Issue Date: Thursday, July 14th, 2022
Issue Time: 2PM MDT
Valid Dates: 7/15 – 7/29
As mentioned on Monday, it looks like it’s going to stay active on the rainfall front through the entirety of this outlook, which nearly goes to the end of July. The water vapor imagery (below) shows the subtropical High still located over the Four Corners region. It should continue to hang around this area through Event #3 with some slight north and south movement anticipated as it ebbs and flows in strength. Currently, it is pulling strong subtropical moisture northwards over western Colorado and Utah. As a small disturbance (orange “X”) begins to move inland tomorrow, and the subtropical moisture plume will be transported northward and then eastward around the High through Saturday (green arrows).
This will put PW well above average (see plumes below), and with some extra mid-level energy helping to provide lift and strong upslope flow forecast, an upgrade to a High flood threat has been issued for Friday and Saturday. Reminder that a High threat in the FTO corresponds to a Moderate threat or higher likely being issued in the daily FTB. Behind the passage of the mid-level disturbance on Sunday, there is a slight downtick in moisture, so rainfall is expected to do the same. However, with PW still at or near average, an Elevated flood threat has been issued for the southern and central high terrains.
The stubborn High sticks around through the end of the weekend into early next week before another Low moves east, north of Colorado’s border. This ridge is expected to support hot afternoon temperatures with the highest temperature anomalies are forecast over eastern Colorado where afternoon cloud cover and precipitation will be less likely to occur. The location of the High during this period should help to hold a nice PW plume overhead. While steering flows will be a bit faster next week, PW values should remain around average, keeping an Elevated flood threat for the near term. There will likely be a lull in precipitation at the end of the week before it looks like another monsoon surge will occur over the weekend. More details about each event can be found below.
The NCEI monthly temperature and precipitation rankings have arrived for June. As you would guess, average temperatures across the state were above average with a ranking of 105 (POR 1895-2022), and southwest Colorado received much above average temperatures. As discussed in previous FTO’s, it was a very wet June for southwest Colorado with much above average precipitation recorded. However, both Sedgwick and Phillips County were much below average in terms of rainfall with the majority of the Northeast Plains also below average. As a whole for rainfall, the state ranked 72, which is near average. Below is a look at the latest drought map on the right with drought conditions at the beginning of June on the left. Overall, there has been improvements to the Extreme and Exceptional drought conditions across the southern border over the last month or so, but an increase in extreme drought for the northeast border counties where it was extra dry during June. With precipitation mostly sticking to the mountains over the next week or so, it is likely there won’t be much relief for eastern plains. However, there is an outside chance for some scattered rainfall over the far Northeast Plains during the evening hours if storms can make their way off the Cheyenne Ridge and cross the border tomorrow.
Lastly, the monthly streamflow tracker will be updated on Monday, since we’re still waiting for a lot of the data to come in.
Event #1: Friday – Monday (7/15 – 7/18)
High/Elevated flood threat as monsoon moisture combines with mid-level energy and slower steering flows under the ridge.
An uptick in storms activity and coverage is forecast for tomorrow and Saturday with the passing shortwave and monsoon moisture over the area. Max 1-hour rain rates up to 1.5 inches will be possible over the Central Mountains, Northern Mountains and Front Range on Friday with the threat likely shifting further south over the high terrains on Saturday. A couple storms over the far eastern plains are likely during this period with the Northeast Plains favored tomorrow. Flood threats include road flooding, field ponding and isolated mud/debris flows over the steeper terrains. During this period, it is likely that a few severe thunderstorms could develop with the main threats being strong outflow winds and some hail with decent shear over the state. Be sure to tune into the daily FTB, which can better track these threats. A downtick in moisture and lift is forecast on Sunday with the flood threat likely isolated to the southern Central Mountains, San Juan Mountains and perhaps the southern Southeast Mountains. More widespread storms are then forecast on Monday over the mountains as the ridge axis is pushed east/south with the passage of the next Low to our north.
Event #2: Tuesday – Friday (7/19 – 7/22)
Elevated/No Apparent flood threat as the ridge breaks down and a cold front returns moisture to eastern and central Colorado.
Elevated moisture remains over the area at the beginning of next week with more westerly flow forecast over the state as the ridge axis is temporarily pushed south. This may allow some storms to reach into the eastern plains on Tuesday. The ridge quickly rebuilds back to the west of Colorado with a day or two break in heavy rainfall chances likely at the end of the week. Faster steering flows are also forecast during this period over northern and central Colorado, which should help limit the flood threat. However, if training storms develop, there could still be a local threat for heavy rainfall.
Event #3: Saturday – Tuesday (7/23 – 7/26)
Elevated flood threat as the robust monsoon season continues and likely pulls another moisture plume into the state.
Uncertainty in the forecast increases after Event #2, but long-range guidance hints at another monsoon surge to begin at the end of next week. An Elevated flood threat has been issued for this reason and due to increased recreation activity anticipated over the weekend. Please tune back into the FTO on Monday as there will likely be changes to the forecast. Due to the uncertainty, no flood map has been drawn.
