{"id":12479,"date":"2020-07-25T10:14:42","date_gmt":"2020-07-25T16:14:42","guid":{"rendered":"https:\/\/www.coloradofloodthreat.com\/?p=12479"},"modified":"2020-07-26T08:21:58","modified_gmt":"2020-07-26T14:21:58","slug":"ftb-07-25-2020-high-flood-threat-for-the-san-juan-mountains","status":"publish","type":"post","link":"https:\/\/archive-coftb.dewberryanalytics.com\/?p=12479","title":{"rendered":"FTB 07-25-2020: High Flood Threat for the San Juan Mountains"},"content":{"rendered":"<p>Issue Date: Saturday, July 25th, 2020<br>\nIssue Time: 10:15AM MDT<\/p>\n<p><em>&mdash; A <strong>HIGH\/MODERATE<\/strong> flood threat has been issued for the San Juan Mountains. This includes the 416 &amp; Decker burn area. This threat continues overnight!<\/em><\/p>\n<p><em>&mdash; A <strong>LOW<\/strong> flood threat has been issued for the Southwest Slope, Central Mountains, southern Front Range, Southeast Mountains, southern Urban Corridor and far Northeast\/Southeast Plains. This includes the Lake Christine and Spring Creek burn areas.<\/em><\/p>\n<p>Western Colorado and the mountains are starting the day with heavy cloud cover. The moisture stream and embedded energy is continuing to stream in from the south, which is helping produce morning rainfall over portions of the Southwest Slope, Grand Valley, and Central Mountains. Western portions of the San Juan Mountains picked up another 0.50 to 1 inch yesterday (<span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;isolated&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;less than 10% areal coverage&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>isolated<\/span> totals closer to 1.5 inches), and gages in local streams and rivers are starting to rise. So, with steady rainfall continuing today and for the area, saturated soils will become a concern for increased runoff into local streams and mud\/debris flows.<\/p>\n<p>The evolution of the rainfall and storms will look similar to yesterday. Expect an uptick in rainfall coverage over the mountains by mid-day with the diurnal flow pattern. Extra mid-level energy is plenty (orange X&rsquo;s), so rainfall is expected be <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;widespread&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;greater than 60% areal coverage&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>widespread<\/span> in the moisture rich environment. Then, storms will start to spill into the adjacent plains by early afternoon as Hurricane Hanna and passing <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;trough&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;An elongated area of relatively low atmospheric pressure; the opposite of a ridge.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>trough<\/span> to the north helps displace the High slightly westward. Additional storms will likely fire over the eastern plains as a <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;shortwave&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;A disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>shortwave<\/span> moves through the flow with plenty of <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;outflow boundaries&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;A surface boundary formed by the horizontal spreading of thunderstorm-cooled air. Outflow boundaries may intersect with each other or with other features (fronts, dry line, low-level jet) and initiate new convection. Brief strong winds are possible with outflow boundaries, and they can also persist for more than 24 hours.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>outflow boundaries<\/span> in the area helping provide supplementary lift. A second wave of rainfall arrives for the overnight hours, and the axis of precipitation will shift eastward. This will put the northern Southeast Mountains and eastern San Juan Mountains under a flood threat overnight.<\/p>\n<p>As for moisture and instability, not much change in the former. Soundings and <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;dew points&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;The temperature to which a given air parcel must be cooled (at constant pressure and water vapor content) in order for saturation to occur.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>dew points<\/span> show elevated values, so this will keep rainfall efficiency higher. Instability will be limited over the mountains with the cloud cover, so stronger thunderstorms will again be most likely over the eastern plains. A Low flood threat has been issued for the eastern plains as <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;training&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;Continuous or repeated rainfall over the same region&nbsp;in a relatively short time span. Training thunderstorms can produce very high rainfall totals and cause flash flooding.