Where snows don’t melt

We’ve got massive snow accumulation in the western USA this year.  It’s not just a few roads being late to open due to the excessive snow clearance effort (WA, CO), the snowpack is way above average this year. Good news for water supply; bad news for riverside communities. Just take a look at the extent of this – the map from 5th June below shows percent of normal snow-water equivalent. The measurements are mostly off the scale. From the lack of blue and green dots, I’m taking it that the red ones are errors.

From mid-May there has been concern over the amount of snow and the potential for flooding, but instead of melting rapidly the snowpack has persisted, and even continued to accumulate.

As of today (09 June) almost all states listed here (with the exception of Alaska, Arizona and New Mexico, which have much less than normal) are showing vast excesses of snow for the time of year. For example Utah:

And a different format depiction for Wyoming:

Accumulated Snow Water Equivalent for Wyoming river basins. Source: http://www.wrds.uwyo.edu/wrds/nrcs/snowmap/snowmap.html

Below is yet another way of looking at it – here for the Upper Colorado (link: http://snowpack.water-data.com/uppercolorado/index.php), specifically the feed into Lake Powell.  Now this really made me sit up.  The levels were ticking along a bit above average until just after mid-April, then they began to rise, and rise, and rise.  This says two possible things are happening – either more snow has been falling, and/or temperatures are just not rising enough to melt what is there.  Either scenario says ‘cold’.

On 5th June:

“April 15th is the date of maximum snowpack and basinwide snowpack is currently 66.6% of the April 15th average
Snowpack is 277.9% of the June 5th average.”

This got me thinking – at what rate does snow melt? I mean we’ve got some truly gargantuan snow drifts in places – how likely is it that significant proportions of them will remain in places that have not retained snow in summer for years?

The last slide in this EPA presentation gives ranges for melt rate with a degree-day factor. The range seems to be 0.07-0.150 inches per day per degree F.  So if we take the example that Anthony Watts posted recently of a 22ft drift in Colorado and look up appropriate degree day figures for the region (calculated between now and the end of September for a 32F base)*:

Key

Then for the higher altitudes we have 1500-2600 degree days before we might expect reasonable additions if not accumulations of snow again, but we’re guessing at what the actual melt rate might be for any given location. So…here is a range:

Starting at 264 inches (22 ft) 8th June, the table shows the estimated snow depth remaining on 30th September depending on the assumed melt rate and number of degree days (above 32F).

[Update: The table above was produced on the assumption that the melt rates referred to depth of snow.  Having covered a lot more background reading on this today I think I should have read the melt rate as “inches SWE/day*F”. Current rates of melting from the NOAA summary table are 0.1-1.6 inches SWE/day.  For a 22ft starting snowpack (estimated as 150 inches SWE) my back-of-envelope calculation suggests melt rates would need to be sustained at >1.25 inches SWE/day to remove this depth of snow by the end of September.]

That suggests to me that at higher altitudes there’ll be significant snow ‘left behind’ this year. Those white patches on the horizon will be a welcome return for many – cameras at the ready.  It is just one year, but how many ‘just one years’ does it take?

*Coop, L. B. 2010. U. S. degree-day mapping calculator. Version 4.0. Oregon State University Integrated Plant Protection Center Web Site Publication E.10-04-1: http://uspest.org/cgi-bin/usmapmaker.pl

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12 Responses to Where snows don’t melt

  1. John F. Hultquist says:

    I live in the great northwest State of Washington. While my eastern relatives have a heat wave, we continue to have cool weather. A recent rain-on-snow event caused road washouts and related damage in several small drainages across the valley from our place. There will local floods across the US west. Certainly not unprecedented.

    What interests me more – long term – is that the lingering snow provides a significant albedo and with the suppression of temps from the melting there should be considerable cold air drainage (again local effect) and a less robust warming of the atmosphere on a regional scale.

    Short season vegetables and cold-hardy plants may provide some tasty things but for those trying to rely on locally sourced food — this could be a lean summer.

  2. gallopingcamel says:

    Great work! It will probably not surprise you to learn that none of this unusual coolness is getting much coverage in the “Main Stream Media” here in the USA. The amazingly cool weather here in Florida has also passed ignored. We should be sweltering in humidity but it is still really pleasant for golf and other outside activities; I can take a lot more of this!

    So what is getting reported? No prizes for guessing “Catastrophic Anthropogenic Global Warming” although this this term has been replaced by the sure winner “Climate Change”.

    Here is a small sample. Enjoy:
    http://www.reuters.com/article/2011/06/08/us-weather-heat-idUSTRE75765220110608

  3. gallopingcamel says:

    Lubos Motl has no trouble pillorying idiots. I find his abrasive style entertaining. Have you seen his recent post on the serious cooling trend in the USA? The USA has been cooling by 5 Kelvin per century since 2001. Of course Motl realises this is meaningless but the deranged James Hansen expects us to believe that short term changes can be projected forward to 2100!

    http://motls.blogspot.com/2011/06/rss-amsu-all-cooling-and-warming-trends.html

  4. Verity Jones says:

    @John F. Hultquist
    my thoughts exactly, however I guess I didn’t articulate that far in the post itself.
    Outdoors we have gone for short season crops and all my tomatoes are indoors this year. We have planted more than ususal because food prices are becoming ridiculous.

    @gallopingcamel
    Indeed – it was only the late pass opening that alerted me to go and look. I’ll see if WUWT will pick this up after a slight rewrite to get this spread a bit more widely.
    Thanks for that link to Lubos’ post. I have less time to ‘do the rounds’ of as many blogs these days and I only stop by there occasionsally.

  5. Pingback: Massive drifts and late-melting snowpack | Watts Up With That?

  6. Taphonomic says:

    “This says two possible things are happening – either more snow has been falling, and/or temperatures are just not rising enough to melt what is there. Either scenario says ‘cold’.”

    Actually, it’s been both. More snow has fallen after the usual maximum date of 4/15, and the temperatures have stayed cooler to allow the snow to melt slowly. Also note that the graph shown of “Upper Colorado Snow Pack” only goes through June 1st of each year. As of 6/11, Snowpack is 277.54% of the June 11th average.

    [Reply – well exactly – I didn’t think I needed to spell it out 😉 Verity]

  7. gallopingcamel says:

    Great to see your rewrite on WUWT!

  8. E.M.Smith says:

    @Verity:

    THE biggest worry is a large warm storm dumping a load of rain that rapidly melts the snow. That is a heat transfer event that doesn’t show up much as “degree days” as the temps remain “near freezing” even though massive heat is being transferred into the snow base. The heat of fusion doesn’t show up as temperature…

    When that happens, we get loads of flooding. Just saw on the news that the Missouri River was having intense flooding as a load of this snow was being melted. It’s going to be a long spring…

    So, might I suggest a “dig” in the garden of “flood dates”?

    [Reply – good one – I didn’t think of that. V]

  9. E.M.Smith says:

    Oh, and I’ll bet some of those “red dots” (perhaps most?) are “device / data outage” from the snow covering it…

    [Reply – Hmm, didn’t think of that one either. I guess checking in every few days might show that up, V]

  10. Jimbo says:

    This is how ice-ages begin apparently. 😦

  11. E.M.Smith says:

    @Jimbo:

    Oh No Mr. Bill, say it isn’t so! 😉

    I’d really rather not get to watch an ice age glacial begin… Then again, better the very beginning than after it’s got a good run started 😉

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