40/70 Benchmark

I expect a similar outcome here.

I was thinking the same thing.

That is a page right out of the Dec 2007 playbook.

I can tell you that it was low level temps IMBY....may have been overcome due to greater evap cooling had lift been in SGZ, and we had better dendrites, but that was not the case......so we rotted between 33.8 and 34.0 during bulk of heavy precip.

Exactly...and as I said to John, it was struggling to accumulate all afternoon in that area.

Exactly my point....even before the precip abated, I was not accumulating efficiently.

It was both.....sure, precip cutoff early in the evening, but it had been accumulating like shit all afternoon, despite heavy fall rates.

Yes....hence the "backlash" member of the fraud five. Bruce Showegler never did manage to wrap his mind around this over the course of a very esteemed 33 year career as an OCM.

Yea, my take is that the lift being JUST below the SGZ was fatal given how marginal the low level thermal envt. was.....we needed optimal dendrite production in order to offset that and we did not get it. The heavy fall rates in and of themselves were not enough...we also needed perfect growth.

Yea, it was east-based....its becoming central at this point. Agreed.

Hi Dave, glad to see you back. The SSW still seems like mostly conjecture at a this point, and I think relying on a dramatic weakening of ENSO as the primary driver for a big second half is always risky...especially in a la nina, which usually do not have big endings in the east.

Makes sense to me. I had Philly in the 11-21" range this season.

Obviously...I just mean that it will melt slowly relative to your average 2" snow pack.

What we know is the odds of a whiff are pretty low with a pattern like this, so its all about having enough cold in the bank, which we should. This doesn't mean that it will be pretty, and it may involve some advisory 2-5" stuff to ice and rain, but its still snow.

I didn't do well Saturday, but it was apparent that I did better than Boston. There are only patches in the Everett/Chelsea area. I have fill coverage at home in Methuen.....and that 2" of concrete will not cede ground easily.

Yea, that doesn't look abysmal to me. I didn't expect December 1998 of December 1999 before the season, nor do I now.

Anafrontal snow, Inverted trough snows, backlash, SNE severe weather and big wind events in the Merrimack valley. Obviously there are times when these do in fact work out, but more often than not, they end up an artifact of modeling.

The very same models that are now implying a warm December were emphatically signalling otherwise a mere several days ago....and this was before they were all very warm previously before that. Unstable to say the least. This is not about "accepting" anything, at least with me...I am anticipating a mild winter with slightly below average snowfall, however, I do feel as though December will be more wintry than guidance currently suggests.

I don't think it means anything for winter, given the lag that exists between ENSO and the atmosphere.

+2". 4" on the season.

Yes.

Guidance is going to waffle...that is what guidance does. Just gotta trust your gut and preseason work...and both tell me we do okay this month. Maybe I will be wrong...it happened alot the past couple of years. We'll see.

Agree.

Should have stuck with First Call back east.

DEC 6 12-5-20 Rain to Snow Verification: A Matter of Lift 12-5-20 Rain to Snow Verification: A Matter of Lift Friday Warmth Not Overcome. It is difficult to fault anyone for having been skeptical of an impending large snowfall on Friday afternoon, as temperatures were a spring like 55-60 degrees across the region. It can and has happened before in the past, however, it goes without saying that everything has to go "right", or wrong, depending on one's perspective. This is because such a warm antecedent airmass leaves virtually no margin for error within the atmosphere. Everything needs to go precisely according to plan, or else the result is the couple inches of slush that many areas saw on Saturday afternoon: vs the forecast: This was a respectable forecasting effort in such a challenging system, but obviously as implied above, something did not go according to plan. First of all, the primary critique of this forecast effort is that it did emphasize the importance of elevation enough with respect to snowfall. While topography was considered in a general sense, as the Connecticut river valley had a lighter forecast range of 2-5", the map failed to address just how much snowfall varied by elevation even in Worcester county and northern Connecticut. Secondly, snowfall was over forecast in much of eastern Mass, which had nothing to do with elevation and everything to do subtle nuances in the mid levels of the atmosphere. Proficient Snowflake Production Can Compensate for Marginal Thermal Profile There is a great deal more to forecasting snowfall than the temperature on the thermometer outside. Snowflakes, or "dendrites" are optimally produced between a temperature of -12 to -18 celcius in the mid levels of the atmosphere. This is referred to as the "snow growth zone". The high quality dendrites that are proficiently produced within this region accumulate very efficiently. In order to get rates that heavy, there is a tremendous amount of "lift", or rising air that is needed to produce the very heavy rates of +1-2" per hour. It is possible to have perfect dendrites falling at only light intensity when lift of paltry, and conversely, ample lift can be occurring outside of the optimal snow growth zone, which is what took place yesterday in eastern Massachusetts. This does not necessarily preclude a heavy snowfall, assuming that low level temperatures are cold, however, yesterday the forecast did not have that margin for error, since we were relying on perfectly formed dendrite falling at very heavy rates owed to well placed lift. We needed everything to go as planned, and it did not. A superior snowfall forecast requires accurately forecasting the temperature at the surface, the temperature at all other levels of the atmosphere, as well as the amount of lift, and where said lift is located relative to that -12C to -18C optimal snow growth region. There is zero margin for error with respect to any of this when temperatures are as marginal as they were yesterday. Forecast Thought Process The forecasting yesterday was for several inches of snow to the northwest of Boston, however, only about 2-5" actually accumulated. The reason was that Eastern Mass Weather underestimated the importance of the fact that the best lift was located slightly beneath the snow growth region, which greatly limited snowfall since the lower levels of the atmosphere were slightly above freezing. There was no question that sufficient lift would exist, as the developing storm created a strong temperature gradient in the mid levels of the atmosphere, which is called "frontogenesis". However, what is evident is that the area in question immediately to the north and west Boston is on the eastern edge of said lift, which further complicated the forecast. Here is the sounding at Lawrence, MA: The thought process was that it would be "good enough" for 5-8" of pasty snowfall, but it was not. There was 2-5" of slush. This was the forecasting error. Had the temperature been 1-2 degrees colder, and the lift been slightly higher, then the forecast would have been for 12-18" of snow. An accurate snowfall forecast is a complex endeavor that incorporates the consideration of a myriad of different factors on a continuum, which necessitates a great deal of critical thinking. A far cry from the linear process of simply considering the low level temperature and the amount of water falling from the sky that many people believe it to be. Compare this to the sounding to the west in Worcester: This is why the Worcester county forecast of 8-12" verified nicely, with the exception of the lowest elevations. Low level temperatures were slightly colder with some elevation, and the strongest lift, which was perfectly centered it he snow growth region, directly traversed the area. Conclusions This was a solid, albeit flawed forecasting effort that will inform future endeavors this throughout the boreal 2020-2021 winter season. Since this is a la nina season, there will likely be many marginal scenarios that will both hone and challenge forecasting skill. Final Grade: B