MillvilleWx Posted December 13, 2020 Share Posted December 13, 2020 I know it's the NAM, but keeping an eye on the Monday storm progression. I took a look through 42hr and the NAM is almost lock-step with the CMC in the evolution at 5H and the SLP movement and strength. The GFS was way stronger and the Euro was much weaker. The CMC is the compromise right now, so I'm curious to see what the NAM shows the rest of the run (Yes, it's at range, but it's something to compare with what we have. Not taking as gospel. Just for reference). 4 Link to comment Share on other sites More sharing options...
schinz Posted December 13, 2020 Share Posted December 13, 2020 It appears to me this NAM run would be a pretty warm solution for many of us. Low looks to track North through Eastern Virginia 1 Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 great disco from LWX this morning .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Synoptically, the forecast has not changed much for the Wednesday through early Thursday timeframe as strong Canadian high pressure looks to situate itself over Quebec and northern New England on Wednesday, helping pump cold air down the eastern slopes of the Appalachians in a classic cold air damming situation. At the same time, a deep upper level trough will be pushing eastward from the Mississippi River Valley, progressing into the Tennessee and Ohio Valley by Wednesday evening. Down at the surface, broad low pressure over the Southeast will lift northward along the Carolina coast Wednesday afternoon and evening, strengthening in the process. Locally, we will see wintry precipitation overspread the area Wednesday morning and midday from southwest to northeast, with snow the likely ptype initial with the colder air locked in the boundary layer thanks to the high to the north. As the low strengthens and moves up the coast Wednesday afternoon and early evening, warmer air will be drawn in off the ocean on an increasing easterly flow at the surface and aloft. This will allow for mixed precipitation to encroach in the vicinity of the I-95 corridor with plain rain favored further eastward near the Bay and eastern shore of Maryland. The upper trough will take on a negative tilt Wednesday night as upper jet support moves overhead. This will combine with the increasing moisture thanks to the strengthening onshore flow. The latest guidance guidance continues to highlight the potential for significant snow accumulation along and west of the Blue Ridge Mountains, where a moderate winter storm threat exists. Further east, confidence is lower due to mix precipitation limiting snow accumulations. When this transition takes place and where it sets up is the million dollar question in these type of events, and that will be something we`ll get a better handle on as the the event nears. As mentioned, plentiful moisture will be associated with this system, as ensemble guidance indicates 1 to 1.5 inches of QPF. Meanwhile deterministic models highlight a potential for 1.5 to in excess of 2 inches of QPF across north central Maryland and adjacent areas in eastern West Virginia and extreme northern Virginia. Thus, those areas that hang on to the cold air and see snow as the dominate ptype, significant snow accumulation is quite possible. Still 4 days out, so plenty of time for models to get a better handle on the situation and exactly where that rain/snow line sets up, which will all hinder on the exact track of the low. Keep up to date on our latest winter forecast at weather.gov/lwx/winter over the next several days. The low will be pulling away from the Delmarva Peninsula Thursday morning, with precipitation lingering across our northern zones and upslope areas. The second half the day Thursday will be on the dry side as the low lifts northeastward and high pressure to our west builds eastward through Thursday night. Below normal temperatures and dry conditions will prevail behind the system with high pressure in control to finish out the work week and heading into the first half of the weekend. 1 Link to comment Share on other sites More sharing options...
MillvilleWx Posted December 13, 2020 Share Posted December 13, 2020 20 minutes ago, yoda said: great disco from LWX this morning I'm glad I'm in agreement with LWX. This system will not be moisture starved, that's for sure. How far west can that boundary layer warmth protrude into the region, and then when does it shift back for those that mix. 6-8" of snow with 1" of sleet is on the table along with areas that see 12-18" of snow with local to 22". All on the table with this setup. 2 Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 WB 6Z GFS 850 400 pm Wed Link to comment Share on other sites More sharing options...
Thanatos_I_Am Posted December 13, 2020 Share Posted December 13, 2020 The places that stay frozen get mauled. Maybe a tad less cold air this run. Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 WB 925 at 7pm is warmest then starts to sink SE again. Surface maps are lagging behind temp maps, Link to comment Share on other sites More sharing options...
Cobalt Posted December 13, 2020 Share Posted December 13, 2020 Just now, Thanatos_I_Am said: The places that stay frozen get mauled. Maybe a tad less cold air this run. 2M temps and 850s seem basically identical, if not just super tiny changes. I'd imagine that's just noise, or maybe due to rates? Idk, but I guess it's a step back but not a Euro type step back. I'll take that track any day and hope the mesos get a good grip on the thermal setup. Link to comment Share on other sites More sharing options...
Cobalt Posted December 13, 2020 Share Posted December 13, 2020 Snowhole bingo card incoming??? 3 Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 lol 0.2 at DCA... nice try 2 Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 I am no expert but surface temps struggle in 30s in 95 corridor throughout Wed afternoon/evening Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 06z GFS is a mauling for i95 corridor and west 1 1 Link to comment Share on other sites More sharing options...
Cobalt Posted December 13, 2020 Share Posted December 13, 2020 1 minute ago, yoda said: 06z GFS was a mauling for i95 corridor and west I think that's the best way to describe it. Whoever stays frozen is gonna bank on those rates piling on the snow. I'll roll the dice with the potential mixing, really excited to see the mesos get a hold of how that mixing will set up Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 WB 6Z GFS....why the mix when all the thermal profiles are below freezing? Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 Rates are silly in the CCB at 96... 3 Link to comment Share on other sites More sharing options...
