Western Regional Climate Center

PROVIDING CLIMATE SERVICES SINCE 1986

April in the West

April 2015

April brought near to slightly below normal temperatures to the West, breaking a four-month stretch of widespread above normal temperatures. This month showed a typical springtime transitional pattern, with two cold storm systems passing across much of the West interspersed with strong high pressure and above normal temperatures. Precipitation was variable across the West, though generally below normal. Scattered areas of the Southwest observed above normal precipitation.

The West saw periods of above and below normal temperatures this month that averaged to near normal for the month. Some parts of the Southwest experienced less variability this month and saw climatologically significant monthly temperatures. California statewide was warmer than average for a 16th consecutive month. San Diego, California, recorded an average April temperature of 65.8 F (18.8 C), 4 F (2.2 C) above normal, the second warmest April since records began in 1939. For the first time in 2015, Los Angeles, California and Tucson, Arizona did not have monthly average temperatures among the top-10 on record. Los Angeles recorded an average 65.8 F (18.8 C) for April, 2.7 F (1.5 C) above normal, the 11th warmest April in a 139-year record. The Tucson average of 69 F (20.6 C) was 2 F (1.1 C) above normal and 16th warmest since records began in 1946. On the cooler than normal side, temperatures at Bozeman, Montana averaged to 41.9 F (5.5 C) for April, 3.2 F (1.8 C) below normal. This value fell within the middle tercile of April temperature observations in this station’s 75 years of record. Elsewhere in the West, temperatures were generally within 1-2 F (0.5-1 C) of normal.

Precipitation was variable across the West this month, though several areas received beneficial rain and snow. Sacramento, California received 1.82 in (46 mm) precipitation for the month, 140% of normal, its first month in 2015 with above normal precipitation. Scattered areas of above normal precipitation were observed in the desert region along the California-Arizona border. Lake Havasu City, Arizona, observed 0.97 in (25 mm), 1600% of the normal 0.06 in (2 mm). Most of this fell during a storm on the 24th. A large area of northwestern Nevada also experienced above normal April precipitation. Winnemucca reported 1.83 in (46 mm), 206% of normal, the 12th wettest April in its 139-year record. Elsewhere in the Southwest, southeastern New Mexico received ample April precipitation. Roswell logged its 13th wettest April in a 123-year record with 1.74 in (44 mm), 1.13 in (29 mm) above normal. Nearly all of this precipitation fell on the 15th. In southeastern Utah, Moab recorded 1.82 in (46 mm) for April, 219% of normal and the 9th wettest April since records began in 1893. Following a dry March, Colorado’s Front Range received beneficial April precipitation. Boulder observed 4.5 in (114 mm) for the month, 156% of normal and the 15th wettest April in a 123-year record.

Along the northern tier of the West, conditions were generally drier than normal for April. In south-central Washington, Yakima had its 5th April since 1946 with no measurable precipitation. Further east in south-central Idaho, Jerome recorded only 0.12 in (3 mm), 11% of normal and the 4th driest April since records began in 1915. In northwestern Montana, Cut Bank reported 0.15 in (4 mm), 19% of normal and the 13th driest April in a 113-year record. Snowpack across the West continued to decline this month. At month’s end, the Sierra Nevada snowpack stood at only 3% of normal and the Cascades were generally at 10% of normal or less. Snowpack in the Rocky Mountains was in the 40-60% of normal range. Drought conditions expanded in northeastern California, eastern Washington, northern Oregon, and southern Idaho, but improved somewhat in southeastern New Mexico, eastern Colorado, and along the Utah-Colorado border consistent with the above normal precipitation observed in these areas.

Near to well above normal temperatures were observed across Alaska this month. Anchorage recorded its warmest April on record at an average 40.7 F (4.8 C), 3.9 F (2.2 C) above normal; records there began in 1952. Precipitation was significantly above normal across southern Alaska. King Salmon reported 2.18 in (55 mm) precipitation, 223% of normal, the 6th wettest April in a 99-year record. Further south, several locations in Hawaii saw wetter than normal conditions and lessening of drought on all major islands. Kahului, Maui, recorded 2.81 in (71 mm) rainfall, 181% of normal. Temperatures were also above normal in many locations throughout the state. On the windward side of Oahu, Kaneohe recorded an average 77.3 F (25.2 C) for the month, 3.2 F (1.8 C) above normal and the warmest April since records began in 1942.

Significant Events for April 2015

April (all month): Severe drought persists in California/Nevada/Oregon: Precipitation in parts of California and Nevada was far from sufficient to alleviate multi-year drought conditions. The region’s precipitation season is coming to an end and this winter’s meager snowpack promises little runoff for the spring and summer months, suggesting the drought may intensify. California’s governor declared a mandatory 25% reduction in urban water use and the replacement of 50 million square feet of lawn with artificial turf or drought tolerant landscapes, among other actions. April 14: Dust storms affect Salt Lake City, Utah and Las Vegas, Nevada: Strong winds ahead of a low pressure system produced dust storms that reduced visibility in these areas. West of Salt Lake City, a 17-vehicle pileup occurred killing 1 person and injuring 25. Additionally, Salt Lake City’s air quality was deemed “unhealthy” and 15,000 people were without power. In Las Vegas, 2,000 homes and businesses were without power and felled trees blocked roads and damaged property.

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