STP 09-27-2016: Pleasant Day across Colorado

Issue Date: Tuesday, September 27th, 2016
Issue Time: 9:00 AM MDT


Colorado was graced with the presence of dry conditions and plenty of sunshine yesterday as high pressure controlled the forecast. Chilly morning temperatures made it feel like Autumn, while afternoon highs climbed to pleasant, seasonable values. As the title of yesterday’s FTO said: We are full-steam ahead into Fall.

For a statewide look at 24-hour precipitation totals, please take a look at the Storm Total Precipitation map below.

Storm Total Precip Legend

FTO 09-26-2016: Full-Steam Ahead Into Fall

Issue Date: 9/26/2016
Issue Time: 10:55 AM


Colorado has settled into the first week of Fall nicely, with chilly temperatures across the state ringing in the day this morning. With the transition to Autumn, however, comes a climatological increase in the frequency of low pressure systems moving across the Continental United States. Gone is the steady summer ridge, replaced by transient upper-level troughs/ridges. Early in this period (Tuesday/Wednesday), dry conditions will prevail as the upper-level ridge will keep stable conditions in place across Colorado. By Thursday, however, a disturbance (purple circle, #1) will move out of the desert southwest and across the region, bringing subtropical moisture back into the state. Precipitation will be focused west of the Continental Divide on Thursday, spreading eastward and including the rest of the High Country (including the Front Range/Southeast Mountains) and adjacent low elevations for Friday/Saturday. By Sunday, the slow-moving disturbance will be northeast of Colorado, with the next event gathering itself over the Pacific Northwest.


Sunday through Tuesday (10/2 – 10/4) have been included in the time frame of Event #2 on the timeline, but little precipitation is expected during those days. Drier and cooler air behind the first disturbance will keep precipitation hindered, but southwesterly flow aloft and weak support from the approaching upper-level low (purple line, #2) will allow for isolated light showers over the High Country during the early week days. The main show, so to speak, is expected mid-week (Wednesday, 10/5), as the upper-level low brings broad-scale support aloft and a surface low over southeast Colorado provides upslope flow. There is uncertainty in the amount of moisture that will be available to this activity, as the location of the surface low will play a role in the resultant moisture return. Right now, the best moisture looks like it will exist across the far eastern plains and into Kansas, so no flood threat is apparent at this time. We will monitor this event closely, and have an update on the time frame in Thursday’s FTO.

Ensemble models hint at an Event #3 following closely behind Event #2, best characterized as a reinforcing wave, or a “double-dip” from the parent upper-level low over Canada. Event #3 also looks to take a more northern track, leaving Wyoming to deal with the heavier precipitation, relatively speaking, while Colorado deals with showers and High Country snow. Stay tuned.

Event #1: Thursday (09-29-2016) through Saturday (10-01-2016)

No Apparent Threat as Showers will be the Dominant Rain Type, Isolated Thunderstorms

A disturbance, currently positioned over the Desert Southwest/California Baja, will slide across the region, bringing subtropical moisture back into Colorado. Precipitation will be focused west of the Continental Divide on Thursday, spreading eastward and including the rest of the High Country (including the Front Range/Southeast Mountains) and adjacent low elevations for Friday/Saturday. No flood threat is apparent at this time, but some locations across far western Colorado may receive a total of 1.0 inches by the end of the three day event.


Event #2: Sunday (10-02-2016) through Thursday (10-06-2016)

No Apparent Flood Threat as Moisture Likely Stays out of State

While Event #2 is categorized as a five-day event, the main show will occur during the mid-week, likely on Wednesday, October 5th. On that day, the best combination of upper-level support, upslope flow, and low-level moisture return will bring the threat of showers/thunderstorms to eastern Colorado. The best moisture appears to be withheld across Kansas, lessening the threat of heavy rain in Colorado. No flood threat is apparent at this time as we await clarification on the magnitude of moisture return.


Event #3: Friday (10-07-2016) through Sunday (10-09-2016)

No Apparent Flood Threat as the Double-Dip Favors Lighter Precipitation

Ensemble models hint at an Event #3 following closely behind Event #2, but at this time it appears to favor a more northern track. This would leave Colorado with mainly showers and High Country snow, and not a flood threat. A more southerly track would change those results, but it is uncertain at this time. Due to this uncertainty, and the current forecast that no locations would receive more than 0.5 inches of rainfall, no precipitation map will be drawn.

FTB 09-26-2016: Great Early Fall Day

Issue Date: Monday, September 26th, 2016
Issue Time: 9:15AM MDT

~ Flooding is not expected today for all regions.

Dry weather will continue today as any chances of precipitation remain well to the south and east and as the High Pressure centered over the Great Basin develops further. Since the circulation around a high pressure is clockwise, and in combination with the associated ridge at upper levels, winds will tend to be out of the northwest today as Colorado is at the leading edge of this high pressure. The air mass that is associated with the high pressure will remain dry and stable as can be seen in the IPW graph below, producing what is going to shape up to be a very nice day for all regions. Frost conditions from yesterday’s lows will yield to slightly warmer temperatures today (4 to 8 degrees higher than yesterday) that should continue to warm throughout the week.


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, jump below the map.

Flood Threat Legend

Zone-Specific Forecasts

All Zones:

It will be dry and sunny today with light winds coming out of the northwest with the approach of a High Pressure from the west. Look for temperatures to be seasonal with a 4 – 8 degree warmup from yesterday. The influence of the Low that formed to the southwest will not impact the region today as all moisture will remain to the south. Enjoy another great day for golf if you can!

STP 09-26-2016: Rainmakers Move out of the Region

Issue Date: Monday, September 26th, 2016
Issue Time: 9:00 AM MDT


The deep trough that has been affecting weather throughout Colorado for the last several days has finally pushed off to the east taking along with it any chances of precipitation yesterday. Any moisture that was advected by the disturbance to the south and west remained south of the region, giving us some respite yesterday from the rain and storminess of the last few days. Clockwise flow associated with a High Pressure ridge that is moving over most of the western portion of the country brought cool and dry northerly flow at its leading edge, resulting in temperatures that were below average as lows dipped down to the low 30’s and upper 20’s and highs barely made it into the 70’s in the Eastern Plains and mid- to upper-60’s throughout most of the High Country.

No precipitation was reported and no flash flooding occurred yesterday.

Storm Total Precip Legend