psuhoffman

Oh I’m paying attention. I’m just exhausted.

RRFS held from its previous run showing a general 6-8" across most of the area before the flip

I posted a forecast 2 days ago...it's likely going to bust a little high...this was just a last minute update on what I am thinking...I won't grade this. And it hasn't started for me yet lol

Final Thoughts, these totals include sleet accumulation. Things really started to tighten up the snow/ice gradient the last 24 hours. I see a path for this to bust low...if we do have really heavy precip in the morning between 10-16Z like the RGEM/Euro/GFS/UK show

Naw DCA will report 3.8” no matter what

I’ll put a final map out in a min but some over unders in my head right now DC: 5” IAD: 6.5” BWI: 6.5” Winchester 10” leesburg 8” Frederick 9” Westminster 9” Owings Mills 8”

DC is just…I dunno it’s like they have some snow dome right there. And even when we get southern sliders they often end up missing the real big totals on those to the south.

Yea if we toss the NAM because it’s in its own universe. (Not saying it might not be right but it’s hard to bet on it v everything else) all other guidance is starting to tighten things up right through our area. Somewhere near us is going to be a very sharp gradient with 8-12” on one side of the line and 10 miles the other side only 3-5”. Right now my best guess is somewhere near you to Baltimore ends up near that line and tiny factors will decide if it’s a few miles one way or the other

UKMET is in the big thump camp. .7 qpf in DC before the flip. About .9 Winchester to Westminster before mix

I was trying to be nice but he forced me to say it. The heavy banding is just north of them on the rrfs during that time. It’s more extreme north VA and northern MD nw of 95 that was directed at

Sorry up here it was higher up at 16z. Assumed it was similar further south. it’s super close 70 north. DC not so much. Unfortunately I think DC south is cooked for the bigger snow totals. Things are tightening up and the gradient looks to end up somewhere near a Leesburg to Baltimore line with snow totals going from 3-5” south of that to 10” north or there pretty quick.

The better argument is that the rgem/euro and other guidance that gives us 8-12” does so by sticking an incredibly intense band over us from 10-16z. It’s a lot easier for WAA to win in light to moderate precip than it will be to advance if there is a band of .1 qpf/hr+ stuff over the area. It’s all going to come down to that really imo. The NAM doesn’t have that. It shifts the heavy banding way up into central PA and the WAA routes us because there is no dynamic cooling to slow it down. Basically if this is what’s going on from 10-16z the snow will hold on longer north of about 66 and definitely north of a Winchester to Baltimore line this on the other hand, ain’t gonna get it done Everyone is focused on the temps on the NAM, the real issue is why is the NAM missing the heavy banding tomorrow morning that all other guidance has. That’s why the mid level warmth surges north from 10-15z there is nothing to slow it down on the NAM.

Forget the NAM. It’s 50 miles off everything else even the other cams. But I Caught something on the RRFS. Verbatim it’s meh with 4-5” across the area. But it has an intense band of precip from 16-19z across the area as sleet but it’s super close. It’s only +1 at about 750 mb. Every other layer is fine. This is 700 which is the closest layer I can get represented but it’s close to the warmest layer. If it’s 1* colder across this area from 16-19z it would be 10” instead of 4” This trend has been on the last 2 runs and now it’s super close to a better result

Every storm is different and this is not scientific at all but I do think there is something to this… A couple days ago I said I liked the wedge presentation in the mid levels over 2007 and 2017, examples when the mid level warmer won quick in a route. When there is a clear southward wedge into VA even in the mid levels and the mix comes at us from the southeast not due south or worse southwest we bang on way way longer. IMO it’s indicative of a deeper cold layer that’s fighting more in the mid levels. Often when we bust high on snow in changeover situations it was when the mix was trying to advance SE to NW into the CAD wedge. Unfortunately the guidance has shifted toward a more straight south to north look to the mid level warmth. Unfortunately it’s been my experience that when the mid levels are advancing uniformly through the cold wedge that way it indicates less resistance to the WAA. The one thing that could offset this would be an epic thump which is what the 18z euro and rgem were showing. Thats what happened in Feb 2015, Dec 2013 in situations where the warmth was advancing straight north but got halted by intense dynamic cooling. It can work out but we need to be getting death banded from 12-15z not just light to moderate precip

Use this one. Cut out the area you want.