AgWeatherNet Winter 2011/2012 Weather Review for Washington

Strong Winds Pummel Eastern Washington on February 21st and 22nd

Nic Loyd, Meteorologist, 509-786-9357
Gerrit Hoogenboom, Director, 509-786-9371

Overview
Washington's weather in February was generally typical of late winter and early spring conditions, and temperatures were near average for the month. While conditions were generally dry in early February, a series of weak weather systems brought periodically damp conditions to western Washington around mid month. Central Washington was very warm on February 21st, as downsloping winds and a warm air mass promoted temperatures rising well into the 60s. During the middle to latter part of February, several cold upper level troughs brought rain to western Washington, wind to central Washington, and snow to the mountains. Overall, monthly temperature trends varied considerably across the state. Despite the spatial variability, all areas ended the month with cooler than normal temperatures. A cold storm on February 28th delivered several inches of snow to parts of Washington, including areas near the coast, the Cascade East Slopes, and northern parts of eastern Washington.

The 2011/2012 winter featured near normal conditions and temperatures overall, although December was abnormally quiet and nearly precipitation free through Christmas. The dry weather and lack of storms, especially during the early part of the winter, contributed to below normal winter precipitation for much of Washington. Despite the cold and snowy weather during the third week of January, most of the winter was less active than normal. There was also a notable absence of any significant intrusion of arctic air that would be similar to numerous recent events that occurred in late February 2011, late November 2010, early December 2009, and December 2008. Most of south central Washington failed even to reach 10 degrees or lower during this winter season. Luckily, heavy mountain snowfall from January 14th to 23rd, along with several moderate snow events in February, has led to a near average late winter snowpack despite a disappointing December.

February 2012 Daily Average Temperatures (°F)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly
Prosser (WSU IAREC; 1989-2012)
46.7
0.1
29.5
-0.6
37.8
-0.1
Moxee (1989-2012)
46.5
-0.1
27.1
1.3
36.4
0.9
Mt. Vernon (WSU NWREC; 1994-2012)
48.7
-0.2
36.6
1.1
42.2
0.3
Wenatchee (WSU TFREC; 1994-2012)
44.6
1.1
28.1
0.9
35.4
0.8
Tri-Cities (1995-2012)
47.2
-1.3
30.2
0.4
38.1
-0.5
Walla Walla (1993-2012)
44.3
-1.5
32.2
0.7
38.3
-0.1
Royal City East (2008-2012)
44.9
NA
30.8
NA
37.3
NA
Pullman (2008-2012)
40.0
NA
29.1
NA
34.4
NA
Long Beach (WSU Long Beach; 2005-2012)
49.8
NA
38.1
NA
43.9
NA

February Weather
Early February
February began with a garden variety winter storm that brought rain to the lowlands and a bit of snow to the mountains. However, high pressure built into the region on February 2nd, and ushered in a period of benign and spring-like conditions. The weather during the first week of the month was generally mild, dry, and calm, especially in the mountains. The weekend following Groundhog Day brought mostly sunny skies to many areas. High were in the 40s in many regions of south central Washington, except areas near the Columbia River which remained mired in fog for part of the daylight hours. Western Washington recorded high temperatures mainly in the 50s, and even low 60s were observed near the coast due to easterly downsloping winds. Air stagnation was the main weather concern, although a strengthening February sun led to greater mixing than was observed in much of December. Mostly cloudy conditions returned with damp conditions and periodic drizzle, even in central Washington, from February 8th to 10th.

Mid February
A period of weak storm systems occurred during the middle of the month. There were periods of light rain and periods of sunshine, with near to above normal temperatures. A cold upper low brought showers to western Washington on February 14th. A stronger and wetter storm caused rainfall and windy conditions in Washington on Saturday, February 18th, while several feet of snow fell in the mountains. It was the largest snowfall in nearly a month in the Cascades. Conditions warmed rapidly in parts of central Washington on Tuesday, February 21st, as strong downsloping winds, sunshine, and a mild air mass caused temperatures to rise to near 70 degrees in parts of the lower Yakima Valley. Wind gusts of 50 to 60 mph were commonplace during the storm. The strong winds were the result of a unique convergence of factors. A strong jet stream and surface low pressure passing to the north of Washington contributed to a westerly pressure gradient and strong winds aloft. Strong surface mixing helped to bring the momentum to the surface, and subsidence associated with a cold frontal passage helped the winds sink to the surface. Heavy rain also fell in parts of western Washington and in the Cascades, with over one inch of rainfall at the coast on February 21st. The front responsible for the heavy rain sagged southward on February 22nd, ending most of the significant precipitation.

