Tuesday, February 24, 2015

Possible Ice and Snow Records: East and West

It's been a remarkable winter and we have the potential for ice and snow records in both the east and the west in the coming days.

East: Great Lakes Ice Cover

The snow and wintery weather back east have gotten quite a bit of press, but I haven't seen a lot on the Great Lakes ice cover.  Modis imagery from yesterday shows Lake Erie to be frozen over and Lakes Superior and Huron to be predominantly frozen over.  Lake Michigan is still hanging on with some open water (and producing some lake-effect clouds and snowfall), as is western Lake Ontario.  If you click on the image to enlarge it, you have a great view at the complexities of pack ice, especially on Lake Huron where large leads (cracks with open water) and openings can be found as the ice is pushed around by wind and currents.

The NOAA Great Lakes Environmental Research Laboratory has some great products for monitoring the ice cover of the Great Lakes (available here) and allowing for comparisons back to the early 1970s.  As of yesterday, the median ice concentration across most of the lake surfaces, with the exception of portions of Michigan and Ontario, exceeded 90%.  I've been watching these analyses over the past week and have noticed both Michigan and Ontario are slowly but surely seeing the median ice concentration increase in their open regions.  They peg the Great Lakes total ice cover at 85.6%.

Last year the ice cover peaked at 92.5% on March 6th, the 2nd highest since the early 1970s (the highest ice cover of 94.7% occurred in 1979). If we compare yesterday to last winter on the same date (below), we find that we are currently running ahead of last year's pace.

Given the cold weather expected over the next several days, it will be very interesting to see if we can take a run at the post-early-1970s record.

West: Alta Snowfall

Despite the snowstorm this weekend, we're still flirting with record low snowfall at Alta for the month of February.  Before proceeding, I need to note that I don't have access to the official records for the Alta cooperative observer site, so there is some uncertainty in this analysis.  However, records at the Utah Avalanche Center suggest that the minimum February snowfall at Alta Guard is 34 inches.  I can access unofficial snowfall records for that site and it appears they've had 19 inches so far this month.  The ski area snowfall history reports 25 inches for the month.  I've been looking at the model runs for the next few days and it appears we will miss a storm passing to our east of us on the 25th, have a weak system coming through on the 26th,  and then are on the fringes of a storm that digs down the Pacific coast and penetrates into southern Utah on the 27th and 28th.  The net impact of this is that in the latest (0600 UTC) GFS, the heaviest precipiation through the end of the month falls to our west, south, east, and north and we're left in a low precipitation region.  If this forecast verifies, we'll probably see some snow before the end of the month, but perhaps not enough to avoid the record.  On the other hand, a shift in storm track or intensity and we might do better, and avoid the dubious honor.

Of course there are the usual problems with snowfall records (see Limitations of Long-Term Snowfall Records), so in the end, there still might be debate about whether or not February 2015 was indeed the worst snow month on record.  The combination of forecast uncertainty and observational uncertainty should make for lively discussions around the office over the next few days!


  1. Speaking of cold, I have noticed that the EC model seems to have had a pretty strong cold bias recently, at least in the medium to long range. A recent example of this.... the 00Z from last night showed the 700-mb temperature over SLC down to as cold as -26 C by mid-week next week. The coldest in the GFS was about -18 C. I see that the 12Z EC is more in line with the GFS, but still there have been several dramatic examples of this recently where the GFS temperatures have verified much more than the EC model. Does anyone know why the EC forecasts have been so cold?

  2. This may be a stupid question but how frequent do the Great Lakes freeze over?

    1. "since the early 1970s (the highest ice cover of 94.7% occurred in 1979)". More info at http://www.glerl.noaa.gov/data/ice/.

  3. About the February snowfall record: Has there ever been a February with zero snowfall down in SLC?

    1. The unofficial records I have access to suggest that February 1886 and 1953 were both goose eggs, but that needs confirmation from the folks from the NWS.