Lookout Posted February 15, 2015 Share Posted February 15, 2015 I think what we need to watch for tomorrow is an earlier onset of precip. The earlier we can get going, the better. this is especially true for ga. If it's real late like the nam, its' going to get too warm tomorrow. early like the gfs and it won't. Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2015 Share Posted February 15, 2015 The 15z SREFs look close to the 09z SREFs, though there appears to be less spread to the NW of the mean surface low, so maybe less amped members? We'll see when the plumes come out shortly. They seem to support a Miller B track with the primary transferring from N GA to offshore of Myrtle Beach or so. Link to comment Share on other sites More sharing options...
Smoked Posted February 15, 2015 Share Posted February 15, 2015 Pretty large changes in the NAM's 500 mb vorticity signature for 00Z Monday comparing the 00Z and 12Z NAM runs. Looks like there is a trend for a deeper trough with less positive tilt displaced further to the south and west which allows for more (and earlier?) interaction with the cut of low. I looked at the surface location of the low during the same time period and it has been trending south for this evening for the NAM, HRR, and RAP which is fairly substantial since the southward trend is seen even on an hourly basis for the last 4-5 hours for the short range models. I'm not entirely sure what importance this has, but I'm hoping the greater energy will allow the trough to dig deeper and promote a further south track. 00Z NAM 12Z NAM Link to comment Share on other sites More sharing options...
SN_Lover Posted February 15, 2015 Share Posted February 15, 2015 RAP has the low in the same place, but high looks much better situated. Think the south trend will continue. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted February 15, 2015 Share Posted February 15, 2015 this is especially true for ga. If it's real late like the nam, its' going to get too warm tomorrow. early like the gfs and it won't. GA is not much at risk of an early start time because they are well south of the overrunning zone because the low tracks over or to their NW...NC/TN/KY are places that would need to watch for the early start time, if anything I think GA may not see much precip til 17-18Z Link to comment Share on other sites More sharing options...
jacobr57 Posted February 15, 2015 Share Posted February 15, 2015 Pretty large changes in the NAM's 500 mb vorticity signature for 00Z Monday comparing the 00Z and 12Z NAM runs. Looks like there is a trend for a deeper trough with less positive tilt displaced further to the south and west which allows for more (and earlier?) interaction with the cut of low. I looked at the surface location of the low during the same time period and it has been trending south for this evening for the NAM, HRR, and RAP which is fairly substantial since the southward trend is seen even on an hourly basis for the last 4-5 hours for the short range models. I'm not entirely sure what importance this has, but I'm hoping the greater energy will allow the trough to dig deeper and promote a further south track. I noticed the southward trend of the surface low on the RAP as well. It's fairly pronounced. Link to comment Share on other sites More sharing options...
RaleighWx Posted February 15, 2015 Share Posted February 15, 2015 5km WRF-ARW from model page valid 2z Tuesday (9pm Monday) Link to comment Share on other sites More sharing options...
strongwxnc Posted February 15, 2015 Share Posted February 15, 2015 Great observation. Been keeping an eye on the actual current surface map with the H5 and 850 low. Currently still off the coast as shown on your NAM and GFS images. Pretty large changes in the NAM's 500 mb vorticity signature for 00Z Monday comparing the 00Z and 12Z NAM runs. Looks like there is a trend for a deeper trough with less positive tilt displaced further to the south and west which allows for more (and earlier?) interaction with the cut of low. I looked at the surface location of the low during the same time period and it has been trending south for this evening for the NAM, HRR, and RAP which is fairly substantial since the southward trend is seen even on an hourly basis for the last 4-5 hours for the short range models. I'm not entirely sure what importance this has, but I'm hoping the greater energy will allow the trough to dig deeper and promote a further south track. 00Z NAM 12Z NAM Link to comment Share on other sites More sharing options...
Jonathan Posted February 15, 2015 Share Posted February 15, 2015 I wouldn't be surprised if the start time is earlier than any of the modeling indicates. It seems that often happens with overrunning. No guarantees, of course. It seems like overrunning events always start earlier than modeled. However, we're going to have some extraordinarily dry air tonight and tomorrow. Wonder how long we get to watch wasted virga fall before we saturate the column? Link to comment Share on other sites More sharing options...
superjames1992 Posted February 15, 2015 Share Posted February 15, 2015 5km WRF-ARW from model page valid 2z Tuesday (9pm Monday) I was just looking at that on your Model Center. Looks like 1-2"/hr rates there. Pretty heavy stuff for I-40/north. Looks like the snow moves in just after noon here. I also notice that it has surface temps well into the teens here and the surface temps below freezing all the way into the NE ATL burbs. I have no idea how accurate teh WRF-ARW is, however. Link to comment Share on other sites More sharing options...
