Overview of the Upcoming Season
George H. Taylor, State Climatologist
Cadee Hale, Publication Manager
Oregon Climate Service, Oregon State University
August 31, 2005

Last Year's Forecast

Last year we said, "We expect generally below-average temperatures during the first half of the season (Oct-Dec), with normal or somewhat above-average precipitation statewide. The second half of the year (Jan-Mar) should see above-average temperatures statewide and average or above-average precipitation (with western Oregon more likely to be above average).

"There appears to be a good chance of one or more extreme events this winter, particularly wind storms and rain storms."

We didn't anticipate the very dry mid-winter (Nov-Feb). Fall was quite wet, however, and spring was even wetter. But we sure didn't expect the dry winter.

On the other hand, in February we predicted a wet spring, at the same time NOAA was predicting a dry one, so we count that a success.

This Year's Forecast

Below are the factors we used to generate this year's forecast, along with the bottom line for this fall and winter: mild and wet.

We have also included forecasts from two government agencies, three Farmer's Almanacs, and two friends, Steve and Grant.

Sea Surface Temperatures

Sea surface temperature (SST) anomalies reported by FNMOC on August 29, 2005 show slightly negative values in most of the eastern Tropical Pacific. There has been a steady decline in SST anomalies since spring, 2005.

Analog Years

In addition to analyzing El Niño and La Niña conditions from past years, we looked for ways in which years in the past resembled this year. Using the months January - July, we compared past years with 2005 and identified the closest matches. These are listed below by year. Some of the criteria we used are:

Based on a composite of those analyses, the analog years which most closely resemble 2005 (considering the months Jan - Aug) are (in descending order of similarity, beginning with the most similar): 1995, 1969, 1952, 1954, 1957 and 1973. Using a map composite tool provided by the NOAA-CIRES Climate Diagnostics Center, Boulder Colorado from their Web site at http://www.cdc.noaa.gov, we created the following temperature and precipitation anomaly maps:

Note that 1995, the best overall fit (the year that most closely resembled 2005), was weighted twice as heavily as the other years.

A breakdown by climate division is as follows:

Extreme Weather Events in Analog Years

Extreme events were fairly common during the analog years identified above (1995, 1969, 1954, 1957, 1973); these included wind storms, floods, and ice storms. For example, major events included:

Wind storms: 1952-53, 1995-96

Floods: 1952-53, 1973-74, 1995-96

Ice storms: 1969-70, 1995-96

1995, the best overall match with this year (2005), had an abundance of extreme events:

Floods in November and February
Ice storms in December and February
Extreme wind storm (biggest in at least 15 years) in December

With that in mind, it would appear that the chaces for an extreme event are quite high this year compared with an average year. An active year seems likely!

Forecast Discussion

It is likely that this year will see relatively mild temperatures, and above-average precipitation, especially in the second half of the year. We expect early fall conditions to remain mild and dry well into October before winter storms begin, probably some time in November.

Every year, the most common question we hear is, "will we see low elevation snow?" we guess (which is all we can do in good faith -- predicting snow is really tough!) is that low elevation snow will not occur. If snow DOES occur, it is more likely after January 1. Sorry, that's as exact as we can be!

Watch for extreme events. The Oregon coast will be especially susceptible to wind storms and flooding.

Other Forecasts

• Climate Prediction Center

CPC's forecasts include monthly and seasonal (3 months) predictions for precipitation and temperature anomalies. For the upcoming winter they are as follows:

Precipitation: October - December

Temperature: October - December

Precipitation: January - March

Temperature: January - March

Predictions for individual monthly temperatures and precipitation are also included.

• Country Farmers Almanac

December 2005
Cooler temperatures will bring occasional snow flurries and cloud cover early in the month, with temperatures ranging from 28 degrees in Washington state and Oregon to 40 degress in northern California. A cold front will visit the area at the end of the month, bringing temperatures down to the low 20's in most areas, while some spots may see stretches in the teens.

January 2006
The overall average temperature for January in the Pacific Northwest will be around 29 degrees—normal for this time of year. Precipitation will also be normal, with only occasional, light storms passing through the area, concentrated in the middle of the month.