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>training<\/span> storms have caused localized flood issues the last couple of days. There is still the chance for <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;isolated&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;less than 10% areal coverage&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>isolated<\/span>, weak thunderstorms over the mountains (slight breaks in the cloud cover), which would cause increased runoff with slightly higher rain rates. This is especially true if they track over an area with already saturated soils.<\/p>\n<p>The main threat from this system over the southern mountains is the multiple days of steady rainfall. This will likely lead to flooding of local streams\/creeks and mud flows\/debris slides as the soil becomes <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;unstable&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;&amp;lt;!-- wp:paragraph {&amp;quot;textColor&amp;quot;:&amp;quot;white&amp;quot;} --&amp;gt;\n&amp;lt;p class=&amp;quot;has-white-color has-text-color&amp;quot;&amp;gt;the atmosphere is considered unstable if it is conducive to air attempting to rise; the opposite of stable; an unstable atmosphere is necessary for thunderstorms&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>unstable<\/span> over the steeper terrains. A&nbsp;HIGH threat has been issued for the western San Juan Mountains for this reason, and highest rainfall totals are expected on the south facing slopes. This HIGH threat includes the 416 burn area. A Moderate threat has been issued for all of the San Juan Mountains and Decker burn area as the rainfall axis shifts to the east overnight.<\/p>\n<p><img loading=\"lazy\" class=\"size-full wp-image-12480 aligncenter\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/wv_20200725.png\" alt=\"\" width=\"657\" height=\"521\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/wv_20200725.png 657w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/wv_20200725-300x238.png 300w\" sizes=\"(max-width: 657px) 100vw, 657px\"\/><\/p>\n<h3><strong>Today&rsquo;s Flood Threat Map<\/strong><\/h3>\n<p>For more information on today&rsquo;s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/FTB_20200725_snap-1.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-12497\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/FTB_20200725_snap-1.png\" alt=\"\" width=\"896\" height=\"610\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/FTB_20200725_snap-1.png 896w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/FTB_20200725_snap-1-300x204.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2020\/07\/FTB_20200725_snap-1-768x523.png 768w\" sizes=\"(max-width: 896px) 100vw, 896px\"\/><\/a><\/p>\n<h3><strong>Zone-Specific Forecasts:<\/strong><\/h3>\n<h4><strong>San Juan Mountains<\/strong><strong>, <\/strong><strong>Southeast Mountains,<\/strong> <strong>Southwest Slope, &amp; San Luis Valley: <\/strong><\/h4>\n<p>Heavy rainfall will allow 48-hour totals to reach close to 3 inches over the western San Juan Mountains by morning. Small rock slides were already being reported yesterday, so the main threat over the next few days will be mud\/debris flows from the saturated soils. Also, expect more rapid rises in local creeks\/streams with the increased runoff. A HIGH flood threat has been issued for this region, which includes the 416 burn area.<\/p>\n<p>As the plume of moisture and instability shifts east overnight, morning totals up to 1.25 inches will be possible over the northern Southeast Mountains and eastern San Juan Mountains. This could cause <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;flash flooding&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;&amp;lt;!-- wp:paragraph {&amp;quot;textColor&amp;quot;:&amp;quot;white&amp;quot;} --&amp;gt;\n&amp;lt;p class=&amp;quot;has-white-color has-text-color&amp;quot;&amp;gt;flash flooding can refer to usually dry areas becoming rapidly inundated with water, or rapid water level rises on streams, creeks, or rivers beyond flood stage; typically caused by heavy rainfall, but can also be caused by meltwater&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>flash flooding<\/span> issues over the Decker burn area, a Low\/Moderate threat has been issued for this region. Looks like the San Luis Valley will also get some much needed rainfall, and <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;isolated&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;less than 10% areal coverage&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>isolated<\/span> totals up to 0.50 inches are possible.<\/p>\n<p>Primetime: 11AM to 8AM &ndash; This threat continues overnight!<\/p>\n<h4><strong>Northern Mountains, Central Mountains, southern Southeast Mountains, Front Range, Raton Ridge, Southeast Plains, Palmer Ridge, Northeast Plains, &amp; Urban Corridor:<\/strong><\/h4>\n<p>Perhaps some better instability can build over these regions, and 1-2 hour totals up to 1 inch will be possible. A Low flood threat has been issued, which includes the Spring Creek and Lake Christine burn areas. Rather than an individual thunderstorm causing <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;flash flooding&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;&amp;lt;!