Ever heard of this happening before?

[roardog]

This is from Gaylord NWS:

FEW ADJUSTMENTS MADE TO THE GRIDS/TEXT PRODUCTS IN THE RECENT

UPDATE...

MORE CLOUDS IN EASTERN UPPER MI TODAY...WITH THE INTRUSION OF A 4-5K

FT DECK THIS MORNING THAT IS TOO HIGH UP TO DOWNSLOPE TODAY.

OSCODA REPORTING 10SM -SN AT 7AM...SO ADDED SOME MORNING FLURRIES

FROM HARRISVILLE TO STANDISH.

AND MOST PERPLEXING OF ALL...SEMI-STATIONARY RADAR ECHOES BETWEEN

APX AND GLR ARE REVEALED BY AN INCOMING STAFF MEMBER TO BE A SNOW

GRAIN SHOWER. GIVEN THESE RETURNS HAVE BEEN THERE FOR SEVERAL

HOURS...NOT SURPRISING TO HEAR WE/VE HAD ENOUGH TO TURN THE ROADS

WHITE IN SPOTS. HAVE ADDED SCT MORNING -SHSN TO OTSEGO CO. THE

PERPLEXING THING IS...WHERE ARE THESE COMING FROM? HAD THEM

YESTERDAY...THOUGH NOT QUITE AS OBVIOUS ON RADAR. GIVEN THE PRESENCE

OF ANOTHER...WEAKER PLUME SW OF BOYNE FALLS...STRONGLY SUSPECT THESE

SNOW GRAIN SHOWERS ARE CAUSED BY SNOWMAKING OPERATIONS AT SKI HILLS

(BOYNE MTN TO OUR NW...OTSEGO CLUB/TREETOPS E OF GLR).

[snowstormcanuck]

This is from Gaylord NWS:

FEW ADJUSTMENTS MADE TO THE GRIDS/TEXT PRODUCTS IN THE RECENT

UPDATE...

MORE CLOUDS IN EASTERN UPPER MI TODAY...WITH THE INTRUSION OF A 4-5K

FT DECK THIS MORNING THAT IS TOO HIGH UP TO DOWNSLOPE TODAY.

OSCODA REPORTING 10SM -SN AT 7AM...SO ADDED SOME MORNING FLURRIES

FROM HARRISVILLE TO STANDISH.

AND MOST PERPLEXING OF ALL...SEMI-STATIONARY RADAR ECHOES BETWEEN

APX AND GLR ARE REVEALED BY AN INCOMING STAFF MEMBER TO BE A SNOW

GRAIN SHOWER. GIVEN THESE RETURNS HAVE BEEN THERE FOR SEVERAL

HOURS...NOT SURPRISING TO HEAR WE/VE HAD ENOUGH TO TURN THE ROADS

WHITE IN SPOTS. HAVE ADDED SCT MORNING -SHSN TO OTSEGO CO. THE

PERPLEXING THING IS...WHERE ARE THESE COMING FROM? HAD THEM

YESTERDAY...THOUGH NOT QUITE AS OBVIOUS ON RADAR. GIVEN THE PRESENCE

OF ANOTHER...WEAKER PLUME SW OF BOYNE FALLS...STRONGLY SUSPECT THESE

SNOW GRAIN SHOWERS ARE CAUSED BY SNOWMAKING OPERATIONS AT SKI HILLS

(BOYNE MTN TO OUR NW...OTSEGO CLUB/TREETOPS E OF GLR).

If it's not precipitating from a cloud, can you really call it a "shower"? Although I suppose if it's perceived as a shower by the public, that's all that really matters.

[Icey]

The only thing I could compare that with is during a blizzard in Feb 2007. One thunderstorm moved into the Madison area right after I got done with work, yes there was thunder and lighting. When I went outside I noticed snow was falling very fast, then I noticed when the flakes hit the ground they exploded, yes exploded! I looked closer while a bit confused why, something like a hail/snow hybrid between the size of dimes and quarters hit the ground at a high rate of speed. My drive home was very fun.

[csnavywx]

If it's not precipitating from a cloud, can you really call it a "shower"? Although I suppose if it's perceived as a shower by the public, that's all that really matters.

Given the fact that they saw a plume on radar, it's more likely that the ice crystals from the snow making operations were being mixed/lofted into low clouds, causing a seeder-feeder type process (whereby the ice crystals come in contact with an otherwise ice-free, supercooled water droplet cloud). Snow grains are formed when there are just enough ice crystals to get the nucleation process started, and then accumulate rime as they form.

[aslkahuna]

Inadvertant seeding of cold clouds or fog (or intended in the latter case) is common. Freezing fog is often cleared out at airports by seeding the fog causing it to fall out as snow. Steam plumes from heating plants, power generating plants, etc can seed cold clouds and cause snow to fall out so snow making operations could easily do the same. Once at Dugway we picked up an inch of new snow at the weather station when the steam plume from the heating plant seeded the fog over the station. It took an explaination of that to the NWS guys at SLC when I called our daily report in to them.

