midatlanticweather Posted March 3, 2014 Share Posted March 3, 2014 Look - I am really hoping for high ratios, but think it is the wild card. We (ME INCLUDED) talk about them every storm. I never see the scientific principals applied other than... "It is cold so it is gonna be high ratios" .. I think it will, but would love a met to jump in, and speak sense into a weenified conclusion!!! And if one did and I missed it.. I am sorry! Link to comment Share on other sites More sharing options...
Deck Pic Posted March 3, 2014 Share Posted March 3, 2014 21z SREF has 0.55" for DC after 9z, so roughly 7", assuming no snow accumulation before then and it starts accumulating after Link to comment Share on other sites More sharing options...
birdsofprey02 Posted March 3, 2014 Share Posted March 3, 2014 state college NWS dropped a lot of warnings down to advisories in southern PA. Link to comment Share on other sites More sharing options...
MN Transplant Posted March 3, 2014 Share Posted March 3, 2014 RR has been rock steady on timing. 1am below freezing at the surface, snow by 5am, 0.5" after. Link to comment Share on other sites More sharing options...
Yeoman Posted March 3, 2014 Share Posted March 3, 2014 21z SREF has 0.55" for DC after 9z, so roughly 7", assuming no snow accumulation before then and it starts accumulating after Better or worse? Link to comment Share on other sites More sharing options...
WxUSAF Posted March 3, 2014 Share Posted March 3, 2014 Look - I am really hoping for high ratios, but think it is the wild card. We (ME INCLUDED) talk about them every storm. I never see the scientific principals applied other than... "It is cold so it is gonna be high ratios" .. I think it will, but would love a met to jump in, and speak sense into a weenified conclusion!!! And if one did and I missed it.. I am sorry! I think it's been explained many times. Snow ratios have to do mostly with air temperatures where the snow crystals are growing. Surface temps don't make much difference. In this case, I think ratios will get pretty high (by our local standards) after ~7am with 12-15:1 or so. Link to comment Share on other sites More sharing options...
Deck Pic Posted March 3, 2014 Share Posted March 3, 2014 Better or worse? same...maybe a tad drier Link to comment Share on other sites More sharing options...
midatlanticweather Posted March 3, 2014 Share Posted March 3, 2014 I finally saw (and this was probably done a long while ago) that I am in the 4 to 8" zone for snow by NWS - That looks right! Hoping these models increase output! Link to comment Share on other sites More sharing options...
usedtobe Posted March 3, 2014 Share Posted March 3, 2014 Look - I am really hoping for high ratios, but think it is the wild card. We (ME INCLUDED) talk about them every storm. I never see the scientific principals applied other than... "It is cold so it is gonna be high ratios" .. I think it will, but would love a met to jump in, and speak sense into a weenified conclusion!!! And if one did and I missed it.. I am sorry! Ratios depend on having a cold surface temp (below freezing) but is more dependent on the temperatures at which snow crystals are forming (you'd like it to be in the minus 12 to minus 16C range and you also don't want a ton of cloud water so you don't want there to be a deep layer with temps in the freezing to minus 4C range. YOu also want to look at the temps are which the strongest lifting is located....again somewhere around minus 15 is good for high ratios. Also, usually the highest ratios aree with storms that are clipper type storms since they don't have a lot of cloud water. Really big storm around our area rarely have ratios in the 20-1 range. More often, you see 12-1 or 15-1, the latter if the snow is dry. Anyway, that's a quick rather simplified primer. Link to comment Share on other sites More sharing options...
nj2va Posted March 3, 2014 Share Posted March 3, 2014 00z RAP: Sleet sounding at 7z...825 at 0.7 and 800 at 0.5. All other levels at/below 0. Maybe good rates would be snow? Snow sounding at 8z. Link to comment Share on other sites More sharing options...
chris87 Posted March 3, 2014 Share Posted March 3, 2014 Dude I get what you are saying. But explain then how you can look at modeled precip, and have it look the same for area A and area B, but in area A there ends up being heavier snow, which aligned with the modeled VVs that were stronger in area A. There must be some flaw or maybe a resolution issue, but I have seen this plenty of times. It does not always align. the setup you described could happen for a number of reasons -- mainly focusing on uvv's at 700 won't tell you the whole story anyways -- but honestly, if you got yourself an analysis tool you think works, who am i to guide you away from it. Link to comment Share on other sites More sharing options...
mitchnick Posted March 3, 2014 Share Posted March 3, 2014 fwiw, 12Z Euro came in too warm for 0Z soundings around the MA ranging from .2C to 1.8C maybe that means it will shift a bit north? a weenie can hope! Link to comment Share on other sites More sharing options...
