Snowfall measuring guide

[gkrangers]

Okay, with the board on the eve of our first big one together, we could use a snowfall measuring guide posted. I know people have posted them before.

Someone in the know want to do it? Would be a good thread to sticky for the duration.

[Alpha5]

Okay, with the board on the eve of our first big one together, we could use a snowfall measuring guide posted. I know people have posted them before.

Someone in the know want to do it? Would be a good thread to sticky for the duration.

A bit antiquated (2004) but still useful for the basics

http://www.crh.noaa.gov/iwx/program_areas/snow_spotters/SnowMeasurement.pdf

[wxnut]

COCORAHS has some good links..

http://www.cocorahs.org/media/docs/Measuring%20Snow-National-Training%201.1.pdf

http://www.cocorahs.org/Content.aspx?page=measuresnow

[jntkwx]

Another good resource:

http://madis-data.noaa.gov/snow_measurements.html

[Stebo]

Just don't measure like this guy.

[thundersnow68]

Oh, that's one for Fail Blog fer sure.

Just don't measure like this guy.

[frostbite_falls]

Oh, that's one for Fail Blog fer sure.

Congrats--first post in 52 minutes with WS Warnings extended from Ga to NH. Where'd everyine go? Folks were at it all night Christmas eve....guess it's nap time?

[Sn0waddict]

I'm SO glad somebody saved that Zonties pic.

[ArtRosen]

When was the last time you had Winter Storm Warnings and Watches from Georgia to Maine?? 1993??

[Gorizer]

Too much puddin' pie... plus 5 nights of no sleep stalking the models... Gotta recharge the batteries for the imminent battle.

Congrats--first post in 52 minutes with WS Warnings extended from Ga to NH. Where'd everyine go? Folks were at it all night Christmas eve....guess it's nap time?

[Gibbsfreeenergy]

Where is Ray? We had this at eastern for sake of measurement accuracy. Ray???

[Thunder Road]

quick question:

plywood or particle board? i've heard both....

[FUCK JOE BIDEN]

Just don't measure like this guy.

What's wrong with a little math?

[wxnut]

Check out this guy's ingenious setup to automatically measure snow on ground in his backyard.. Scroll down the webpage to see how he does it. Very cool!

http://www.weather.sydenham.com/

[famartin]

Where is Ray? We had this at eastern for sake of measurement accuracy. Ray???

I was playing in the snow and hiding in my own little corner of the board

Anyway, this came out yesterday (I know, a day late and a dollar short) from Nolan Doesken at the Colorado State University (He's the guy who runs CoCoRaHS, and is also the Colorado State Climatologist). I highlighted the important points for measuring snowfall itself.

Here are a few tips on measuring snow under duress -- 16 tips to be

exact. Read at your leisure or as the next snow storm approaches. If

you have other questions, please ask.

1) When in doubt, follow the instructions :-) There are many

training resources on the CoCoRaHS website to help you learn how to

measure snow and its water content. Use them.

2) Don't put your body and health at risk just to try to get a good

measure of snow and it's water content. Yes, the data are important,

but so are you. So be careful. As easy as it may normally be to go out

and check your gauge, in a blizzard or an ice storm, it's a whole

different story.

3) Remember that Precipitation (water content) and Snowfall are two

separate measures. Don't enter your snowfall amount (e.g. 3.5") as your

precipitation amount. We've had a lot of those lately so we programmed

the computer so that you can't enter the precipitation amount and the

snowfall amount to be the same.

4) If you can't or prefer not to get a measure of the water content --

that's OK. For example, if you measure 12" of new snow but you didn't

melt it down to get a precipitation amount, then just enter NA for "Rain

and melted snow" and enter 12.0" for the snowfall amount.

5) If there is a lot of blowing and drifting, you may not find any

ideal place to measure the accumulation of new snowfall. Your favorite

snow measurement surface may be blown clear or may be buried by a

drift. Plan to take several measurements and compute an average.

Under extreme blizzard conditions you may need to simply provide an

"educated guess" based on reasonable measures.

