dendrite

December

I probably should add that melting is a latent cooling process too. If you think of the stages of water as having increasing energy from solid to liquid to gas, anytime you go up a phase change to a higher energy state it requires taking the energy from the environment. So the snow needs heat energy to complete the phase change from solid to liquid. It takes that thermal energy from the air around it. Up in a cloud, if you have condensation (gas to a liquid droplet) or deposition (gas directly to an ice crystal) the H2O is "losing" heat to the environment. We talk about latent heating a lot with convection and hurricanes because of the massive amounts of condensation being produced by those types of systems. Deposition, Condensation, Freezing >>> Latent heating of the air Sublimation, Evaporation, Melting >>> Latent cooling of the air So in the case of a day like today, we have temps near 40F in much of NH with RH near 15%. So we're getting a little of all 3 latent cooling processes. IOW, not much loss in the heart of the pack, but probably a decent amount lost along exposed edges.

Death Valley right there. Looks like they just seabreezed. 51/-5 to 43/22

BAF with 49/-2 for 12%

38/-3 17% Nose bleed wx

Evaporation and sublimation are cooling processes. Snow sublimates and water evaporates more quickly with lower relative humidities and wind. So one of two things happens during the day when it's something like 34/5. Some of the snow is melting due to adjacent warmer surfaces and that moisture will readily want to evaporate. The snow/ice not melting will be primed to sublimate as well if the temp is close to enough to freezing or lower. So any evaporation and/or sublimation will create latent cooling on the snow surface. The wetbulbs tell the story. That's the temp the air would have if it was completely saturated. In this case, the snow surface temp can approach the 2m wetbulb since the surface is continuously cooling due to the sublimation and evaporation. My wetbulb is 25F...not exactly conducive for big snow melt. Of course the sun is getting high enough to do damage on snow and ice adjacent to darker surfaces. So even with the low wetbulbs, snow banks go down pretty quickly. A leaf in the middle of the pack may sink down through it a few inches simply from heating up so much from the sun. Higher RH slows the evaporation rate. So those 53/53 airmasses we get in December annihilate the pack. At near 100% RH there's no evaporation to cool the snow surface to limit the melting. So with our wetbulb in the low 20s today the snow surface temp is probably leaning below freezing due to the melting/freezing processes. Also, at temps going above +4C, the water molecules start losing their hexagonal structure. So at wetbulbs around 39F the snow melt really starts to accelerate.

Lisa has showed me a few of the trailers. Josh is a science guy, but he definitely has a flair for the dramatic too.

The dews definitely give it an arctic feel versus a 34/25 type airmass. There's another push of CAA overnight so it should be quite the chilly evening once the sun goes down. This airmass flies out of here starting Wednesday though. 'Tis the season when the sun sets with -12C 850s and by sunrise 850s are near 0C and still climbing. You get a low in the teens with rad cooling and then mix out through the following afternoon and pull off a high near 60F.

Didn't he move to Maine at one point?

34/5 30% I wish those numbers were 10F higher for a combo of good melting and evaporation. It's just not warm enough to melt anything except snow adjacent to low albedo surfaces.

Was it the same feeling you got when watching another guy touch your girl?

Last I knew he was in New Boston, NH.

Hence I asked if he moved. This guy is probably just a lurker that followed us quite a bit before deciding to jump into the fray.

His IP definitely resolves to N. Billerica. I'm not sure what Joe has been up to. Has he moved at all?

Not sure. 1.4 NE according to the cocorahs info... wherever that places it.

Randolph, NH had a 53” depth this morning. Not bad.

You guys need some of these at the ski area. I think they’re replacing the snow pillows in many sites. https://www.sommer.at/en/products/snow-ice/snow-scales-ssg-2

It’s been done many times. I’ll look for some of them later, but I need to go out and corral some chooks.

He measures on an elevated board too. Those early season fluff events struggle on the depth side of things since there’s still enough warmth in the ground to try to slowly melt/compact it from the bottom upward. When it’s 31° in Novie and pounding upslope fatties it gives the measuring surface a cooler surface to accumulate on.

See I just hate that. You penalize the snow in the second half of a major storm because of all of the weight building upon the first half. In those LES events, at some point the depth almost stops growing because for every 3” you had you probably compact 2”.

idk if they’re as concerned about comparing different sites as much as they are keeping the same measuring methods for sites over the historical data period. The COOPs have been measuring only at 6-8am for a long time because they’re just volunteers that have other jobs and responsibilities too. The LCDs have historically had paid observers measuring hourly at the airports for many decades now. So they are keeping the 6hr measuring there to keep the methodology continuous. I’ve always thought 6-8 hours was a happy middle ground for allowing some compaction, but not letting it sit too long. I’ve always mimicked CON with my observing methods so I’ve stuck to 6hrs when I can. But part of me wishes I started at 8hrs so I could measure, go to bed, sleep 7.5hrs, and then wake up to an on-time measurement rather than setting my alarm for 11z after measuring at 5z. lol

Well that is depth over 5 days so you would at least get a handful of clearings in. But yeah...maybe 55-60” instead of 44”? They also went from a depth of 44” to 29” in a few days despite the warmest temp in that period being 25°.

BUF had 81.5” in a 5 day span during Dec 2001, yet their highest depth was “only” 44”. They may have had 120” if they cleared every 3 hours.

Beautiful morning. Up to 41F after a low of 24.7F. Should push mid 50s here before the clouds and front approach.

A nice look on vis of Tolland his morning with the clear skies. https://weather.cod.edu/satrad/?parms=local-Rhode_Island-02-48-1-100-1&checked=counties-map&colorbar=undefined