Flash Flood Watch: Unstable air mass delivers many thunderstorms

Photo shows flooding by the wakeboard park in St. George, Utah, July 18, 2015 | Photo courtesy of Jennie Cooper, modified composite by St. George News

ST. GEORGE – The National Weather Service has issued a “Flash Flood Watch” for most of central and southern Utah in effect until 10 p.m. Friday.

Dots indicate areas subject to the flood warning; 4:45 a.m., Southern Utah, Aug. 7, 2015 | Photo courtesy of National Weather Service, St. George News | Click image to enlarge
Dots indicate areas subject to the flood warning; 4:45 a.m., Southern Utah, Aug. 7, 2015 | Photo courtesy of National Weather Service, St. George News | Click image to enlarge

Monsoon moisture will surge north across Utah today, setting the stage for thunderstorms capable of producing heavy rainfall.

The deep monsoon moisture combined with an unstable air mass and a weather disturbance moving through the Great Basin will lead to numerous showers and thunderstorms across Utah through the evening. Some of these storms will be capable of producing heavy rainfall, especially across central and southern Utah.

The flash flood threat will be greatest in slot canyons, normally dry washes, burn scars, urban areas with poor drainage and small streams in deep terrain.

Areas affected

Castle Country, San Rafael Swell, Sanpete/Sevier Valleys, Southwest Utah, Utah’s Dixie and Zion National Park, south-central Utah, Glen Canyon Recreation Area/Lake Powell, central and southern mountains including the cities of Price, Castledale, Emery, Green River, Hanksville, Manti, Richfield, Beaver, Cedar City, Milford, St. George, Kanab, Escalante, Bullfrog, Cove Fort, Koosharem, Fish Lake, Loa, Panguitch and Bryce Canyon.

Flash flood watch

A “Flash Flood Watch” means that conditions may develop that lead to flash flooding.  Flash flooding is a very dangerous situation.

Turn around. Don’t drown

Safety precautions

The National Oceanic and Atmospheric Association and the National Weather Service offer safety rules for flash flooding:

  • Flash flooding is a very dangerous situation
  • Flash flood waves, moving at incredible speeds, can roll boulders, tear out trees, destroy buildings and bridges and scour out new channels. Killing walls of water can reach heights of 10 to 20 feet. You will not always have warning that these deadly, sudden floods are coming. When a flash flood warning is issued for your area or the moment you first realize that a flash flood is imminent, act quickly to save yourself. You may have only seconds.
  • Most flood deaths occur in automobiles. Do not drive your vehicle into areas where the water covers the roadway. Flood waters are usually deeper than they appear. The road bed may not be intact under the water. Just one foot of flowing water is powerful enough to sweep vehicles off the road. If the vehicle stalls, abandon it immediately and seek higher ground. Rapidly rising water may engulf the vehicle and its occupants and sweep them away
  • Do not hike rivers and especially slot canyons while flash flood warnings are in place
  • Do not hike alone and always tell someone where you and your buddy and others are going
  • Get out of areas subject to flooding, including dips, low spots, canyons and washes
  • Avoid already flooded and high velocity flow areas. Do not try to cross a flowing stream on foot where water is above your knees
  • Be especially cautious at night when it is harder to recognize flood dangers
  • Do not camp or park your vehicle along streams and washes, particularly during threatening conditions

During any flood emergency, stay tuned to your NOAA weather radio, commercial radio or television, follow St. George News at STGnews.com and St. George News Facebook for weather alerts and updates relevant to Southern Utah. Information from the National Weather Service and disaster and emergency services may save your life.

Read more: Rescue commander tells how to survive a flash flood

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Copyright St. George News, SaintGeorgeUtah.com LLC, 2015, all rights reserved.

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