On a national scale, March ranked as the 39th warmest and 34th wettest March in the 1895-2011 record
NOAA National Climatic Data Center (NCDC)* –?? A westerly flow dominated the circulation with many weather systems and cold fronts moving in the flow. These systems produced 115 preliminary reports of tornadoes and over 1000 hail and high wind damage reports, mostly in the southeastern third of the nation.
Snow cover expanded and contracted during the month as winter storms moved across the country, with daily coverage ranging from 19 percent (on the 19th) to 44 percent (on the 8th).
Integrated over the month, March 2011 snow cover ranked as the 7th largest in the 45-year (1966-2011) satellite record for the contiguous U.S. and 6th largest for North America.
Drought coverage remained about the same as February
While drought conditions intensified in the southern Plains it improved in the Southeast and Mid-Atlantic. Moderate to exceptional drought coverage remained about the same as February covering approximately 24 percent of the country.
Cold fronts and low pressure systems moving in the storm track flow are influenced by the broad-scale atmospheric circulation. The large-scale atmospheric circulation indicators during March were generally weak.
These included a continually weakening La Ni??a, which is the phenomenon created by cooler-than-average sea surface temperatures in the eastern tropical Pacific Ocean.
The Pacific/North American (PNA) index was slightly positive during the month and the Arctic Oscillation (AO) index was slightly positive at the beginning of the month but became more positive by the end of March.
The North Atlantic Oscillation (NAO) index was positive during the first half of the month but turned negative during the last part.
Of these, the March temperature pattern (warmer than normal in the southern states, cooler than normal in the north central and west coast areas) is most consistent with a La Ni??a and positive NAO.
The dryness in the Southern Plains is consistent with La Ni??a, even though it continued to weaken this month.
Climate Highlights – March
- The average temperature in March was 44.0 ??F (6.7 ??C), which is 1.4 ??F (0.8 ??C) above the long-term (1901-2000) average. March precipitation, while extreme in the Southern Plains and Southern Rockies, was overall 0.22 inch (6 mm) above the long-term average.
- For the nation, the year-to-date temperature was near-normal, while average precipitation was below-normal.
- Above-normal warmth dominated much of the southern U.S. and Rocky Mountains during March.
- The largest temperature departures were in western Texas and New Mexico, which had its fifth-warmest March on record. Midland, Texas had four consecutive days???March 16 through 19???of temperatures that tied existing records.
- Cooler-than-normal temperatures were present in the northern and western areas of the country.
- Conditions were especially cool from southwestern Minnesota across the Dakotas into eastern Montana. Within this belt, March temperatures were as much as six degrees below the 20th century average.
- Precipitation varied across the country as the west and east coasts received above normal precipitation, while the central and southern United States was largely dry.
- Texas had its driest March on record, with a statewide average of 0.27 inch (7 mm). This was 1.47 inches (37 mm) below its 20th Century average, and broke the previous record of 0.28 inch (7 mm) set in 1971.
- It was the third driest March in New Mexico and tenth driest in Oklahoma.
- Record warm maximum temperatures at individual stations across the U.S. exceeded record cold minimum temperatures by a ratio of about 5-to-1 during March.
- On the Pacific coast, Washington, Oregon and California had their second, fifth, and ninth wettest March on record, respectively. Regionally, it was the second wettest March on record for the Northwest.
- In the Northeast, Pennsylvania had its third wettest such period.
- Drought conditions continued to intensify across much of the nation during March.
- According to the U.S. Drought Monitor, the overall footprint of drought did not increase, holding fairly steady at about 24 percent of the country. However, the area covered by the “Severe” and “Intense” drought categories almost doubled, from about 12 percent early in the month to more than 20 percent at month’s end.
- Dry conditions across the Southern Plains contributed to above average wildfire activity during March.
- Across the U.S., approximately 385,000 acres burned, marking the second most active March on record in terms of wildfires, behind March 2006.
- Tornado activity during March was above average, with 115 preliminary tornado reports. Most of the tornado activity was confined to the Southeast and Gulf Coast, which is typical of early spring.
- An active storm pattern across the western and northern tiers of the country was associated with several significant snowstorms impacting those regions during March.
- The monthly snow cover extent for March ranked as the seventh largest in the 45-year period of record.
- Climate Highlights – First quarter of 2011 and Rolling Six- and Twelve-month Periods
- It was the tenth driest first quarter for both the South and Southwest climate regions. New Mexico, Oklahoma, and Texas experienced their second, fifth and ninth driest January-March period, respectively.
- Both the rolling six-month and twelve-month periods show that the northern United States has been generally wet, while the South has been dry.
- On the six-month timescale, October 2010 through March 2011, above-average precipitation occurred across much of the West, the Northern Plains and the Northeast.
- Nevada and Vermont each had its third-wettest such period.
- Other states with top-ten precipitation during the period were Pennsylvania (fifth wettest), New York (eighth), and Utah (ninth).
- The Southern Plains, Midwest and Southeast were generally dry during the period, with more unusual dryness focused in the south central United States.
- It was the fourth driest such period for Texas, sixth driest for Oklahoma, seventh for Arkansas and Louisiana, and the eighth driest for New Mexico.
- Over the past twelve months, April 2010-March 2011, a belt of abnormal wetness stretched from the western Great Lakes to the Pacific Northwest. Wisconsin had its wettest such period; its precipitation average of 41.52 inches (1055 mm) was more than 10 inches (254 mm) above the 20th century average.
- Additionally, Iowa, Minnesota and North Dakota experienced their second wettest such period.
- Precipitation was below normal in the South during this period. It was the fourth driest such period in Louisiana, fifth driest in Arkansas, ninth driest in Florida, and tenth driest in Mississippi.
* This article is an extracted and edited partial version of the complete NCDC online report for March.
See NCDC’s Monthly Records web-page: http://www.ncdc.noaa.gov/extremes/records.php for more details about March 2011 weather and climate records in the USA for March and earlier.
For additional national, regional, and statewide data and graphics from 1895-present, for any period, please visit the Climate at a Glance page.
PLEASE NOTE: All of the temperature and precipitation ranks and values are based on preliminary data. The ranks will change when the final data are processed, but will not be replaced on these pages.
Graphics based on final data are provided on the NCDC Temperature and Precipitation Maps page and the Climate at a Glance page as they become available.
NOAA National Climatic Data Center, State of the Climate: National Overview for March 2011, published online April 2011, retrieved on April 22, 2011 from www.ncdc.noaa.gov/sotc/national/.