A tranquil winter... so far

Early in the week of Thanksgiving a slug of cold, moist air in British Columbia was poised to plunge southward, and the Pacific Northwest appeared to be in the crosshairs. While the frigid air was not of arctic-like intensity, it was potent enough to cause potential problems for holiday travelers. And that it did.

Snow began falling in Sisters late on November 26 that continued throughout the next day and into Thanksgiving on November 28.

Weather records show that a foot-and-a-half of snow fell during the two-day period. Even greater amounts were measured in other areas around Sisters.

Because temperatures have remained relatively cool since the storm, the snow is only now disappearing. And at this writing no additional snow has yet accumulated.

Thus far the only winter-like weather we’ve had this season occurred nearly a month before the official start of winter on December 21. Will this trend continue going forward? Before peering too intently into the future, let’s go back and look at the last quarter of 2019 and see how it squares with the weather we were told to expect.

The Climate Prediction Center (CPC) felt the period from October through December would see above-normal temperatures throughout the entire country and below-normal precipitation in Central Oregon. Pete Parsons of the Oregon Department of Forestry called for a cool start and mild finish during that same time. Precipitation levels would be about average, drier in November and wetter in December.

Data collected at the Ranger Station in Sisters shows precipitation for all three months was below normal, particularly in October and December. Temperatures were far below normal in October and close to normal in November and December. The lowest recorded temperature for the period was -7 F, occurring on December 2.

According to meteorologist Joe Solomon of the National Weather Service office in Pendleton, the water-equivalent snowpack in the Central Oregon Cascades was less than half of normal on January 2.

As defined by the calendar, there are still more than two and a half months of winter left before spring arrives. What do the seasonal forecasters see going forward?

In the short term, current upper-air charts are showing a change in the jet stream configuration that might draw down cold air from British Columbia by the weekend of January 11-12.

In fact, for the next two weeks a narrative put out by the CPC that is updated weekly states, “The overall pattern described by guidance features a high-amplitude ridge south of the Aleutians, arctic air over Canada and a trough extending into the western U.S. which may promote cold air outbreaks in the West…” During the same time period, above-normal precipitation levels are expected.

While below-normal temperatures are anticipated to continue throughout the remainder of January, precipitation should taper off by then, resulting in normal amounts of moisture.

Although odds favor colder-than-normal temperatures for January, the Arctic Oscillation is still in its positive phase which should tend to keep the coldest air confined to the arctic region.

The CPC’s forecast for the period January through March is for temperatures to average slightly above normal and an equal chance for above-normal, normal, and below-normal precipitation levels in our area.

If the advertised changes to our weather pattern materialize this month and persist longer than expected, the three-month period may be cooler and wetter. Otherwise, it’s likely that February and March will be warmer and drier than normal.