cast4 Posted October 28, 2011 Share Posted October 28, 2011 DYL looking good after hour 27. Seems like over 1.5" fall as snow. http://68.226.77.253...NAM212_kdyl.txt Yeah, NW burbs look to change over between hr 27 and 30. CCB crushes them after hr 30. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted October 28, 2011 Share Posted October 28, 2011 Here is the Lehigh Valley with the 12z NAM. This is hour 27, or 11am Saturday. Precip starts around 8am when the lowest layers (925mb and below) are above freezing to about 4C at the surface. From 8am to 11am, about 1/4" of precip falls, probably a mix. After 11am, the column cools completely and it's all snow, and total precip is near 2". I think it's waaay overdone, but that's what it's showing. Link to comment Share on other sites More sharing options...
bluehens Posted October 28, 2011 Share Posted October 28, 2011 Chubbs what do you think for our neck of the woods in extreme SE PA/Northern DE? I can't see how we avoid getting at least a few hours of decent snows. Agree that heavy precip rates are an important factor. 12z NAM has actually increased snow in immediate phl area vs 06z Link to comment Share on other sites More sharing options...
rickrd Posted October 28, 2011 Share Posted October 28, 2011 Here is the Lehigh Valley with the 12z NAM. This is hour 27, or 11am Saturday. Precip starts around 8am when the lowest layers (925mb and below) are above freezing to about 4C at the surface. From 8am to 11am, about 1/4" of precip falls, probably a mix. After 11am, the column cools completely and it's all snow, and total precip is near 2". I think it's waaay overdone, but that's what it's showing. Thanks, we'll take half that and by extremely happy, worried about power loss though. Link to comment Share on other sites More sharing options...
hazwoper Posted October 28, 2011 Share Posted October 28, 2011 Warm But lets see what happens as it deepens next frame. Link to comment Share on other sites More sharing options...
B Dawk 20 Posted October 28, 2011 Share Posted October 28, 2011 Yeah forward this to hr 30 and the column looks identical for KLOM., and at hr 33 for KPHL. By hour 33 the majority of the forecast area should be all snow. It just will depend on the precip rate at that point. Here is the Lehigh Valley with the 12z NAM. This is hour 27, or 11am Saturday. Precip starts around 8am when the lowest layers (925mb and below) are above freezing to about 4C at the surface. From 8am to 11am, about 1/4" of precip falls, probably a mix. After 11am, the column cools completely and it's all snow, and total precip is near 2". I think it's waaay overdone, but that's what it's showing. Link to comment Share on other sites More sharing options...
hazwoper Posted October 28, 2011 Share Posted October 28, 2011 Far less precip, which I am guessing helps to keep the temps up a bit as well. Throw it out Link to comment Share on other sites More sharing options...
dryslotted Posted October 28, 2011 Share Posted October 28, 2011 Warm But lets see what happens as it deepens next frame. The city on SE is getting demolished at 33. It does look warm verbatim, but dynamics may have already taken over at that point...0c line along I-95 at 36 and finally crash to the coast at 39... Link to comment Share on other sites More sharing options...
NaoPos Posted October 28, 2011 Share Posted October 28, 2011 The city on SE is getting demolished at 33. It does look warm verbatim, but dynamics may have already taken over at that point...0c line along I-95 at 36 and finally crash to the coast at 39... What city you talking about? Link to comment Share on other sites More sharing options...
B Dawk 20 Posted October 28, 2011 Share Posted October 28, 2011 What city you talking about? Probably PHL Link to comment Share on other sites More sharing options...
snowlurker Posted October 28, 2011 Share Posted October 28, 2011 Chubbs what do you think for our neck of the woods in extreme SE PA/Northern DE? I can't see how we avoid getting at least a few hours of decent snows. I'm not Chubbs, but I've been following this closely. Both the 12Z NAM and GFS (especially!) are warmer at 850mb compared to 0Z. If they're right, and that's a big if, I'm afraid we won't see much flakeage. I was holding onto yesterday's and last night's NAM as a snowy potential outcome but the 12Z NAM and GFS have really rained on the parade. Good luck to you and other fellow Delawareans! Link to comment Share on other sites More sharing options...
dryslotted Posted October 28, 2011 Share Posted October 28, 2011 Probably PHL Sorry, yes. My mistake. Only have time to link the image right now. I'll fix later... Link to comment Share on other sites More sharing options...