Steve

[wall_cloud]

There is a power plant to the NNE of Amarillo, TX that can cause something similar on days that are particularly cold. If the boundary layer is cold enough (usually -10C or colder) and sufficiently moist, the particulates from the some plumes will act as dendrites allowing the moisture to form snow. Most of the area will just be cloudy but if the wind is from the NNE, there will be a ~1 mile strip of light snow across Amarillo. I've seen enough snow from this scenario to cover the ground. Really sucks when you have a dry forecast.

Now that I read all the posts, it is very similar to what aslkahuna explained. It forms at such low levels that radar has little chance of picking up on it unless it is right outside the door.

[baroclinic_instability]

Inadvertant seeding of cold clouds or fog (or intended in the latter case) is common. Freezing fog is often cleared out at airports by seeding the fog causing it to fall out as snow. Steam plumes from heating plants, power generating plants, etc can seed cold clouds and cause snow to fall out so snow making operations could easily do the same. Once at Dugway we picked up an inch of new snow at the weather station when the steam plume from the heating plant seeded the fog over the station. It took an explaination of that to the NWS guys at SLC when I called our daily report in to them.

Steve

They used to seed the fog at SLC airport during inversion season, but apparently they stopped this due to the snow fallout.

SLC though gets some of the nastiest inversions in winter with pollution acting as nuclei. There is a smelter plant in downtown SLC that produces so much pollutant road crews will treat I-80 for fog fallout. I think other populated mtn valleys have some similar issues such as Helena.

[baroclinic_instability]

There is a power plant to the NNE of Amarillo, TX that can cause something similar on days that are particularly cold. If the boundary layer is cold enough (usually -10C or colder) and sufficiently moist, the particulates from the some plumes will act as dendrites allowing the moisture to form snow. Most of the area will just be cloudy but if the wind is from the NNE, there will be a ~1 mile strip of light snow across Amarillo. I've seen enough snow from this scenario to cover the ground. Really sucks when you have a dry forecast.

Now that I read all the posts, it is very similar to what aslkahuna explained. It forms at such low levels that radar has little chance of picking up on it unless it is right outside the door.

SLC NWS actually will throw in snow into the grids for fog fallout events. Pretty gross to think about, but I guess snow is snow to the public.

[wall_cloud]

SLC NWS actually will throw in snow into the grids for fog fallout events. Pretty gross to think about, but I guess snow is snow to the public.

just don't eat that stuff!

[binovc]

Kind of have something similar here with a power plant. So much fog they have to close the road.

http://www.hollandsentinel.com/news/x549836881/Zeeland-residents-reject-road-closure-proposal-on-Washington

[aslkahuna]

They used to seed the fog at SLC airport during inversion season, but apparently they stopped this due to the snow fallout.

SLC though gets some of the nastiest inversions in winter with pollution acting as nuclei. There is a smelter plant in downtown SLC that produces so much pollutant road crews will treat I-80 for fog fallout. I think other populated mtn valleys have some similar issues such as Helena.

Tell me about those inversions-at Dugway during dense fog episodes in Winter it would be about 16F while at the top of Johnson's Pass 2000 feet higher it would be 56F. SLC is about the most polluted city in the US during inversion situations. We get air stagnation down here as well especially in PHX during the winter and the brown cloud sits over the city. Low moisture so it's all air pollution. Tucson isn't quite as bad but still has problems-that's why we have special (more expensive) gasoline blends in the Winter here.

Steve

[baroclinic_instability]

Tell me about those inversions-at Dugway during dense fog episodes in Winter it would be about 16F while at the top of Johnson's Pass 2000 feet higher it would be 56F. SLC is about the most polluted city in the US during inversion situations. We get air stagnation down here as well especially in PHX during the winter and the brown cloud sits over the city. Low moisture so it's all air pollution. Tucson isn't quite as bad but still has problems-that's why we have special (more expensive) gasoline blends in the Winter here.

Steve

Haha, yeah they are bad. We used to call Salt Lake City and the GSL the "Salty Toilet" as stagnant wintertime air would slosh around the Salt Flats and the Valley as high pressure dominated. Even moderate fronts would have a tough time mixing the garbage out once it sat around too long as it just became way too stable. Freakish freezing rain events would occur near the bottom of SLC Valley along the Jordan River where the stable inversion would mix out everywhere except the bottom usually below 4250 feet--sometimes down the lowest 100 feet of the valley.

Speaking of Johnsons, the Stansburys are a neat range. Probably the beginning of the true "Basin and Range" mountains as you head W from the Wasatch. Rush Valley, as you mentioned with Dugway, is even worse with the inversions than SLC Valley. SLC would be beautiful if the air quality wasn't so awful in the winter. Even in the summer when the mixed layer gets to 500 hpa, if the flow is too weak, a haze sits over the SLC/Utah Valleys.