Snowiest Place - CFS Reanalysis

Continuing with the discussion of normal snowfall patterns across interior Alaska, I thought it would be worthwhile to look at the CFS (Climate Forecast System) Reanalysis to see what kind of spatial variability of winter precipitation is represented in the model.  The CFS Reanalysis (CFSR) is NOAA's modern gridded historical analysis of atmospheric and oceanic conditions back to 1979; here's a paper describing the project.

The advantage of this data set for our purpose here is that the model - being run at fairly high resolution (about 38km grid spacing) - should be able to capture some localized features of the winter precipitation patterns across Alaska; it can "fill in the gaps" in the sparse observing network.  However, it's critical to bear in mind that the CFSR precipitation analysis is basically just a very-short-range model forecast and is not tied to observed precipitation, so it will have all the biases and errors that models are normally subject to.

Moving immediately to the results, the figure below shows the 1981-2010 mean November-March precipitation according to the CFSR over most of the state.  I apologize for the lurid color scheme, but it's designed to make it easy to pick out differences and specific values.  At first glance the precipitation patterns look very reasonable; it's good to see the dry zones along the Tanana River valley and immediately northwest of the Denali area.  However, the precipitation amounts are much too high in western Alaska; Bethel and Nome only see about 5" of precipitation in November-March, whereas the model says there is 10" or more.

Zooming in on the interior, and using a different color scale, we see numerous areas of enhanced precipitation in regions of elevated terrain; the black contours indicate the 500m elevation contour.  This fully supports reader Andy's comment that topography produces dramatic local variations in precipitation.  Andy mentioned the snowfall gradient from Takotna to Nikolai, and this is very clearly depicted in the model results; the marker labeled "2" shows the location of McGrath, which lies in the middle of a strong east-west precipitation gradient.  I've also added markers for several other locations, including those mentioned in the previous post.

The CFSR clearly shows the precipitation enhancement in the Nulato Hills to the west of Kaltag, and the model believes precipitation is even higher farther to the south, but as noted in Gary's comment, rain occurs more often as you go farther south.

From the point of view of "snowiest location", perhaps the most intriguing aspect of the CFSR data is the high precipitation amounts in the Kuskokwim mountains, and especially a bullseye of high precipitation at the northeast end of the range, about half way between Tanana and Minchumina.  It's interesting that reader Gary noted a preponderance of poor weather in this area north of Lake Minchumina, and I wonder if the region is particularly favored for upslope generation of snowfall during both westerly and easterly flow regimes.  According to the CFSR data, this might well be one of the snowiest places in interior Alaska, but unfortunately I'm not aware of any ground-level data to verify the claim.

The figure below compares observed 1981-2010 normal November-March precipitation to the CFSR data for 8 different locations.  Disregarding the pronounced wet bias, it's clear that the CFSR does have an ability to at least broadly discern relative differences in precipitation, and this gives a modest degree of confidence that the spatial patterns shown above probably do bear some resemblance to reality.