Late February
Another storm system brought more rain to western Washington, wind to eastern Washington, and heavy mountain snow on February 24th and 25th, and ushered in a pattern change to cooler weather for late February. Ironically, it occurred during the same time of the year as last year's late winter arctic blast on February 26th. However, temperatures in 2012 were not nearly as cold as the arctic blast of late February 2011. Conditions were cool for the remainder of the month. A Leap Day storm system delivered additional rain, wind, and snow to Washington. The month ended with near to below average temperatures. Many locations east of the Cascades failed to reach 40 degrees during the final three days of the month. Several inches of snow fell on February 28th across Washington, including the coastal regions, in northeast Washington, and along the eastern slopes of the Cascades.

February 2012 Daily Temperatures
2012 Temperature Time Series Graph for Prosser 2012 Temperature Time Series Graph for Moxee
2012 Temperature Time Series Graph for Wenatchee 2012 Temperature Time Series Graph for Tri-Cities
2012 Temperature Time Series Graph for Walla Walla January 2012 Temperature Time Series Graph for WSU Pullman
January 2012 Temperature Time Series Graph for WSU Long Beach January 2012 Temperature Time Series Graph for WSU Mt. Vernon

February-By The Numbers
Prosser's February mean temperature of 37.8°F was near average for the month. The average high temperature of 46.7°F was 0.1 degrees above average, while the average low temperature of 29.5°F was 0.6 degrees below average. The warmest temperature of the month was 65.8°F on February 21st, while the coldest temperature of the month was 20.4°F on February 28th. The normal range of February temperatures at Prosser (WSU IAREC) is from 16.8°F to 59.7°F. The coolest daily high temperature was 39.4°F on February 28th, while the warmest daily low temperature was 38.1°F on February 10th. The warmest day of the month was February 22nd, with an average temperature of 50.0°F. The coldest day of the month was February 28th, with an average temperature of 29.9°F. 0.52 inches of precipitation fell during the month, and the average wind speed was 5.1 mph.


Notable February Weather Events
  • February 17th: The winds at Huntsville gusted to 68 mph.
  • February 21st: More than one inch of rain fell at Tokeland and Montesano in southwestern Washington.
  • February 21st: The temperature at Buena in the lower Yakima Valley reached 69 degrees.
  • February 25th: 15 minute sustained winds at St. John peaked at 47 mph.

February Temperature Extremes
  Observed in 2012 Normal Range Record Monthly Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2012)
65.8
2/21/2012
20.4
2/28/2012
69.8
2/20/1995
-13.0
2/3/1996
Moxee (1989-2012)
62.8
2/21/2012
16.2
2/29/2012
66.8
2/19/1991
-22.4
2/1/1996
Mt. Vernon (WSU NWREC; 1994-2012)
61.5
2/7/2012
27.2
2/27/2012
62.6
2/22/2009
7.8
2/26/2011
Wenatchee (WSU TFREC; 1994-2012)
55.1
2/21/2012
19.4
2/6/2012
62.1
2/22/2002
-8.1
2/1/1996
Tri-Cities (1995-2012)
63.3
2/21/2012
20.2
2/28/2012
67.9
2/8/1996
-10.8
2/2/1996
Walla Walla (1992-2012)
65.2
2/24/2012
21.4
2/5/2012
76.0
2/20/1995
-15.0
2/1/1996
Royal City East (2008-2012)
58.5
2/21/2012
21.2
2/28/2012
63.7
2/12/2011
8.1
2/26/2011
Pullman (2008-2012)
49.3
2/21/2012
10.9
2/27/2012
54.0
2/14/2011
-14.8
2/26/2011
Long Beach (WSU Long Beach; 2005-2012)
61.0
2/6/2012
26.9
2/27/2012
70.0
2/3/2009
16.9
2/19/2006

