Issue Date: Wednesday, September 21st, 2016
Issue Time: 10:00AM MDT
— Flooding is NOT expected today
The large-scale trough, which has been predicted rather well over the past 3-4 days, is finally coming onshore on the US west coast (see water vapor image below). The dynamics with this feature are impressive, but Colorado will have to wait at least one more day before our weather is impacted. In addition to the trough, a weak disturbance is also noted on the CO/KS border this morning. This is causing widespread mid/high clouds east of the Divide, along with some virga in far eastern Colorado. The main impact of this feature will likely be to limit afternoon heating, though it will remain warm east of the Continental Divide. Moisture has increased markedly over the past 24-hours with most of western CO now approaching precipitable water (PW) values of near 1 inch. Even east of the Divide, PW values have slowly increased into the 0.6 – 0.8 inch range. Despite this increase in moisture, it is limited to such high altitude that it will simply not be a factor in generating heavy rainfall. Moreover, as the low pressure trough approaches, upper-level warm air advection will actually build a weak ridge over Colorado today. Overall, expect scattered rain showers and a few weak thunderstorms mainly west of the Divide, but flooding is once again not expected today.
Today’s Flood Threat Map
For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, scroll below the map.
Zone-Specific Forecasts:
Southeast Plains, Northeast Plains, Palmer Ridge, Raton Ridge, Front Range, Urban Corridor, Southeast Mountains:
Mostly cloudy early then turning partly cloudy and continued warm with high temperatures up to 15F above normal towards the CO/KS border. An isolated shower or weak thunderstorm cannot be ruled out. Favored areas will be along the foothills of the entire I-25 corridor (max 1-hr rainfall 0.3 inches) as well as the far southeast (max 1-hr rainfall 0.6 inches). However, flooding is not expected today.
San Juan Mountains, Southwest Slope, Grand Valley, Central Mountains, San Luis Valley, Northwest Slope, Northern Mountains:
Partly to mostly cloudy skies and seasonably warm today. Isolated showers will increase in coverage with a few weak thunderstorms possible by mid-afternoon. Max 1-hour rain rates up to 0.4 inches are possible. Max 24-hour rain totals up to 0.9 inches are possible by tomorrow morning over favored higher elevation, west-facing regions of the San Juans, Central Mountains, Southwest Slope and Grand Valley. However, flooding is not expected today.
