Western Regional Climate Center

PROVIDING CLIMATE SERVICES SINCE 1986

April in the West

Temperatures were distinctly different across the West, being generally above normal in the southeastern third and cooler to much cooler than normal in the northern two-thirds. Some locations in Washington reported temperatures of 8 degrees F (4 C) below normal while various locations in New Mexico were 6-8 degrees F (3-4 C) above normal.

Precipitation was a mixed bag with pockets of wet and dry throughout the region. Generally, the northern half was wetter and the southern half drier, especially New Mexico and California. Parts of NE Montana were 300% of normal for the month while numerous locations in California, Nevada, Arizona and New Mexico recorded little or no rainfall. As a consequence the southern half of New Mexico and a portion of southeast Arizona were in extreme drought. A large local rain event hit the Oregon-California border coast on the 15-16th with some locations receiving nearly 10 inches (254 mm) of rain.

Thanks to a mostly cool and cloudy April and consequent minimal runoff, mountain snowpack remained quite healthy with most mountain sensors reporting well over 100% of normal by the end of the month. Only Arizona and New Mexico had below normal snow pack. Glasgow MT added 3.3 inches (8 cm) to its record seasonal snowfall of 108.6 inches (276 cm), 372 percent of its 29.2 inch (74 cm) average through April. The central Sierra snowpack was near 200% of normal while most of the intermountain and Cascades were 150% or normal. On April 27th, 71 Snotel sites in the Wasatch and Uinta Ranges, and the upper Green River and Colorado River headwaters, registered the highest snow water content for the date since station installation (generally early to middle 1980s). The closely monitored April through July forecast of inflow to Lake Powell was around 119 percent of average.

Significant Events for April 2011

Although April was rather cool, blustery and unpleasant throughout the region there were relatively few damaging storm events.

April 1-6: Wildfire near Fort Collins, CO: The Crystal Fire destroyed 13 homes just west of Fort Collins, CO, and burned nearly 3,000 acres. The fire started on the 1st and burned rapidly in the dry, windy conditions.

April 7: Powerful storm in Alaska: A strong storm hit Alaska with winds of up to 110 mph in some areas near the Bering Sea which shut down marine and air traffic, damaged buildings and produced blizzard conditions. The cities of Kotzebue and Nome were mostly shut down to air traffic. Strong down slope winds in Anchorage downed trees and produced areas of blowing and drifting snow disrupting traffic and causing power outages to more than 5,500 residents in Palmer and Anchorage due to downed power lines.

April 7-8: Southwest. A late season cold front hit much of the west. In Montana, up to 31 inches (78.7 cm) of snow fell in parts of Jefferson County. Although very little precipitation fell in the Southwest, conditions were quite cold and windy throughout the region, with some local damage from hail and gusty winds in excess of 70 mph in California and Nevada. A small tornado (EF0) was reported in Solano County, CA. An automated weather station in Yosemite National Park recorded a minimum temperature of -14 F (-25.5 C) on the morning of the 8th.

April 11-16: Flooding in Northern Montana: Record winter snowfall in north central and northeast Montana led to moderate to major flooding along the Milk River. At least 11 roads in Valley and Phillips counties were under water and over 90 residences in the region faced evacuation.

April 2011 Departure from Normal Temperature and Percent of Normal Precipitation for Western United States

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