SPM 09-30-2017: Rain And High Elevation Snow Mainly Across Western Colorado

Issue Date: Saturday, September 30, 2017
Issue Time: 10:45AM MDT

Summary:

Unsettled weather continued for Colorado as a large-scale trough continued to envelop the western United States. Over the last week, temperatures have ranged anywhere from 2 to 10F below normal across the state (see below), one indicator of frequent cloud cover that has limited heating.

Despite the active weather, rainfall rates continued to be limited due to weak instability and limited boundary layer moisture. Isolated twenty four rainfall amounts up to 1 inch occurred over the higher terrain of southwestern Colorado on Friday. However, hourly rain rates were limited to less than about 0.4 inches. Despite the limited instability, a few reports of small hail were reported along the counties by the New Mexico border. This was probably more of a testament to low freezing levels than atmospheric instability.

Flooding was not reported on Saturday. For rainfall estimates in your area, check out our State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.

SPM 09-29-2017: Ongoing Showers with Northward Movement of the Upper Level Low

Issue Date: Friday, September 29, 2017
Issue Time: 10:40AM MDT

Summary:

The upper level low to the west of Colorado continued to promote rain and cloudiness across the majority of the state again yesterday. The morning began with showers over the high terrain sustained by weak upslope flow and high moisture. Heavier rain was occurring over the eastern plains, which was supported by the upper level jet as the Low tracked north. By mid-afternoon, the showers over the eastern plains had worked their way over the KS border, and the dry slot had moved into western Colorado. The drier air to the west limited widespread showers and heavy rainfall, though some storms still dropped a decent amount of precipitation over the valleys and Northern Mountains. Overnight showers and snow lingered in the mountains with the highest accumulations over the Southeast Mountains/Raton Ridge. The showers over the south were enhanced by a shortwave rotating around the Low, which helped increase 24-hour rainfall totals. By early this morning, the showers had drifted into the Southeast Plains and have sustained themselves with lift from the jet stream and the shortwave. The isolated showers will continue to gradually move to the northeast throughout the morning.

Southwest flow over western Colorado helped limit rainfall totals when compared to Wednesday. A bit more moisture managed to maintain itself over the eastern San Juan Mountains. CoCoRaHS stations near Pagosa Springs recorded totals from 0.15 to 0.3 inches. A bit of instability was able to build over the western valleys and afternoon thunderstorms produced hail and storm totals of 0.5 inches. Along the Front Range, the Eldora SNOTEL station recorded 0.9 inches. Radar rainfall estimates were up to 1 inch in this area. The highest accumulations were again over the Southeast Mountains and Raton Ridge. The heavier rain fell in ungagged areas, but there was a report of 1 inch in Kim, Colorado. Radar rain estimates are up to 1.5 inches with 2-hour totals up to 1 inch.

There were no reports of flooding Thursday. To see how much rain fell in your area, scroll down to the State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.

SPM 09-28-2017: Multiple Rounds of Rain for the San Juan and Southeast Mountains

Issue Date: Thursday, September 28, 2017
Issue Time: 10:50AM MDT

Summary:

Another gloomy and rainy day across the Front Range and southern mountains yesterday as the upper level Low over AZ provided lift for multiple rounds of showers. The Low continued to produce southerly winds over Colorado, which sustained the stream of moisture from the Gulf of Mexico. As the jet streak moved over the state with the northward movement of the Low, showers/snow continued overnight along the Front Range and Southeast Mountains. The jet also enhanced the intensity and increased the coverage of storms overnight. This morning, the jet continues to provide lift for the showers east of the Continental Divide over the Southeast Plains. Drier air began working its way into western Colorado during the evening yesterday, so showers over the SW corner of the state ended by 9PM and produced lower 24-hour accumulations.

Several CoCoRaHS stations across the Southeast Mountains recorded amounts greater than 1 inch. The USGS Fort Carson automated gage recorded 1.76 inches. Over Las Animas County, a USGS gage to the northeast of Trinidad, recorded 2.32 inches. A SNOTEL site in the southern Sangre de Cristo range recorded 1.4 inches of rain. Radar rainfall estimates show multiple areas receiving more than 2 inches with 2-hour rain rates up to 0.5 inches. To the west, Pagosa Springs recorded 24-hour totals around 1.15 inches. The highest radar rainfall estimates are over San Juan and eastern Dolores Counties where radar indicates just over 0.5 inches of rain fell. While river gages did record elevated flows due to runoff, there was no riverine flooding reported.

There were no reports of flooding yesterday as of this morning. To see how much rain fell in your area, scroll down to the State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.

SPM 09-27-2017: Showers for the Front Range and Southeast Mountains

Issue Date: Wednesday, September 27, 2017
Issue Time: 10:50AM MDT

Summary:

As the disturbance from the end of last week began to move eastward, general subsidence occurred across the state. The settled weather pattern did not last long as the next trough began to dig south over the desert southwest. By late afternoon, showers associated with the Low pressure over Arizona arrived to the southern mountains. At the same time, weak upslope flow initiated showers along the Front Range. Precipitable Water (PW) and instability were limited, so the precipitation yesterday was in the form of general showers and stratiform rain. Rain continued overnight and into this morning along the Southeast Mountains. Overnight low temperatures remained relatively warm due to the increased cloud cover.

Despite relatively low atmospheric moisture, persistent rainfall yielded some impressive 24-hour totals along the Front Range and Southeast Mountains. Over the Front Range, a handful of CoCoRaHS stations in Clear Creek, Jefferson and Park Counties recorded 0.65 inches. Over the Southeast Mountains, CoCoRaHS totals were in the 0.3 to 0.5 inch range. Radar estimated 24-hour rainfall just over 1 inch in Las Animas County. Drier air over the southwest Colorado state made showers more isolated in nature yesterday. SNOTEL stations over the San Juan Mountains recorded up to 0.3 inches. While there was no flooding reported Tuesday, it is important to note the 24-hour totals. Increased moisture is forecasted from Wednesday to Friday, and an uptick in rainfall intensity is expected. Antecedent rainfall can saturate the soil, which will increase runoff and the potential for mud flows and debris slides in the high country.

To see how much rain fell in your neighborhood, scroll down to the State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.