Issue Date: Saturday, September 10th, 2022
Issue Time: 8:45AM MDT
— Flooding is NOT expected today
Very active atmospheric dynamics overlie Colorado on this Saturday morning, as a large-scale trough axis is currently directly overhead (see visible satellite image, below). Yesterday’s cool front has easily cleared the entire state, but temperatures have continued to fall under steady northerly cool air advection. Twenty-four hour temperature changes are generally 10-15F statewide, though a few isolated pockets of relatively warmer temperatures remain embedded within the hard-to-reach southern valleys. A very large moisture gradient was observed this morning with Grand Junction’s PW measuring a paltry 0.37 inches while the Platteville research station came in at 0.76 inches. Even higher column moisture exists over southeast Colorado today with PW likely in the 1.0-1.1 inch range over parts of the Southeast Plains. However, total moisture will peak by late morning and begin to decline by later in the afternoon as much drier air infiltrates the entire state from the northwest.
There are two predominant features dictating today’s weather across our state. The primary of the two is a vigorous, large-scale trough that will continue to trek quickly southeastward through the day. With significant mid-level and upper-level (i.e. jet stream) dynamics in support, it will cause synoptic scale lift over southern and eastern Colorado this afternoon. Additionally, a large-scale cloud deck is noted draped east-west along the CO/NM and UT/AZ borders. This is the result of modest mid-level lift courtesy of the subtropical disturbance that was formerly Hurricane Kay. However, this feature will likely be pushed southwestward out of Colorado by early afternoon by the trough.
All in all, we expect mostly cloudy conditions east of the Continental Divide with the ongoing drizzle and light rain showers moving slowly south and east through the afternoon. Meanwhile, pleasant fall weather is expected over most of western Colorado. The only chance of heavy rain today will be in a limited area over the southeast San Juan Mountains, San Luis Valley and perhaps southern fringe of the Southeast Mountains. Instability of up to 1,200 J/kg CAPE should spark a few clusters of storms by mid-afternoon. However, with the increasing S/SE steering flow of 20mph or greater, only brief heavy rainfall is expected along with gusty winds and the threat of hail. Thus, 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:
San Juan Mountains, Southwest Slope, San Luis Valley & Southeast Mountains:
Mostly cloudy skies with an increasing chance of showers and embedded thunderstorms by mid-afternoon. Max 30-min/1-hour rainfall up to 0.8/1.0 inch is possible but only over localized areas. Thus, some ponding of runoff is possible, but flooding is NOT expected today.
Primetime: 3PM through 8PM, with lighter rain possible into the overnight hours
Northeast Plains, Southeast Plains, Front Range, Urban Corridor, Palmer Ridge & Raton Ridge:
Overcast and cool/cold conditions today with drizzle and light rain showers expected through at least the late afternoon. The best chance of precipitation will be over the Northeast Plains as well as the foothills along and west of I-25 from the Denver metro all the way through the NM border. Max 1-hour rain rates up to 0.25 inches with total accumulation up to 0.6 inches possible by Sunday morning.
Primetime: Ongoing through 10PM
Northern Mountains, Central Mountains, Grand Valley & Northwest Slope:
Mostly clear skies with pleasant fall temperature today. Breezy winds of 15-25 mph are expected this afternoon. Flooding is NOT expected today.
