In terms of year-to-date snowfall, Fairbanks is at 46.1", which already exceeds last winter's total snowfall of 43.8". It's only the 5th time that 46" has been reached by this date. The earliest this snow accumulation was reached was 1992 (November 12), following the record September snows. Approximately one quarter of winters in Fairbanks don't reach 46" of snow in the entire winter.
All this snow led me to wonder what the snowiest location is in interior Alaska. Some time ago Rick Thoman indicated on this blog that Kaltag has a normal annual snowfall of around 120", and after looking at the NCDC normals and GHCN data, I'm unable to find any location that exceeds this (excluding sites at elevation in the Alaska Range). In the official 1981-2010 normals, which are rather sparse because of the stringent requirements for data completeness, the highest mean annual snowfall in the interior is a (to me) surprisingly high 97" in McGrath, with Bettles (91") coming in second. Fairbanks comes in at 65" (mean, not median).
Looking at all GHCN data for Alaska, the highest mean annual snowfall for a valley-level interior station with at least 10 years of at least some data is at Ambler, with 113" on average from 1981-82 to 1991-92. This includes a remarkably high 197" in the winter of 1988-89, of which 66" purportedly fell in April 1989. At first glance this is implausible, but the daily observations do not look at all unreasonable, and there is no doubt it was a snowy month in the region; Kotzebue reported one of their snowiest Aprils on record. The NCEP reanalysis, which provides an independent estimate of conditions (i.e. it is not influenced by surface station reports), indicates an unusually wet month across northwestern Alaska (see below).
Next in line after Ambler for mean annual snowfall are Coldfoot and Indian Mountain, both of which average 99" of snow according to my calculations; both locations are slightly above 1000' elevation. Indian Mountain was the site of the largest annual snowfall on record in the interior, at 217" in 1966-67. Interestingly this again included a very large 48" in April, and the reanalysis estimate of precipitation backs this up, with a swath of more than 4" liquid equivalent extending east of the Seward Peninsula to the vicinity of Indian Mountain.
It's generated by topography and normal flow of incoming winter weather systems. Your figure #2 describes the portion of the Lower Yukon Valley bordered by the Nulato Hills to the west, the Kuskokwim Mountains to the east, and headed by the Yukon-Tanana Uplands to the north and east. The NWS frequently forecasts winter weather and snow for zones 215,216,217, and 219.
ReplyDeleteAny lifting and containment via an increase in elevation will produce orographic weather, and indeed it does snow there. Similarly, Indian Mountain is, well, just that and makes its own weather.
Same for the upper Kobuk and Koyokuk drainages that lift, slow, and contain incoming systems from the west.
I've worked and flown near most of those areas, including two years off and on at Coldfoot on the Koyukuk. It does snow well.
Also the lower Yukon from Koyukuk to St. Mary's is a windy stretch in winter...SW and NE as the isobars tighten over that region.
Gary
I polled my friend Steve (and an excellent airplane mechanic/pilot) that grew up between Grayling and Nulato at Eagle Island (an Iditirod dog race checkpoint) on the lower Yukon re: snow. Here's his reply:
ReplyDelete"the costal temps collide with cold interior temps and makes it snow a lot I've seen times when we have had a foot snowfall and Galena have 6 inches then from grayling south instead of snow its rain were we are getting snow that's my theory !! "
Also note that Kaltag lies at the eastern end of the Unalakleet River drainage along the Yukon River...a migratory route for weather (and humans) from the Bering Sea to the west. No doubt there are orographic and temp changes with a SW>NE flow that contribute to precip.
Gary
Gary, I couldn't agree more - topography and path of weather systems are the key factors in this. Locally enhanced temperature gradients are also an interesting element. Thanks for your comments, and please thank Steve for his insight. It does seem likely that the changeover to rain decreases average snow amounts in the southwestern interior.
DeleteSteve's a "Bush Boy" having grown up in a remote area and has a close tie to his environment...I've seen that many times.
DeleteOf course the other factor in the records is the database is currently dependent upon the location of the direct observations by man or machine. There are likely spots with potentially more precipitation and temperature records, but go unnoted. Someday this reanalysis process will improve, perhaps via UAV's or sensors on commercial aircraft that relay critical information in real time.
Happy Thanksgiving,
Gary
Here's a repeat link to a fun model of earth weather derived from supercomputers. Click on "Earth" at the lower left corner to access the menu and select the feature and display of interest. Scroll the mouse to zoom in and out; click hold on a spot and move the focus location around the globe with the mouse:
ReplyDeletehttp://earth.nullschool.net/#current/wind/isobaric/500hPa/orthographic=-151.47,65.33,448
Gary
The topography of the interior Alaska produces really incredible micro and meso-scale climates.
ReplyDeleteThe McGrath area is interesting, because of how the Alaska Range affects the flow of low level moisture from the south. Just 40 miles to the east, Nikolai receives considerably less snow than McGrath because of the orientation of the range, and also because McGrath is closer to the higher terrain of the Kuskokwim mountains to its north and west. Just 15 miles west of McGrath, Takotna receives even more snow because it is in the actual foothills of the Kuskokwim Mountains.
The Kaltag/Nulato snow zone is also interesting, because the coastal stations of Unalakleet and Shaktoolik receive far less snow than the interior stations to the east, which is counter-intuitive for a lot of folks. Of course, surface low pressure is typically to the south of the region, which means the low level flow moves from east to west, depositing more precipitation on the east slope of the Nulato Hills.
Almost every bit of terrain in the Interior receives more precipitation on its southern and eastern side, which I guess is to be expected.
Hi Andy and good comments. This micro climate is real. The hills between Nenana and Fairbanks for example...in winter snow and fog hang over the elevated terrain...we can forecast incoming weather by observing the incoming precip over the hills. Same for the terrain west of the Kantishna river north of Lake Minchumina. It'll be IFR/500 and one with fog and precip there, but fly 15 miles east and it's usually better. This surely makes forecasting a challenge.
DeleteGary
Andy, thanks for the excellent input. I'll be showing some reanalysis results that illustrate your point very nicely - it's all tied to topography.
Delete