NortheastPAWx Posted October 28, 2011 Share Posted October 28, 2011 By another thread I meant a banter thread. Whomever our Metfan is can create it. I guess we just stick with this? Link to comment Share on other sites More sharing options...
okie333 Posted October 28, 2011 Share Posted October 28, 2011 NAM clown map through 48 (take with a grain of salt) More like a pitcher of salt... they use a faulty method to generate their maps (notice my thread in the main forum about TwisterData for details). That map is not accurate. Usually you (roughly) divide by 2 with any snow depth maps other that Earl Barker and InstantWeatherMaps... at any case, those two sites actually use the snow depth parameter of the GRIB files, whereas the other sites do some faulty voodoo with the water equivalent of snow parameter. Here is snowfall (clown map) with the Modified Kuchera algorithm: REAL snow depth: By the way, I experiment with GrADS and GRIB files myself on a regular basis, and I must say these maps are easily the closest I've seen to the actual intentions of the model... even Earl Barker's site has a few minor shortcomings (showing too much snow when changing from rain to snow and too little when changing from snow to rain). Also, for the GFS: Snow Depth: Total Snowfall Link to comment Share on other sites More sharing options...
tombo82685 Posted October 28, 2011 Share Posted October 28, 2011 gfs looks like it goes over to snow after hr 33 looking at soundings for immediate burbs and city Link to comment Share on other sites More sharing options...
chubbs Posted October 28, 2011 Share Posted October 28, 2011 I'm not Chubbs, but I've been following this closely. Both the 12Z NAM and GFS (especially!) are warmer at 850mb compared to 0Z. If they're right, and that's a big if, I'm afraid we won't see much flakeage. I was holding onto yesterday's and last night's NAM as a snowy potential outcome but the 12Z NAM and GFS have really rained on the parade. Good luck to you and other fellow Delawareans! Bluehen - Agree that extreme NW DE and Chester County should see at least couple hours of snow at back-end. GFS is much less snowy though than NAM. Link to comment Share on other sites More sharing options...
hazwoper Posted October 28, 2011 Share Posted October 28, 2011 gfs looks like it goes over to snow after hr 33 looking at soundings for immediate burbs and city Yeah, we need some of those heabvy precip totals to verify as the low deepnes off the coast, or we are going to have a hard time cooling the column. I still like our chances though. Link to comment Share on other sites More sharing options...
tombo82685 Posted October 28, 2011 Share Posted October 28, 2011 the nam and gfs mslp track is pretty close. The difference comes in the strength. The nam has a sub 994 while the gfs has a sub 1000, which is why the gfs is warmer imho Link to comment Share on other sites More sharing options...
NaoPos Posted October 28, 2011 Share Posted October 28, 2011 the nam and gfs mslp track is pretty close. The difference comes in the strength. The nam has a sub 994 while the gfs has a sub 1000, which is why the gfs is warmer imho Yeah, the hi-res of the nam is showing better dynamics at play, hence, heavier precip, and the column cooling... GFs, less dynamics, less qpf, modest BL issues. GFS seems a bit more climo favored attm, but i'm not ready to discount the NAM Link to comment Share on other sites More sharing options...
Sunny and Warm Posted October 28, 2011 Share Posted October 28, 2011 gfs looks like it goes over to snow after hr 33 looking at soundings for immediate burbs and city so similar to the NAM in that regard. The 12z GFS drifted very slightly east to near the 12z NAM position. The real difference is that the GFS is slightly warmer at the start until the dynamical cooling brings it in line with the NAM. Since we are in mesoscale time, I'll side with the NAM over the global GFS, although I do believe the NAM is overdoing QPF and thus cold temps. They go hand in hand. Link to comment Share on other sites More sharing options...
Parsley Posted October 28, 2011 Share Posted October 28, 2011 so similar to the NAM in that regard. The 12z GFS drifted very slightly east to near the 12z NAM position. The real difference is that the GFS is slightly warmer at the start until the dynamical cooling brings it in line with the NAM. Since we are in mesoscale time, I'll side with the NAM over the global GFS, although I do believe the NAM is overdoing QPF and thus cold temps. They go hand in hand. Yup, overall both the 12Z NAM and GFS advertise snow for the Lehigh Valley and Susq. Valley and give the remainder of SE PA a 6-9 hour window for a changeover to snow before things shut down by 3z on Sunday. For locations near or just southeast of I-95 in DE, PA and NJ that window of oppurtunity appears to be 2-4 hours...or less if the dynamics are lacking. Link to comment Share on other sites More sharing options...