-- wp:paragraph {&amp;quot;textColor&amp;quot;:&amp;quot;white&amp;quot;} --&amp;gt;\n&amp;lt;p class=&amp;quot;has-white-color has-text-color&amp;quot;&amp;gt;flash flooding can refer to usually dry areas becoming rapidly inundated with water, or rapid water level rises on streams, creeks, or rivers beyond flood stage; typically caused by heavy rainfall, but can also be caused by meltwater&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>flash flooding<\/span>, higher 24-hour totals may cause soils over the burn areas to become <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;unstable&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;&amp;lt;!-- wp:paragraph {&amp;quot;textColor&amp;quot;:&amp;quot;white&amp;quot;} --&amp;gt;\n&amp;lt;p class=&amp;quot;has-white-color has-text-color&amp;quot;&amp;gt;the atmosphere is considered unstable if it is conducive to air attempting to rise; the opposite of stable; an unstable atmosphere is necessary for thunderstorms&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>unstable<\/span>.<\/p>\n<p>Over the eastern plains (Northeast Plains &amp; northern Southeast Plains), <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;training&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;Continuous or repeated rainfall over the same region&nbsp;in a relatively short time span. Training thunderstorms can produce very high rainfall totals and cause flash flooding.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>training<\/span> storms will be possible again. These very high totals can cause local <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;flash flooding&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;&amp;lt;!-- wp:paragraph {&amp;quot;textColor&amp;quot;:&amp;quot;white&amp;quot;} --&amp;gt;\n&amp;lt;p class=&amp;quot;has-white-color has-text-color&amp;quot;&amp;gt;flash flooding can refer to usually dry areas becoming rapidly inundated with water, or rapid water level rises on streams, creeks, or rivers beyond flood stage; typically caused by heavy rainfall, but can also be caused by meltwater&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>flash flooding<\/span> issues as storms often continuously fire along <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;outflow boundaries&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;A surface boundary formed by the horizontal spreading of thunderstorm-cooled air. Outflow boundaries may intersect with each other or with other features (fronts, dry line, low-level jet) and initiate new convection. Brief strong winds are possible with outflow boundaries, and they can also persist for more than 24 hours.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>outflow boundaries<\/span>. Thus, the threat includes the high moisture area all along the eastern border as it is difficult to predict the <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;outflow boundaries&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;A surface boundary formed by the horizontal spreading of thunderstorm-cooled air. Outflow boundaries may intersect with each other or with other features (fronts, dry line, low-level jet) and initiate new convection. Brief strong winds are possible with outflow boundaries, and they can also persist for more than 24 hours.&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>outflow boundaries<\/span>.<\/p>\n<p>Primetime: 11AM to 8AM<\/p>\n<h4><strong>Northwest Slope<\/strong><strong> &amp;<\/strong><strong> Grand Valley<\/strong><strong>:<\/strong><\/h4>\n<p>These are the two areas that won&rsquo;t see as much rainfall today, but light showers should be expected. Totals up to 0.50 inches will be possible along the higher terrains in both regions. So, over the Northwest Slope closer to mountains over the elevated plateaus. Flooding is not expected here.<\/p>\n<p>Primetime: 11AM to 11PM<\/p>","protected":false},"excerpt":{"rendered":"<p>Issue Date: Saturday, July 25th, 2020 Issue Time: 10:15AM MDT &mdash; A HIGH\/MODERATE flood threat has been issued for the San Juan Mountains. This includes the 416 &amp; Decker burn area. This threat continues overnight! &mdash; A LOW flood threat has been issued for the Southwest Slope, Central Mountains, southern Front Range, Southeast Mountains, southern [&hellip;]<\/p>","protected":false},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[6],"tags":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/12479"}],"collection":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12479"}],"version-history":[{"count":5,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/12479\/revisions"}],"predecessor-version":[{"id":12498,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/12479\/revisions\/12498"}],"wp:attachment":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12479"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12479"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12479"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}