AgWeatherNet April 2012 Weather Review for Washington

April 2012 Is Not a Repeat of Last Year's Record Cold

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

Overview
It was a great relief to most Washingtonians that the weather last month was nothing like the weather in April of 2011. In stark contrast to last year, this spring has already featured an abundance of warm and sunny weather. April of 2012 was the fifth warmest since 1990 at Prosser (WSU IAREC), and the warmest since 2000. The average April temperature was 53.3°F, which is 1.7 degrees above normal. Generally, temperatures were 1 to 2 degrees above normal across the state during April, with warm conditions during both the day and night. The heat wave that occurred from April 22nd to 24th brought record warmth to the region, with temperatures around 90 in some locations, and lows in the 50s and 60s. The high temperature at Moxee on April 23rd was 88.2°F, which was an April high temperature record (1989 to present). The April 24th low temperature at WSU Tri-Cities was 56.5°F, which eclipsed their previous April daily low temperature record (1996 to present) by 1.5 degrees. Monthly high temperature records also occurred at Prosser (WSU IAREC) and Wenatchee (WSU TFREC). Temperatures of 20 degrees above normal were common across the state. Thunderstorms brought rain and high winds to parts of eastern Washington on April 23rd, with wind gusts up to 70 mph at St. John. Significant snowmelt, along with heavy rain on April 26th, led to flooding on many eastern Washington rivers. In fact, all of the 138 AgWeatherNet weather stations recorded rain on the 26th. The month consisted of a variety of weather patterns that ranged from hot and sunny to cool and wet. Despite the late April heat wave, the spring weather pendulum swung back toward cool temperatures on the final day of the month, as snow fell in the Cascade high country. Temperatures varied from the teens in places like Broadview (Ellensburg) early in the month to 91°F at Desert Aire on April 23rd.

April 2012 Daily Average Temperatures (°F) and Rainfall (Inches)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly Rainfall 8 Inch Soil Temperature
Prosser (WSU IAREC; 1989-2012)
65.1
1.7
40.5
1.9
53.3
1.7
0.98
53.6
Moxee (1989-2012)
64.5
1.6
36.0
3.1
51.4
2.1
0.36
51.5
Mt. Vernon (WSU NWREC; 1994-2012)
58.1
1.1
42.3
1.4
49.8
1.0
4.31
51.9
Wenatchee (WSU TFREC; 1994-2012)
64.6
1.4
40.0
1.1
52.5
1.0
0.58
52.8
Tri-Cities (1995-2012)
67.0
1.4
41.3
1.2
54.6
1.3
0.76
57.4
Walla Walla (1993-2012)
63.8
2.4
42.2
1.0
52.8
1.5
3.56
52.9
Moses Lake (1989-2012)
64.3
1.7
39.0
1.2
51.8
1.2
0.89
53.1
Omak (Pogue Flat; 2005-2012)
63.2
NA
38.7
NA
51.3
NA
0.71
48.4
Royal City East (2008-2012)
63.5
NA
41.1
NA
52.2
NA
0.66
52.3
Pullman (2008-2012)
57.6
NA
38.1
NA
47.7
NA
2.12
47.1
Long Beach (WSU Long Beach; 2005-2012)
54.9
NA
40.3
NA
47.9
NA
7.27
51.1
April 2012 Daily Rainfall
2012 Rainfall Time Series Graph for Prosser 2012 Temperature Time Series Graph for Moxee

April Weather
Early April
April began with slightly cooler than seasonal conditions, in the wake of a storm system. Warm southerly flow on April 2nd pushed temperatures well into the 60s in parts of western Washington. Following high temperatures that were in the 50s to 60s, and even 70s around Walla Walla, a cold frontal passage on the night of the 3rd brought cooler, unsettled weather to Washington, with frost in parts of the lowlands. Cold air aloft and an upper level disturbance combined to create unstable conditions and even thunderstorms on April 4th and 5th. Broadview (Ellensburg) dropped to 18 degrees on the morning of April 7th.

Mid April

Southerly flow aloft brought warmer weather on April 8th, as temperatures rose to around 70 degrees in the Tri-Cities area. Temperatures also reached to around 70 degrees in much of the Puget Sound area due to a warm air mass and downsloping southeasterly flow. Near to above normal temperatures continued for the rest of the week, with highs reaching near the mid 70s in parts of central Washington. Conditions cooled slightly later in the week as an upper level low pressure system approached the coast. Although the 8 to 11th time frame was generally dry, persistent high cirrostratus provided for filtered sunshine and hazy conditions. More unstable conditions arrived with a trough of low pressure on the 12th, which brought scattered showers, and cooler temperatures to western and eastern Washington. Warm weather returned over the weekend, with highs above 70 degrees in warm locations. Bright sunshine on the 14th gave way to filtered sunshine and high clouds on the 15th. However, rain on the morning of the 16th ushered in a more unsettled period of weather, with cooler than normal high temperatures returning to the region through Thursday, April 19th.