CoastalWx Posted October 28, 2011 Share Posted October 28, 2011 Area from MDT-ABE and up into MPO looks to get crushed...esp above 600' or so. Great banding signal evident by placement of mid level lows and 850-500 VV/RH. As always, there will be little nuances and screw zones..but wow. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted October 28, 2011 Share Posted October 28, 2011 Yup, overall both the 12Z NAM and GFS advertise snow for the Lehigh Valley and Susq. Valley and give the remainder of SE PA a 6-9 hour window for a changeover to snow before things shut down by 3z on Sunday. For locations near or just southeast of I-95 in DE, PA and NJ that window of oppurtunity appears to be 2-4 hours...or less if the dynamics are lacking. I agree. As to the bolded part, considering how these changeover events usually work, 6-9 hours is a good amount of time to accum snow. Normally, you get no more than a couple hours max. I agree that southeast of I95 will find it hard to get more than an inch of slush considering temps during most of the event. Link to comment Share on other sites More sharing options...
mattinpa Posted October 28, 2011 Share Posted October 28, 2011 Yup, overall both the 12Z NAM and GFS advertise snow for the Lehigh Valley and Susq. Valley and give the remainder of SE PA a 6-9 hour window for a changeover to snow before things shut down by 3z on Sunday. For locations near or just southeast of I-95 in DE, PA and NJ that window of oppurtunity appears to be 2-4 hours...or less if the dynamics are lacking. Are you thinking we are enough north to get accumulating snow in the Collegeville area? Even 1-3 would be a nice little treat. Link to comment Share on other sites More sharing options...
tombo82685 Posted October 28, 2011 Share Posted October 28, 2011 this looks like a classic early season snow on the gfs...the soundings at hr 36 for kphl has the frz level around 940mb... with surface temp around 34-35...seems like a rain snow mix which goes over to snow at the very tail end with a sloppy coating or so...once from the fall line on north and west i believe thats where you start to see some accumulation of an inch or greater, based on the gfs Link to comment Share on other sites More sharing options...
LVblizzard Posted October 28, 2011 Share Posted October 28, 2011 The GFS worries me slightly, it almost gets the 850mb 0C line into upper Bucks/Montco. That's the farthest north I've seen it on any major model. It is a good sign, however, that the SREF mean and NAM have remained fairly consistent since yesterday evening. Those are the models we want to use for things like banding and dynamics at this range. Link to comment Share on other sites More sharing options...
Parsley Posted October 28, 2011 Share Posted October 28, 2011 Are you thinking we are enough north to get accumulating snow in the Collegeville area? Even 1-3 would be a nice little treat. I think the relatively lower elevations (under 400 ft) in Chester, Montgomery and Bucks should be able to pick up a sloppy 1-3" if precipitation is as intense as depicted on the the models between 18z Sat-03z Sun. Link to comment Share on other sites More sharing options...
NaoPos Posted October 28, 2011 Share Posted October 28, 2011 12z UKIE with a sigh of relief: And this stolen from the NYC thread: (thanks ag3!) Link to comment Share on other sites More sharing options...
RobbTC Posted October 28, 2011 Share Posted October 28, 2011 AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1243 PM EDT FRI OCT 28 2011 .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... UPDATE...MIDDAY GRIDS HAVE PUSHED THE SNOW CLOSER TO THE COAST. WILL LOOK AT 12Z GFS AND HPC WWD GRAPHICS THE NEXT COUPLE OF HOURS. MIGHT HAVE TO MAKE A BUMP IN ACCUMULATIONS. Link to comment Share on other sites More sharing options...
NaoPos Posted October 28, 2011 Share Posted October 28, 2011 another map stolen from the NYC thread i post periodically there, so i deserve to grab a few maps for the PHL region. anyhow, getting into range of the HRRR, AWR and other super hi-res models. Link to comment Share on other sites More sharing options...
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