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.