{"id":15324,"date":"2021-08-02T15:06:57","date_gmt":"2021-08-02T21:06:57","guid":{"rendered":"https:\/\/www.coloradofloodthreat.com\/?p=15324"},"modified":"2021-08-05T09:30:44","modified_gmt":"2021-08-05T15:30:44","slug":"fto-08-02-2021-a-busy-48-hours-then-significant-drying-before-next-monsoonal-surge","status":"publish","type":"post","link":"https:\/\/archive-coftb.dewberryanalytics.com\/?p=15324","title":{"rendered":"FTO 08-02-2021: A Busy 48 Hours, Then Significant Drying Before Next Monsoonal Surge"},"content":{"rendered":"<p>Issue Date: Monday, August 2nd, 2021<br>\nIssue Time: 3:05PM MDT<br>\nValid Dates: 8\/3-8\/17<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline.png\"><img loading=\"lazy\" class=\"wp-image-15329 aligncenter\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline-1024x147.png\" alt=\"\" width=\"882\" height=\"127\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline-1024x147.png 1024w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline-300x43.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline-768x110.png 768w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/threat_timeline.png 1189w\" sizes=\"(max-width: 882px) 100vw, 882px\"\/><\/a><\/p>\n<p>It is obvious to most folks over the Western Slope that the 2021 <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;monsoon&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;a seasonal wind that brings moisture and rain to the region into which it blows; there is also a dry phase to monsoons, but popular usage refers only to the wet phase; these winds occur in many places around the world, and where they occur they are responsible for a majority of that location&rsquo;s annual precipitation&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>monsoon<\/span> season has been very impressive thus far. Total precipitation over the past month or so has been running up to three times above normal 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> locations. However, perhaps even more impressive is the persistent nature, and hydrologic response of all the rainfall. As shown below, the Colorado River flow at Cisco, Utah, which is after the confluence of the Dolores River, captures the essence of most of the Western Slope&rsquo;s monsoonal runoff&nbsp;(though it does miss the San Juan River that flows into NM). Impressively, the flow here has been generally rising for the past 30+ days, which is extremely unusual given the Colorado River&rsquo;s snowpack-dominated hydrology. In fact, the current flow is actually the highest on the river since June 17th, a time of year that typically sees a median flow of nearly 20,000 cfs versus the ~4,000 cfs in early August. This has only happened once since reliable records began in 1913. Interestingly, that year was 2012, another year with a very low snowpack.<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/cisco_flow.png\"><img loading=\"lazy\" class=\"wp-image-15327 aligncenter\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/cisco_flow.png\" alt=\"\" width=\"565\" height=\"419\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/cisco_flow.png 580w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/cisco_flow-300x222.png 300w\" sizes=\"(max-width: 565px) 100vw, 565px\"\/><\/a><\/p>\n<p>Switching gears to the current Outlook, the visible satellite image below shows that the monsoonal ridge remains over the Four Corners, for now. Although significant changes are in store, the next 48 hours will continue to see heavy rainfall over the high terrain, warranting a High\/Elevated threat for Event #1. A plume of very high moisture is in place over Colorado and will continue to produce persistent moderate to heavy rainfall along the <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;Continental Divide&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 dividing line that separates the watersheds of the western and eastern United States; rivers west of the divide empty into the Pacific Ocean, while rivers east of the divide empty into the Atlantic Ocean or Gulf of Mexico&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>Continental Divide<\/span> higher terrain. Precipitation will have a hard time spilling east of the higher terrain, however, so the eastern plains will unfortunately miss out on this monsoonal moisture surge.<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/wv_markup.png\"><img loading=\"lazy\" class=\"wp-image-15330 aligncenter\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/wv_markup.png\" alt=\"\" width=\"717\" height=\"488\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/wv_markup.png 810w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/wv_markup-300x204.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/wv_markup-768x522.png 768w\" sizes=\"(max-width: 717px) 100vw, 717px\"\/><\/a><\/p>\n<p>As shown in the forecasted <span class=\"glossaryLink\"  aria-describedby=\"tt\"  data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;PW&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;(Stands for: Precipitable Water) The total atmospheric water vapor contained in a vertical column of the atmosphere. It is typically measured in inches, and anomalously (deviation from normal) high values of precipitable water generally correlate to heavy rainfall potential.&lt;\/div&gt;\"  data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>PW<\/span> plumes, below, a steep drop in moisture is expected as dry air infiltrates from the west. Thereafter, the upper-level ridge moves east while simultaneously elongating westward. This is not a favorable position for precipitation in Colorado, although residual moisture could be underestimated leading to at least <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> showers and storms later this week. By this weekend, however, an incoming <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> is expected to interact with sufficient monsoonal moisture, aided by 3 tropical cyclones in the eastern Pacific to produce an increase in shower and storm coverage across Colorado. At this time, this event, Event #2, looks to carry a low-end Elevated threat.