nw baltimore wx Posted January 16, 2013 Share Posted January 16, 2013 And there we have it....LOL I wish I had a memory like zwyts and co with how exactly storms played out in comparison to models. Strong 5h lows always have that sick "yellow stripe" on the NW side. Best case scenario for dc-bwi areas would be to get in on a piece of it. Prob a stretch but not fantasy. Well said. As for me, I would definitely side on the "it still might come north" camp if it wasn't for the crappy winters the last two years. I'm a big believer in the notion that patterns begets patterns, and until we see some snow here, I remain pessimistic. Albeit, cautiously pessimistic. Link to comment Share on other sites More sharing options...
MN Transplant Posted January 16, 2013 Share Posted January 16, 2013 Ok, model summary time (DCA centric): Hits: 18z GFS, 18z RGEM, 15z SREF mean, 12z JMA Fringes: 12z Euro, 12z WRF-ARW, 12z UKMET, 12z NOGAPSComplete misses: 18z NAM, 12z WRF-NMM Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 Well this gets awfully close to DC, but just SE verbatim. Link to comment Share on other sites More sharing options...
nflwxman Posted January 16, 2013 Share Posted January 16, 2013 Ok, model summary time (DCA centric): Hits: 18z GFS, 18z RGEM, 15z SREF mean, 12z JMA Fringes: 12z Euro, 12z WRF-ARW, 12z UKMET, 12z NOGAPS Complete misses: 18z NAM, 12z WRF-NMM The hits versus the fringes make for an evenly matched competition when verification is taken into account. Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 Most of the lift in the DC area is like 600-500mb which if strong enough, could really put down decent snow. But, 25 miles will mean everything and it appears DC rides the line. Link to comment Share on other sites More sharing options...
NOVAForecaster Posted January 16, 2013 Share Posted January 16, 2013 I haven't seen anyone ask about this yet, but what are the ratios going to be on the rain-snow conversion? Because if it's a heavy wet snow, that .3 qpf won't be 3 inches, it would be more like 1 of slush. Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 This could be a nice pants tent for Midlo. Link to comment Share on other sites More sharing options...
yoda Posted January 16, 2013 Share Posted January 16, 2013 Most of the lift in the DC area is like 600-500mb which if strong enough, could really put down decent snow. But, 25 miles will mean everything and it appears DC rides the line. Coastal, could you explain this a lil bit? I don't quite follow what you mean Link to comment Share on other sites More sharing options...
mitchnick Posted January 16, 2013 Share Posted January 16, 2013 This could be a nice pants tent for Midlo. I don't think he needs snow for that! Link to comment Share on other sites More sharing options...
wxmeddler Posted January 16, 2013 Share Posted January 16, 2013 I haven't seen anyone ask about this yet, but what are the ratios going to be on the rain-snow conversion? Because if it's a heavy wet snow, that .3 qpf won't be 3 inches, it would be more like 1 of slush. Probably 8:1 to start ending off as 12:1 Link to comment Share on other sites More sharing options...
clskinsfan Posted January 16, 2013 Share Posted January 16, 2013 .01 for MBY. It's not looking good for those of us to NW. I am glad the rest of u are finally going to get some winter though. Midlo looks to be in great shape. Maybe time for one of your GIfs? Link to comment Share on other sites More sharing options...