Casualbrain Posted March 3, 2014 Share Posted March 3, 2014 MidAtlantic - Not a met, but QPF Snow to Liquid Ratio is determined by a HUGE number of factors like percent of water content in the air and snow itself, specific gravity, density, temperature, void space within the ice crystals as they form, upper level winds causing crystal fragmentation, sublimation/evaporation into dry atmosphere, etc. Because of all that exact measurements are impossible to predict in advance of an event. You can guess using averages like 10:1 or 20:1 ratios but it's all a guess Link to comment Share on other sites More sharing options...
MN Transplant Posted March 3, 2014 Share Posted March 3, 2014 NAM is freezing by 2am in the city. Snow by 5am Link to comment Share on other sites More sharing options...
ravensrule Posted March 3, 2014 Share Posted March 3, 2014 By 7 a.m NAM looks to have 2" on the ground. Link to comment Share on other sites More sharing options...
chris87 Posted March 3, 2014 Share Posted March 3, 2014 NAM is freezing by 2am in the city. Snow by 5am yeah i think most will like the trends on the NAM Link to comment Share on other sites More sharing options...
CAPE Posted March 3, 2014 Share Posted March 3, 2014 the setup you described could happen for a number of reasons -- mainly focusing on uvv's at 700 won't tell you the whole story anyways -- but honestly, if you got yourself an analysis tool you think works, who am i to guide you away from it.. So looking at the vertical velocity does not give a better indication of where thunder may occur, as compared looking at modeled qpf or sim radar? Why do we have the mid and upper level tools if we can discern everything from looking at sim radar and qpf plots? Link to comment Share on other sites More sharing options...
ravensrule Posted March 3, 2014 Share Posted March 3, 2014 3" by 8 a.m. looks very good so far. Looks close to 1" per hr rates, almost 4" by 9 a.m. Link to comment Share on other sites More sharing options...
Ji Posted March 3, 2014 Share Posted March 3, 2014 NAM is freezing by 2am in the city. Snow by 5am thats really late Link to comment Share on other sites More sharing options...
usedtobe Posted March 3, 2014 Share Posted March 3, 2014 Sorry for the non-contributing question: Do soundings support LWX's "some thunder is possible" argument? That's tough question as there is a near surface unstable layer but I'm not sure it's deep enough to support convection. I've seen a similar look near Chicago and there was convection with it but the layer was deeper. The other thing I can't look at is for COnditional Symetric instabilty. We'll have goo frontogenesis with the very strong frontal boundary but you need cross sections or you need to look at layered EPV which is beyond what we can do hear and is too complicated to explain here. Link to comment Share on other sites More sharing options...
TL97 Posted March 3, 2014 Share Posted March 3, 2014 Welcome to the storm NAM. Huge area of great rates moves into the area at 9am. Link to comment Share on other sites More sharing options...
yoda Posted March 3, 2014 Share Posted March 3, 2014 Hi ho hi a north movement the NAM wil show Link to comment Share on other sites More sharing options...
snowfan Posted March 3, 2014 Share Posted March 3, 2014 Oh, NAM. Nice to see you. Link to comment Share on other sites More sharing options...
ravensrule Posted March 3, 2014 Share Posted March 3, 2014 This run is rocking. About time. Link to comment Share on other sites More sharing options...
Deck Pic Posted March 3, 2014 Share Posted March 3, 2014 NAM is north Link to comment Share on other sites More sharing options...
Heisy Posted March 3, 2014 Share Posted March 3, 2014 NAM ticked north def. Link to comment Share on other sites More sharing options...
ravensrule Posted March 3, 2014 Share Posted March 3, 2014 By 10 a.m. DC has 6". Sweet. Link to comment Share on other sites More sharing options...
BTRWx Posted March 3, 2014 Share Posted March 3, 2014 Hi ho hi a north movement the NAM wil show Heaviest rates fizzle over the District, but the longer duration of moderate snow looks good Link to comment Share on other sites More sharing options...
Yeoman Posted March 3, 2014 Share Posted March 3, 2014 NAM is north and slower Link to comment Share on other sites More sharing options...
ravensrule Posted March 3, 2014 Share Posted March 3, 2014 By 11 a.m. DC and BWI have 7" on the ground. Link to comment Share on other sites More sharing options...
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