psuhoffman

Plus I don’t see much of a difference with the SW coming onshore

But then it wouldn’t be so over amplified

Last 24 hours of EPS

@PhineasC not saying your wrong but the QPF didn’t actually match those crazy model output. I know the coop a couple miles from here recorded 19” in that 2009 Storm but on only 1.26”qpf. We actually had pretty good ratios in most of MD in those storms due to beautifully perfect mid and upper level low passes. ETA: BWI had 18” on 1.57qpf

Did models over estimate qpf more back then though. I know the high res models back then had horrible wet biases

Those maps.... the difference is if you are NW of 95 a lot more of that snow is REAL on the 18z and not some clown map fantasy. The thermal profile was 1-2 degrees colder and that makes a big difference when you are talking about these 1C warm layers at 850 during the height of the storm when a few hours one way or the other can be the difference between 5" and 10" of snow.

That really would be a "give me that and we're good the rest of winter" storm...40" lol We are in good shape I think. Even if this takes one of the more inside tracks like that one GFS or some of the euro runs, historically that track with a pretty stout high in southern Quebec would still produce a 8"+ snowfall up here. If this stays offshore we could do REALLY well. But for us I think it is more of a matter of how significant will the snow be not whether it will be significant. Assuming your bar for significant isn't Ji level. His zones are ok but somewhere in that 6-12 will be a 12+. I get that its too soon to nail down where though.

EPS is tightening the goalposts...as it should. But if you are from 95 NW odds have slightly improved each of the last several runs. trends mean more importantly odds of 3”/6”

That was just my snark

I have not dug into the members yet...might not for a while busy. But from previous runs the ens were always warmer on those mean plots because the handful of crazy cutters that run up the Piedmont were skewing the mean. The colder runs aren’t as much “colder” along the edges as the warm outliers are warmer. Plus I think the lower resolution of the ensembles makes them have a warmer representation in general. Not picking up the extreme meso features and CAD as well. I would focus more on track of the Eps and focus on the ops for meso details like exact thermal structure.

I’ll throw out a guess later today

I saw that...that warm pocket gets right to our door then stalls and sits there for 6 hours...I don't buy that. Some of that period we are getting .2 QPF per hour. I would adjust that. Even with that there we would likely be puking snow/sleet mix during that 6 hour period...low ratio but we would likely still go way over a foot...just not those stupid totals on the clown maps. But again, worrying about a little warm layer pocket like that and banding at this range is useless. I am analyzing for the DC/Baltimore area where most people in here are. Not only talking to the 3 people that live near me. But sorry. I will try to focus on my yard more.

If we were to assume this run verbatim looking at the 1 hour temps at all levels and the precip I would say about 3-6 before a change to sleet for people from 95 NW. Then it gets tricky...there is about 6 hours of crazy banding with pockets cold enough to support snow and pockets in the subsidence in between that are sleety. The odd thing is some of the warm pockets don't line up with the banding. Has a warm pocket over the NW burbs around 3z while they are getting smoked by the deform. But I am NOT sweating that kind of thing at this range. I actually think temps crash a little faster once the storm reaches our latitude and we probably mix out that warm layer better for the back end. But as is...it only flips back to pure snow for a couple hours at the end..but its puking snow so maybe another 2-3" on the back side after a crap ton of sleet. But again...that is not my forecast...I would adjust this slightly to the southeast and mix out some of those warm pockets a little better during the deform. Not a lot...but the euro is often SLIGHTLY overdone. Slightly makes a huge difference on the edges like we are.

I am mostly happy with this run. It was a much colder run, especially at the surface. Never gets places from 95 NW above freezing. Probably means more sleet then rain during the "mixy" period. Unfortunately a slightly more tucked in track mean't it did blast a warm layer pretty far west at 850...it gets right to my doorstep at its furthest NW. For big totalys into 95 we would want to see that surface track judge just a bit southeast...but the good news is if the euro and ggem are correct on the colder thermal structure of the storm we wouldn't need the track to adjust all the way to the GFS. That's good because in the end I expect a 60/40 compromise track between the usually progressive GFS and the usually amped euro, biased toward the euro, to be reality. That is going to cut it really close for getting big totals into 95. But if we adjust the euro just a slight bit southeast on the surface track it gets it done.

