FTB 06-25-2020: Continued Hot with More Storm Coverage, but No Flood Threat

Issue Date: Thursday, June 25, 2020
Issue Time: 9:45AM MDT

— Flooding is NOT expected today

This morning’s water vapor imagery, below, shows a rather disorganized mass of mainly mid-level moisture and some cloud cover across the Rocky Mountain states. As one may be able to guess, summer early morning cloud cover in Colorado often suggests the present of some atmospheric dynamics overhead. Such is the case today, as a stretched-out shortwave “digs” southeast into the Four Corner area. The feature is currently centered from western Montana southwestward into Nevada, and will slowly move into Colorado today and tomorrow. As has been the case many times in the past few weeks, limited moisture will prevent anything aside from brief heavy rainfall. However, storm coverage should increase, compared to yesterday.

This morning’s soundings showed a PW of 0.55 inches at Denver and 0.58 at Grand Junction. However, a very deep elevated mixed layer meant that most of this moisture was in the mid and upper-levels of the atmosphere. With a very steep lapse rate exceeding 9 Celsius/km between 500mb and 700mb at both sites, we can expect storms to be capable of producing gusty winds today (the motto of the 2020 summer so far!). Compared to yesterday, the storm-level steering flow will be a bit faster with a predominantly westerly direction. A deep-layer westerly flow tends to limit heavy rainfall east of the Continental Divide.

Overall, expect scattered showers and storms early this afternoon across most of the higher terrain, spreading eastward over the plains by mid-afternoon and into the evening. The vast majority of storms will be short-lived and produce 10-15 minutes of moderate to heavy rainfall over lucky locations. The only exception will be parts of the Northeast Plains, where a bit more moisture will support higher instability and the potential for severe thunderstorms. The main hazard is straight-line winds up to 65mph. A southerly to south-southeasterly component of the low-level flow will support heavier rainfall than areas farther west, but flooding is not expected today.

Today’s Flood Threat Map

For more information on today’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.

Zone-Specific Forecasts:

Northeast Plains, Front Range, Palmer Ridge, Urban Corridor, Southeast Plains, Raton Ridge, Southeast Mountains:

Partly cloudy early then scattered showers and thunderstorms developing by early afternoon over the higher terrain and spreading eastward. Continued very hot with temperatures up to 10F above normal, approaching 100F in the lowest elevations of the South Platte River and Arkansas River valleys. Max 1-hour rainfall up to 0.5 inches for western areas to 1.3 inches across far eastern areas by the Nebraska and Kansas borders. Severe storms are possible across the I-76 corridor mainly northeast of Fort Morgan, with the primary hazard being straight line wind gusts to 65 mph. A second round of storms could occur over far northeast areas around sunset as an expected convective complex moves southeastward out of Wyoming.

Flooding is not expected today, but some nuisance field ponding and localized urban flooding could occur for areas by the Kansas and Nebraska borders.

Central Mountains, Northwest Slope, Grand Valley, Northwest Slope, Southwest Slope, San Juan Mountains, San Luis Valley:

Partly cloudy early then isolated to scattered showers and thunderstorms developing by noon. Highest coverage over the higher terrain, though there will be overall more coverage than yesterday. Continued warm with high temperatures 5-8F above normal. Max 1-hr rainfall up to 0.4 inches. Gusty winds, up to 50mph, will be possible with the strongest storms during the late afternoon and early evening hours.

Flooding is not expected today.