{"id":10294,"date":"2019-08-12T13:36:19","date_gmt":"2019-08-12T19:36:19","guid":{"rendered":"https:\/\/www.coloradofloodthreat.com\/?p=10294"},"modified":"2019-08-19T14:12:23","modified_gmt":"2019-08-19T20:12:23","slug":"fto-08-12-2019-dry-air-and-northwest-flow-is-forecast-to-bring-a-pause-in-heavy-rainfall-events","status":"publish","type":"post","link":"https:\/\/archive-coftb.dewberryanalytics.com\/?p=10294","title":{"rendered":"FTO 08-12-2019: Dry Air and Northwest Flow is Forecast to Bring a Pause in Heavy Rainfall Events"},"content":{"rendered":"<p>Issue Date: Monday, August 12th, 2019<br>\nIssue Time: 1:45PM MDT<br>\nValid Dates:&nbsp;8\/13 &ndash; 8\/27<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/FTO_20190812-1.png\"><img loading=\"lazy\" class=\"alignnone wp-image-10299\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/FTO_20190812-1.png\" alt=\"\" width=\"880\" height=\"137\"\/><\/a><\/p>\n<p>Event #1 from the last FTO is the low pressure system that is now over Montana. This <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> and the dry air associated with, has caused moisture to drop off across the western US (yellow and oranges in the water vapor imagery below). This dry air will continue to work its way into Colorado from west to east with westerly flow aloft. The <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;zonal&lt;\/div&gt;&lt;div class=glossaryItemBody&gt;refers to the east-west direction; usually used to describe atmospheric flow that roughly follows lines of latitude&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>zonal<\/span> atmospheric pattern the next couple of days is expected to keep quieter weather over the state and limit the amount of precipitation in the forecast. A weak cold front will continue to push through the eastern plains today, which will keep temperatures a bit cooler, too. Not expecting much rainfall with this frontal passage due to capping at 500mb (temperature <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;inversion&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;when temperature increases with height in the atmosphere; the presence of an inversion means the atmosphere is stable&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>inversion<\/span> preventing air parcels from lifting), but a few storms over the Southeast Plains may be possible near the NM border. Flow shifts to the northwest Tuesday night into Wednesday as the subtropical high rebuilds over the four corners region. This is pattern will also cause the low to retrograde back to the east (marked below).<\/p>\n<p>By Friday, a weak troughing pattern looks to set up over the west coast. As this moves to the northwest sometime between Friday into Sunday (timing still unknown), the 500mb high will push east as well (NM\/TX\/OK panhandle area). This would likely return subtropical moisture to the state, and mid-level energy from the 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>, may also act to create more <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> coverage of showers and thunderstorms one of those days. Thus, the brief Elevated Threat for Event #1. Note that this looks like a weaker heavy rain event compared to the last two (coverage\/strength) and confidence is still low. This is due to the strength of the system (not well-pronounced and trending downwards), and the details of ingredients needed for heavy rain could easily change. The other reason for the Elevated flood threat is for burn areas.<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/wv_20190812.png\"><img loading=\"lazy\" class=\"aligncenter wp-image-10296\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/wv_20190812.png\" alt=\"\" width=\"700\" height=\"425\"\/><\/a><\/p>\n<p>After a very strong <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> surge, heavy rainfall, and severe weather, <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> values looks to drop off drastically east and west of 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> for the remainder of this week. Friday into Sunday (end of the graphs) shows why there is such low confidence in the next system producing heavy rainfall. At best, it looks like <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> values recover to climatological values, but there is still a lot of spread in the models. If values are able to move closer to climatology, storms may be capable of causing flooding issues over recent burn areas. Interestingly, Grand Junction usually sees a second moisture surge, after a climatological lull, about this time of year. This can be seen in the image below with the black arrow. This surge isn&rsquo;t looking likely this season with the current set up, and <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> values looking closer to the 10% moving average. Right now, not thinking any daily minimum <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> records are going to be broken, but the dry air is a concern for fire weather. Elevated fire weather may be possible over the northwest corner of the state late this week (Thursday-Saturday) when the jet pushes into northern Colorado and orients itself west to east. We will be watching this closely in the FTB and updates to the FTO on Thursday will include more information.