Winter Weather
While Washington experienced a winter that would be considered more benign than a typical La Niña winter, the majority of the country witnessed an almost total absence of winter this year. Temperatures were well above normal for most of the US, especially in the north and from the Rocky Mountains eastward. A strongly positive Arctic Oscillation (AO) indicates that cold air has largely remained bottled up in the arctic regions, and a strong and zonal jet stream has maintained a feed of mild air of Pacific Ocean origin in most of the eastern United States. This is in stark contrast to many of the winters of the past decade, when cold air masses regularly moved southward into the United States, leaving the arctic with relatively mild conditions. In fact, even during the mild Washington winters of the mid 2000s, arctic air regularly affected the eastern United States. In more recent winters, arctic air has periodically affected both the western and eastern United States, although usually not at the same time. However, during the 2011/2012 winter, most of the United States has been mild, with little arctic air affecting any part of the lower 48 states. No air masses of truly arctic origin affected Washington this winter, in contrast to most of the recent winters. In fact, the coldest temperature recorded this winter (December 2011 to February 2012) at Prosser (WSU IAREC) was warmer than any winter minimum since the 2002/2003 winter.

December and January Review
Although Washington's 2011/2012 winter featured fairly average conditions overall, there were several interesting aspects to this seemingly moderate winter season. Despite the expectation of wet conditions, December 2011 was very dry due to a persistent ridge of high pressure situated over the region. The month was drier than normal, and was one of the driest La Niña Decembers on record, with almost no precipitation across the state until Christmas. The lack of storms meant that very little snow fell in the mountains during what is historically one of the snowiest months of the year. Despite warm conditions aloft and in the mountains, stable conditions and widespread fog led to cold temperatures in the valleys and basin of central Washington. Minimal atmospheric mixing also contributed to poor air quality for much of the early and middle part of the month. A series of mild and windy weather systems brought significant rain to western Washington and warm temperatures to eastern Washington during the final week of 2011. However, benign conditions returned in early January.

Winter finally made a brief, albeit forceful, entrance in mid January. A series of winter storms impacted Washington from the 14th to the 23rd, and brought periods of heavy snow, ice, cold air, wind, heavy rain, and flooding to the state. A strong winter storm on January 18th buried the Centralia area under upwards of 17 inches of snow. The snow was the result of a clash of two distinct air masses over Washington, as mild and moist Pacific air collided with cold and dry, arctic air. Temperatures were cold in northern Washington, as readings fell into the single digits. Strong northerly winds and bitter wind chill values affected the Bellingham and Omak areas. The cold, Canadian air was pulled southward as a strong and warm low pressure approached Washington from the southwest. The snow quickly changed to rain, which led to flooding in parts of southwestern Washington. Other parts of the state including the Tri-Cities and Seattle areas amassed significant ice accumulations on January 19th. As snow continued to fall in parts of eastern Washington, some areas along the Cascade east slopes from Yakima to Wenatchee had more than one foot of snow on the ground by January 23rd. Much calmer and milder conditions prevailed during the end of January and beginning of February. However, conditions became increasingly wet in mid to late February, as a series of upper level troughs brought periodic rain, wind, and mountain snow to the region. Windy and sunny conditions caused temperatures in parts of south central Washington to rise to near 70°F on February 21st. A pattern change on February 24th ushered in cooler weather for the end of the month. A cold storm on February 28th brought several inches of snow to parts of the lowlands of Washington.

Winter-By The Numbers
The average winter temperature at Prosser (WSU IAREC) was 33.9°F, which was 0.5 degrees below the average of 34.5°F. The average high temperature was 42.3°F, which was one degree above average, while the average low temperature was 26.2°F, which was nearly two degrees below average. The larger than normal diurnal temperature range that was recorded this winter is consistent with the observed weather pattern that featured less active than normal conditions. Days were warmer than normal due to mild air masses and periodic sunshine under persistent ridges of high pressure. Nights were cooler than normal due to fewer storms resulting in decreased atmospheric mixing, and periodically clear skies leading to increased radiational cooling. It should be noted that the slightly below average winter temperature at Prosser was not the result of an increased transport of cold, polar air into Washington. Despite the warm conditions aloft and in the mountains, generally stable conditions helped to insulate the surface from the above average atmospheric heat content.

