WEATHER53 Posted January 2 Share Posted January 2 4 minutes ago, Ravens94 said: Lots of wobbling in the same general area. We are known to loose a storm for a few runs only to have it trend better within 72 hours I would say this one will be no different. Immediate DC area being between 3-8” for 48 consecutive hours is very reassuring. 1 Link to comment Share on other sites More sharing options...
Chris78 Posted January 2 Share Posted January 2 GEFS dropped all of the Ohio Valley lows. Pure coastal it appears. 10 1 Link to comment Share on other sites More sharing options...
Terpeast Posted January 2 Share Posted January 2 1 minute ago, Chris78 said: GEFS dropped all of the Ohio Valley lows. Pure coastal it appears. Could just be the thing that helps us keep “just” cold enough air west of i95 6 Link to comment Share on other sites More sharing options...
BristowWx Posted January 2 Share Posted January 2 2 minutes ago, Terpeast said: Just by looking at this, it seems like the 18z gfs is depicting a completely different synoptic setup than any of the previous runs. It has an anafront look almost with that strip. Link to comment Share on other sites More sharing options...
AtlanticWx Posted January 2 Share Posted January 2 im confused, this run looked worse before it played out? what makes 18z gfs even better? am i missing some weird vort Link to comment Share on other sites More sharing options...
WEATHER53 Posted January 2 Share Posted January 2 1 minute ago, Chris78 said: GEFS dropped all of the Ohio Valley lows. Pure coastal it appears. Trying to close off 1012 contour to a 1004 didn’t seem likely 1 Link to comment Share on other sites More sharing options...
WxUSAF Posted January 2 Author Share Posted January 2 5 minutes ago, Terpeast said: Just by looking at this, it seems like the 18z gfs is depicting a completely different synoptic setup than any of the previous runs. If there’s been any real trend over the last 24-48 hours, I think it’s been away from a big phased system and toward a weaker southern wave sliding east alone. 18z gfs is the biggest step yet on that. That removes the big upside potential, but maybe allows us to get something respectable still? 12 Link to comment Share on other sites More sharing options...
jayyy Posted January 2 Share Posted January 2 Def was not expecting that output on the HH GFS. That banding setup is insane. End up with 7-10” imby despite the evolution looking meh at first. The GEFS is also interesting to say the least. Essentially removes the OV lows and focuses everything along the coast. Less precip but less mixing concerns up this way. Certainly curious to see what 0z looks like. 2 Link to comment Share on other sites More sharing options...
Terpeast Posted January 2 Share Posted January 2 6 minutes ago, WxUSAF said: If there’s been any real trend over the last 24-48 hours, I think it’s been away from a big phased system and toward a weaker southern wave sliding east alone. 18z gfs is the biggest step yet on that. That removes the big upside potential, but maybe allows us to get something respectable still? Yes, a bigger phased system would only have worked with a block that holds the 50/50 low down and keeps cold air close by. But for marginal in situ airmasses without a block, a weaker slider is what we usually want. Sure, a very dynamic storm can and has dropped heavy snow with big rates in a marginal airmass but that tends to be the exception 7 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted January 2 Share Posted January 2 47 minutes ago, clskinsfan said: Chuck is upping his troll game. GFS is fine. 3-5 seems like a nice storm to break the ice for the season. Hopefully plenty more to come. If we could manage 3" - 5" or even something like 4" - 7", that would be the biggest event for many in years. 9 Link to comment Share on other sites More sharing options...
87storms Posted January 2 Share Posted January 2 The 540 line is near Detroit this run...what could possibly go wrong. 4 Link to comment Share on other sites More sharing options...
high risk Posted January 2 Share Posted January 2 Now would be a good time for a few quick reminders about model snow accumulations: - Most of the American models (I'm not entirely sure about our international friends) generate a water equivalent of snow. It's then up to the user to apply a reasonable snow-to-liquid ratio. Some sites compute one (i.e. Kuchera), but that tends to be somewhat generous. 10:1 is the most commonly displayed field, but while it's a nice one-size-fits-all approach, it's not always applicable to the temperature profile. The key here is that if you're looking at a GFS 10:1 map in a marginal temperature situation, don't say that the GFS shows 6-8 or whatever amount. It doesn't. Mentally adjust that "starter map" as needed. - Along those lines, the water equivalent of snow is not always a measure of how much snow can accumulate. Sleet goes into the same bucket as snow, so an all sleet event will still show large water equivalents, and a 10:1 map looks absurd. Even an event with 1" of liquid that consists of a 50-50 mix of rain and mangled snowflakes will show 0.5" of snow water equivalent. If you use a 10:1 map, you get 5", even though the model never really thought that anything would stick. - Those issues with sleet or snow that won't accumulate due to warm ground or marginal temps are largely handled by the snow depth field which is the actual amount that the model thinks will be on the ground. 10:1 and snow depth maps look amazingly different in sleet events, as they should. But they also often look different in events with marginal temps or very warm ground. The snow depth maps are usually good, but they do tend to underestimate when the ground is quite warm heading into an event or if big rates overcome marginal temps. In those events, a blend of the 10:1 and snow depth maps is often a good call. - RAP/HRRR actually predicts accumulations (with a temperature-dependent SLR) that account for compacting and melting, although they're not displayed on Tropical Tidbits. - The NBM computes SLRs for each member with snow, and the system overall uses a lot of inputs (including ensembles) and is calibrated, so it's worth a look. Remember, though, that it won't respond immediately to big shifts in guidance. Knowing the limitations of the products you're examining helps to limit the confusion, frustration, and ugly analysis. Thanks for coming to my TED talk. 16 20 Link to comment Share on other sites More sharing options...