Colder so far through 72

Gem isn’t as awful as some are making it. It’s a LOT colder then the GFS even with a worse track. If you are N or W of DCA it’s a big time thump snow 6-10” with 12” up near PA. Reason it’s not more is it’s hauling A and lost the nice wrap around deform. I NEVER rely on that. Treat it like bonus. That’s why I was meh on last nights 0z euro because ALL the snow was back end. That’s living dangerous. Give me the gem idea of a really cold profile and a guaranteed front end thump then if the back happens we go big...if not we still have a very good snow for December. It’s got less upside but a safer way to roll then the warmer runs that rely on the wrap around to get big totals. Plus if you take the gem thermal representation and assume a Gfs track and speed it’s a big win. That option isn’t impossible still.

You’re correct in your analysis and pessimism wrt big totals 95se. The problem with his post is that he says the exact same things EVERY threat in this range. And because our climo sucks he is right most of the time. But when we eventually do get a hit he is wrong. His posts aren’t useful because they’re a generic canned response. He simply assumes the worst and says why the worst case scenario is likely everytime. Unfortunately that’s usually true.

I guarantee you places west of the fall line are getting WAY over 10-1 in that band. If in a heavy band that’s likely very wet (very low ratio) bombs. It helps that the lift is crazy in the DGZ. I am so sorry. As a parent the crippling fear from just the thought of that is agonizing. There are no words. I truly hope you find some peace and get through your pain. The more I dig into the GFS and GEFS the more I like it. Those in trouble know it. There isn’t an Arctic airmass in place, it’s mid Dec, and the SST are scorched. SE of 95 is gonna be a struggle. But for everyone along and NW of 95 this run implies a lot of fun. Perfect placement of the surface mid and upper level features. fgen. Crazy lift in the dgz. Everyone except Ji would be satisfied imo. Even in the cities I think they do pretty good if...big if...this run is representative of the reality.

I haven’t seen the soundings for this run yet but the gfs has been aggressive punching a surface or near surface warm layer right up the Potomac. More so then any other guidance when compared to track. It’s there on other guidance but not as aggressive. It’s fairly short lived once the low starts to turn NE and bomb and the CCB deform takes over and heights crash under the upper level Centers. Maybe it’s overdone. I’ve seen the GFS run warm near the surface. We also know how DC rolls though so I never assume.

It’s a crazy dump before dryslot north of DC and NW of 95 though.

One last comp 0z v 6z EPS >6”%

You have been a rockstar. Thank you! I have zero cushion bro... You know better. It might seem that way by acreage but you know geography and climo. There is a world of difference between seeing that shallow warm boundary layer punch up the Potomac and Bay to the fall line and seeing it penetrate another 35 miles west into the piedmont. Latitude and proximity to a very warm body of water (relative to temps needed for snow). There is a lag effect on the temperatures during seasonal changes. A lot of this is due to waters influence. Water takes longer to gain and release heat. Some due to the PV taking time to mature. But even though solar is at a min in December the thermal profile of the northern Hemisphere won’t bottom out until sometime later in January and the Jet often becomes most favorable due to buckling and shortening wavelengths as the PV starts to wane in Feb. Our snow chances are centered in Jan and Feb. Even early March is probably better then most of Dec for a big snow. This is the ugliest point also. If you look at the last two frames the low has halted it’s due north motion and turned NE at this point. It’s not earth shattering and it won’t help some. But if you’re on the edge that shift is significant.

Maybe, those things count sleet as snow and looking at the temperatures at different levels...I think there is a LOT of sleet up here. It isn't AS bad as I originally thought...that deform really clips us good at the end...but the front end is really not good at all...and relying all on the wrap around is living dangerously if you want a big storm. First of all I was analyzing the thermal structure to get an idea what I think falls as SN/PL/RN, not using those ptype maps that are awful. By 21Z we are losing a snow look imo. We are still at about -2 at 850 but there is likely a warm layer somewhere with that screaming southeast wind. I see about .23 qpf before that...so we likely only get 2-3" before a flip to sleet on this run. We waste a LOT of qpf as sleet in the next 6 hours or so. I count about .7 qpf that falls as sleet. At least I think it is sleet...its close whether the cold layer is thick enough or if it goes over to just rain for a time. Maybe freezing rain with a temp at 30 but whatever. That is probably about 2" of sleet if it is sleet. But we lose a lot of the meat of the storm there. The deform clips us after that and we get about .8 QPF as snow...assuming our typical high ratios once temps crash at all levels...we probably get 10" on the back. But again...I am always nervous relying on that back side for the bulk of our snow. Those deform bands can be really tricky for models to nail down this far out. If for whatever reason that shifts north some...suddenly we are looking at a messy muck storm instead of a big snow. Not gonna over react to one op run of the typically most amped model. But it was the worst run for us so far. Those maps are LOL. It counted a period where my 850's are +2C as snow.

It does what the 18z GFS op did...tucks the storm north up the bay before shifting east.

It's pretty meh even up here