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Iditarod

What weather can mushers expect on new northern Iditarod route?

On Feb. 10, the Iditarod Trail Committee announced the race restart will take place in Fairbanks due to poor snow conditions along much of the normal route across Alaska. Video of the Iron Dog race between the Alaska Range and the Nikolai checkpoint on the banks of the South Fork Kuskokwim River revealed a trail completely absent of snow for at least 100 miles. This section of trail was particularly hard on mushers and their sleds during the 2014 Iditarod race, and the Iditarod Trail Committee did not want a repeat. So, off to Fairbanks we go.

I wondered what the conditions have been like over the last 40 years along the route chosen for this year's run. Since the Iditarod began in 1973, there are 42 years of information about the range of conditions along the standard routes (minus the 2003 restart in Fairbanks,) but all we know about this year's route is that it is probably colder and hopefully snowier for mushers.

The National Climate Data Center's archives certainly help. In the last 20 years, the average winning time for the Iditarod is 9 days, 7 hours, and 28 minutes. The top tier of mushers usually finishes in about 10-11 days. Therefore, I chose a time period of 10 days for the historical analysis, beginning on the actual restart date for each year. The analysis is akin to asking what the race would have been like if it were run along the 2015 route every year since 1973.

Eleven climate stations are along the route between Fairbanks and Nome. Some stations, like Fairbanks and Nome, have outstanding data for all years. Other stations have incomplete or interrupted data. However, the stations are nicely spaced along the route, about 100 miles apart, and enough stations have data for most years to compute a meaningful average.

Temperatures

Between 1973 and 2014, the average temperature along the 2015 route ranged from 24 degrees (1981 and 1984) to minus 11 degrees (2007). This is an average of all stations for all 10 days starting with the restart date. It includes high and low temperatures. Approximately 13 percent of days experienced a high temperature above freezing and 57 percent of days reported a low temperature below zero. Remember that the climate stations are all some distance from the rivers. When the mushers are running down a river, it can be 10 degrees colder than in town.

Climatology tells us that reliably cold conditions are present nearly every year. The vast majority of years reported a 10-day average temperature between 20 degrees and minus 5 degrees with no worrisome warm outliers. Interestingly, the years since 2006 have been noticeably colder than most years between the 1970s through the early 2000s. A note of caution: Don't over-interpret the trend in annual temperatures. Remember, for instance, that this year's Yukon Quest started in Whitehorse during a brutally cold week in one of the warmest winters on record.

Snow

What does a musher really care about? Snow, of course. During the last four decades along the 2015 route, the snow has ranged from pretty good to outstanding. The average snow depth of the half dozen stations that make those measurements in any given year was 21 inches and the lowest was 9 inches (1986). Six years have seen an average snow depth of over 30 inches with a peak of 45 inches in 2009. Unfortunately only three stations have up-to-date snow depth measurements this year. As of Wednesday, Fairbanks reported 13 inches of snow on the ground, Tanana reported 9 inches, and Nome reported 7 inches. So this year is near the bottom of the snow-depth list.

As for new snow, stations typically receive 2 to 4 inches during the 10-day Iditarod period. Three years (1977, 1982, 1985) saw more than 5 inches of new snow. Based on the historical analysis, we can say that it is reliably cold and snowy along the 2015 Iditarod route during the race window. Hopefully, this year does not break the trend.

Forecast

The restart is still about 10 days away and long-range forecasts, while much better than nothing, should be taken with a grain of salt. Alaska National Weather Service offices issue local forecasts up to seven days in the future, so in only a few days the first official forecasts will be available.

The Climate Prediction Center issues long-range forecasts for North America and its latest prognostication for eight to 14 days in the future calls for a slightly elevated chance of above-normal temperatures during the March 5-11 window.

However, March 9 is a long way out and very little stock should be placed in those forecasts.

On the precipitation side of things, the center says most of Alaska with has a high chance of above-normal precipitation. Since March is one of the driest months of the year for Interior Alaska, above-normal precipitation still may not mean a lot of new snow.

Brian Brettschneider is an Anchorage-based environmental planner and climatologist who writes an Alaska weather blog on Facebook.

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