6) When you compute an average, don't include the depth of the largest

drifts in your sample/

7) If there are many buildings and roofs in your neighborhood, keep in

mind that the snow often blows off the roofs and collects below. As a

result, we sometimes see measurements that are likely too high from

densely populated neighborhoods. Keep that in mind as you measure.

8) When there is considerable wind, your gauge will likely catch only a

fraction of the snow that fell. What you find in your gauge may be very

unrepresentative. For example, there were places on the East Coast on

Monday who had snowfall amounts up around 15-20" but who had

precipitation measurements less than 0.75". This is certainly possible

for dry snows with lighter winds, but wind-driven blizzard snows are

usually compact and dense and will likely have between 0.07" and 0.12"

for each 1.0" of new snow.

9) If you suspect undercatch (less snow landing in your gauge than what

actually fell) then take a representative core sample of the new snow on

the ground.. Take a core at a location where the snow is an average depth.

10) Your outer cylinder is 12" tall (unless you are an official NWS

Cooperative Observer, in which case your gauge is 24 inches tall) You

would think that a 12" gauge would be able to handle a 12" snow but it

usually can't. The gauge begins to fill to the top and begin spilling

after only about 6" of new snow has fallen.

11) The rain gauge outer cylinder is for collecting snow to measure its

water content. Do not measure the new snowfall in the outer cylinder.

Measure new snowfall on the ground at one or more locations.

12) It is really, really handy to have an extra outer cylinder for

helping with snow measurements. You can order an extra cylinder by

itself for a reasonable cost from www.WeatherYourWay.com and possibly

from other companies, too. Also check with your state or regional

coordinator in case there are any spares available.

13) Before submitting your daily report, always do a "reasonableness

check". Does each measurement make sense and do the set of readings

match up? For example if you measured 10" of new snow and 2.05" of

water content is that reasonable? It might be if the snow was extremely

wet or if there was a lot of rain mixed in with the snow. If it was only

snow with a fairly typical density, then this report would be

unreasonable -- either the snowfall is too low or the water content is

too high. While snow rarely has an exact ten to one ratio of snow to

water, that may be a good first guess for a wet or wind compacted snow.

14) (similar to 8) Always check your snow- to-water-content ratio..

You can tell a lot about snow just by walking through it, shoveling it,

squeezing it, etc. You may be able to make a good estimate of the water

content just by lifting a shovelful of snow. Five inches of wet snow

may have 0.50 to 0.60" of water content and it will feel very heavy when

you lift it. But a dry, low density snow of 5" may weigh very little

and may only contain 0.15 - 0.30" of water content or even less.

15) Report your total depth of snow on ground. That is a separate

measure from your daily snowfall. Report total depth to the nearest

0.5" whenever there is any snow on the ground even if no precipitation

fell today or in recent days. Knowing how much snow remains on the

ground and watching it settle from day to day is very helpful

information for many applications.

16) Snow depth decreases quite rapidly after recent large snowfalls.

(this is called "settling", "compaction" or "densification". Find a

favorite representative location and measure in that same area each day

if the snow is no longer blowing and drifting An average of several

measurements may be necessary to get a good reading of the total depth

of snow on ground. Watch the snow settle. And measure the water

content (Snow Water Equivalent) too. It is fascinating to see that as

snow depth goes down, its water content may or may not go down.

[famartin]

quick question:

plywood or particle board? i've heard both....

I used particle board, because it was available. There really isn't much difference.

[famartin]

I'll add that the recent storm even had me wondering if my measurements were valid, as the winds were so strong and from a somewhat uncharacteristic direction (NW) that there was some roof snow blowing into my measurement location. Apparently most of that ended up blowing away, as the measurement I got from the snow board ended up matching what I measured in an open field about a block up the street as the storm was winding down. Most lawns had less than that field, though.

[NorthShoreWx]

I use two 12" x 18" x 1" pieces of solid pine shelving, painted with a white enamel. I pull them inside and wipe them off after the snow has stopped to keep them from warping. For what its worth, they were useless this past storm. I wiped them and replaced them about 8 hours after the storm began and shortly after noticed that where they had been level with the snow, they were now elevated above the snow surface. The wind had scoured snow away from them except where they protected the underlying snow. I replaced them immediately, but they really weren't of much use.

