SPM 09-26-2017: Precipitation Coverage Decreased, But Clouds Persisted For Some

Issue Date: Tuesday, September 26, 2017
Issue Time: 11AM MDT

Summary:

The past weekend’s storm system slowly departed from Colorado on Monday, and precipitation coverage and intensity took a big downward step. Nonetheless, scattered showers and weak thunderstorms rumbled in two separate areas of the state: one area in the Front Range and Palmer Ridge and a separate area in the Southeast Plains. With limited instability, rainfall rates were subdued, especially compared to Saturday and Sunday. Highest 24-hour totals of 0.5 – 0.75 inches were reported in El Paso and Baca counties, falling over a 2-3 hour period. In other regions, most totals were limited to 0.25 inches or less.

For areas west of the Continental Divide, plenty of sunshine resulted in a boost in temperatures to just below seasonal normal. However, for areas to the east, a pesky low cloud deck insulated the cold air near the surface. High temperatures continued to run up to 20F below normal on Monday.

With the storm system moving away, we can now assess the total precipitation over its roughly 72 hour duration (see map below). Widespread amounts exceeding 1 inch were reported across the eastern third of the state. Of particular note were areas in southeast Colorado that received over 2 inches (with local maximums up to 4 inches). A separate maximum was observed in the Front Range where up to 2 inches of rainfall occurred in Larimer and Weld counties. Finally, another area of enhanced amounts was over the Central Mountains and Grand Valley where between 1 and 1.5 inches of precipitation (both rain and snow) fell.

Flooding was not reported on Monday. 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 09-25-2017: Continuing Rain for Southeast Plains and Northern Mountains

Issue Date: Monday, September 25, 2017
Issue Time: 10:30AM MDT

Summary:

The upper level low continued to sit just to our west yesterday over northern Utah and lifted to the northeast throughout the day and overnight. Most areas west of the Continental Divide were under the influence of the dry slot, so only light rainfall accumulated over the higher terrains. Further north, there was enough residual moisture to allow for another round of rain and snow in the late afternoon and evening. Counterclockwise rotation around the upper low focused the highest accumulations on the south and southwest facing slopes. Higher moisture remained east of the Continental Divide, though SW surface winds helped dry out the atmosphere a bit from the previous day. Showers were more isolated in nature except over the far Southeast Plains where multiple rounds of showers were aided by ample moisture. Multiple rounds of rain added to the already high accumulations from the previous two days.

Over the Northern Mountains and Northern Front Range, freezing levels had dropped quite a bit, so the higher elevations saw more snow that rain. A few SNOTEL stations reported totals up to 0.6 inches in the central, northern high terrains. Along the northern Front Range, totals were a bit higher. West of Fort Collins in the foothills, just under 1 inch of rain fell with totals in and around 0.5 inches for the cities of Fort Collins and Loveland.

The Pueblo radar was back up and working Sunday morning, so estimates yesterday were much more accurate than Saturday. Over the southeast corner of the state, a few rounds of precipitation yesterday and last night added up making some impressive 48-hour totals. Over the last 48-hour period, radar estimates over the eastern plains have been around 5 inches (close to a 1 in 25 year event). An Areal Flood Advisory was issued late last night for Prowers and Baca Counties as a line of thunderstorms moved over an area that had already seen 1.5 inches of rain earlier in the day. Yesterday alone, portions of Baca and Prowers Counties recorded 3-3.5 inches of rain. Fortunately, no flooding has been reported, which includes riverine flooding in and around the Arkansas River. Most stations (as seen below) are showing two distinct peaks from the rainfall on Saturday and Sunday. High running rivers, creeks and arroyos will start to recover as the system begins moving further east and the Southeast Plains dry out.