nj2va Posted January 2 Share Posted January 2 Eye balling on the 10:1 (caveats aside) snowfall maps, looks like about 3 more members than 12z have the 2” line into DC on the 18z GEFS. About 19/30. 2 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted January 2 Share Posted January 2 1 minute ago, high risk said: Now would be a good time for a few quick reminders about model snow accumulations: - Most of the American models (I'm not entirely sure about our international friends) generate a water equivalent of snow. It's then up to the user to apply a reasonable snow-to-liquid ratio. Some sites compute one (i.e. Kuchera), but that tends to be somewhat generous. 10:1 is the most commonly displayed field, but while it's a nice one-size-fits-all approach, it's not always applicable to the temperature profile. The key here is that if you're looking at a GFS 10:1 map in a marginal temperature situation, don't say that the GFS shows 6-8 or whatever amount. It doesn't. Mentally adjust that "starter map" as needed. - Along those lines, the water equivalent of snow is not always a measure of how much snow can accumulate. Sleet goes into the same bucket as snow, so an all sleet event will still show large water equivalents, and a 10:1 map looks absurd. Even an event with 1" of liquid that consists of a 50-50 mix of rain and mangled snowflakes will show 0.5" of snow water equivalent. If you use a 10:1 map, you get 5", even though the model never really thought that anything would stick. - Those issues with sleet or snow that won't accumulate due to warm ground or marginal temps are largely handled by the snow depth field which is the actual amount that the model thinks will be on the ground. 10:1 and snow depth maps look amazingly different in sleet events, as they should. But they also often look different in events with marginal temps or very warm ground. The snow depth maps are usually good, but they do tend to underestimate when the ground is quite warm heading into an event or if big rates overcome marginal temps. In those events, a blend of the 10:1 and snow depth maps is often a good call. - RAP/HRRR actually predicts accumulations (with a temperature-dependent SLR) that account for compacting and melting, although they're not displayed on Tropical Tidbits. - The NBM computes SLRs for each member with snow, and the system overall uses a lot of inputs (including ensembles) and is calibrated, so it's worth a look. Remember, though, that it won't respond immediately to big shifts in guidance. Knowing the limitations of the products you're examining helps to limit the confusion, frustration, and ugly analysis. Thanks for coming to my TED talk. Excellent information. For the record, all Maryland Mesonet sites will have 2", 5", 10", 20" and 1 meter soil temperatures values. All data will be sent to NOAA for incorporation into whatever system they have for ground temp monitoring. We have 5 sites online. It might be worthwhile for folks to bookmark this site as we start dancing around snowfall probabilities. 5 4 Link to comment Share on other sites More sharing options...
BTRWx's Thanks Giving Posted January 2 Share Posted January 2 Is the nbm publicly available? Link to comment Share on other sites More sharing options...
clskinsfan Posted January 2 Share Posted January 2 3 minutes ago, Eskimo Joe said: Excellent information. For the record, all Maryland Mesonet sites will have 2", 5", 10", 20" and 1 meter soil temperatures values. All data will be sent to NOAA for incorporation into whatever system they have for ground temp monitoring. We have 5 sites online. It might be worthwhile for folks to bookmark this site as we start dancing around snowfall probabilities. Cool site. Thanks! Link to comment Share on other sites More sharing options...
