mattmfm Posted February 12, 2014 Share Posted February 12, 2014 Colder, significantly wetter. Woah. Link to comment Share on other sites More sharing options...
Ian Posted February 12, 2014 Share Posted February 12, 2014 18-20" showing up just west of DC People should keep lowering forecasts and worrying about the mix IMO. (that was a joke) Link to comment Share on other sites More sharing options...
Snowden Posted February 12, 2014 Share Posted February 12, 2014 Link to comment Share on other sites More sharing options...
Ji Posted February 12, 2014 Share Posted February 12, 2014 looks like we are trending better for once..... but we also trended better in March 2013 Link to comment Share on other sites More sharing options...
wxmeddler Posted February 12, 2014 Share Posted February 12, 2014 NAM dumps .55" in 3 hours with the front thump. My golly. Link to comment Share on other sites More sharing options...
BTRWx Posted February 12, 2014 Share Posted February 12, 2014 Unfortunately the NAM has several hours of ice according to the instant weathermaps map, but I'm certainly not complaining. I think it stays snow longer than it has been showing earlier, great run! Link to comment Share on other sites More sharing options...
DCAlexandria Posted February 12, 2014 Share Posted February 12, 2014 Remember 24 hours ago when folks said models never trend back to snow. Link to comment Share on other sites More sharing options...
EasternUSWX Posted February 12, 2014 Share Posted February 12, 2014 Now that's nice. Link to comment Share on other sites More sharing options...
usedtobe Posted February 12, 2014 Share Posted February 12, 2014 I saw some 2 inch an hour rates and NAM would even give me 8-12. Link to comment Share on other sites More sharing options...
Bob Chill Posted February 12, 2014 Share Posted February 12, 2014 We'll see how it shakes out but the nam has been a bit of a rock the last 24 hours with general evolution and thermals. I'm impressed. This run is a destruction. Those rates are going to be ridiculous if they verify. Link to comment Share on other sites More sharing options...
usedtobe Posted February 12, 2014 Share Posted February 12, 2014 NAM dumps .55" in 3 hours with the front thump. My golly. I noticed a .20 in one hour on the graphics. Link to comment Share on other sites More sharing options...
WxMan1 Posted February 12, 2014 Share Posted February 12, 2014 18Z NAM looks good, though unfortunately meteorologists may be overly suspect of the NAM, SREF, and RAP nearing the event because of what happened last March 6th, when these models were "trending" better and better prior to the onset of the event. I say "overly suspect" because while we need to keep in mind the typical colder BL bias of these runs -- we want to be wary of "overcorrecting". I say this because when BL are initially marginal to begin with -- as with the March 6th event -- then there's certainly a better chance of these biases coming back to haunt forecasters. However, with the antecedent arctic air in place, and cold Bay and Atlantic shelf water temps, one has to ask him/herself if what's being portrayed by the NAM/SREF/RAP is truly too cold. Along these lines, as I noted on FB, because of the cold air going in and (thus) the fact that our entire region should see a good front-end thump (some more than others obviously), I do not see this as being a case similar to an early season/late season one where the snow total contours are aligned more SSW-NNE, parallel to I-95 or the fall line. Climatology would favor that being the case when BL temps are suspect, which (again) is not so much the case this time around as compared to where the dry slot gets. I think the distribution of snow amounts will be more SW-NE oriented instead of SSW-NNE as a result, which is why I'm thinking the latest official forecast amounts east of I-95 might be a bit underdone. Link to comment Share on other sites More sharing options...
Ian Posted February 12, 2014 Share Posted February 12, 2014 That 90th percentile map seems pretty wrong locally. Getting to 12" IMBY is not that hard on a number of current runs. Link to comment Share on other sites More sharing options...