<\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/PW_20190812.png\"><img loading=\"lazy\" class=\"alignnone wp-image-10298\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/PW_20190812.png\" alt=\"\" width=\"880\" height=\"297\"\/><\/a><\/p>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/GJT_climo.png\"><img loading=\"lazy\" class=\"aligncenter wp-image-10297\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/GJT_climo.png\" alt=\"\" width=\"250\" height=\"440\"\/><\/a><\/p>\n<p>&nbsp;<\/p>\n<h3><strong>Event #1: <\/strong><strong>Friday<\/strong><strong> (8\/<\/strong><strong>16<\/strong><strong>) &ndash; Monday (8\/<\/strong><strong>19<\/strong><strong>)<\/strong><\/h3>\n<p><span style=\"color: #ff6600;\"><strong>Elevated Threat<\/strong><\/span><strong><span style=\"color: #ff6600;\">\/<\/span><span style=\"color: #0000ff;\">No Apparent Threat<\/span><\/strong><em> as the next weak <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> develops over the west coast. When it pushes to the northeast this weekend, slight eastward movement of the ridge may allow for a modest moisture surge. &nbsp;<\/em><\/p>\n<p>Should be a quiet week with slightly cooler temperatures anticipated under westerly and northwesterly flow. While some afternoon storms are possible (minus Wednesday) over the far eastern plains and mountains each afternoon, not thinking there is any flood threat due to the lack of moisture and swift movement of the storms. Mostly anticipating storms to produce gusty winds as well light rainfall. Lee troughing sets up on Friday and lasts through the weekend. This may allow for some stronger storms to develop during this event. However, with the jet overhead, storms should be moving quickly Friday and Saturday and best dynamics looks to line up east of Colorado. This again looks to be more of an eastern Colorado event, and the best chances for rain will over western Colorado will occur on Sunday and Monday. Going to <span class=\"glossaryLink\" aria-describedby=\"tt\" data-cmtooltip=\"&lt;div class=glossaryItemTitle&gt;Watch&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 weather watch is issued when conditions are favorable for a specific weather event to occur&amp;lt;\/p&amp;gt;\n&amp;lt;!-- \/wp:paragraph --&amp;gt;&lt;\/div&gt;\" data-gt-translate-attributes='[{\"attribute\":\"data-cmtooltip\", \"format\":\"html\"}]'>watch<\/span> for a possible, small scale <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> surge over the southwest corner at the beginning of next, but at this time, it looks like the larger values will stay to our south.<\/p>\n<div style=\"position: relative;\"><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/FTO_20190812_e1.png\"><img loading=\"lazy\" class=\"alignnone wp-image-10346\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2019\/08\/FTO_20190812_e1.png\" alt=\"\" width=\"880\" height=\"497\"\/><\/a><\/div>\n<p><a href=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2015\/05\/Legend.png\"><img loading=\"lazy\" class=\"alignnone size-full wp-image-230\" src=\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2015\/05\/Legend.png\" alt=\"Legend\" width=\"94\" height=\"158\"\/><\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>Issue Date: Monday, August 12th, 2019 Issue Time: 1:45PM MDT Valid Dates:&nbsp;8\/13 &ndash; 8\/27 Event #1 from the last FTO is the low pressure system that is now over Montana. This <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> and the dry air associated with, has caused moisture to drop off across the western US (yellow and oranges in the water vapor [&hellip;]<\/p>","protected":false},"author":8,"featured_media":0,"comment_status":"open","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\/10294"}],"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=10294"}],"version-history":[{"count":4,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/10294\/revisions"}],"predecessor-version":[{"id":10410,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=\/wp\/v2\/posts\/10294\/revisions\/10410"}],"wp:attachment":[{"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10294"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10294"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/archive-coftb.dewberryanalytics.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10294"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}