WesternFringe Posted January 2 Share Posted January 2 1 hour ago, Heisy said: 24 hour change lol . Some of this looks like artifacts of timing to me, since the sw has sped up. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted January 3 Share Posted January 3 1 Link to comment Share on other sites More sharing options...
psuhoffman Posted January 3 Share Posted January 3 1 hour ago, Heisy said: Meh, I’m always selling GFS temp profile. All I’m getting from this run is that it’s completely folded the stronger wave idea. Bump the snow map a good bit NW imo. Not to be deb. Just experience and blending other guidance . There is a path to a decent snow still, especially NW. We don’t have much experience with the new upgraded GFS. It’s supposed to be better with the cold bias. We will see. 1 hour ago, Chris78 said: Option 1 I would think is safer but with less upside. I know your moose hunting but I would gladly take a squirl , fox or anything in between. Edit: @psuhoffman can you explain why our qpf increased even with the system being weaker? 51 minutes ago, Terpeast said: Just by looking at this, it seems like the 18z gfs is depicting a completely different synoptic setup than any of the previous runs. The SW continued to trend weaker. 18z gfs found the seeet spot that @WxUSAF alluded to where the NS SW washes out completely such that the primary gets killed completely and all the focus is on the coastal wave. This increased qpf this run because we were stuck in between the dynamics from the weak primary and secondary on the 12z runs. There was a qpf max to either side of us. This focused all the lift over us. The danger being if the system continues to weaken that will degrade from here. But maybe there is a limit to that since there is almost no NS component anymore on the 18z. Not sure how much weaker it can get, famous last words. 3 1 Link to comment Share on other sites More sharing options...
psuhoffman Posted January 3 Share Posted January 3 1 hour ago, CAPE said: lol thanks. I'm good. If this winter goes as expected, the last 6 weeks or so of met winter should make most in this region happy. Otherwise, I chase. Kinda thinking about hanging out in Gettysburg this weekend. Gettysburg is a perfect town to be in the snow! Do you know is that little cider micro brew still there on the main square? Lots of places like that didn’t survive Covid unfortunately. Link to comment Share on other sites More sharing options...
frd Posted January 3 Share Posted January 3 13 minutes ago, psuhoffman said: The danger being if the system continues to weaken that will degrade from here. good thread, and talking about the this very thing. 1 2 Link to comment Share on other sites More sharing options...
Heisy Posted January 3 Share Posted January 3 I think 18z euro would have been a touch or 2 better had we seen it beyond 90 hours. . 1 1 1 1 Link to comment Share on other sites More sharing options...
Heisy Posted January 3 Share Posted January 3 . 2 Link to comment Share on other sites More sharing options...
CAPE Posted January 3 Share Posted January 3 4 minutes ago, psuhoffman said: Gettysburg is a perfect town to be in the snow! Do you know is that little cider micro brew still there on the main square? Lots of places like that didn’t survive Covid unfortunately. I've been there before in the snow. It's great. Not been since just before Covid, but sadly I know the story of places like that that didn't survive. Link to comment Share on other sites More sharing options...
BristowWx Posted January 3 Share Posted January 3 1 minute ago, Heisy said: . I’ll admit I cannot see anything other than a tick better confluence. Am I way off on that? Link to comment Share on other sites More sharing options...
Terpeast Posted January 3 Share Posted January 3 Just now, BristowWx said: I’ll admit I cannot see anything other than a tick better confluence. Am I way off on that? No, I was seeing the same 1 Link to comment Share on other sites More sharing options...
Chris78 Posted January 3 Share Posted January 3 1 minute ago, Terpeast said: No, I was seeing the same Looks like heights are just slightly lower over us. Maybe 20 miles or so. But that could make a big difference in sensible weather. 1 Link to comment Share on other sites More sharing options...
Heisy Posted January 3 Share Posted January 3 18z gfs vs 18z euro H5 Pressure. 4 1 Link to comment Share on other sites More sharing options...
TinGTown Posted January 3 Share Posted January 3 Hello All! I posted a similar question on the Penn sub forum but wanted to ask here as well. I have a freshman kid at Penn State in State College, PA. I am going to drive from DC to State College on Sunday. I have never driven to SC in winter conditions. Can anyone give me an idea of how much snow to expect in central PA? Do any of you know how the roads hold up traveling to State College? Thank you for Amy information you can share with me! Link to comment Share on other sites More sharing options...
psuhoffman Posted January 3 Share Posted January 3 4 minutes ago, Heisy said: I think 18z euro would have been a touch or 2 better had we seen it beyond 90 hours. . Forgive me but given the last few years and your MO at first glance I thought it said I think 18z euro would have been a torch As of right now I don’t think anything is “trending” per se. guidance picked up on a major shift due to that western SW. euro at 6z. Gfs at 12z. Oddly the ggem had this first then reverted to what other guidance had yesterday. But other than catching on to the trend towards stronger trailing SW that dampens our SW they aren’t trending just settling into the new paradigm. on a side note the ggem does this a lot. Will have an idea then just when everything else trends towards it…it goes off on a tangent. I know it scores better than tie gfs but anecdotally it seems less reliable. 2 Link to comment Share on other sites More sharing options...
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