February in the Mid-Willamette Valley and Portland

After a three-week hiatus, winter returned to the Northwest in mid-February. But the theme of the month was not “rain” – it was “cold.” In the mid-Valley, February of 2011 was the coldest in 18 years: the average monthly temperature of 40.5 degrees was the lowest since 1993, and 2.5 degrees below the “normal,” or long-term average, for the month.

No daily temperature records were set. The lowest temperature al month was 19 on the morning of the 26th, one of 16 days with low temperatures of 32 degrees or less (normal is 10 days).

We tied a record with 3 inches of snow on the 24th; the record was originally set in 1917.

Most of the cold winter months are drier than average, and this February was no exception. Total monthly precipitation was 3.30 inches, which is 2.35 inches below the normal for the month.

Portland’s month was even more extreme. According to Steve Pierce (http://www.piercevideo.com/bio.shtml),

* February 2011 was the coldest February in 18 years (since 1993) with an average monthly temperature of just 40.3 degrees, nearly 3 degrees below normal for the month.

* February of 2011 is now ranked as the 8th coldest February (average monthly temperature) on record dating back to 1949 (62 years). The coldest years are:

1956                35.8

1989                36.0

1950                38.8

1949                39.1

1969                39.7

1993                40.0

1964                40.1

2011                40.3

1955                40.4

1994                40.8

* February 26th 2011 posted an overnight low temperature of 18 degrees. It has never been this cold, this late in the season, dating back to 1940 (71 years).

* Portland experienced its first area-wide snow event and sub-freezing temperatures in the second half of February since 1993 (18 years).

* Monday’s (2/28) record daily rainfall of 1.66″ was the single wettest February day in Portland in the past 15 years. February 8th 1996 was the last February day to register more rainfall when 1.86″ fell. That was during the great flood of 1996 when more than 7″ of rain fell over three days, on top of 6-10″ of snow that fell in the days just prior.

* February of 2011 registered 4.29″ of rainfall. That is the single wettest February since the year 2000 (11 years ago) when 4.50″ fell.

Turning to the mountains, the high elevation snowpack has improved considerably in the past several weeks. As of March 4, most basins had about 90 percent of average “snow water equivalent” (SWE — the amount of water in the snowpack, if melted) for the date. For example, the Willamette drainage (high elevation areas whose runoff flows into the Willamette) had 90 percent of average SWE; but a month ago, only 69 percent of average was observed. The Mt. Hood area is now 92 percent of average, up from 63 percent a month ago. No water shortages are predicted for summer.

Looking ahead to March, I expect the current cool-wet weather to continue for much of the month. Winter isn’t over, folks! I still believe that late spring will be dry and mild compared to normal. And I sure hope I’m right – I am READY for warm, dry and sunny!

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