Lamar, CO Weather

Key Messages

- Flood Watch in effect from this afternoon through Friday afternoon for the eastern San Juan mountains and the Upper Rio Grande Valley.

- Periods of moderate to heavy rain for the Continental Divide, focusing on the San Juan Range starting this afternoon and lasting through Friday, with the heaviest amounts forecast for Thursday.

- Heavy rain on top of saturated soils and higher elevation snow already in place will bring the threat of flooding, with rock/mud slides also possible along the Continental Divide.

- Generally warm and dry across the plains through Friday, then much cooler and unsettled starting Saturday.

Short Term

Issued at 1232 AM MDT Wed Oct 21 2026

Currently...Strong Pacific low centered off the CA coast was producing southwest flow across the Desert SW and the Four Corners overnight with just a few clouds pushing into the southwestern quad of CO. Otherwise, a mostly clear night with low temps expected to dip into the 30s for the high valleys, and 40s across the plains.

Today and tonight...Pacific low will linger off the CA coast through the day today, keeping a steady, moist southwest flow in place across the Four Corners, feeding moisture into western CO. At the same time, an upper ridge over the central US, with the ridge axis positioned over eastern CO, will help keep the plains warm and dry. Models indicate that the low center will finally push onshore overnight tonight. This timing seems to be slightly slower than previous runs, meaning that shower activity holds off on pushing across the Continental Divide until midday, then gradually increases in areal coverage and intensity through the afternoon and evening. This slower progression seems to keep CAPE somewhat subdued, so even though showers and some storms are anticipated, just general thunder is expected. As for QPF amounts through the first 24 hours, plan on a few tenths along the Continental Divide, with up to around .6 of an inch across the favored SW mts. Flood Watch remains in effect starting this afternoon through Friday afternoon. Look for high temps today in the 60s across the high valleys and 70s for the plains. Increasing sw flow, coupled with moisture advection and increasing clouds, should keep overnight lows a bit more mild, with temps bottoming out in the 40s for the high valleys, and mid 40s to mid 50s for the plains.

Long Term

Issued at 1232 AM MDT Wed Oct 21 2026

Thursday...All indications point to Thursday as seeing the greatest impacts from this Pacific storm. As the low continues moving east across CA and NV through the day, an upper shortwave rotates across AZ and into the Four Corners region. This upper support, coupled with increasing proximity of the system, will mean periods of heavy rainfall across western CO and along the Continental Divide through the entire day. The focus area continues to be the southwest mts, with total additional rainfall amounts ranging from an inch up to 2.75 inches possible through the day, while the remainder of the higher terrain could see around half an inch. SPC shows the Marginal area for strong to severe thunderstorms creeping into the southwestern corner of the state, giving a nod to the abundant moisture plus upper level support, so periods of heavy convective rainfall falling on already saturated ground and some high elevation snow pack leading to excessive runoff will be possible, hence the ongoing flood Watch. Those living or traveling across the southwest mountains should stay weather aware through the rest of the week, and have multiple ways to receive weather warnings. As for the eastern plains, dry and continued warm conditions anticipated, though the upper ridge axis finally pushes east out of the area. Look for highs in the 60s for the high valleys, and 70s to lower 80s for the plains.

Friday...Friday will be an interesting day as the system starts to weaken and split into two pieces by the evening. The northern piece pushes up into MT, while the southern piece drops south and tries to gather some strength over the Desert SW. Rain totals of an additional .40 of an inch for the eastern San Juans, and up to a tenth of an inch elsewhere, are forecast, then showers and isolated thunderstorms push along the southern border and up across the far southeast corner through the late afternoon and evening. This will be the last really warm day for the eastern plains as temps once again climb into the 70s to around 80F, but there are some hints that perhaps it might end up a few degrees cooler due to increased cloud cover.

Saturday through Tuesday...While one low center lingers across the Four Corners, the northern piece cross the northern Rockies and pushes a cold front south into eastern CO Saturday morning. This front will bring significant cooling to the forecast area as well as widespread precipitation chances for both Sat and Sun as the southern piece of the low weakens and finally moves east across the state. Long range models indicate that Mon and Tue will remain unsettled and cool across the region, but confidence remains low on what that actually looks like. For now, the NBM drops temps into the 50s and 60s on Sat, 50s regionwide Sun and Mon, then some gradual warming by Tue.

Aviation

Issued at 522 AM MDT Wed Oct 21 2026

Clouds will remain VFR into Wednesday afternoon, with flow turning more southerly across the region, approaching 10-15 knots at times. Showers and thunderstorms will begin to move across the area from the west throughout the day and into tonight. Clouds will increase across the terminals, approaching MVFR cigs. Showers will move near KALS first after 01-05Z, becoming more widespread afterwards, while KCOS and KPUB see overall lower chances for precipitation, so stuck with PROB30s for now.