February 2006
The Pacific Northwest will experience true winter weather in February when temperatures regularly fall below freezing and severe snowstorms plague the area early in the month. Temperatures will be quite cold for the first two weeks—in the teens in many areas—but warm up after February 16. The end of February will see a real melting period, especially in southern sections.

March 2006
Relatively warm weather continues into March, with temperatures reaching the high 40's and even the 50's in some areas. Overall, the average temperature will be above normal at 45 degrees and precipitation will also be close to average for the season, with light rain occurring occasionally throughout the month.

• Harris Almanac

November 2005
Slightly below normal temperatures and near normal precipitation. Average temperatures should range from 41 to 46 at lower elevations. Coolest November 1-4, 8-10, 19-21 and 27-30; Warmest November 6, 13-17 and 24-26. Periods of rain or showers heaviest about November 1-2, 7-9, 18-20 and 26-29. Widely scattered showers at almost any time. Windy especially on the coast.

December 2005
Temperatures near normal and precipitation near normal. Temperatures should average from 39 to 43 at lower elevations. Coolest December 1-2, 19-22 and 26-30; warmest December 5-8, 13-16 and 24-25. Significant storminess with locally heavy rain, snow at higher elevations, about December 26-29. Otherwise, showers at 3 to 4-day intervals through the month. Gusty.

January 2006
Near normal temperatures and slightly above normal precipitation. average temperatures from 36 to 40 at lower elevations. Coolest January 3-6, 11-14, 20-23 and 25-28; warmest January 8-9, 17-19 and 30-31. The best chance of rain and snow at lower elevations and snow elsewhere about January 2-5, 10-13, 20-22 and 24-27. A few showers at other times. Cloudy.

February 2006
Temperatures slightly below normal and precipitation near normal. Temperatures should average from 38 to 43 at lower elevations. Coolest February 2-5, 10-12, 18-21 and 25-27; warmest February 1, 7-9, 15-16 and 23-24. A good chance for periods of rain mixed with snow at times at lower elevations and snow in the Cascades about February 1-4, 9-11, 17-20 and 24-26.

March 2006
Below normal temperatures and slightly below normal precipitation. Average temperatures should range from 40 to 45 at lower elevations. Coolest March 1-6, 12-18 and 22-27; warmest March 9-11, 20-21 and 30-31. Periods of rain and brief heavy showers at lower elevations and snow and rain at higher elevations about March 1-4, 12-16 and 21-15. Changeable weather.

• Old Farmers Almanac

November 2005
Temp. 47 degrees (avg.); precip. 10.5" (4" above avg.). 1-3 Showers, cool. 4-13 Stormy; heavy rain. 14-16 Snow north, rain south. 17-19 Heavy rain. 20-23 Sunny, cool. 24-30 Rain, then sunny; cool.

December 2005
Temp. 41 degrees (avg. north; 1.5 degrees below south); precip. 4.5" (2" below avg.). 1-3 Sunny, cool. 4-13 Rain, mild. 14-17 Misty, seasonable. 18-28 Cool; rain, then sunny. 29-31 Heavy rain.

January 2006
Temp. 49.5 degrees (7.5 degrees above avg.); precip. 7.5" (avg. south; 3" above north). 1-11 Rain, windy, mild. 12-16 Sunny; mild, then cool. 17-21 Rain, then sunny; mild. 22-31 Rain, mild.

February 2006
Temp. 46 degrees (2 degrees above avg.); precip. 10" (5" above avg.). 1-5 Stormy; heavy rain. 6-12 Rain, seasonable. 13-15 Rain, windy. 16-22 Sunny, then heavy rain. 23-28 Cold, rain and snow.

March 2006
Temp. 49 degrees (2 degrees above avg.); precip. 5.5" (1" above avg.). 1-6 Rain, seasonable. 7-13 Rain, mild. 14-20 Rain, seasonable. 21-25 Sunny, mild. 26-31 rain, then sunny; seasonable.

• Steve Pierce's Forecast

• Grant LeBlanc's Forecast