OceanStWx

Was just looking this up for someone. Radial accretion is like 20-40% efficient (median 28%). And flat surface is like 60-80% efficient (median 72%).

I want to say something snarky, but we do. So does BOX. Since we started probabilistic snow we’ve documented this. My SOO’s gut check is: is there is any real chance that your forecast is too low? If you say no, then you have a high bias.

The key is really high position. The over the top and northeast look allows flow to be easterly into the mountains. That works twofold: one rising air into the mountains cools adiabatically, two pressure gradient is direct north to south. Northeast flow develops and feeds the low level cold (as can evaporational cooling). As long as the high stays in that position there is little mechanism to scour out low level cold.

24" is on the table, but I wouldn't be banking it at this point. I'm fine with that being the upper end of the range though. I'm more comfortable with the 12-18" range at the moment.

Also we were a little too high I think vs BOX to our south. Would prefer to match a little closer at this range and deviate as we get to go time when trends become more apparent.

Just about equally likely at this point that QPF busts as low as a borderline warning event as it is over 1.5" for SNE. Your Pike north line, that gives you goalposts of safely like 5 to 15" right now. Not a bad spot to be.

How about we be happy with 12-20"? It was a cosmetic update for all intents are purposes to get rid of widespread 20:1 snowfall during the peak of the QPF.

You may actually hit for cycle on ptypes. Start as snow, to mix, to rain. Then flip back to a mix and end as snow as the cold tuck undercuts the warmth aloft.

Seems you're really stretching your definition of damage now. I think right now the best chances for higher ice totals will be where Will was talking about yesterday. Near the coast could have the best combo of staying below freezing but near the warmth aloft. Forecast soundings from the NAM near HVN and GON show much more of an ice look, and the NAM is actually decent with low level thermal profiles. GFS has them flipping to rain...

Where exactly? It just looks sleety with so much low level cold. Even the GFS that loves to be warm in the boundary layer is cold enough for sleet at BDL. There will be ice, but unless things change significantly I don't see a widespread damaging ice signal.

Meh, the average cost per person is $3 a year. I could find worse uses for the money. You can gripe about things government spends tax dollars on, but honestly weather is not one of them.

Their temp forecasts are actually quite accurate, but that snowfall forecast was just so far on the extreme that the only thing it was based off of was QPF and high ratios.

I mean that was a pretty irresponsible forecast from TWC. The PWM storm of record is a hair over 30", yet they go with 3' at like 84 hours lead time. Rip and read.

Euro actually ticked warmer aloft. But it's 00z heights are definitely verifying too low out west.

So the 12z ensemble sensitivity was mainly in the wave coming out of the Arctic. Lower heights there across western Canada was matched with a farther north low track. Makes sense that a deeper northern stream could lead to more downstream phasing. Well the 00z raobs show that the 12z Euro and 00z GFS were both too low with heights across western Canada. That argues for a southern low track. And I wouldn't be shocked the 00z Euro ticked in that direction based on it's 12z hour 12 forecast vs verification.

To clarify what was going on with snow maps this morning for everyone: We had this "appetizer" that occupied all the local WFOs Storm Total Snow grid. We decided the weekend storm was a bigger deal, and watch text would show up on all our winter pages anyway so it could be confusing having a Sunday watch and Friday snow map. So we ran the Storm Total Snow grids for the weekend storm, but then had to decide where to cut them off. WPC only had grids for probabilities out to 12z Sunday, so I think BOX originally ended their Storm Total Snow grid at that time to make the probabilities make sense. The problem is it wasn't truly storm total amounts, so we eventually all decided to damn the probabilities and make the map say what we thought would happen. Turns out some were higher than others.

I hate these long event horizon events that have, in some cases, 10 separate snowfall forecasts before a flake falls. Sometimes it feels like we change amounts just to change amounts. Sometimes we jump on every new model run. But mostly I just wish we treated snowfall more like climatology with temps. If models spit out record temps on day 7, we typically don't put it in the forecast. We factor climo and probabilities in. Snowfall we just lurch with each new piece of guidance. Two foot storms are rare, so maybe we don't put that in the grids on day 4 or 5, and start conservatively and adjust up. We've been pretty much 12-16" from the jump, and I think that's a fine place to be. We could tweak down if things slip a little, or adjust up if it continues to be juicy, without looking like a leap either way. Start high and there's nowhere to go but down (despite what some posters think).

Don't exist anymore! It's on the table though. After 12z Sunday, the NE LLJ really cranks, the question may be whether +SN is still falling long enough.

They definitely split their zones by elevation not just county level. As far as directives go though, there is no stated difference in criteria. It's possible it's like us with MWN, that the majority of the zone doesn't reach criteria. Also possible that lack of verification means they don't issue blizzard warnings.

On the table for sure, but the ingredients are so mesoscale in nature that we can’t say much beyond there is potential for someone to get a V-day 2007-like scalping, or some bigger ice totals. I’m leaning sleet given the cold air depth, but there will be freezing rain somewhere in there too.

It's actually the shortwave I marked here. You can see a secondary WCB forming just to its east. \ This shortwave is the one that moves downstream and forces the lee cyclone.

Basically. The impact of more snow is really just the snow removal aspect, which plows keep up with to the point that 18 inches isn't sitting on roads (i.e. there is never more than a few inches on the road at any time). The step up is really blizzards, when plows can't even find the roads to clear them.

The 500 mb heights we want samples of are roughly 24 hours from now, so the 00z runs.

Not happening. If anything we'll be trimming the number of warning types we issue. That was the goal of getting rid of the heavy snow warning. It covered similar space to a winter storm warning. When we verify events we can still call it heavy snow vs a winter storm (which would have mixed precip and/or wind).

I can't stand snow maps period. This event is going to have so much sleet and freezing rain dragged into those maps. I mean say you sit at +2C at 850 mb for the event, or at least a good chunk of it. That spits out a Kuchera ratio of 4:1. At 1-1.5" QPF you're talking 4-6" snow, despite not really have any realistic shot at it.