Wednesday, May 20, 2015

Flash Flood Danger Continues into Memorial Day Weekend As Rainfall Nears May Records

Chris Dolce
Published: May 20,2015





 
For most of this month, the weather pattern has been in a configuration that has allowed repetitive bouts of thunderstorms to move through the Plains states. As a result, rainfall totals for the month of May are nearing historic levels, approaching 20 inches in parts of Texas and Oklahoma. Those totals are bound to climb still higher in the coming days with more showers and thunderstorms in the forecast.
(MORE: Latest Updates on Flash Flooding and Severe Weather)

Radar and Flood Alerts














Many cities have already clinched a top five wettest May in their weather records. At least one location, Fort Smith, Arkansas, has now recorded its wettest May on record.
Thunderstorms have repeatedly developed over this region for more than two weeks. In fact, every day since May 5 – that's 16 straight days as of this writing – has brought at least 4 inches of rainfall to at least one location in the state of Texas, according to CoCoRaHS, the Community Collaborative Rain, Hail and Snow Network. At least 68 of the network's 1,690 volunteer observation sites in Texas have recorded at least 10 inches of rain this month. The wettest of all has been Archer City, about 120 miles northwest of Dallas, with total of 19.31 inches through the morning of May 20.
Oklahoma has also taken a drenching this month, with month-to-date totals topping 10 inches across much of the southern half of the state. One CoCoRaHS site on the northeast side of Norman has reported 19.84 inches of rain since May 1, including three different days with 24-hour rainfall totals topping 3 inches.
The repetitive and slow-moving thunderstorms have led to numerous instances of flooding in the last couple of weeks.
Early Wednesday morning, the Choctaw Nation hospital and a nursing home were among buildings flooded in Talihina, Oklahoma. Homes were also flooded in Bridgeport, Texas. Tuesday afternoon, water rescues were performed in the city of Norman, Oklahoma.
(FLOOD RECAPS: San Angelo, Texas | Nebraska | North Texas | Houston Area | Oklahoma City | Manhattan, Kansas)
With the weather pattern remaining virtually the same through Memorial Day weekend, additional flooding is likely to occur.

Forecast: More Dangerous Flooding Through the Weekend


Forecast Rainfall














As mentioned already, a persistent weather pattern has been fueling the heavy rain in the Plains.
In short, a southward dip in the jet stream has been locked in place over the western states, allowing it to launch disturbances into the Plains. Those disturbances provide the necessary lift in the atmosphere to trigger thunderstorm development as they intercept a warm, moist air mass in place near the surface of the earth.
Unfortunately, it appears this weather pattern will stay in place through Memorial Day weekend, triggering additional rounds of rain and thunderstorms.
Somewhat cooler, drier air will give a brief break from the heaviest rain to waterlogged north Texas, Oklahoma and the panhandles through at least Thursday morning.
Beyond that, additional rounds of locally heavy rain will move through portions of these states beginning Thursday night into Friday, then again during the holiday weekend.
(MORE: Daily Rain Forecast)
Though it's difficult to pinpoint the exact areas of the heaviest rain and thunderstorms late this week and into next Monday, it's safe to say that additional, serious flash flooding is likely to occur. Severe storms are also possible at times in the Southern Plains. To see where the severe thunderstorm threat is each day, click the link below.
(MORE: Severe Weather Forecast)
Our forecast rainfall map shows a swath of heavy rainfall is expected, at times, through the Memorial Day weekend in west, central and north Texas and Oklahoma.
Keep in mind that slow-moving thunderstorms can produce heavier rainfall totals in localized areas in a short period of time. Also, the exact areas where the heaviest rainfall amounts (i.e. 3-5 inches) occur may differ from what is shown on our forecast map given that small-scale details are hard to predict several days in advance.
That said, the threat of additional significant flash flooding is high in Oklahoma and Texas through the holiday weekend.
(INTERACTIVE MAP: Latest Flood Alerts)
As always, stay informed about the latest flood watches and warnings for your area. If you are in a vehicle and encounter a flooded roadway, DO NOT attempt to drive through the water. From 1995-2010, 64 percent of flood-related deaths occurred in vehicles. As the National Weather Service stresses, turn around, don't drown.
(MORE: Your Vehicle is a Danger in Flooding)

May Rainfall Nearing a Record


Estimated Rainfall in May 2015














From Nebraska to Oklahoma, Texas and Arkansas, several cities have already seen one of their wettest Mays on record. Here's a look at where things stand right now:
Fort Smith, Arkansas – This western Arkansas city has now recorded its wettest May in history with 13.84 inches of rain through 7 a.m. CDT on Wednesday. The old record was 13.67 inches from May 1943.
Oklahoma City – With 13.88 inches of rain through May 19, Oklahoma City is less than an inch away from not only seeing its wettest May on record, but also its wettest month. The current wettest May was just two years ago in 2013 when 14.52 inches was recorded. June 1989 holds the title as the wettest month overall with 14.66 inches of rain.
Lubbock, Texas – 7.40 inches of rain has fallen through May 19, ranking as the third wettest May on record. Less than an inch of additional rain will vault Lubbock to its second wettest May. The total would have to rise to 12.69 inches to claim the title for the wettest May. According to the National Weather Service, the last time it rained 7.20 inches or more in a month in Lubbock was September 2008.
Wichita Falls, Texas – 12.43 inches of rain has fallen through May 19, and 12.50 inches of rain as of 7 a.m. CDT May 20. Either way, it's the third-wettest May and third-wettest month on record. Less than an inch of additional rain would make this the wettest month in city history; the top two months are May 1982 (13.22 inches) and May 1901 (12.79 inches).
Corpus Christi, Texas – Rainfall in May 2015 is at 8.12 inches through May 19. This total needs to climb to 10.44 inches to tie the May record set in 1941.
Amarillo, Texas – 6.17 inches of rain has fallen through May 19, tying as the eighth wettest May on record. The all-time record is 9.81 inches in May 1951.
Lincoln, Nebraska – 10.38 inches of rain has fallen through May 19, ranking as the second wettest May in the Nebraska capital. Just over a third of an inch of rain will surpass the current wettest May record of 10.72 inches set in 1903.
Colorado Springs, Colorado – 6.00 inches of rain through May 19 ranks as the second wettest May on record. The wettest May was in 1935 when 8.10 inches was recorded.
Pueblo, Colorado – A total of 4.55 inches of rain has fallen through May 19, making it the second wettest May on record. The wettest May was in 1957 when 5.43 inches was measured.
Senior meteorologist Nick Wiltgen contributed to this report.

PHOTOS: Severe Weather Strikes the Plains May 8-11, 2015

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