Late April

Much warmer air arrived on April 21st, bringing the first summer-like heat wave of the spring. Temperatures reached the 80s in much of the state on April 22nd, under warm, southerly flow aloft and abundant sunshine. April 23rd was the hottest day of the month, featuring record-breaking temperatures near or above 90 degrees at several AWN locations. Overnight temperatures were also very balmy, with lows in the low 60s in some locations. Thunderstorms moved through eastern Washington during the evening of the 23rd, dropping up to 0.4 inches of rain. Strong winds associated with the convective activity included a gust of 68.6 mph at St. John. Cooler air heralded a return to more seasonal spring weather on April 25th, as significant rain fell in many areas through the 26th. In a rare event, rain fell at all 138 AgWeatherNet locations on the 26th, with the most significant rain falling in areas east of the Cascades. Nearly an inch of rain fell near Oroville and Walla Walla. Snowmelt and heavy rainfall combined to cause some area rivers to run high and overflow their banks. Despite sunny skies, below normal temperatures prevailed on April 27th. The transition to cool air was particularly apparent following the record heat that occurred earlier in the week. Some areas recorded subfreezing low temperatures on the mornings of the 27th. The chill yielded to warmer, seasonal weather during the final weekend of the month. However, snow returned to the high elevations of the Cascades on the final day of the month.

April 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 April 2012 Temperature Time Series Graph for WSU Pullman
2012 Temperature Time Series Graph for Moses Lake April 2012 Temperature Time Series Graph for Omak
April 2012 Temperature Time Series Graph for WSU Long Beach April 2012 Temperature Time Series Graph for WSU Mt. Vernon

April-By the Numbers
The average April temperature at Prosser (WSU IAREC) was 53.3°F, which is 1.7 degrees above normal, and was the warmest mean April temperature since 2000. The monthly average high temperature was 65.1°F, which is 1.7 degrees above normal, and was the warmest since 2004. The average low temperature was 40.5°F, which is 1.9 degrees (0.8 standard deviations) above normal, and was the warmest since 1994. The warmth of April 2012 is notably different than the chill of April 2011, such that the average high, average low, and mean temperatures were 7.1, 5.6, and 6.1 degrees warmer than last April. The daily high temperatures varied from 87.2°F on April 23rd, which was an April record, to 50.8°F on April 5th. The daily low temperatures varied from 54.3°F on April 23rd to 28.0°F on April 7th. The daily average temperatures varied from 71.1°F on April 23rd to 41.8°F on April 5th. April 23rd featured record heat across central Washington. The high temperatures of 88.2°F and 87.6°F at Moxee and Wenatchee (WSU TFREC) were also monthly records, while the low of 56.5°F on April 24th at WSU Tri-Cities was a monthly record warm low temperature. 0.98 inches of rain was recorded during the month at Prosser (WSU IAREC), while the average wind speed was 5.9 mph.


April 2012 Recent Temperatures Graph

Notable April Events:
  • April 2nd: Winds gusted to nearly 39 mph at Long Beach.
  • April 3rd: 1.2 inches of rain fell at Long Beach.
  • April 7th: The temperature at Broadview (Ellensburg) fell to 18 degrees.
  • April 8th: The temperature at 21 Acres (near Seattle) rose to 71 degrees.
  • April 23rd: The temperature at Moxee rose to 88.2 degrees.*
  • April 24th: The low temperature at WSU Tri-Cities was a balmy 56.5 degrees.*