1.45 inches of precipitation fell during the winter season at Prosser (WSU IAREC), and the average wind speed was 4.5 mph. The warmest temperature of the winter was 65.8°F on February 21st, while the coldest temperature of the season was 14.1°F on January 13th. The warmest daily low temperature was 51.6°F on December 28th, while the coolest daily high temperature was 23.0°F on January 19th. The warmest day of the winter was December 28th, with an average temperature of 54.8°F, while the coolest day of the winter was January 19th, with an average temperature of 20.6°F.

Winter 2011/2012 Daily Average Temperatures (°F)
(Winter = Dec, Jan, Feb)
Location (Period of Record) Maximum Minimum Mean
Prosser (WSU IAREC; 1989-2012)
42.3
26.2
33.9
Moxee (1989-2012)
41.4
22.0
31.1
Mt. Vernon (WSU NWREC; 1994-2012)
46.6
34.9
40.6
Wenatchee (WSU TFREC; 1994-2012)
39.6
24.3
31.3
Tri-Cities (1995-2012)
42.8
26.6
34.3
Walla Walla (1992-2012)
43.2
29.5
36.2
Royal City East (2008-2012)
40.1
26.9
32.9
Pullman (2008-2012)
38.8
26.6
32.7
Long Beach (WSU Long Beach; 2005-2012)
48.8
35.1
41.8
Notable Winter Weather Events
  • December 27th: 1.6 inches of rain fell at Long Beach.
  • December 28th: Temperatures rose to near 60 degrees in the Walla Walla area.
  • January 18th: 14+ inches of snow fell in the Centralia area of interior southwestern Washington.
  • January 23rd: 10 day snowfall totals in the Cascades measured five to eight feet.
  • February 29th: A cold, late season storm delivered several inches of snow to coastal areas.
Winter Temperature Extremes (°F)
  Observed in 2011/2012 Record Seasonal Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2012)
65.8
2/21/2012
14.1
1/13/2012
69.8
2/20/1995
-13.0
2/3/1996
Moxee (WSU IAREC; 1989-2012)
62.8
2/21/2012
6.7
1/23/2012
66.8
2/19/1991
-22.7
1/31/1996
Mt. Vernon (WSU NWREC; 1994-2012)
61.5
2/7/2012
16.6
1/16/2012
65.0
12/24/2005
7.8
2/26/2011
Wenatchee (WSU TFREC; 1989-2012)
55.2
1/30/2012
10.4
1/19/2012
62.1
2/22/2002
-13.4
1/31/1996
Tri-Cities (1995-2012)
63.3
2/21/2012
10.3
1/12/2012
67.9
2/8/1996
-10.8
2/2/1996
Walla Walla (1992-2012)
67.9
1/4/2012
17.8
1/19/2012
76.0
2/20/1995
-15.0
2/1/1996
Royal City East (2008-2012)
58.5
2/21/2012
11.4
1/20/2012
63.7
2/12/2011
-1.4
12/20/2008
Pullman (2008-2012)
52.0
12/28/2011
10.9
2/27/2012
55.0
12/1/2008
-17.5
1/26/2009
Long Beach (WSU Long Beach; 2005-2012)
61.0
2/6/2012
22.5
12/12/2011
70.0
2/3/2009
14.5
12/8/2009

Weather Summary By Month
  • December: Very dry until the final week of the year.
  • January: High impact winter weather from the 14th to the 23rd.
  • February: Average conditions with a few stormy periods.

Agriculture Report
Oyster and clam harvest continued in western Washington in February, while berry vine tying and the planting of Christmas tree seedlings also occurred. Pruning occurred in tree fruit orchards and vineyards in central Washington, while equipment preparation continued in advance of the spring season. Dry land wheat looked good in Grant County, while eastern Washington growers remained concerned about the lack of moisture and the low precipitation totals since last autumn (NASS).

This Month in History
On February 1st, 1996, the temperature at the Moxee weather station east of Yakima fell to -22.4 degrees.

Climate Outlook
The Climate Prediction Center (CPC) outlook continues to suggest slightly enhanced odds of cooler and wetter than normal conditions in the spring, and then warmer and drier than normal weather for the late summer and early fall.

Washington State University