To find out how much precipitation has fallen around your area the last 24 to 72 hours, 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 09-24-2017: Widespread Heavy Rain and Some Snow for the Higher Elevations

Issue Date: Sunday, September 24, 2017
Issue Time: 10:35AM MDT

Summary:

Widespread showers and thunderstorms formed across the state yesterday as the trough began to slide in from the west. South and southwesterly winds aided in the return of moisture to the state, especially over the eastern plains and southern high country. This allowed for some very impressive rain rates in the early afternoon. Yesterday morning, showers and thunderstorms were already active over the eastern plains and the western portion of the state at the lower elevations. As the system began pulling to the northeast, showers and snow quickly filled in over the mountains. Over the eastern plains, showers and thunderstorms were focused along and behind the slow, eastward propagating cold front. The more convective rain quicwas just east of the Colorado border. By late evening showers over the western portion of the state ceased as drier air worked its way in from the west. Showers over the mountains ended by midnight, and rain continued through this morning over the far eastern plains along the Kansas border.

Over the western portion of the state, CoCoRaHS stations over the higher terrains recorded up to 0.6 inches of precipitation. A SNOTEL station in Grand Mesa National Forest recorded 1.8 inches. Due to the high elevation (above 10,000 feet), most of this precipitation fell as snow. There was a report of 6.3 inches of snow out of Delta County near the SNOTEL gage. Over the Southeast Mountains and southern Front Range, there were two areal flood advisories. The first was for a storm over Colorado Springs that was produced 0.5 inches of rain in 30 minutes. For the 24-hour period, a USGS gage recorded 2.04 inches at Cottonwood Creek and Woodmen Road. The Fountain Creek gage (seen below) reached action level, but it was able to avoid minor flooding. The second areal flood advisory was for the Junkins burn scar where moderate rain was reported falling. Fortunately, there was no flooding reported and creeks are expected to recover today.

Over the eastern plains, quite a bit of rain fell throughout the day and overnight. A USGS gage in Delhi, CO recorded 2.29 inches. Just over the border in Oklahoma, a USGS gage near Kenton, OK recorded 3.6 inches of rain. Radar rainfall estimates are as high as 3 inches with 1-hour rain rates of 2 inches. There was no flooding reported along the Arkansas River, but some of the smaller creeks and arroyos are running in the 90th percentile due to the widespread rainfall. These will be monitored closely as another round of heavy rainfall is likely today over the Southeast Plains and eastern Raton Ridge.

To see how much rain fell in your area, take a peek at 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 09-23-2017: Increasing Rainfall as the Trough Moves West

Issue Date: Saturday, September 23, 2017
Issue Time: 11AM MDT

Summary:

The upper level tough that has been building to our west finally started to move into the state yesterday. West of the Continental Divide, showers began early yesterday morning over the San Juan Mountains with embedded shortwaves moving across the region. By early afternoon, shower coverage increased across the Western Slope and higher terrains. Limited atmospheric moisture over these areas helped keep rainfall totals under flood threat criteria. Over the eastern plains, a surface low pressure helped pull in higher moisture on its east side. To the west, dew points remained in the 30s and 40s, which kept accumulating rainfall over the higher terrains. The increased moisture over the far eastern plains paired with upper level energy from the approaching trough, which sparked another round of showers and thunderstorms beginning around 7am this morning. As the cold front continues to drop south and moisten the low levels, the frontal zone will also promote an area of lift for showers to organize on.

Due to the lack of moisture over the majority of the state, gusty outflow winds were reported with many of the stronger thunderstorms that formed yesterday. The highest reported gust was over Rio Blanco County where an automated station captured a gust of 55 mph. These strong winds are often associated with the inverted-V atmospheric soundings. Over western Colorado, several CoCoRaHS stations reported rainfall ranging from about 0.25 inches to 0.4 inches. The highest rainfall reported by a CoCoRaHS station was in Rio Grande County, and it reported 0.61 inches. Radar estimated rainfall was up to 0.5 inches west of the Continental Divide. Over the mountains, east of the Continental Divide, a CoCoRaHS station near Westcliffe recorded 0.41 inches near the Hayden Pass burn scar. Luckily no flooding was reported. Rainfall over southeastern Colorado began after 7am, so those totals will be rolled over into tomorrow’s rainfall totals.

There was no flooding reported on Friday. 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.