This past month was the coolest April in 11 years for the lower 48 United States, and fell into the lowest twenty-five percent of all Aprils based on records going back to 1895, according to an analysis by NOAA’s National Climatic Data Center in Asheville, N.C
The average April temperature, 51 degrees F, during April was one degree below the 20th century mean, and was the 29th coolest, or 86th warmest, based on preliminary data.
The combined average global land and ocean surface temperatures for April ranked 13th warmest since worldwide records began in 1880.
Fifteen states, all in the Northeast, Great Lakes, and Mid-Atlantic regions, were warmer than average. New York ranked third warmest and Rhode Island, fourth warmest. Sixteen states, all west of the Mississippi, were cooler than average.
Washington state ranked second coolest and Oregon fifth coolest. The monthly temperature for Alaska was 1.2 degrees F below average, the 43rd coolest April on record.
The University of Washington’s Climate Impacts Group says April temperatures (through the 28th) were at least 2 degrees F cooler than the 1971-2000 mean throughout the Pacific Northwest, with cold departures in excess of 4 degrees F over Idaho, and eastern Oregon and Washington. This continued a pattern of colder than normal temperatures that was observed in March and, to a lesser extent, for the winter season as a whole.
April precipitation through April 28 was drier than the 1971-2000 mean throughout the PNW, with deficits exceeding 0.75 inches in magnitude in western Oregon and Washington. This pattern of dryness was also observed through the last 90 days, while for the water year (October through April 28), the precipitation pattern was more varied. The precipitation that did fall during the past winter produced an April 1st snowpack that was near or above normal for the Columbia Basin, and well above normal in the central Washington and Oregon Cascades. Consistent with this heavy snowpack, streamflows are forecast to be near or above normal for spring and summer.
The Climate Prediction Center's outlook for May-June-July temperature in western Washington is for April's cooler than normal temperatures to continue (greater than a 33 percent chance). For the remainder of the region, the CPC projects a greater than 33 percent chance of above normal May-June-July temperatures in southern and eastern Oregon and central Idaho, and a greater than 40 percent chance for the same in southeast Oregon and southern Idaho.
The precipitation forecast is for a continuation of April's dry conditions throughout the region (greater than a 33 percent throughout the PNW, exceeding a 40 percent chance for the same in eastern Oregon and southern Idaho).
The forecasts should be interpreted as the tilting of odds towards general categories of conditions, and should not be viewed as a guarantee that the specified conditions will be realized. The forecasts tend to have most skill in years of significant warm or cold ENSO conditions, like this one.
For more information about PNW climate forecasts go to http://www.cses.washington.edu/cig/fpt/cloutlook.shtml
NOAA’s Temperature Index highlights:
--- In April, precipitation was below normal across most of the West, compared to the 1971-2000 average. Areas in California and Nevada reported their driest March-April total precipitation. Mountain snowpack, however, remained healthy with most of the intermountain and Northwest regions reporting above normal snow packs by the end of the month.
--- An average of 2.4 inches fell across the contiguous U.S. in April, which is 0.04 inches below average.
--- Iowa, Missouri, Virginia, and Wisconsin were much wetter than average for April, with Iowa and Wisconsin ranking fourth wettest on record. Arizona, California, Nevada, and Utah were much drier than average, with Arizona having the third driest April on record and California ranking fifth driest.
--- Twenty-one tornadoes were reported on April 4 across Louisiana, Mississippi, Alabama, North and South Carolina. The next week, 62 tornadoes ravaged Texas and Oklahoma between April 9-11. In Richmond, Va., heavy rains from April 20-22 brought the city’s monthly total to 8.32 inches.
--- Last month, Babbit, Minn., recorded 26 inches of snow, while 32 inches fell near the town of Virginia, Minn. This was the largest ever April multi-day snowfall in the Iron Range of northern Minnesota. The combination of snow melt and heavy rain continued to flood rivers and streams throughout northern Illinois and southern Wisconsin. At the end of April, major flooding was occurring on the Mississippi River between Rock Island, Ill., and Burlington, Iowa. Heavy rains in the upper reaches of the lower Mississippi River spawned historic water levels downstream.
--- Bethel, Alaska, received 11.7 inches of snow during the month, bringing its seasonal total to 102.4 inches, nearly twice the average and only the second time in the last 30 years with over 100 inches of accumulated snowfall. By April 19, Nome accumulated 105.4 inches of snowfall, ranking as the second-snowiest winter on record behind 1994-95.
--- Rainfall across parts of the Southeast improved drought conditions, with about 43 percent of the region classified in moderate-to-extreme drought at the end of April compared to 59 percent a month ago.
--- April’s combined global land and ocean surface temperature was 0.74 degrees F above the 20th century mean of 56.7 degrees F.
--- Continued weakening of La Niña, the cold phase of the El Niño-Southern Oscillation, occurred during April. The global average ocean surface temperature in April was the ninth warmest on record, with a monthly anomaly of 0.59 degrees F above the 20th century mean.
--- Typhoon Neoguri brought torrential rains and flash flooding to Hainan, China, April 18. This was the season’s earliest and perhaps the strongest typhoon to strike China since 1949.
--- Snow cover extent over Eurasia during April 2008 was the lowest on record for April, following a record low March extent, and a marked contrast to the record January expanse. For the Northern Hemisphere, this month was the eighth least extensive April snow cover extent in the 42-year historical satellite record.