Based on the fact that I was one of the lowest totals around I had some concerns that I may have underreported, but after doing all kinds of sampling, I still think the total I reported (11.5") was a best guess reasonable estimate. Therefore, either I was truly in a snow hole, or many around me have overreported (or both). I'm not really set on an answer, but would like to compare a radar loop to the following map of totals from the latest PNSOKX:

[famartin]

I use two 12" x 18" x 1" pieces of solid pine shelving, painted with a white enamel. I pull them inside and wipe them off after the snow has stopped to keep them from warping. For what its worth, they were useless this past storm. I wiped them and replaced them about 8 hours after the storm began and shortly after noticed that where they had been level with the snow, they were now elevated above the snow surface. The wind had scoured snow away from them except where they protected the underlying snow. I replaced them immediately, but they really weren't of much use.

Based on the fact that I was one of the lowest totals around I had some concerns that I may have underreported, but after doing all kinds of sampling, I still think the total I reported (11.5") was a best guess reasonable estimate. Therefore, either I was truly in a snow hole, or many around me have overreported (or both). I'm not really set on an answer, but would like to compare a radar loop to the following map of totals from the latest PNSOKX:

It would not surprise me if there were a lot of excessive reports. While the total I reported was 10.1" via snowboard (clearing every 6 hours), I measured 14" on the south side of my parents' house, so that gives an idea of what can happen if you decide to measure in a less than ideal location (in case its not obvious, the south side of the house is where most of the snow from the roof ended up).

[Storm017]

Don't know if anyone posted this before:

New Snowfall to Estimated Melted Water Conversion Table

http://www.ncdc.noaa...ewsnowfall.html

[famartin]

Don't know if anyone posted this before:

New Snowfall to Estimated Melted Water Conversion Table

http://www.ncdc.noaa...ewsnowfall.html

I wouldn't use that table. Its an old table from decades ago, and current research shows that what happens above the surface is much more important as far as as snow:water ratios as compared to temperature at the surface. For example, I've had temps near 30 with 15:1 ratio snow, while I've seen temps in the teens with 10:1 ratios. Surface temps are *not* the key (unless its above freezing and you are getting some melting).

[LocoAko]

I'm working on a snow map for this last storm currently, and it really seems, even despite the banding that occurred, densely urban areas are coming up with higher totals due to the inevitable blowing from the roofs. Of course there is no way to avoid this. For myself, I measured in my backyard because I noticed the snow from my roof blowing towards my front yard - but again, a few feet away lies the next block over, so it is all pretty futile at that point. It explains the airport measurements and the disagreement between nearby urban areas. Not sure how to prevent this... just has to be taken into consideration.

[tamarack]

I wouldn't use that table. Its an old table from decades ago, and current research shows that what happens above the surface is much more important as far as as snow:water ratios as compared to temperature at the surface. For example, I've had temps near 30 with 15:1 ratio snow, while I've seen temps in the teens with 10:1 ratios. Surface temps are *not* the key (unless its above freezing and you are getting some melting).

Very true. I'd offer for evidence the two big snowstorms I had in Dec 2003. Both were all snow, no mix, no rimey flakes.

#1, 12/6-7.

Temps: upper teens

Winds: 25G40 with lots of drifting

QPF: 1.63"

#2, 12/15

Temps: mid teens

Winds: 20G30, significant drifting but nothing like #1.

QPF: 1.53"

Just from the above, one might infer than #2 was as deep or deeper an event (cooler, less windy) despite the slightly lower precip. However, #1 had excellent denditic formation throughout while #2 had lots of grains and such.

#1: 24.0"....ratio 14.7

#2: 13.0" ....ratio 8.5

[uncle W]

snowfalls like the last blizzard is impossible to get a correct amount unless your measuring spot is in an open field...My back yard isn't and is obstructed by trees...Now that most of the snow has melted imby I measured how high it was against my wooden benches and picnic table...I had 24" in that area...The highest level of snow was closer to the house due to wind direction and snow blown off the roof...I estimated 24" after the snow ended...my beady eyes still work fine...This is a picture that morning...The open field behind my property is perfect to measure snow...I est around 4" left on the ground now...

