April in the West
April saw several slow-moving closed low-pressure systems travel across the West, bringing above normal precipitation to places such as the Southwest and Great Basin that had been drier than normal in the two preceding months. The Pacific Northwest and northern California saw a turn to drier conditions this month, accompanied by well above normal temperatures.
Strong high pressure over the Pacific Northwest produced well above normal temperatures during the beginning and middle of the month. Seattle, Washington observed its warmest April since records began in 1945 at an average 56.7 F (13.7 C). This included Seattle’s all-time warmest April temperature of 89 F (31.7 C) on the 18th, which was also the first day of 2016 exceeding 80 F (26.7 C). Average Seattle high temperatures do not reach 80 F until May 28. In eastern Washington, Spokane observed its second warmest April in a 136-year record at 54.7 F (12.6 C), 7.7 F (3.2 C) above normal. Medford, Oregon, also recorded its second warmest April at 58.2 F (14.6 C), 5.5 F (3.1 C) above normal. This included the earliest >90 F (>32.2 C) day on record, when the mercury rose to 91 F (32.8 C) April 7th. Records for Medford began in 1911. In the western Great Basin, Reno, Nevada, observed its second warmest April at an average 54.9 F (12.7 C), in a record that begins in 1937. Warm temperatures helped to accelerate snow melt in the West, with many locations in the Sierra Nevada and Cascades seeing an earlier than usual maximum snowpack, up to a month early in the northern Cascades.
April brought above normal precipitation to the Desert Southwest, which had seen drier than normal conditions and increasing drought severity over the latter part of the winter. Las Vegas, Nevada, recorded 2.26 in (57 mm) over the course of the month, 54% of the city’s typical annual precipitation and the second wettest April since records began in 1948. Needles, California, recorded 1.59 in (40 mm), 723% of the normal 0.22 in (6 mm) and the 4th wettest April since records began in 1941. In Arizona, Tucson observed 0.71 in (18 mm), 230% of normal precipitation. Areas of New Mexico also saw beneficial precipitation as well; Truth or Consequences recorded 0.95 in (24 mm), 305% of normal, and the 5th wettest April since records began in 1950. In the eastern Great Basin, Elko, Nevada logged its 6th wettest April on record at 1.99 in (51 mm), 200% of normal. Records for Elko began in 1888. Scattered areas of the Rocky Mountain states noted above normal precipitation as well. Riverton, Wyoming, received 3.82 in (97 mm), 390% of normal and the wettest April since records began in 1907. In north-central Montana, Chinook recorded its wettest April in a 122-year record at 4.03 in (102 mm), 443% of normal. At the month’s end, snowpack was down to 75% of normal across the Cascades and northern and central Rockies. April snowfall helped put Great Basin ranges and the Colorado Rockies at near-normal snowpack. The Eastward draining basins of the Sierra Nevada were near normal, while basins on the western side of the Crest averaged to 61% of normal snowpack.
The Pacific Northwest and coastal southern California saw drier than normal conditions in April. In eastern Oregon, Burns recorded 0.11 in (3 mm) for the month, 12% of normal and the driest since records began in 1973. On Washington’s Olympic Peninsula, Forks logged 3.28 in (83 mm), 35% of normal, tied for 8th driest since records began in 1907. On the southern California coast, Los Angeles saw 0.24 in (6 mm) rainfall, 26% of normal.
Temperatures in the upper tercile were observed across Alaska, with several locations experiencing record warmth. On the state’s western coast, both Bethel and Kotzebue observed record warm Aprils, with 41.5 F (5.3 C), 14.5 F (8.1 C) above normal and 25.5 F (-3.6 C), 12.2 F (6.8 C) above normal, respectively. Records for Bethel began in 1923 and records for Kotzebue in 1897. Further south, Hawaii saw above normal temperatures throughout the state. Hilo recorded an average 75.3 F (24 C), 3.2 F (1.8 C) above normal and the warmest since records began in 1949. Precipitation was near normal for many windward locations and below normal in leeward areas. Lihue, Kauai logged 0.84 in (21 mm) of rainfall, 37% of normal and the 5th driest April in a 67-year record. Drought conditions expanded on the southern and western portions of Big Island this month, while some improvement was seen on windward coasts of all islands.
Significant Events for April 2016
April 9th, 30th: Flooding in Las Vegas: Heavy rains in Las Vegas on the 9th produced flash flooding, resulting in 6 rescues from floodwaters. The airport recorded a daily record 0.81 in (21 mm). Heavy rains occurred again April 30th, with police responding to 90 vehicle crashes in the area. The flooding events resulted in minor damages.
April 15-17th: Heavy snow in Colorado’s Front Range: A slow-moving closed low pressure storm stalled over Colorado on April 15-17th, producing upslope flow in the Front Range and resulting in snowfall totals up to 50 in (127 cm) in some higher elevation locations.