April 2013 Climate and Hydrology Summary

Tulsa: April 2013 was the 7th coldest (56.3°F; since 1905) and the 54th driest (3.35"; since 1888) April on record.

Fort Smith: April 2013 was the 54th coldest (60.9°F; since 1883) and the 64th driest (3.73"; since 1883) April on record.

Fayetteville: April 2013 was the 18th coldest (55.3°F; since 1950) and the 17th wettest (5.53", tied 1996; since 1950) April on record.

Fayetteville recorded its latest last occurrence of a hard freeze (28°F) on April 25, 2013 with a minimum temperature of 27°F. The previous record was April 20 (in 1953).

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for April 2013 ranged from 2” to near 10”, with the highest totals along an Oklahoma City to Wagoner to Bentonville line. Choctaw County, far east central Oklahoma and west central AR ended the month only receiving 50% - 90% of the normal April rainfall, while northwest of I-44, April was near normal. The remainder of eastern OK and northwest AR had above normal rainfall, receiving 110% to around 200% of normal.

April 2013 was a cold month across eastern OK and northwest AR, with much needed rainfall helping to eliminate drought over a large portion of the region.

After a wet ending to March 2013, the rainfall continued during the first few days of April. The heaviest rainfall occurred on April 2 and into the early morning hours of the 3rd, with much of Pittsburg, southern McIntosh, southern Haskell, Latimer, northern Pushmataha, and Le Flore Counties receiving 2” to 4” of rain. This is also the same region that had heavy rain over Easter weekend at the end of March, resulting in 5-day rainfall totals of 4” to 6”. This heavy rain resulted in minor river flooding along the Poteau River near Panama.

Another heavy rain event occurred April 17-18, resulting in a corridor of widespread 3”-5” of rain from Shawnee to Wagoner to Bentonville. A CoCoRaHS Observer measured 7.00” 4.1ESE of Wagoner. Several State Highways were impassible due to high water, as well as many smaller city, town, and county roads. Water rescues were reported in Rogers, AR and a truck was reported stranded near Mazie, OK. Minor river flooding occurred along Flint Creek near Kansas and along the Illinois River near Watts and Tahlequah. 9 tornadoes also occurred during this event, affecting Broken Arrow, Inola, Spavinaw, Salina, and Butler. More information about the tornadoes and this event is available.

According to the Drought Monitor from April 30, 2013, only a small portion of eastern OK remained in Moderate to Extreme drought. Several rainfall events this month helped to alleviate short term drought conditions across much of the HSA. Extreme drought (D3) conditions were still affecting portions of northeast Kay and Osage Counties in eastern OK. Severe (D2) drought was present across parts of Osage, Pawnee, Washington, and Nowata Counties in eastern OK. Moderate (D1) conditions existed over sections of western Craig, southeast Nowata, Rogers, Tulsa, Creek, and Choctaw Counties in eastern OK. Abnormally dry conditions continued in portions of Craig, Mayes, Rogers, Tulsa, Okmulgee, and Okfuskee Counties in eastern OK and Crawford, Madison, and Carroll Counties in northwest AR.

According to the Oklahoma Climatological Survey, April 2013 was the 30th wettest for northeast Oklahoma, the 25th wettest for east central Oklahoma, and the 37th wettest for southeast Oklahoma. Records go back to 1921.

According to the Oklahoma Climatological Survey, for the 365-day time period May 1, 2012 - April 30, 2013, northeast Oklahoma ranked as 5th driest, east central Oklahoma ranked as 6th driest, and southeast Oklahoma ranked as 4th driest. Records go back to 1921.

Outlook

The Climate Prediction Center CPC outlook for May 2013 (issued April 30, 2013) indicates a greatly enhanced chance for below normal temperatures across all of eastern OK and northwest AR. This outlook also indicates equal chances for above, near, and below median precipitation across all of northeast OK and northwest AR. This outlook is based primarily on short-range computer models, which suggest below-normal temperatures during at least the first ten days in May across much of the Plains.

For the 3-month period May-June-July 2013, CPC is forecasting an enhanced chance for above normal temperatures and an equal chance for above, near, and below median precipitation across all of eastern OK and northwest AR (outlook issued April 18, 2013). This outlook is primarily based on dynamic computer model output, with some input from statistical forecast tools and long-term trends.

According to CPC, ENSO neutral conditions remained through April. ENSO neutral conditions are expected to continue through Summer 2013, followed by uncertain conditions in the ENSO state from late Summer 2013 and beyond.