[Bluescat1]

I had so much blowing and drifting that it was very hard to get an accurate reading. I had no snow on my front sidewalk at all and 2ft+ drifts in the back..

[famartin]

I'm working on a snow map for this last storm currently, and it really seems, even despite the banding that occurred, densely urban areas are coming up with higher totals due to the inevitable blowing from the roofs. Of course there is no way to avoid this. For myself, I measured in my backyard because I noticed the snow from my roof blowing towards my front yard - but again, a few feet away lies the next block over, so it is all pretty futile at that point. It explains the airport measurements and the disagreement between nearby urban areas. Not sure how to prevent this... just has to be taken into consideration.

Here's what I came up with for NJ, for better or for worse:

[wxnut]

I wouldn't use that table. Its an old table from decades ago, and current research shows that what happens above the surface is much more important as far as as snow:water ratios as compared to temperature at the surface. For example, I've had temps near 30 with 15:1 ratio snow, while I've seen temps in the teens with 10:1 ratios. Surface temps are *not* the key (unless its above freezing and you are getting some melting).

Absolutely correct. That table does not take stability or winds into account. These have huge impacts on snow:water ratios due to snow crystal shape and fragmentation. Lake effect snows (unstable atmosphere) can give you 20-40:1 ratios over a large temperature range. Snow in very cold air air (below -20C) tends more towards a 10-15:1 ratio due to the fine nature of the crystals and the way they compact when they settle (as opposed to larger fluffier flakes at higher tempertaures) Strong winds will fragment the snow crystal and lead to greater compaction and lower ratios. And as famartin stated, what happens aloft is critically important to the compostion of the snowflake especially in that 5-10 thsd foot range. To correlate snowfall strictly on surface temperature is as bad as using the 10:1 rule for every snowfall. It's much more involved than that.

[Storm017]

I wouldn't use that table. Its an old table from decades ago, and current research shows that what happens above the surface is much more important as far as as snow:water ratios as compared to temperature at the surface. For example, I've had temps near 30 with 15:1 ratio snow, while I've seen temps in the teens with 10:1 ratios. Surface temps are *not* the key (unless its above freezing and you are getting some melting).

Thanks that is good to know.

[famartin]

Okay, with the board on the eve of our first big one together, we could use a snowfall measuring guide posted. I know people have posted them before.

Someone in the know want to do it? Would be a good thread to sticky for the duration.

Just watch this video, it covers most things...

http://www.erh.noaa.gov/gsp/coop/snow_measurement_guide.htm

[famartin]

Just watch this video, it covers most things...

http://www.erh.noaa....ement_guide.htm

To elaborate on the video (and bump this thread with another storm coming):

1 - Measure in an area with limited drifting, AWAY from structures (or at least as far away as possible). An opening in a grove of trees is THE ideal. A deck may *seem* ideal, but proximity of buildings means that it is not (readings likely to be inflated no matter which way the wind is blowing).

2 - Use a snow board to measure on if possible. (A snow board is really any flat, thin, portable surface perhaps 1-2 feet wide by 1-2 feet long or so, painted white. Plywood works best). Measurements on a lawn are likely to be inflated by the underlying grass. Measurements on pavement are likely to be underdone due to melting.

3 - Clear the board at an interval no smaller than once every 6 hours. Absolutely do NOT clear the board hourly.

4 - Snowfall is defined as the maximum accumulation on the board during the 6-hour (or longer if necessary) interval between clearing. In other words, you can measure as often as you like as long as you don't clear the board.

5 - If the snow stops or changes to another form of precipitation, measure immediately. Don't wait until you are scheduled to clear the board.

6 - When you clear the board, DO NOT leave it in a hole in the snow. Place it on top of the existing snow cover, elevate it such that it is even with the existing snow cover, or clear the snow away from a LARGE area around the board. Otherwise, blowing and drifting will inflate your readings.

7 - If blowing and drifting is hard to avoid at your location, have multiple boards and use an average of measurements on them as your total. Don't rely on just one board.

That's all I can think of at this moment...