumulated snow depth) starts with the accumulated snow parameter (liquid equivalent) out of the model and applies a ratio of choice (10:1, Kuchera, Ferrier....). The problem is that the accumulated snow parameter is misleading. First, it tallies sleet in with snow. But more importantly, it's computed by just taking the QPF x % of frozen precip (the percentage of hydrometeors falling as snow or sleet). That means if you have 1" of liquid comprised of 50% snow flakes and 50% rain drops, even though we know that would never accumulated, the parameter shows 1" x .5 = 0.5" liquid of accumulated snow. Link to comment Share on other sites More sharing options...
clskinsfan Posted February 17, 2018 Share Posted February 17, 2018 RGEM looks similar to the NAM with a healthy thump. We have to hope the short range models are right at this point. We need that heavy stuff. Sun is back out. 33/21 Link to comment Share on other sites More sharing options...
usedtobe Posted February 17, 2018 Share Posted February 17, 2018 1 minute ago, high risk said: Wes, none of the snow maps use the soundings. Any snow map for NAM and GFS (other than the accumulated snow depth) starts with the accumulated snow parameter (liquid equivalent) out of the model and applies a ratio of choice (10:1, Kuchera, Ferrier....). The problem is that the accumulated snow parameter is misleading. First, it tallies sleet in with snow. But more importantly, it's computed by just taking the QPF x % of frozen precip (the percentage of hydrometeors falling as snow or sleet). That means if you have 1" of liquid comprised of 50% snow flakes and 50% rain drops, even though we know that would never accumulated, the parameter shows 1" x .5 = 0.5" liquid of accumulated snow. Thanks, I've never liked the snow products that much as too many people seem to get stoked on the amounts where the real way of figuring snowfall accumulations is to look at sounding as also at the ground and near surface temps. In this case none of them argue for high ratios and there are big questions about how quickly the temps aloft will warm up. Link to comment Share on other sites More sharing options...
RDM Posted February 17, 2018 Share Posted February 17, 2018 1 minute ago, Bob Chill said: LWX browses this sub and Ji got on their nerves. Haha - rotflmao - I did think about poor ole Ji, but didn't want to prod his ire... Could be a new subroutine programmed into the CRAYs... to take into account "local anomalies" Link to comment Share on other sites More sharing options...
Interstate Posted February 17, 2018 Share Posted February 17, 2018 The system has really blossomed since last night. Link to comment Share on other sites More sharing options...
usedtobe Posted February 17, 2018 Share Posted February 17, 2018 15 minutes ago, high risk said: 12z GFS is noticeably lighter than the 12z NAMs with QPF and is therefore warmer. That's why I think our CWG forecasts are more likely to bust low than high as I don't trust the NAm amounts and because of that don't trust the temps. hope I'm wrong. Link to comment Share on other sites More sharing options...
87storms Posted February 17, 2018 Share Posted February 17, 2018 i don't know what's going to happen and not gonna go down the reserve psychology nancy route, but it's definitely not a boring storm. the only thing i can think of is feb 87. different systems, but the rates were ridiculous for several hours and we ended up with 10"+. still one of the more savage short-term storms i've seen here. if this ends up being 1/3 of that, then it's probably a win. Link to comment Share on other sites More sharing options...
mappy Posted February 17, 2018 Share Posted February 17, 2018 37/25 here. Storm cancel, gonna open the pool Link to comment Share on other sites More sharing options...
WxUSAF Posted February 17, 2018 Share Posted February 17, 2018 Temp can stop rising now. Up to 41. Sun still out. Link to comment Share on other sites More sharing options...
MD Snow Posted February 17, 2018 Share Posted February 17, 2018 If we end up with half of what the NAM is showing in terms of accumulations than it's a win. If the band's depicted on the RGEM and NAM's come in and are snow for a time...then I think a couple inches is not out of the realm. If snow, it would would be 1-2" per hr rates. 40/28 with a southeast wind kicking up. Chances of all rain south and east of the cities seem to be on the rise. Link to comment Share on other sites More sharing options...
usedtobe Posted February 17, 2018 Share Posted February 17, 2018 6 minutes ago, 87storms said: i don't know what's going to happen and not gonna go down the reserve psychology nancy route, but it's definitely not a boring storm. the only thing i can think of is feb 87. different systems, but the rates were ridiculous for several hours and we ended up with 10"+. still one of the more savage short-term storms i've seen here. if this ends up being 1/3 of that, then it's probably a win. That was a much different storm. It had a really strong southern system and had a 50 50 low to help lock in the cold air. There never really were any question concerning ptype for DC. Link to comment Share on other sites More sharing options...