Ian Posted February 12, 2014 Share Posted February 12, 2014 lwx added rain to my zone for tomorrow. i'm tempted to lol but maybe. Link to comment Share on other sites More sharing options...
usedtobe Posted February 12, 2014 Share Posted February 12, 2014 18Z NAM looks good, though unfortunately meteorologists may be overly suspect of the NAM, SREF, and RAP nearing the event because of what happened last March 6th, when these models were "trending" better and better prior to the onset of the event. I say "overly suspect" because while we need to keep in mind the typical colder BL bias of these runs -- we want to be wary of "overcorrecting". I say this because when BL are initially marginal to begin with -- as with the March 6th event -- then there's certainly a better chance of these biases coming back to haunt forecasters. However, with the antecedent arctic air in place, and cold Bay and Atlantic shelf water temps, one has to ask him/herself if what's being portrayed by the NAM/SREF/RAP is truly too cold. Along these lines, as I noted on FB, because of the cold air going in and (thus) the fact that our entire region should see a good front-end thump (some more than others obviously), I do not see this as being a case similar to an early season/late season one where the snow total contours are aligned more SSW-NNE, parallel to I-95 or the fall line. Climatology would favor that being the case when BL temps are suspect, which (again) is not so much the case this time around as compared to where the dry slot gets. I think the distribution of snow amounts will be more SW-NE oriented instead of SSW-NNE as a result, which is why I'm thinking the latest official forecast amounts east of I-95 might be a bit underdone. Brian, I pretty much agree, it's the temps above the ground that warm so there shouldn't be as big a discrepancy between DC and my house as when the flow at the surface is easterly. Link to comment Share on other sites More sharing options...
HM Posted February 12, 2014 Share Posted February 12, 2014 Misdiagnosing of stability in March storm was the main culprit. There wasn't any CSI of significance because the CI was wiping it out across VA. When the precipitation isn't a solid shield, that usually means CI is playing a role. CI becomes more likely as lows vertically stack, which also happened last year. This time, that does not occur until well Northeast of the area. Link to comment Share on other sites More sharing options...
clskinsfan Posted February 12, 2014 Share Posted February 12, 2014 The NAM just keeps the back end going forever. Crazy. Link to comment Share on other sites More sharing options...
Bob Chill Posted February 12, 2014 Share Posted February 12, 2014 Misdiagnosing of stability in March storm was the main culprit. There wasn't any CSI of significance because the CI was wiping it out across VA. When the precipitation isn't a solid shield, that usually means CI is playing a role. CI becomes more likely as lows vertically stack, which also happened last year. This time, that does not occur until well Northeast of the area. I've forced myself to watch the loop of the march debacle to better understand when a lock isn't a lock. When the upper level low approached and the circulation got going near ric it was like the electricity got turned off in the advancing waa precip. Then as the slp got really cranking down in se va we had more problems with crappy thermals and spotty precip. I can't find any valid reason to expect the advancing waa shield to lose any punch. H5 isn't closed and the source region for moisture originated in the gulf. There are some big differences with the current storm. I know you know all this and a million other things better than me. Just speaking out loud there there really isn't much of a panic button in play with the front end thump. Link to comment Share on other sites More sharing options...
WxMan1 Posted February 12, 2014 Share Posted February 12, 2014 Misdiagnosing of stability in March storm was the main culprit. There wasn't any CSI of significance because the CI was wiping it out across VA. When the precipitation isn't a solid shield, that usually means CI is playing a role. CI becomes more likely as lows vertically stack, which also happened last year. This time, that does not occur until well Northeast of the area. Very true. It wouldn't appear we have that degree of disruption in the pcpn field this go around. I also agree with an earlier post -- CI (convective instability for "upright" convection), which would dominate over CSI, does not appear to be as much of an issue here looking at the cross sections of theta-e/geo momentum/RH/UVV/EPV. However, given the weakening static stability, even without "folding" theta-e surfaces, the strong horizontal component to the momentum surfaces would certainly support CSI and thus more slantwise convective bands W-NW-N of the 700-500 mb dry slot. Link to comment Share on other sites More sharing options...
DCWeatherGuy Posted February 12, 2014 Share Posted February 12, 2014 Do I have this right: In the 12Z runs, the NAM and Euro had huge front-end hits and weaker back-end hits, while the GFS had a weak-ish front end hit but suddenly showed more on the back-end than the other models (or prior GFS runs). Now the 18Z NAM is ramping up with back-end hit. If I have that right, should we consider the possibility of an emerging consensus on the back-end hit being stronger than initially suspected? Link to comment Share on other sites More sharing options...
Bob Chill Posted February 12, 2014 Share Posted February 12, 2014 My goodness. I can't wait for high res. Link to comment Share on other sites More sharing options...