BristowWx Posted December 13, 2020 Share Posted December 13, 2020 5 minutes ago, yoda said: 06z GFS is a mauling for i95 corridor and west You pick the best words..mauling is a particular favorite. And yes the snow hole fake map got me from Cobalt. It did..I’ll own it. 1 Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 So that is a very heavy snow, not ice? Sorry no coffee yet and half asleep, confused... Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 I see the snow maps on TT correspond to your mauling...unlike the WB snow maps. Interesting. 1 Link to comment Share on other sites More sharing options...
MillvilleWx Posted December 13, 2020 Share Posted December 13, 2020 The 850-700mb frontogen on the 06z GFS is otherworldly. Whoever stays all snow with this system is gonna shovel well over 12". Mark my words. Crazy aviation shift over here this evening, so bare with me. 11 2 Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 7 minutes ago, Weather Will said: So that is a very heavy snow, not ice? Sorry no coffee yet and half asleep, confused... @MillvilleWx would probably be better able to explain, but I believe so yes. Looking at the 6 hour snowfall amounts, 06z GFS is printing out 2" per hour rates (and higher in some spots) due to the extreme frontogenisis. I think this is causing the algorithm to show mix instead of the very heavy snow. 1 1 Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 Just now, MillvilleWx said: The 850-700mb frontogen on the 06z GFS is otherworldly. Whoever stays all snow with this system is gonna shovel well over 12". Mark my words. Crazy aviation shift over here this evening, so bare with me. Thanks for taking your time to post in our thread... esp with your detailed posts. Its greatly appreciated 5 1 Link to comment Share on other sites More sharing options...
MillvilleWx Posted December 13, 2020 Share Posted December 13, 2020 7 minutes ago, Weather Will said: So that is a very heavy snow, not ice? Sorry no coffee yet and half asleep, confused... Just now, yoda said: @MillvilleWx would probably be better able to explain, but I believe so yes. Looking at the 6 hour snowfall amounts, 06z GFS is printing out 2" per hour rates (and higher in some spots). I think this is causing the algorithm to show mix instead of the very heavy snow. The issue is the shallow layer between 850-750 that has a warm nose near the 0C isotherm, so pending the site and algorithm based, one will have ice/sleet and other will have snow. With intense lift within the low to mid boundary layer, I'd lean snow with that look. Lighter rates would switch to a mix. Banding will be prominent with this setup. People here need to not sleep on this setup when it comes to meso. This is how you get your 2-3"/hr snowfalls. 7H and 85H frontogen with this setup is silly. Someone in the Mid Atlantic is gonna get absolutely destroyed, and it won't be till gameday till we know who...... we all know who 2 1 2 1 Link to comment Share on other sites More sharing options...
yoda Posted December 13, 2020 Author Share Posted December 13, 2020 06z RGEM at 84 looks good to me as well Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 2 minutes ago, MillvilleWx said: The issue is the shallow layer between 850-750 that has a warm nose near the 0C isotherm, so pending the site and algorithm based, one will have ice/sleet and other will have snow. With intense lift within the low to mid boundary layer, I'd lean snow with that look. Lighter rates would switch to a mix. Banding will be prominent with this setup. People here need to not sleep on this setup when it comes to meso. This is how you get your 2-3"/hr snowfalls. 7H and 85H frontogen with this setup is silly. Someone in the Mid Atlantic is gonna get absolutely destroyed, and it won't be till gameday till we know who...... we all know who I also want to thank you! 1 Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 WB 6Z GEFS ticked SE with heavier snow... 1 3 Link to comment Share on other sites More sharing options...
MillvilleWx Posted December 13, 2020 Share Posted December 13, 2020 Oh btw, there's a chance at thundersnow in this storm. Just wanted to throw that tidbit out there looking at regional soundings. Slight tilt back with weak elevated CAPE sig within the deformation axis as the storm cranks off OCMD. So....yeah 7 1 Link to comment Share on other sites More sharing options...
Weather Will Posted December 13, 2020 Share Posted December 13, 2020 WB 6Z GEFS snowfall prob. 3, 6, 12, 18. 2 1 3 Link to comment Share on other sites More sharing options...
NorthArlington101 Posted December 13, 2020 Share Posted December 13, 2020 Morning everyone. Headed back to sleep but my dog woke me up. Glad to see the 06z GFS held down the fort. Happy to say the 06x GEFS was a complete repudiation of the 00z EPS. On my phone and the maps always get shrunk on my phone so I won’t bother posting, but every single member has the LP offshore OBX and lows never really get all that near the Chesapeake Bay. 7 Link to comment Share on other sites More sharing options...
CAPE Posted December 13, 2020 Share Posted December 13, 2020 27 minutes ago, Weather Will said: WB 6Z GFS....why the mix when all the thermal profiles are below freezing? Those surface maps are not accurate, for the umteenth time. The 6z GFS is a classic NW of fall line snowstorm, with some mixing on the SE edge. For DC to BWI points east, the surface gets toasty for a good part of Wed, and 925 mb temps are also problematic. 850s actually look ok this run. I-95 and east will need some serious dynamical cooling during the day Wed to overcome the warming lower levels, and then hope the backside delivers at night as the low pulls away from the coast. 3 1 1 Link to comment Share on other sites More sharing options...
Ji Posted December 13, 2020 Share Posted December 13, 2020 Icon with its best run yet. Euro outlier? Link to comment Share on other sites More sharing options...
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