<br><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw.png\"><img loading=\"lazy\" class=\"wp-image-15328 aligncenter\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw-1024x360.png\" alt=\"\" width=\"890\" height=\"313\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw-1024x360.png 1024w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw-300x105.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw-768x270.png 768w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/gefs_pw.png 1209w\" sizes=\"(max-width: 890px) 100vw, 890px\"\/><\/a><\/p>\n<p>Each of the two identified precipitation events are described below.<\/p>\n<h3><strong>Event #1: Tuesday &ndash; Wednesday (August 3 &ndash; August 4)<\/strong><\/h3>\n<h4><strong><span style=\"color: #ff0000;\">High Threat<\/span> On Tuesday, Then <span style=\"color: #ff6600;\">Elevated Threat<\/span> By Wednesday<\/strong><\/h4>\n<p><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> moderate to heavy rainfall is expected over the higher terrain once again on Tuesday, shifting slightly east compared to Monday&rsquo;s placement. We are expecting <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> amounts over 1 inch above 8,000 feet. Hourly rainfall intensity will not be particularly impressive, perhaps 1.0 inch\/hour, but 3-6 hour totals approaching 2 inches warrant a High threat especially due to the existing saturated soils. By Wednesday, the moisture plume shifts southeast and the Southeast Mountains and Raton Ridge will likely see the bullseye of heavy precipitation. Up to 2 inches of rainfall is expected once again, though storm coverage will likely be slightly lower, hence the expected Elevated threat.<br><img loading=\"lazy\" class=\"aligncenter wp-image-15384\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e1_snap.png\" alt=\"\" width=\"880\" height=\"591\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e1_snap.png 1786w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e1_snap-300x202.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e1_snap-768x516.png 768w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e1_snap-1024x688.png 1024w\" sizes=\"(max-width: 880px) 100vw, 880px\"\/><\/p>\n<h3><strong>Event #2: Sunday &ndash; Wednesday (August 8 &ndash; August 11)<\/strong><\/h3>\n<h4><strong>Low-end <span style=\"color: #ff6600;\">Elevated Threat<\/span> Expected in Climatologically Favored Regions<\/strong><\/h4>\n<p>After a lull of several days, <span class=\"glossaryLink\"  aria-describedby=\"tt\"  data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;PW&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;(Stands for: Precipitable Water) The total atmospheric water vapor contained in a vertical column of the atmosphere. It is typically measured in inches, and anomalously (deviation from normal) high values of precipitable water generally correlate to heavy rainfall potential.&lt;\/div&gt;\"  data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>PW<\/span> is expected to once again exceed 1 inch over southern and central Colorado, leading to an uptick in storm coverage and rainfall intensity by this weekend. Daily rounds of showers and storms are expected in the San Juans, Central Mountains, Southeast Mountains and possibly Front Range. Up to 1.0 inch per hour in rainfall intensity appears possible, which would be enough in sustaining the threat of debris slides and mud flows over the higher terrain. The degree to which storms are able to persist east of the foothills is uncertain, but the best chance for this would be east of the Palmer Ridge, in consistency with climatology.<\/p>\n<p><img loading=\"lazy\" class=\"aligncenter wp-image-15386\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e2_snap.png\" alt=\"\" width=\"880\" height=\"593\" srcset=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e2_snap.png 1786w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e2_snap-300x202.png 300w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e2_snap-768x518.png 768w, https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/08\/FTO_20210802_e2_snap-1024x690.png 1024w\" sizes=\"(max-width: 880px) 100vw, 880px\"\/><\/p>","protected":false},"excerpt":{"rendered":"<p>Issue Date: Monday, August 2nd, 2021 Issue Time: 3:05PM MDT Valid Dates: 8\/3-8\/17 It is obvious to most folks over the Western Slope that the 2021 <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;monsoon&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;a seasonal wind that brings moisture and rain to the region into which it blows; there is also a dry phase to monsoons, but popular usage refers only to the wet phase; these winds occur in many places around the world, and where they occur they are responsible for a majority of that location&rsquo;s annual precipitation&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>monsoon<\/span> season has been very impressive thus far. Total precipitation over the past month or so has been running up to three times above normal 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> locations. However, [&hellip;]<\/p>","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/15324"}],"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\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15324"}],"version-history":[{"count":13,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/15324\/revisions"}],"predecessor-version":[{"id":15387,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/15324\/revisions\/15387"}],"wp:attachment":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15324"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15324"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15324"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}