Smoked Posted February 15, 2015 Share Posted February 15, 2015 Great observation. Been keeping an eye on the actual current surface map with the H5 and 850 low. Currently still off the coast as shown on your NAM and GFS images. Thanks. I think (hope) we will finally be able to nail this down by the 0Z runs tonight when all aspects of the storm are properly sampled and the short range models really come into play. Link to comment Share on other sites More sharing options...
deltadog03 Posted February 15, 2015 Share Posted February 15, 2015 I wasn't around last night to see the models but looking at them this morning, i have to agree this is pretty extraordinary and frustrating. Even though it's bleak, I still have some concerns that areas that appear out of the woods in terms of freezing rain over northeast ga and sc are actually not. The last 2 runs of the gfs in fact suggest temps still get to freezing from around gainesville to my location...as low as 28 or 29 around gainesville northeast. In fact tomorrow it even has the northern burbs of atlanta getting to freezing before warming up. So for areas along and east/northeast of a line from gainesville to athens/elberton I still believe there is a chance for a period of icing..though confidence is real low at the moment. . I think areas north of 85 and at/east of gainesville get major icing still...especially up around toccoa, cornelia, etc When there are huge dewpoint depressions/high potential for evap cooling..they normally do not cool the temps as much as From my experience in cad situations, the nam and gfs are typically 1 to 3 degrees too warm after saturation. That's a pretty big deal when they model progs are 32/33 degrees such as in this . There have been many a ice events here where the models insisted on it being 33 or 34 degrees after saturation. With this system, i've seen the gfs and nam hiking dewpoints 20 to 25 degrees after precip starts without much of a temp response. For example, across portions of north ga the nam/gfs have insisted on temps being roughly 35 degrees with dp's in the single digits to around 10 before precip starts and only dropping the temp to 33 or 34 when the wetbulb is actually 28 or 29. That said, it's possible that can happen if ONLY the near surface is that cold and dry. In other words, if it's cold and dry from 950 to 925mb down to the surface, temps are more likely to fall close to the wetbulbs if there is appreciable precip to do so. if there is strong waa and the near surface cold layer is only a couple of hundred feet deep the temp will not respond nearly as much. In this case, at least initially, temps at 925mb to the near surface are below freezing so i expect quite a temp drop in those areas where the cold extends up to 950mb at least...which is over a good portion of north ga/sc midlands. For those on the edge, watch for how much surface warming there is tomorrow and how low the dewpoints are when precip is likely to start. If temps end up warming too much before precip arrives and based on wetbulbs/dewpoints that is generally 40 degrees, or dewpoints start rising before precip arrives, it should remain rain. (except starting out as sleet or mix). I agree, Lookout...I actually put in the new forecast map how I think your area still sees ICE, but there is a VERY high bust factor because I could honestly see yalls area hit hard to be honest. Link to comment Share on other sites More sharing options...
griteater Posted February 15, 2015 Share Posted February 15, 2015 Some info on precipitation type determination... Link to comment Share on other sites More sharing options...
Jon Posted February 15, 2015 Share Posted February 15, 2015 I was just looking at that on your Model Center. Looks like 1-2"/hr rates there. Pretty heavy stuff for I-40/north. Looks like the snow moves in just after noon here. I also notice that it has surface temps well into the teens here and the surface temps below freezing all the way into the NE ATL burbs. I have no idea how accurate teh WRF-ARW is, however. It's one of the wettest solutions out there, that's all I know, so it could be a bias...total QPF map is a little much for this system it seems. Link to comment Share on other sites More sharing options...
Lookout Posted February 15, 2015 Share Posted February 15, 2015 GA is not much at risk of an early start time because they are well south of the overrunning zone because the low tracks over or to their NW...NC/TN/KY are places that would need to watch for the early start time, if anything I think GA may not see much precip til 17-18Z noon or 1pm is what I meant by "early". since only the gfs really starts precip by then. rest of the modeling has it starting later. Another important factor is a thick cloud cover moving in early in the morning to limit surface heating. The gfs has it moving in/lowering sooner and the nam doesn't..and that is one reason why the gfs is a lot colder and the nam warmer....but quite a few of the modeling doesn't support thickening cloud cover until it's too late and the damage has been done with respect to warming. Link to comment Share on other sites More sharing options...
strongwxnc Posted February 15, 2015 Share Posted February 15, 2015 12 HR snow fall mean off the 15Z SREF http://weather.cod.edu/forecast/ Link to comment Share on other sites More sharing options...
DixieBlizzard Posted February 15, 2015 Share Posted February 15, 2015 noon or 1pm is what I meant by "early". since only the gfs really starts precip by then. rest of the modeling has it starting later. Another important factor is a thick cloud cover moving in early in the morning to limit surface heating but even that doesn't appear too likely based on many of them. Mid-level overcast moving into NW GA now after a very clear morning and early afternoon. 31.8F with 0F DP. Link to comment Share on other sites More sharing options...
packfan98 Posted February 15, 2015 Share Posted February 15, 2015 SREF plumes look like much less snow and more ip/fzrn Link to comment Share on other sites More sharing options...
