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Flash Flood in Little Wildhorse

Discussion in 'Accidents and Near Misses' started by Ram, May 11, 2020.

  1. Ram

    Ram

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    Big Sigh!

    At least one person killed in flash flood near Goblin Valley State Park

    By Sahalie Donaldson May 11, 2020, 8:36pm MDT
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    A search is underway in Little Wildhorse Canyon in Emery County after flash flooding ripped through the area and killed at least one person on Monday, May 11, 2020.
    Emery County Sheriff’s Office
    EMERY, Emery County — A search is underway in slot canyons near Goblin Valley State Park after flash flooding killed at least one person Monday.

    The Emery County Sheriff’s Office said in a news release that at least 21 people made it out of Little Wildhorse Canyon, but vehicles parked at trailheads in the area led searchers to believe there are hikers in the area still unaccounted for. As of Monday at 8 p.m., officials reported one fatality.

    The search is being conducted by multiple agencies, including two helicopters from Classic Air in Moab and another from the Department of Public Safety, six ambulances, and search and rescue teams from four different counties, according to the Emery County Sheriff’s Office.

    The flash flooding in slot canyons was caused by an “isolated thunderstorm” that crossed the San Rafael Swell Monday afternoon.

    The National Weather Service in Salt Lake City tweeted that part of the storm, capable of “nickel-sized hail and strong winds,” crossed directly over Goblin Valley State Park.
  2. Scott Patterson

    Scott Patterson

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    I was hoping to do a technical canyon today. This weekend/Monday was the first time I did something outside with a non-household member in several months.

    Anyway, I checked the weather forecast both last night and this morning. It was bad. In the San Rafael Swell, there was a 30% chance of rain in the morning and a 60-80% chance of rain in the afternoon, depending on which forecast you looked at. I checked a lot of other places too. Because of the bad forecasts all over the region, we decided to do a non technical hike. Here is this morning's text conversation (mine are on the right):

    20200511_233557.

    We scrapped the plans of a slot canyon because of the forecast and just hiked a trail.

    As mentioned, the forecast for the Swell said 60-80% in the afternoon. I don't have a screen shot of that, but I do have one of the Moab forecast (no we didn't go to Moab, but I have a screenshot of the forecast):

    20200511_232840.

    So rain was forecast is a wide area of Eastern Utah, not just the Swell.

    Here is another conversation from last night with a coworker about the rain (I am the one on the right):

    20200511_191553.

    Anyway, my point is that the weather forecast was bad all over the region. I don't mean to criticize anyone, but why go into a slot canyon which such a bad weather forecast? It seems that it was a lot of people, not just one group (not to mention social distancing).

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    Last edited: May 12, 2020
  3. jsb4g

    jsb4g

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    This is really sad. The National Weather Service has a website specifically for flash flooding potential in Utah Canyons. Of course, you can also do a spot forecast on the NOAA/NWS website. I think the following had the Swell as probable flash flooding for yesterday a solid 24 hours in advance, but I did not get a screen shot.

    https://www.weather.gov/slc/flashflood
  4. Scott Patterson

    Scott Patterson

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  5. Kevin

    Kevin

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    Wow, that is just awful :(
  6. Dan Ransom

    Dan Ransom Staff Member

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  7. Kevin

    Kevin

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  8. Brian in SLC

    Brian in SLC Brian in SLC

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    https://wasatchweatherweenies.blogspot.com/

    I was up Little Wild Horse Canyon (where this occured) with @tayloragowan and a friend during this freak incident. We knew the chance of heavy rain producing thunderstorms was low, but when we heard thunder, we turned around and got out of the slots.

    From the NWS on 11 May:

    upload_2020-5-12_16-22-38.

    Forecast discussion from Sunday indicated a chance for microburst type activity. But, not a strong warning that I could find. Maybe someone knows how to mine the archived forecasts?

    Some discussion of the weather here:

    https://wasatchweatherweenies.blogspot.com

    Wrong place at the wrong time. Crazy.
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  9. Dan Ransom

    Dan Ransom Staff Member

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    From the NWS Forecast discussion on Monday morning - best I can find and only covers the entire zone, not specific to Emery County. But doesn't make it seem like there's much chance of a violent thunderstorm.


    Area Forecast Discussion
    Issued by NWS Salt Lake City, UT
    Area Forecast Discussion...UPDATED
    National Weather Service Salt Lake City UT
    640 AM MDT Mon May 11 2020

    .SYNOPSIS...A couple of weak weather systems will cross the
    forecast area today through Wednesday. Mild conditions will
    remain in place through Tuesday, before somewhat cooler weather
    with a chance of showers arrives midweek.

    .SHORT TERM (Through 12Z Thursday)...A weak upper level disturbance
    will push the mid-high level moisture over mainly eastern Utah by
    this afternoon for a chance of mainly high-based showers and
    thunderstorms. However, instability caused by heating of the
    mountains will allow for a slight chance of high-based showers and
    thunderstorms to remain over the central and northern mountains
    into this afternoon. Gusty winds in excess of 30 mph are possible
    with any of these storms.

    Another disturbance will brings its associated dry cold front
    into northwest Utah this evening and into central Utah by Tuesday
    afternoon. Warm and breezy conditions will prevail ahead of this
    front, while temperatures will fall by 6-10 degrees behind this
    front across the north.
  10. Scott Patterson

    Scott Patterson

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    Tayloragowen (who you mention above) pointed out to me that NOAA showed 20% chance of t-storms in the verbal synopsis from the area when he checked it. I saw 60% from the NOAA point forecast and 80% on another one.

    Why the difference? It is because I was checking San Rafael Knob and some were checking out Hanksville or Green River.

    I always check the headwaters forecast vs. the nearest town or area forecast. Places like San Rafael Knob get more than three times the average precip as Hanksville, Goblin Valley, or Green River.

    I tend to check the forecast in places like San Rafael Knob vs Hanksville for the Swell, Horse Pasture Plateau vs Springdale for Zion, or Elk Ridge vs Hite for White Canyon. Usually the upper parts of the drainage have a higher percent chance of rain. The upper elevations are more often than not where a bulk of the precip comes from and the forecast usually have a higher percentage of rain.

    I don't know where the rain fell this time though.
  11. Dan Ransom

    Dan Ransom Staff Member

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    I asked the NWS what the forecast was for yesterday at Goblin Valley:

    upload_2020-5-12_18-3-29.
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  12. Scott Patterson

    Scott Patterson

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  13. ratagonia

    ratagonia

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  14. Scott Patterson

    Scott Patterson

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    On another note, news articles indicate that the family was there over Mother's Day weekend. If this was the case, they might not have seen the updated weather forecast since they were already out camping. People who were out camping for a few days might not have seen the change in the forecast.
  15. Chris Benson

    Chris Benson

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    One tool we developed at our outdoor education program was a decision-support-tool to help people assess the weather and flash flood hazard.
    It gives phone numbers for people to get weather info and flash-flood-potential ratings using a satellite phone, or maybe information if they are in a place where they don't have LTE reception.

    Super sad, and I hope our community can work towards more outreach to the general public to prevent such incidents in the future.

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  16. Ram

    Ram

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  17. Brian in SLC

    Brian in SLC Brian in SLC

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    Flash flood forecast by NOAA on Monday morning (cut and paste from the wasatch weather weenie blog):

    upload_2020-5-14_8-21-42.
    Scott Patterson likes this.
  18. jsb4g

    jsb4g

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    From the NWS:

    "Possible - Some slot canyons, dry washes and small streams may experience flash flooding"

    https://www.weather.gov/slc/flashflood
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