*-Denotes Monthly Record

April Temperature Extremes (°F)
  Observed in 2012 Record Monthly Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2012)
87.2
4/23/2012
28.0
4/7/2012
87.2
4/23/2012
25.3
4/1/2008
Moxee (1989-2012)
88.2
4/23/2012
22.1
4/7/2012
88.2
4/23/2012
14.8
4/21/2008
Mt. Vernon (WSU NWREC; 1994-2012)
68.7
4/8/2012
33.0
4/7/2012
79.5
4/11/2004
25.4
4/1/2008
Wenatchee (WSU TFREC; 1994-2012)
87.6
4/23/2012
27.6
4/7/2012
87.6
4/23/2012
23.5
4/3/2007
Tri-Cities (1995-2012)
89.0
4/23/2012
26.8
4/7/2012
91.7
4/30/1998
20.5
4/1/2008
Walla Walla (1992-2012)
84.5
4/23/2012
31.6
4/7/2012
85.0
4/29/1998
25.9
4/1/2008
Moses Lake (1989-2012)
86.1
4/23/2012
25.4
4/7/2012
87.6
4/30/1998
20.5
4/1/2008
Omak (Pogue Flat; 2005-2012)
85.5
4/23/2012
26.5
4/7/2012
85.5
4/23/2012
27.7
4/1/2008
Royal City East (2008-2012)
85.5
4/23/2012
31.1
4/7/2012
85.5
4/23/2012
27.7
4/1/2008
Pullman (2008-2012)
80.5
4/22/2012
29.0
4/7/2012
80.5
4/22/2012
20.0
4/19/2011
Long Beach (WSU Long Beach; 2005-2012)
66.1
4/21/2012
29.0
4/7/2012
75.5
4/12/2008
28.0
4/2/2008

Agriculture Report
The growing season was under way during April, as orchards bloomed to life. As of the end of April, the above average GDD values were at their highest level in the last five years. The condition of the winter wheat and the Kittitas County hay crop was above average, while spring grain seeding progressed well as of April 22nd. Winter wheat greened nicely in southeastern Washington, although it was generally shorter than normal as of April 29th. Yellow spots were found on winter wheat in excessively wet fields in Pend Oreille and Spokane Counties. Spring wheat was beginning to emerge in Asotin County. Apples and pears reached full bloom in colder regions of the upper Yakima Valley, while most areas were in post petal fall at the end of April. Fire blight prevention and fruit thinning spray application were occurring on fruit trees in Chelan County. Excellent pollination weather allowed for tree fruit bloom in the Yakima Valley, while asparagus harvest continued without delay. The heat wave in late April made for rapid flower development and continued excellent pollination conditions. Corn, potato, and bean planting continued in Franklin County. Despite interesting weather events during the month, Washington crops generally fared well with no significant weather related losses occurring in April (National Agricultural Statistics Service).

April 2012 Frost Table
(Frost day = Low < 32°F)
Location # Frost Days
Prosser (WSU IAREC)
3
WSU Tri-Cities
3
Wenatchee (WSU TFREC)
1
Moses Lake
7
Royal City East
1
Omak (Pogue Flat)
6
Moxee
11
Broadview (Ellensburg)
12
Pullman
5
Walla Walla
1
Long Beach (WSU Long Beach)
2
Mt. Vernon (WSU NWREC)
0
Wahluke Slope
0
Cowiche
2
Wapato
4

April 1 to April 30 Accumulated Growing Degree Days
  Base Temperature (°F)
32 43 50
Location 2012 5 Year Avg Difference 2012 5 Year Avg Difference 2012 5 Year Avg Difference
Prosser (WSU IAREC)
623
520
103
296
200
96
131
67
64
Tri-Cities
666
584
82
336
257
79
158
94
64
Walla Walla
629
532
97
301
207
94
123
65
58
Wenatchee (WSU TFREC)
609
527
82
280
207
73
115
69
46
Moxee
547
407
140
230
122
108
97
37
60
Omak (Pogue Flat)
568
466
102
245
157
88
108
49
59
Moses Lake
589
508
81
264
190
74
109
61
48
Pullman
474
353
121
175
90
85
70
30
40
Royal City East
609
511
98
280
190
90
119
64
55
Mt. Vernon (WSU NWREC)
545
466
79
216
145
71
54
25
29
Long Beach (WSU Long Beach)
468
416
52
146
1005
46
18
9
9

GDD are calculated by subtracting a base temperature from the average daily temperature (°F). If the resulting value is less than 0, then it is set to 0. Thus GDD are always 0 or greater.

GDD = (Tmax+Tmin)/2 - Tbase


This Month in History
On April 15th, 2011, the high temperature was only 49 degrees at Prosser (WSU IAREC). The spring season was the coolest in recent memory for central Washington.

Climate Outlook
La Niña has completed the transition to neutral conditions, which will continue into the summer. For next autumn and winter, El Niño or neutral conditions are possible, with El Niño being the most likely climate state. According to the Climate Prediction Center (CPC), below normal temperatures are most likely during May for areas west of the Cascades, with no strong temperature signal present for eastern Washington. Drier than normal conditions are most likely beginning in early summer, which represents a slight change from previous forecasts, and is indicative of the diminishing impacts of La Niña. Dry conditions are forecast by the CPC to linger into the autumn, while near to above normal temperatures are forecast by late summer.

Washington State University