Eskimo Joe Posted January 5 Share Posted January 5 2 minutes ago, AtlanticWx said: isn't it 00z though? Correct. Saw a comment early about sampling and the 18z suite. 1 Link to comment Share on other sites More sharing options...
wxmvpete Posted January 5 Share Posted January 5 5 minutes ago, SnowenOutThere said: The 3k Nam does the @psuhoffman way to victory and keeps the 850s considerably cooler during that critical 3 hour window, just a tick or two more and even the immediate suburbs would be on the snowy side. 3kmNAM really went full blown NAM'd here. A notable change was the stronger frontogenesis at 850mb and 700mb (attached). Taking a sample sounding (it is basically eastern Frederick County, all of Carroll, and western Baltimore County, as far south as I-70 and on north to the M-D), the intense vertical velocities lineup well with the DGZ. This stronger FGEN held on for a good 6 hour span. This is the way to an over performer. Now, whether that actually occurs or not, well, we still have time to see. 8 10 Link to comment Share on other sites More sharing options...
Buddy1987 Posted January 5 Share Posted January 5 3 minutes ago, MillvilleWx said: The reasoning for the shift in the colder solution on the NAM is the development of a closed 850mb low tracking south of the Potomac over north-central VA. Pay close attention to the wind barb across the northwest area and how the 850mb southeasterlies hit a brick wall over Parrs Ridge and the wind direction flips. This would allow for cold air to advect into the northern and western side of the circulation creating a more beneficial PBL and keep everything frozen, or even all snow. Check out the wind barbs to the east of RNK... As a result, watch the 850mb temp profile as we work through time. This is actually how you get surprises and periods of heavy snow when you weren't expecting. MAJOR CAVEAT.... THIS IS JUST ONE RUN OF ONE MODEL!!! We are going to want to see other guidance pull this off and have it become something to watch. This could be a one run and done deal, but there is potential for this. I will not be committing anything until I see some agreement from other guidance. It was interesting to see and point out as a possibility. It would affect the forecast in a big way. These are why these marginal events are so tricky. One thing can make or break a forecast. Let's hope it's right. Right now, no changes from my current thinking. Great post! I do feel like with cad setup here Nam does have some superiority or at least some credibility for 850s and 2m specifically. Everything else is really a crapshoot as to what it shows (or what it doesn’t sometimes haha) 2 Link to comment Share on other sites More sharing options...
clskinsfan Posted January 5 Share Posted January 5 RGEM still didnt flinch on track. sub 1000 just north of OC. A bit warmer in the upper levels. But it refuses to change storm track for like 65 days straight. EDIT: And that 12 inch lolli NW of Winchester is real close to @EastCoast NPZ old home. 2 1 Link to comment Share on other sites More sharing options...
wxmvpete Posted January 5 Share Posted January 5 9 minutes ago, high risk said: The NAM 10:1 maps look huge even along the I-95 corridor, because even after the precip type maps show rain, the model microphysics are generating sleet which is going into the snow water equivalent tally.. Here is a sounding from the "rain" area: That's heavy sleet. Not saying that the thermal profile will be correct, but it explains the generous 10:1 totals. Something that has been on my mind, especially for those to the west maybe more along Parrs Ridge, is are we seeing guidance bring that warm nose in as-advertised, but also not capturing just how cold the low levels will be once they wet bulb initially? I can see an avenue that still certainly result in a less snowy regime. But if those N-NE winds at low levels holds, some areas may end up more icy than just rain. That will be worth watching on the CAMs in future runs. And the CAMs will be more included in the WPC PWPF now that we are inside of 60 hours for this event. 5 1 Link to comment Share on other sites More sharing options...
TSSN+ Posted January 5 Share Posted January 5 Lwx issued a was for Carroll but dropped my snow totals, makes sense lol Link to comment Share on other sites More sharing options...
Imgoinhungry Posted January 5 Share Posted January 5 Lwx issued a was for Carroll but dropped my snow totals, makes sense lolIce? I was surprised to see significant ice in the watch that was posted for frederick/carroll. Link to comment Share on other sites More sharing options...
ers-wxman1 Posted January 5 Share Posted January 5 9 minutes ago, MillvilleWx said: The reasoning for the shift in the colder solution on the NAM is the development of a closed 850mb low tracking south of the Potomac over north-central VA. Pay close attention to the wind barb across the northwest area and how the 850mb southeasterlies hit a brick wall over Parrs Ridge and the wind direction flips. This would allow for cold air to advect into the northern and western side of the circulation creating a more beneficial PBL and keep everything frozen, or even all snow. Check out the wind barbs to the east of RNK... As a result, watch the 850mb temp profile as we work through time. This is actually how you get surprises and periods of heavy snow when you weren't expecting. MAJOR CAVEAT.... THIS IS JUST ONE RUN OF ONE MODEL!!! We are going to want to see other guidance pull this off and have it become something to watch. This could be a one run and done deal, but there is potential for this. I will not be committing anything until I see some agreement from other guidance. It was interesting to see and point out as a possibility. It would affect the forecast in a big way. These are why these marginal events are so tricky. One thing can make or break a forecast. Let's hope it's right. Right now, no changes from my current thinking. Guidance did this on the Wed 00Z run, closed off the 850 low tracking to our south and frozen went up dramatically. 9 1 Link to comment Share on other sites More sharing options...