87storms Posted February 17, 2018 Share Posted February 17, 2018 Just now, usedtobe said: That was a much different storm. It had a really strong southern system and had a 50 50 low to help lock in the cold air. There never really were any question concerning ptype for DC. yea i just remember we were forecast to have about 1-3" and ended up with about a foot, though it sounds like the lack of accuracy was due to amounts/rates, not so much temps. Link to comment Share on other sites More sharing options...
gymengineer Posted February 17, 2018 Share Posted February 17, 2018 57 minutes ago, high risk said: 12z GFS is noticeably lighter than the 12z NAMs with QPF and is therefore warmer. And yet its positive snow depth change product is much more generous than the NAM for the cities and southeastern suburbs. Is the same algorithm for that product across all models? Link to comment Share on other sites More sharing options...
MN Transplant Posted February 17, 2018 Share Posted February 17, 2018 42.1 Beautiful day out. Link to comment Share on other sites More sharing options...
Chris78 Posted February 17, 2018 Share Posted February 17, 2018 The clouds need to roll in asap. Sitting at 36 currently in Smithsburg. The radar looks really sweet in Kentucky and Tennessee with a good trajectory. Hopefully it comes in like a wall. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted February 17, 2018 Share Posted February 17, 2018 37 minutes ago, high risk said: 12z GFS is noticeably lighter than the 12z NAMs with QPF and is therefore warmer correct. There you go. Link to comment Share on other sites More sharing options...
attml Posted February 17, 2018 Share Posted February 17, 2018 My snow shovel and ice melt has been outside on the porch waiting for the next storm which hasn't materialized for several weeks due to my over anticipation! I have brought them both inside in anticipation of not needing them so plan on this storm to overachieve! Sorry for screwing up the pattern for the last several weeks! Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted February 17, 2018 Share Posted February 17, 2018 Clouds have finally arrived. But the damage has been done. 40F. Link to comment Share on other sites More sharing options...
Mordecai Posted February 17, 2018 Share Posted February 17, 2018 40F here in Tyson’s. It’s pretty sunny right now and sure doesn’t feel like a snowstorm is coming. This has been a fun one to track. The quickness of the storm was always going to be an issue, and it’s looking like a 4-8pm event. Hopefully we can cash in before the switch over to rain. I don’t live in a favored area, so I’ll take what I get. Onto March... Link to comment Share on other sites More sharing options...
PrinceFrederickWx Posted February 17, 2018 Share Posted February 17, 2018 42 here and rising. Starting to feel that sun angle. :-) Southern MD already had PD3 (2015) and PD4 (2016). This will definitely NOT be PD5 for me, but I’m just hoping we can at least get on the board, then I can say I had snow in three of the last four President’s Day weekends. Hope you guys north and west can get something good! Link to comment Share on other sites More sharing options...
clskinsfan Posted February 17, 2018 Share Posted February 17, 2018 28 minutes ago, Interstate said: The system has really blossomed since last night. Decent moisture tap out of Baja. It's a shame we cant seem to get a HP over the top in a good spot this year. Been unlucky with timing all winter. Link to comment Share on other sites More sharing options...
clskinsfan Posted February 17, 2018 Share Posted February 17, 2018 5 minutes ago, EastCoast NPZ said: Clouds have finally arrived. But the damage has been done. 40F. No way. You are 40 down there? Link to comment Share on other sites More sharing options...
wxdude64 Posted February 17, 2018 Share Posted February 17, 2018 Snow and sleet lightly falling here in last 10 minutes, 36.8/30.3. Definitely NOT starting as a 'wall'. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted February 17, 2018 Share Posted February 17, 2018 1 minute ago, clskinsfan said: No way. You are 40 down there? Yep, can always count on Stephens City being the warmest spot in the valley. https://www.wunderground.com/personal-weather-station/dashboard?ID=KVASTEPH1 Link to comment Share on other sites More sharing options...
WVclimo Posted February 17, 2018 Share Posted February 17, 2018 5 minutes ago, clskinsfan said: No way. You are 40 down there? 39.3° here under filtered sunshine. Up 3.6° in the past hour. Link to comment Share on other sites More sharing options...
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