December 2018 Climate and Hydrology Summary

Tulsa: December 2018 was the 52nd warmest (41.3°F; since 1905), the 21st wettest (3.58"; since 1888), and the 28th least snowy (Trace, tied 26 other years; since 1900) December on record.

Fort Smith: December 2018 was the 34th warmest (44.6°F; since 1882) and the 15th wettest (5.51"; since 1882) December on record.

Fayetteville: December 2018 was the 28th warmest (39.7°F, tied 1954, 1951; since 1949), the 21st wettest (3.66"; since 1949), and the 15th least snowy (Trace, tied 20 other years; since 1949) December on record.

Fayetteville: Daily records set or tied this month include a record cold maximum temperature.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for December 2018 ranged from 1.50” to near 9” from north to south across eastern OK and northwest AR. This corresponds to 110% to around 200% of the normal December rainfall across the area, with only the far northeast corner of OK receiving 75%-100% of the normal rainfall this month.

All but far northeast OK received above normal rainfall this month, resulting in minor to moderate flooding along some mainstem rivers.

Minor to Moderate flooding occurred along the Poteau River, and Minor flooding occurred along the Neosho River near Commerce. Rises also occurred along the Illinois River, but the river remained below flood stage.

According to the Drought Monitor from January 1, 2019, Abnormally Dry (D0) but not in drought conditions encompassed portions of Pawnee, Osage, Washington, Rogers, Mayes, Nowata, Craig, Ottawa, Delaware, and Cherokee Counties in eastern Oklahoma and Benton, Washington, and Crawford Counties in northwest Arkansas.

According to the Oklahoma Climatological Survey, December 2018 was the 15th wettest for northeast Oklahoma, the 13th wettest for east central Oklahoma, and the 6th wettest for southeast Oklahoma. Records go back to 1921. For the Year 2018, northeast Oklahoma ranked as the 40th driest, east central Oklahoma was the 14th wettest, and southeast Oklahoma was the 10th wettest Year.

Showers impacted southeast OK and west central AR for much of the day on the 8th as an upper-level low moved across the area. The majority of the precipitation remained as a cold rain along and south of I-40, while areas of light snow and a light wintry mix occurred across the higher terrain areas in northwest AR. Rainfall and liquid equivalent rainfall totals ranged from 0.10” to 1”.

Scattered showers and isolated thunderstorms moved northeast out of TX across southeast OK into northwest AR after midnight on the 13th. This activity continued through the morning, becoming more widespread across eastern OK and northwest AR through the afternoon hours as an upper-level low moved from north TX toward the lower Mississippi River Valley and a cold front moved across the region. The widespread rain continued through the evening hours, before decreasing in coverage after midnight on the 14th. Wrap around showers and isolated thunderstorms continued through the morning and afternoon southeast of I-44 as the associated surface low passed south of the area. By 6 am on the 14th, rainfall totals ranged from 0.25” to 3” across eastern OK and northwest AR. An additional 0.10” to 1.5” fell during the remainder of the 14th, southeast of an Okemah to Bentonville line. This rainfall led to minor flooding along the Poteau River near Panama.

Scattered showers and thunderstorms began to affect eastern OK mid-day on the 26th within a region of warm air advection as forcing strengthened over the High Plains downstream of a strong upper-level wave. The rain expanded eastward, and by evening, had become widespread across all of eastern OK and northwest AR. The rain finally shifted east of the area by sunrise on the 27th. Rainfall totals ranged from around 0.50” to 4”. 2.5”-4” of rain fell over the Poteau River basin, which had received heavy rain a couple of weeks previously. Minor to Moderate flooding occurred along the Poteau River at Poteau and Panama, respectively, with this latest rainfall. Rises also occurred along the Illinois River, but flood stage was not reached.

During the late evening hours of the 30th, rain developed across eastern OK and northwest AR as an upper-level low lifted out of northern Mexico and to the northeast across the Southern Plains. This activity spread over the entire area during the overnight hours before shifting northeast by mid-morning of the 31st. Some additional wrap-around precipitation affected northeast OK before noon. Rainfall totals were around 0.50” to near 1.5”. This rainfall, combined with the higher amounts from the 26th, resulted in minor flooding along the Neosho River near Commerce.

Year 2018

Tulsa: 2018 was the 42nd warmest (61.2°F, tied 2010; since 1905), the 47th driest (34.08"; since 1888), and the 14th least snowy (1.7", tied 2012, 1991, 1974, 1936, 1904; since 1900) Year on record.

Fort Smith: 2018 was the 23rd warmest (62.8°F, tied 2007, 1927, 1925; since 1883), the 14th wettest (54.17"; since 1882), and the 4th least snowy (Trace, tied 2016, 2005, 2002, 1998, 1992, 1991, 1957; since 1884) Year on record.

Fayetteville: 2018 was the 23rd warmest (57.7°F, tied 2010, 2001, 1981, 1973, 1964, 1962, 1955; since 1950), the 31st wettest (46.63"; since 1950), and the 4th least snowy (0.3", tied 2016; since 1950) Year on record.

Rainfall totals for the year 2018 ranged from 25” to near 80” across eastern OK and northwest AR. Most of the area received 35”-60”. This corresponds to 110% to near 175% of the normal annual rainfall along and south of I-40, and 50% to 110% of the normal annual rainfall north of I-40.