87storms Posted January 5 Share Posted January 5 NAMs can’t be trusted no matter how good they look. It is encouraging to see models upping the precip thoughI found the nam to be generally unreliable for precip throughout the summer, so I just started using the gfs. It’s good for scoping out potential banding and I suppose temps, but that’s about it imo. I want it to be right, but I’m a veteran now…it’s hard to fool me lol. 1 Link to comment Share on other sites More sharing options...
high risk Posted January 5 Share Posted January 5 5 minutes ago, wxmvpete said: Something that has been on my mind, especially for those to the west maybe more along Parrs Ridge, is are we seeing guidance bring that warm nose in as-advertised, but also not capturing just how cold the low levels will be once they wet bulb initially? I can see an avenue that still certainly result in a less snowy regime. But if those N-NE winds at low levels holds, some areas may end up more icy than just rain. That will be worth watching on the CAMs in future runs. And the CAMs will be more included in the WPC PWPF now that we are inside of 60 hours for this event. Totally agree about the low-level temps. The EC and Canadian bring much of the I-95 corridor into the upper 30s by Saturday evening, but the NAMs this evening keep that area around 33. With the north-northeast wind direction shown on most guidance, a quick rise into the upper 30s while precip is falling seems unlikely. 3 2 Link to comment Share on other sites More sharing options...
Weather Will Posted January 5 Share Posted January 5 WB 0Z RGEM 4 Link to comment Share on other sites More sharing options...
Deck Pic Posted January 5 Share Posted January 5 The NAM actually keeps most of DC snow or snow/mix until mid afternoon. hmmm 9 Link to comment Share on other sites More sharing options...
TSSN+ Posted January 5 Share Posted January 5 6 minutes ago, Imgoinhungry said: Ice? I was surprised to see significant ice in the watch that was posted for frederick/carroll . Don’t see much chance of freezing rain. Link to comment Share on other sites More sharing options...
Imgoinhungry Posted January 5 Share Posted January 5 Don’t see much chance of freezing rain. Neither do I, which is why I was surprised by the wording of the watches. . Link to comment Share on other sites More sharing options...
Deck Pic Posted January 5 Share Posted January 5 5 minutes ago, Deck Pic said: The NAM actually keeps most of DC snow or snow/mix until mid afternoon. hmmm 2pm Saturday at my house 1 Link to comment Share on other sites More sharing options...
Weather Will Posted January 5 Share Posted January 5 ICON is a tick SE with snow line as well. Link to comment Share on other sites More sharing options...
EastCoast NPZ Posted January 5 Share Posted January 5 18 minutes ago, clskinsfan said: RGEM still didnt flinch on track. sub 1000 just north of OC. A bit warmer in the upper levels. But it refuses to change storm track for like 65 days straight. EDIT: And that 12 inch lolli NW of Winchester is real close to @EastCoast NPZ old home. Right over top. Wouldn't that be a kick in the nutz. 1 Link to comment Share on other sites More sharing options...
WEATHER53 Posted January 5 Share Posted January 5 1 hour ago, Kevin Reilly said: On Tuesday morning here it was 24 that cold just vanished when the sun came up Tuesday temps zoomed back up to 44. Last night I went to bed at 10:30 it was 33 got up at 5:45 am it was still 33 not too much cold air available around these parts. Fresh surge of cold air this afternoon with few degree temp drop and dews falling 8/9/10 in two hours 2 Link to comment Share on other sites More sharing options...
pazzo83 Posted January 5 Share Posted January 5 2 minutes ago, WEATHER53 said: Fresh surge of cold air this afternoon with few degree temp drop and dews falling 8/9/10 in two hours i think we'll be stuck in the 30s tomorrow. Link to comment Share on other sites More sharing options...
Weather Will Posted January 5 Share Posted January 5 WB ICON snow is too high 10-1 but also higher compared to 18Z. 1 Link to comment Share on other sites More sharing options...