HM Posted February 12, 2014 Share Posted February 12, 2014 I've forced myself to watch the loop of the march debacle to better understand when a lock isn't a lock. When the upper level low approached and the circulation got going near ric it was like the electricity got turned off in the advancing waa precip. Then as the slp got really cranking down in se va we had more problems with crappy thermals and spotty precip. I can't find any valid reason to expect the advancing waa shield to lose any punch. H5 isn't closed and the source region for moisture originated in the gulf. There are some big differences with the current storm. I know you know all this and a million other things better than me. Just speaking out loud there there really isn't much of a panic button in play with the front end thump. I agree with you that I do not see anything that could kill the shield right now. Very true. It wouldn't appear we have that degree of disruption in the pcpn field this go around. I also agree with an earlier post -- CI (convective instability for "upright" convection), which would dominate over CSI, does not appear to be as much of an issue here looking at the cross sections of theta-e/geo momentum/RH/UVV/EPV. However, given the weakening static stability, even without "folding" theta-e surfaces, the strong horizontal component to the momentum surfaces would certainly support CSI and thus more slantwise convective bands W-NW-N of the 700-500 mb dry slot. Thanks for verifying with an actual cross section! Much appreciated! I'm mostly interested in the stuff before the dry slot. After looking again, I think the dendritic growth zone is large enough with enough lift that ratios could exceed 10:1. What do you think? It would only happen at max banding and max UVV at say 500mb. Early, my only concern, really, was that the D.G.Z. was too high/shallow that some negative effect to them was possible/riming...but I was grasping there to find a negative. Link to comment Share on other sites More sharing options...
WxMan1 Posted February 12, 2014 Share Posted February 12, 2014 My goodness. I can't wait for high res. Link to comment Share on other sites More sharing options...
JCT777 Posted February 12, 2014 Share Posted February 12, 2014 Looking at radar and recent model trends, that front-end thumping is going to be fantastic for your region. Definitely some double-digit snow accumulations will be happening from this. Link to comment Share on other sites More sharing options...
mdsnowlover Posted February 12, 2014 Share Posted February 12, 2014 we have a wrestling enthusiast, yes"?? That is the guy from WWE?? Link to comment Share on other sites More sharing options...
WxMan1 Posted February 12, 2014 Share Posted February 12, 2014 I agree with you that I do not see anything that could kill the shield right now. Thanks for verifying with an actual cross section! Much appreciated! I'm mostly interested in the stuff before the dry slot. After looking again, I think the dendritic growth zone is large enough with enough lift that ratios could exceed 10:1. What do you think? It would only happen at max banding and max UVV at say 500mb. Early, my only concern, really, was that the D.G.Z. was too high/shallow that some negative effect to them was possible/riming...but I was grasping there to find a negative. Very good points. "Flirting" with the dry slot is sort of analogous to flirting with a supermodel. You can easily get burned, but IF all goes well, it also can result in the night of your life On a more serious level, you *need* to be near it to attain the potential instability aloft, *but* cannot be too far into it (dry slot extending to far down in the atmosphere) where you have no moisture reaching the -10C, which often times is approximated ~700 mb give or take 50 or so mb. So ideally, you want to see some drying above 700 mb, but not down to or (especially) below 700 mb. In the absence of CI, as you noted, CSI can play out, and do so (often times) farther w-nw-n of the dry slot where the static stability aloft is still weakening, yet not as much so (certainly not to the degree that would support upright convection). Link to comment Share on other sites More sharing options...
clskinsfan Posted February 12, 2014 Share Posted February 12, 2014 Looks like the NAM adjusted the dry slot slightly east. It is just an epic run for our entire area. Link to comment Share on other sites More sharing options...
WxMan1 Posted February 12, 2014 Share Posted February 12, 2014 we have a wrestling enthusiast, yes"?? That is the guy from WWE?? Well, not overly so. Yes, straight from WWE, but his animated GIFs when he's enthusiastic are pretty good Link to comment Share on other sites More sharing options...
mdsnowlover Posted February 12, 2014 Share Posted February 12, 2014 Well, not overly so. Yes, straight from WWE, but his animated GIFs when he's enthusiastic are pretty good yeah he's kinda small for wrestling, but he's very enthusiastic. Link to comment Share on other sites More sharing options...
JMU2004 Posted February 12, 2014 Share Posted February 12, 2014 Looks like the NAM adjusted the dry slot slightly east. It is just an epic run for our entire area. a bit...but really "dry slot" is kind of a misnomer with this storm! Link to comment Share on other sites More sharing options...
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