mitchnick Posted January 16, 2013 Share Posted January 16, 2013 For phone viewers. At least there's some room to spare n of dc for *something* to accumulate. Well, room to spare on this run anyways. gfs18qpf.JPG Bob, if you compare that close up with attention to the cut off with the 12Z run cutoff, this run is much more smoothed with lighter precip heading further n and w could just be a blip or maybe a sign for 0Z Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 Coastal, could you explain this a lil bit? I don't quite follow what you mean Well this is an 850-500 averaged VV an RH product. As you can see, it has a pretty good slug of VV as inidcated by the oranges and reds over VA and the shaded contour indicated greater than 90% RH through the layer which is good. You can see on 03z Friday that the deep VV as inidicated by purple is more towards VA and the tidewater area. However, things in the atmosphere tilt in the vertical. In our hemisphere, things tilt from east to west or SE to NW so deep VV at 700mb in one area many times extends to 600 and 500mb, but perhaps 50 miles west of where the good 700mb VV are located. IMHO putting all this together would have the band near or just SE of DC proper...but this is just one model's interpretation. Basically, the edge of that shaded area is probably the back edge of the heaviest echoes. Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 You guys can loop H7 on the NCEP products and see a nice linear line of lift starting after 12z tomorrow. Notice at 18z we have strong lift over central VA. This is due to strong frontogenesis. Look at those wind vectors from west to east over DC and south to north near RIC. This is frontogenesis folks. You are tightening the thermal gradient and as a result, creating a steeper slope to which air moves upwards. Without getting technical, the atmosphere loves to set up a circulation on the warm side of this gradient in order to restore this thermal imbalance we have in a short distance. Link to comment Share on other sites More sharing options...
yoda Posted January 16, 2013 Share Posted January 16, 2013 Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 I couldn';t attach an image, but here is what I was referring to. Link to comment Share on other sites More sharing options...
yoda Posted January 16, 2013 Share Posted January 16, 2013 Federal Agencies in D.C. have the option for unscheduled leave/telework Thursday, OPM has announced on Twitter. Link to comment Share on other sites More sharing options...
yoda Posted January 16, 2013 Share Posted January 16, 2013 Topper -- T-1 N of DC... 1-2 DC south... EZF to Culpepper south 2-4... CHO 4-6 Link to comment Share on other sites More sharing options...
ravensrule Posted January 16, 2013 Share Posted January 16, 2013 Federal Agencies in D.C. have the option for unscheduled leave/telework Thursday, OPM has announced on Twitter. Lol, let the fun begin. Link to comment Share on other sites More sharing options...
wxmeddler Posted January 16, 2013 Share Posted January 16, 2013 I couldn';t attach an image, but here is what I was referring to. avn_24_700.gif That confluence zone is just nasty.. Link to comment Share on other sites More sharing options...
HM Posted January 16, 2013 Share Posted January 16, 2013 You guys can loop H7 on the NCEP products and see a nice linear line of lift starting after 12z tomorrow. Notice at 18z we have strong lift over central VA. This is due to strong frontogenesis. Look at those wind vectors from west to east over DC and south to north near RIC. This is frontogenesis folks. You are tightening the thermal gradient and as a result, creating a steeper slope to which air moves upwards. Without getting technical, the atmosphere loves to set up a circulation on the warm side of this gradient in order to restore this thermal imbalance we have in a short distance. Agreed. This is a classic deformation zone with positive frontogenesis. I haven't seen bufkits in the area but if dendritic growth is there where the RH/lift is maximized (looks like it), there will be a solid area of 1-2"/hr type bands sitting over a spot for quite enough time to bust high. Link to comment Share on other sites More sharing options...
Bob Chill Posted January 16, 2013 Share Posted January 16, 2013 Bob, if you compare that close up with attention to the cut off with the 12Z run cutoff, this run is much more smoothed with lighter precip heading further n and w could just be a blip or maybe a sign for 0Z I saw that earlier but wasn't really significant enough to make a point about. But on that note, I do think we will see another move better tonight. I think the lighter qpf on the fringe covers more area to the n&w. This is a dynamic system even though it's small. Give it any room to move north and it will. It comes down to how strong that wall wants to be to our north. That wall already took a major step back since last night on the models. We'll see tonight. I honestly wouldn't be surprised with a move in any direction on the guidance. If I was forced to bet I would go more N&W with both the deform band and lighter qpf further out. Link to comment Share on other sites More sharing options...
Amped Posted January 16, 2013 Share Posted January 16, 2013 It's mostly the nrn stream that is dictating where the precip shield is. The southern stream is too far south to do anyone south of Richmond any good. Slower and more amped is what will bring it north. Link to comment Share on other sites More sharing options...
wxmeddler Posted January 16, 2013 Share Posted January 16, 2013 Agreed. This is a classic deformation zone with positive frontogenesis. I haven't seen bufkits in the area but if dendritic growth is there where the RH/lift is maximized (looks like it), there will be a solid area of 1-2"/hr type bands sitting over a spot for quite enough time to bust high. It's looks pretty sick with the highest lift located in the snow growth zone and at 95%+ humidity. This is the 18z GFS at 3z tomorrow. Link to comment Share on other sites More sharing options...