GaWx Posted February 15, 2015 Share Posted February 15, 2015 GA is not much at risk of an early start time because they are well south of the overrunning zone because the low tracks over or to their NW...NC/TN/KY are places that would need to watch for the early start time, if anything I think GA may not see much precip til 17-18Z Of course, this is assuming the low really tracks that far north. Link to comment Share on other sites More sharing options...
NC_WX10 Posted February 15, 2015 Share Posted February 15, 2015 SREF plumes look like much less snow and more ip/fzrn 12 HR snow fall mean off the 15Z SREF http://weather.cod.edu/forecast/ Screen Shot 2015-02-15 at 2.37.59 PM.png So I'm guessing this map is all frozen precip? Link to comment Share on other sites More sharing options...
NCSNOW Posted February 15, 2015 Share Posted February 15, 2015 Grit, that is some interesting info. Did I read correctly that it's not the depth of the warm layer, but really how cold the cold layer is (-8c) guranteed snowflake will survive warm nose if it originates in that cold of snow growth area. Also if you go no more than 1c in the warm nose, flake will survive. Past 3c it's frzng rn or rn gurantee. Link to comment Share on other sites More sharing options...
strongwxnc Posted February 15, 2015 Share Posted February 15, 2015 So I'm guessing this map is all frozen precip? That is my assumption. New this this site. Link to comment Share on other sites More sharing options...
strongwxnc Posted February 15, 2015 Share Posted February 15, 2015 15Z SREF plume for my area is a major IP storm. Mean Snowfall is less than 1".. Link to comment Share on other sites More sharing options...
PackGrad05 Posted February 15, 2015 Share Posted February 15, 2015 Someone mentioned earlier that the SREF plumes have a slight warm bias... Therefore, they may be undergoing the snow amounts in favor of more mixed precip? Link to comment Share on other sites More sharing options...
GaWx Posted February 15, 2015 Share Posted February 15, 2015 5km WRF-ARW from model page valid 2z Tuesday (9pm Monday) For N ATL-AHN, this 5 km WRF-ARW (12Z 38 hour projection) is pretty ominous looking with its ZR throughout that corridor and with it being pretty late (9 PM). That map has ZR back through most of Gwinnett, the N DeKalb/Fulton line just a few miles north of the Perimeter, all of Cherokee, and even back to Cartersville! It is clearly a huge outlier and must be taken with a big grain, but is it possible it is better at considering the wedge? Also, keep in mind that the 12Z GFS is not all that far off from this if it is just a few degrees too warm, which was the case at 1 PM as I noted. Link to comment Share on other sites More sharing options...
NCSNOW Posted February 15, 2015 Share Posted February 15, 2015 Cold rain I can't quote your post over the phone. I've seen it sleet with temps 18-19 on 2 seperate ovcasions. Once in the 90s here in asheboro and the biggest one was in Rocky Mount mid 80s. Actually had thunder with it. So as crazy as it sounds it does happen. Seen it freezing rain a inch of qpf with a temp of 21 in Dec 2002. Link to comment Share on other sites More sharing options...
HurricaneTracker Posted February 15, 2015 Share Posted February 15, 2015 15Z SREF plume for my area is a major IP storm. Mean Snowfall is less than 1".. SREF mean snow for KAVL is 0.25". Wow. Mean QPF is still near 1.00". That's a lot of sleet and freezing rain for the mountains. Sent from my iPad using Tapatalk Link to comment Share on other sites More sharing options...
HKY_WX Posted February 15, 2015 Share Posted February 15, 2015 This is what i'm thinking for this storm at this point: Asheville - 2 - 4 inches of snow/sleet, .25 zr Greensboro - 4-6 inches of snow/sleet, Trace zr Hickory - 4-6 inches of snow/sleet Raleigh - 1-3 inches of snow/sleet, .25 zr Roanoke - 6 - 10 inches of snow HIGHEST ICESTORM THREAT Charlotte - T - 1 inch of snow/sleet, .25 - .5 zr Fayetteville - Trace of snow/sleet, ,.5 - .75 zr Greenville, SC - 1 inch of snow/sleet, .5-.75 zr Link to comment Share on other sites More sharing options...
Wow Posted February 15, 2015 Share Posted February 15, 2015 18z NAM is a bit slower and farther west with the storm so far at 24 Link to comment Share on other sites More sharing options...
mrdaddyman Posted February 15, 2015 Share Posted February 15, 2015 18Z NAM has the precip shield further West and the LP is much further SW than the 12Z run at hour 24 Link to comment Share on other sites More sharing options...
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