psuhoffman Posted January 5 Share Posted January 5 31 minutes ago, MillvilleWx said: The reasoning for the shift in the colder solution on the NAM is the development of a closed 850mb low tracking south of the Potomac over north-central VA. Pay close attention to the wind barb across the northwest area and how the 850mb southeasterlies hit a brick wall over Parrs Ridge and the wind direction flips. This would allow for cold air to advect into the northern and western side of the circulation creating a more beneficial PBL and keep everything frozen, or even all snow. Check out the wind barbs to the east of RNK... As a result, watch the 850mb temp profile as we work through time. This is actually how you get surprises and periods of heavy snow when you weren't expecting. MAJOR CAVEAT.... THIS IS JUST ONE RUN OF ONE MODEL!!! We are going to want to see other guidance pull this off and have it become something to watch. This could be a one run and done deal, but there is potential for this. I will not be committing anything until I see some agreement from other guidance. It was interesting to see and point out as a possibility. It would affect the forecast in a big way. These are why these marginal events are so tricky. One thing can make or break a forecast. Let's hope it's right. Right now, no changes from my current thinking. It is just one run and I’m not expecting it yet BUT I was noting the NAM and euro were hinting at this at 12 and even more 18z. They’ve been trending towards starting to amplify the coastal and develop a closed mid level circulation sooner, thus cutting off that trowal that was killing us. Not sure how far it can go but there were hints it was heading this way before this run. 2 Link to comment Share on other sites More sharing options...
WEATHER53 Posted January 5 Share Posted January 5 Took a nice long break Im liking so many things . I know the dews won’t be nearly like this come crunch time but they will still be around 25 . Temp around 35 Baro above 30.25 now has risen stoutly since the dew point plunge. Sun is about zip now with solid cloud cover. Ground decently cold 48 hours leafing in More later Link to comment Share on other sites More sharing options...
wxmvpete Posted January 5 Share Posted January 5 27 minutes ago, MillvilleWx said: The reasoning for the shift in the colder solution on the NAM is the development of a closed 850mb low tracking south of the Potomac over north-central VA. Pay close attention to the wind barb across the northwest area and how the 850mb southeasterlies hit a brick wall over Parrs Ridge and the wind direction flips. This would allow for cold air to advect into the northern and western side of the circulation creating a more beneficial PBL and keep everything frozen, or even all snow. Check out the wind barbs to the east of RNK... As a result, watch the 850mb temp profile as we work through time. This is actually how you get surprises and periods of heavy snow when you weren't expecting. MAJOR CAVEAT.... THIS IS JUST ONE RUN OF ONE MODEL!!! We are going to want to see other guidance pull this off and have it become something to watch. This could be a one run and done deal, but there is potential for this. I will not be committing anything until I see some agreement from other guidance. It was interesting to see and point out as a possibility. It would affect the forecast in a big way. These are why these marginal events are so tricky. One thing can make or break a forecast. Let's hope it's right. Right now, no changes from my current thinking. This is a great catch. Just comping a couple other CAMs at 23Z Saturday, the HRRR and ARW remain more southeasterly and don't pinch off that 850mb low as far south as the 3kmNAM. While it isn't to say the 3kmNAM isn't on to something, there isn't any guidance showing an 850mb low evolution quite like what the 00Z 3kmNAM just did. It's something you keep in the back of your mind, but going to need to see it get more support before buying in (and that is assuming if it even still maintains this in future runs). 6 Link to comment Share on other sites More sharing options...
wxmvpete Posted January 5 Share Posted January 5 5 minutes ago, psuhoffman said: It is just one run and I’m not expecting it yet BUT I was noting the NAM and euro were hinting at this at 12 and even more 18z. They’ve been trending towards starting to amplify the coastal and develop a closed mid level circulation sooner, thus cutting off that trowal that was killing us. Not sure how far it can go but there were hints it was heading this way before this run. Ahh it did start to try to hint at it on the 18Z ECMWF. Hadn't gotten a chance to look at it. Will be curious to see if it keeps making that adjustment at 00Z. 2 Link to comment Share on other sites More sharing options...
clskinsfan Posted January 5 Share Posted January 5 GFS drops 5 inches in Winchester in 3 hours. Its a Mauling. If its half right will be the heaviest snow I have seen since 2016. Literal crush job. 8 Link to comment Share on other sites More sharing options...
NorthArlington101 Posted January 5 Share Posted January 5 GFS drops 5 inches in Winchester in 3 hours. Its a Mauling. If its half right will be the heaviest snow I have seen since 2016. Literal crush job. They good at clearing the roads in Winchester? If consensus shifts toward 6”+, I might head out that way 1 Link to comment Share on other sites More sharing options...
Weather Will Posted January 5 Share Posted January 5 WB 0Z GFS Link to comment Share on other sites More sharing options...
nj2va Posted January 5 Share Posted January 5 Quite the Loudoun gradient. 0.5” to over 6” from SE to NW. 0.1” line runs through MBY, woo! Link to comment Share on other sites More sharing options...
clskinsfan Posted January 5 Share Posted January 5 Just now, nj2va said: Quite the Loudoun gradient. 0.5” to over 6” from SE to NW. 0.1” line runs through MBY, woo! The Blue Ridge is the cutoff. Makes some sense. The Valley is colder. But too close for comfort even here. Link to comment Share on other sites More sharing options...
clskinsfan Posted January 5 Share Posted January 5 3 minutes ago, NorthArlington101 said: They good at clearing the roads in Winchester? If consensus shifts toward 6”+, I might head out that way You would be fine until you get to the top of the mountain just past Round Hill. Then you take your own life in your hands 1 Link to comment Share on other sites More sharing options...
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