Issue Date: Thursday, September 1st, 2022
Issue Time: 2:30PM MDT
Valid Dates: 9/2 – 9/16
It’s officially meteorological fall today, although the well above average temperatures feel like it’s a continuation of summer. Above average temperatures are forecast through at least this next week with an upper-level ridge overhead. Event #1 is a quick 2-day event beginning tomorrow. Some diurnally driven storms are expected over the mountains with some isolated storms possible over the plains tomorrow. After Saturday, dry air should circulate around the building High, which should keep precipitation chances limited over Colorado next week. Event #2 is not expected to begin until the end of next week when flow could turn southerly and pull some tropical moisture northwards over the state. There is still a lot of uncertainty with this forecast as the plume could easily stay south and east of the state. Details should start to become clearer at the beginning of next week.
PW plumes are not overly impressive with values likely remaining below climatology through Thursday. There is a slight uptick in moisture over eastern Colorado tomorrow and Saturday behind a weak cold front. This front should help to produce isolated storms over the Southeast Mountains and possibly the adjacent plains tomorrow afternoon and evening. By Saturday, storms are expected to be confined to the mountains with northerly (north) and NNE (south) steering flows forecast. With only weak mid-level lift, quicker steering flows on Friday, and limited moisture, there is No Apparent flood threat issued for Event #1.
Event #1: Friday – Saturday (9/2 – 9/3)
No Apparent flood threat as weak dynamics and moisture produce isolated storms.
Isolated storms are forecast tomorrow over the mountains, Southeast Plains and elevated ridges. Storms that are able to develop over the adjacent plains along the boundary should have limited surface moisture, which means they could produce some strong outflow winds and plenty of virga. Over the mountains, isolated storms are most likely to develop along and near the Continental Divide and over the Southeast Mountains. There’s a better chance for widely scattered storms to develop over the southern high terrain on Saturday. During this period, storms should be short-lived and produce rain rates under 0.5 inches. Therefore, there is No Apparent threat has been issued.
Event #2: Thursday – Sunday (9/8 – 9/11)
Potential tropical moisture surge with added dynamics may cause an uptick in rainfall coverage, although at this time, there is No Apparent flood threat issued.
There’s a lot that can change over the next week and key ingredients that need to come together for Event #2. At the moment, long-term model guidance isn’t showing consensus either, so choosing to keep this forecast on the lower-end of the flood potential scale. A passing of a trough to our north, northward movement of the tropical moisture and the position/existence of a weak shortwave to our southeast will have to have the right timelines and tracks to get the moisture plume over the state. The likelihood of all the ingredients coming together is low, but stay tuned to the FTO on Monday as their will likely be an update to the forecast. At the most there would be a 1- or 2-day category upgrade to the event, but only if it looks more likely that the plume will move overhead.