PhineasC Posted January 16, 2013 Share Posted January 16, 2013 I am pretty confident that the BWI area will be into the blues in the 00Z suite. Euro will show some drizzle. Link to comment Share on other sites More sharing options...
WxMan1 Posted January 16, 2013 Share Posted January 16, 2013 Agreed. This is a classic deformation zone with positive frontogenesis. I haven't seen bufkits in the area but if dendritic growth is there where the RH/lift is maximized (looks like it), there will be a solid area of 1-2"/hr type bands sitting over a spot for quite enough time to bust high. Agreed. Recall the Jan 30 or 31st event in 2010, the one before Snowmageddon II and III 6-10 days later. Granted, it was a colder event, but one where southern and central VA were targeted for the highest accums. While that was largely thd case, there were bands of 6+ inches that extended well north into CHO, EZF, and DCA, which had every bit to do with the fact that the layer of max fgen lift and moisture, while farther up in the atmosphere compared to 50-100 miles south, just so happened to be in the sweet spot in terms of optimizing dendritic growth (i.e. in the -12 to -18C layer). So, even without as much QPF, the snow ratios were much higher, as portions of northern VA got in on warning-criteria snowfall well north of where the highest liquid equiv pcpn was. Again though...that was a notably colder event in the BL going in compared to this one... Link to comment Share on other sites More sharing options...
HM Posted January 16, 2013 Share Posted January 16, 2013 It's looks pretty sick with the highest lift located in the snow growth zone and at 95%+ humidity. This is the 18z GFS at 3z tomorrow. This is the reason that model QPF can really suffer on fringes of deformation zones. At some point, these bands will be made and they will move north and stall. If they reach DC and sit, then the low end stuff isn't going to work out so well. A famous example of this was in the 2009-10 winter where Maryland was on QPF fringe and they ended up with 6-10" ...I'm sure someone can recall this one.... The low level temps do suck but nothing is going to stop that dendrite machine at 3z! Edit: See Brian's post above about Jan 2010. That is the event I'm talking about. Link to comment Share on other sites More sharing options...
HM Posted January 16, 2013 Share Posted January 16, 2013 Agreed. Recall the Jan 30 or 31st event in 2010, the one before Snowmageddon II and III 6-10 days later. Granted, it was a colder event, but one where southern and central VA were targeted for the highest accums. While that was largely thd case, there were bands of 6+ inches that extended well north into CHO, EZF, and DCA, which had every bit to do with the fact that the layer of max fgen lift and moisture, while farther up in the atmosphere compared to 50-100 miles south, just so happened to be in the sweet spot in terms of optimizing dendritic growth (i.e. in the -12 to -18C layer). So, even without as much QPF, the snow ratios were much higher, as portions of northern VA got in on warning-criteria snowfall well north of where the highest liquid equiv pcpn was. Again though...that was a notably colder event in the BL going in compared to this one... Yes that's the exact storm I was thinking about. Thanks! What happens then if we have similar type banding / dendrite production but it falls into a BL that's warmer? I would imagine if a band stalls over someone, it will cool the BL sufficiently but still warm enough for compacting. Tough call here for accumulation. The low level temps are pretty solid 950-850mb and secondary circulation could really cool some folks even more than modeled. Link to comment Share on other sites More sharing options...
WxMan1 Posted January 16, 2013 Share Posted January 16, 2013 Ha ha HM, we were thinking about the same event! I think it was Jan 30, a Saturday.. Link to comment Share on other sites More sharing options...
CoastalWx Posted January 16, 2013 Share Posted January 16, 2013 Ha ha HM, we were thinking about the same event! I think it was Jan 30, a Saturday.. It's pretty classic with these srn vorts and a strong confluence zone. The most classic setup for these bands. Link to comment Share on other sites More sharing options...
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