frostfern

Yea. It's way more complicated than temperature. The highest ratios seem to be from shallow clouds with a cloud-base dewpoint around 10-15 degrees. When dewpoints at the cloud base are in the single digits or lower the snow gets more dense again as you have mostly diamond dust plates. It's lighter than a wet snow, but denser than fluff. Lots of drifting decreases the ratio as well because the aggregate flakes get broken up into individual crystals and land flat. Snow that has blown off the roof can be especially dense even when it's cold. Wind-sculpted cornices can be rock-hard and exceptionally dense, probably because the loose flakes all blow away leaving very dense semi-fused crystals behind. Also, snow that forms in really deep strong updrafts is denser due to rimed flakes. Light-intensity lake-effect is more fluffy than the stuff that falls from really intense bands. It seems a bit of a nonlinear curve. Very weak vertical motion will produce mostly plates due to supersaturation not being great enough for dendrites. Moderate vertical motion will produce big dendrite flakes that form aggregates and really boost the fluff factor. Extreme vertical motion leads to rimed flakes and eventually graupel, which is dense.

18z GFS is whack.

Expectations went from 0 to 100 over the past week.

5G waves aren't in the models yet.

Then it's the other way around when spring comes. Warmth always gets farther north faster the farther west you go.

Yea. The initial burst of snow Thursday night reminded me of a spring snowstorm out west, like in the mountains of New Mexico or Arizona. There was graupel mixed in with the flakes at times. I wasn't surprised it started producing lighting when it moved farther east, the convective elements got deeper as they moved east.

There is a 6" glacier base under the fluff here. I didn't hear thunder Thursday night so you still have bragging rights to that.

Extend that map out another day please. There is an epic storm in progress over MI on the 16th LOL.

GRR reporting over 2" more than what I've measured in my driveway. It's fickle though. Lake effect zone is probably highly variable with more fine-scale streaks than the map shows. Most of it has been falling in localized heavy showers under very narrow bands. Very fluffy with a lot of drifting too. I added up 6" from the synoptic event, then another 4 of lake effect so far. Most of that happened in a 3 hour period when a couple heavier convergence bands passed over between 4pm and 7pm last night. Had a complete whiteout that dropped an inch in 20 minutes around 6:00pm (worst timing with rush hour traffic), but most of the time it has been flurries or very light snow.

Really dumping here at times. It snowed about an inch in 20 minutes when I was in the store. It isn't persistently that heavy, but really difficult driving in the most intense bursts. It cranks for 20 minutes, then lets off for a bit, then cranks again. At least 3 inches of fluff in the past 3 hours though. That's on top of the 6 inches from last night. Up to about 9 total.

Right under a nice band now. Snowing good with big flakes.

It seems like the SE side has been stuck between bands most of the day.

I was wondering why I've been stuck between bands most of the day. It's like there's been a hole over the SE side of Grand Rapids. Some could be due to being close to the radar source, but I can confirm the GRR hole is at least partially real as accumulations have been pretty nonexistent so far IMBY. It's finally starting to fill in now. Still nothing too heavy so far.

Total IMBY is for the synoptic event is right around 6". I think about 3 fell in the WAA event, then there was a "warm sector lull" as the center of the low passed nearby, then the cold front swung through with an additional burst that added up another 3". It was pretty wet and heavy shoveling. Definitely more synaptic than lake effect. Also a lot of accumulation on tree branches, signs, etc... despite 40 mph+ wind gusts last night. Think it's frozen on. Lake effect has underpeformed. Just very light mood flakes. Kinda positioned between bands all day. Less than an inch so far. Might pick up in intensity or at least fill in some this evening though.

Went up to 33 degrees with some drizzle in the past hour. Now a it's ripping snow again. Nice lake-enhanced burst moving inland. Roof dripping has stopped now so I assume the temperature is also dropping.

Another intense convective band rotating through here now. Really coming down.

Getting much bigger flakes now. First hour had a lot of pellets mixed in. Intensity is variable. Seems very convective.

Very heavy wet snow coming through with this first band. Seems convective... like mountain snow you get out west. Pellets mixed in with the flakes at times. You can hear it making a "shhhhhh" sound against the windshield.

Clippers often bring some of the highest impact weather of winter IMBY. Don't get any lake enhancement with southern stream storms but often do with the clippers especially if they are associated with a re-enforcing arctic surge. Totals usually aren't over 6", but it often comes down fast and with wind and low visibility. Spreads the wealth inland much better than typical lake-effect too.

Snow from a single dominant band may have updrafts strong enough to cause significant riming of flakes. Places in northern and western Michigan don't get those kinds of bands most of the time. It's typically persistent light snows from weaker bands with some orographic enhancement added in the slightly higher areas up north. Also, immediate GRR area gets a lot of nickle-and-dime 2-3" snowfalls that add up to more when measured over days than if the same liquid were to fall in a single 24 hour period. The relationship between depth and liquid content isn't linear. Seems more logorithmic to me with fluffy snow as the bottom layers compress under the weight of new snow added on top, especially when you get over 6". This biases smaller snowfalls to higher ratios than big ones.

Lake effect is always weird in terms of measurement. Very high winds can cut down on the fluff factor, as can a low DGZ causing more plate-dominant snow. Think you'd need 25:1 ratio at least to get three feet out of any model output. Lake effect is always better than 10:1, but you need temps in the mid 20s and wind under 15 mph to get the crazy 20:1 ratio dendrite-dominant feather-fluff. Even then it doesn't really feel like as much as the official measurement because when it gets deeper than 6" it settles fast under it's own weight even within 6-12 hours of falling.

How much of that in SW Michigan is post-frontal lake-enhanced snow? WAA stuff will be dense, but behind the front I'm assuming 10:1 is on the low end.

I'm hoping for a quick front-end snow, followed by dry slot, then a heavy west-flow lake effect event behind the occluded front as the system pivots away to the north.

Haven't had a good clipper-train / lake-effect pattern in a long time. Hopefully this pans out. GFS almost looks too cold for good accumulations though. Would prefer the DGZ rise above 5000 feet with waves coming across the lake. I remember Jan 28-31 2018 had decent small accumulations with waves that added up to over a foot of snowpack despite a very low DGZ a lot of the time.

About 3" total here. It came down good for brief period late last night. Just lacked duration due to lack of back-end deformation snows being all to the southwest. It's added on top of 4" remaining from the last system so there's finally a decent snowpack. Hopefully we get some more to add to it.