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May 2017 & Spring 2017
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- Tulsa: No daily records were set or tied this month.
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- Fort Smith: No daily records were set or tied this month.
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- Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for May 2017 ranged from around 0.50” to 2” for much of Choctaw and Pushmataha Counties, and 3”-15” elsewhere across eastern OK and northwest AR. The highest totals were from Okfuskee County northeast to Ottawa County. This corresponds to 10% to near 200% of the normal May rainfall across the region.
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- A significant rainfall event at the end of April 2017 resulted in widespread river flooding, which continued into May. Widespread heavy rain and flooding continued through May 2017, with several storm systems affecting eastern OK and northwest AR this month. 19 rivers exceeded flood stage this month, some of them flooded several times in May.
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- During the late evening of the 2nd, showers and thunderstorms developed over northeast OK in an area of low-level warm air advection and frontogenesis. Storm coverage increased through the overnight hours, with storms training over the same area of northeast OK, along and north of Highway 412. This area received 0.50” to around 3” of rain by sunrise on the 3rd. This additional heavy rain resulted in minor river flooding along portions of the Caney River, Bird Creek, Spring River, and Deep Fork River. The Neosho River near Commerce was still experiencing minor flooding from the end of April, and this early May rainfall resulted in the river levels remaining high for a longer period of time. This rain also caused an increase in the flow along the Arkansas River near Muskogee, with minor flooding occurring there as well. Flooded roads were also reported in Dewey (Washington Co. OK). As the northern storms were dissipated shortly after sunrise, new convection was developing further south along the low-level cold frontogenetic zone across east central and southeast OK and west central AR. These storms quickly shifted east of the area by early afternoon. Mid/upper-level cyclogenesis occurred over the Ozarks during the evening as potential vorticity was advected poleward on the nose of a strong upper jet. Wrap-around showers brought some additional light rain to the Ozarks during the evening and overnight hours. Rainfall totals ranged from around 0.25” to 1” along and southeast of a McAlester, OK to Springdale, AR line.
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- Isolated thunderstorms moved across northeast OK and far northwest AR during the mid-morning hours of the 11th. By noon, showers and thunderstorms began to develop and increase in coverage across southeast OK and west central AR, and continued to spread northward during the afternoon. At mid-evening, a line of storms developed over northeast OK along an advancing cold front and moved southeast into east central and southeast OK and northwest and west central AR. After the line of storms had exited the region, wrap around showers and thunderstorms moved into northeast OK during the early morning hours of the 12th, and translated east into northwest AR after sunrise. The rain finally came to an end by early afternoon. Most of eastern OK and northwest AR received 0.25” to 1” of rain, though several areas received 1.5”-4” of rain. Once again, river flooding ensued after this rainfall. Moderate flooding occurred along portions of Bird Creek, the Caney River, and the Neosho River, with minor flooding along the Arkansas River near Muskogee. Three tornadoes occurred during the afternoon and evening hours of the 11th, an EF-1 in Owasso, an EF-1 near Oologah Lake, and an EF-0 near Ramona. The severe thunderstorms also produced hail, with several reports of golf ball sized hail. More information about this event can be found at http://arcg.is/2sttYk1
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- A line of severe thunderstorms developed over western OK and moved through eastern OK and northwest AR during the evening hours of the 18th and the early morning hours of the 19th. Strong instability and very strong low-level wind shear was present across the area as the storms moved through the region, supporting the development of persistent and strong low-level circulations along the leading edge of the line of thunderstorms. These circulations resulted in the development of at least 16 tornadoes. More information can be found at http://arcg.is/2stiwop. A second round of thunderstorms developed under the influence of a strong low-level jet and moved through northeast OK and far northwest AR during the pre-dawn hours of the 19th. Rainfall totals ranged from 0.25” to 4”. The heaviest rainfall occurred in two bands, one from Okfuskee County to Ottawa County and the other across Pittsburg County to Le Flore County. By mid-morning, a third round of convection moved northeast out of south central OK and through northeast and east central OK. These storms continued into far northwest AR during the afternoon. Meanwhile, more convection developed along a boundary just south of I-44 from Okfuskee County to Delaware County. Storms trained along this area while also expanding northwest for several hours. By mid- to late-evening, this line of thunderstorms began to push eastward, developing into an MCS and forming a line echo wave pattern (LEWP) along the leading edge. Strong to severe wind gusts were reported within the bowing segments of the LEWP. Rainfall rates of 3”/hour were also observed. Behind the leading edge of the storms, widespread showers and thunderstorms continued as well. It took until after sunrise on the 20th for this MCS to move east out of the area. Most of eastern OK and northwest AR received 0.50” to 3” of rain, but locations along and southeast of I-44 and north of a northern Latimer to southern Le Flore County line received 2”-6” of rain. This resulted in widespread flash flooding due to the antecedent saturated soil moisture conditions from the heavy rains just prior to this event. Pittsburg County Emergency Management reported significant flood damage with many county roads washed out or closed. A train derailed due to a washed-out rail bridge, and one home had flood damage. Numerous other county roads and state highways were also closed or damaged throughout the heavy rain area. In addition to the flash flooding, minor to moderate river flooding occurred along the lower Arkansas River, Lee Creek, Polecat Creek, the Neosho River, the Illinois River, the Poteau River, and the Deep Fork River.
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- On the 27th, extreme instability was in place over eastern OK and northwest AR. Supercells initially developed along a boundary across northeast OK into far northwest AR during the late afternoon hours. Then during the evening hours, additional supercells developed near the dry line over south central Oklahoma. The storms then moved east, affecting eastern OK and western AR. Very large hail, winds of 60-80 mph, and tornadoes all occurred. A supercell produced two tornadoes in Okfuskee County, OK during the evening. These storms eventually transitioned into a line of storms. A bowing line segment developed a strong cyclonic circulation just north of its apex as it moved into eastern Sequoyah County, OK and produced an EF-1 tornado. Additionally, some of these storms produced very large and damaging hail, including several reports of hail stones of 2.5" in diameter (tennis ball size). One report included a hail stone that measured about 4.5" across (grapefruit-softball size) about 2 miles south southeast of Welty, OK! More information on this event can be found at http://arcg.is/2oNlC7g. These storms continued to move southeast through the early morning hours of the 28th, finally dissipating/exiting the area around sunrise. The highest rainfall totals of 0.50” to around 3” occurred across Okfuskee County, far northeast OK, northwest AR, and southeast OK. County roads were washed out in Okfuskee County.
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- According to the Drought Monitor from May 30, 2017, drought conditions were no longer occurring in eastern OK and northwest AR. D0 (abnormally dry conditions but not in drought) were present across portions of Pushmataha and Choctaw Counties in eastern OK.
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- According to the Oklahoma Climatological Survey, the last 30 days ending on May 31, 2017 was the 19th wettest for northeast Oklahoma, the 32nd wettest for east central Oklahoma, and the 26th driest for southeast Oklahoma. Records go back to 1921. For the Year-to-Date period Jan. 1-May 31, 2017, northeast Oklahoma ranked as the 4th wettest, east central Oklahoma was the 11th wettest, and southeast Oklahoma was the 42nd driest period. For the last 365 days (June 1, 2016-May 31, 2017), northeast Oklahoma was the 26th wettest, east central Oklahoma was the 39th driest, and southeast Oklahoma was the 12th driest.
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| Spring (March-April-May) 2017 |
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