News and Opinion from Sisters, Oregon
News and Opinion from Sisters, Oregon
It appears, as this column is being compiled, that winter is on its way. (Mr. Hatton was his usual, prognosticating self. His column was submitted 36 hours before we awoke to Tuesday's white blanket -- Ed.) This is, of course, too late for skiers, snowboarders, snowmobilers and other lovers of the big white outdoors whose hopes for some winter sports activity over Thanksgiving were melted by the exceptionally mild, rainy weather that occurred on and off throughout November.
Although November started with winter-like weather, air masses whose origins were from near Hawaii, streamed over Oregon during most of the month. This situation was reminiscent of what occurred in December 1964 when widespread floods occurred in the Pacific Northwest and Northern California.
The rains that fell in November helped restore the soil moisture before a possible deep freeze that would make the soil impervious to infiltration by future rains or melting snows.
What meteorological conditions accounted for the absence of mountain snows this past month? George Taylor, State Climatologist in Corvallis, explained what had occurred and ventured his snow forecast for the coming winter.
El Nino conditions (warm ocean current off Peru that causes some bizarre weather throughout the world and drought conditions in parts of the Pacific Northwest) have ended -- for now.
Taylor contends that under an El Nino episode the Aleutian Low (low pressure system in the Gulf of Alaska) forms early and results in cool weather and early snowfall to this region. Then a ridge of high pressure takes over and essentially shuts off the moisture supply.
Thus, while winter sports get an early start, a paucity of renewed snowfalls leads to some marginal ski conditions during parts of the winter season.
This November, according to George Taylor, there has been more convective (heating) in the mid-Pacific and, as we now know, a stream of mild, moist air was aimed at Washington State and Northern Oregon. California has been exceptionally dry and warm and Sierra ski resorts received neither rain nor snow.
Air which is "warm" has greater potential holding capabilities than air which is "cold." For example, air at 70 degrees F. can contain four times as much moisture as can air that is 30 degrees F.; hence, the heavy rainfalls in parts of the Pacific Northwest.
Taylor predicts that this tropical moisture supply will be replaced by colder, drier air. As the winter progresses, George forecasts the likelihood of more storms whose origin is in the North Pacific and, as a result, there is the strong likelihood of "normal snowfall." (Bend's average yearly snowfall is about 34 inches; Sisters would be comparable).
From 95 years of weather records, I have identified the 20 mildest Novembers. All but four occurred in the period 1901-49!
Snowfall the following winter and spring (it can and does snow in Central Oregon during March and April and even in May!) ranged from a skimpy 4.7 inches 1933-34 to a prodigious 71.0 inches 1949-50.
The average "winter" snowfall was 28.6 inches, and most of it (an average of 18.2 inches fell) in the month of January.
In short, while this is not to be taken as a forecast, statistically the odds are in favor of a normal Central Oregon winter and hopefully good conditions for winter sports.
Raymond Hatton is author of "Sisters' Country Weather and Climate" and other books.
Reader Comments(0)