Published: 2008-10-12 13:25:34
Updated: 2008-10-12 13:25:34
Posted October 12, 2008
By Ginger Brown
MIKE MOSS SAYS: Ginger, Unfortunately there is no confident way to make a meaningful forecast about snowfall amounts very far in advance, and about the only seasonal forecasts that can be made regarding the wintertime are some vague comparisons of how seasonally averaged temperatures and precipitation are likely to compare against normals for the time period. These forecasts have somewhat higher confidence when there is a strong climate-influencing feature such as El Nino or La Nina in place that helps modulate weather patterns in a known (though still variable) manner, but this year even those are lacking as most ocean-atmosphere models indicate a probable "La Nada" winter with "neutral" conditions in the Pacific. With that influence lacking, the current outlooks for the winter from the Climate Prediction Center are based largely on how trends from the past 10-15 years compare to longer term historical averages, and they are calling for warmer than normal temperatures and below normal precipitation for our area.
At first glance, this would seem to equate to a lower than normal chance for snow, and that's a reasonable interpretation. However, snowfall in our area is dependent on some very specific short-term combinations of lift mechanisms (fronts, surface lows and upper level disturbances), moisture sources, and temperature structure, that can all come together a time or two and produce big snows even during a warm, generally dry winter or on the other hand can consistently "just miss" during a cold, wet winter, making it hard to put too much stock in relating the overall seasonal outlook to snowfall amounts. All of that is a long way of saying that most of the time we just have to wait and see, and most snow events can only be forecast reasonably well with a few days lead time, and as we all know there is plenty of room for error regarding specifics even that close in...