textproduct: Grand Junction

KEY MESSAGES

- Light showers continue across northwest Colorado through Friday morning with sub-freezing temperatures expected for the central Yampa River Basin.

- A Red Flag Warning is in effect for southwest Colorado valleys Friday with more localized conditions possible on Saturday.

- Drier and warmer conditions return for the weekend with isolated mountain storms being replaced by wetter and cooler conditions as we move through early to mid next week.

DISCUSSION

Issued at 1035 PM MDT Thu May 21 2026

Light showers persist across northwest Colorado mountains and will slowly taper off in the early morning hours Friday as the shortwave trough lifts to the northeast across the Front Range and northern High Plains. We will see some partial clearing overnight which should be enough time for the central Yampa River Basin to see below freezing temperatures, a bit colder and more widespread than last night...so Freeze Warning remains in effect for COZ002. Clouds will increase once again by day break as a weaker shortwave pushes across the Intermountain West and Great Basin in northwest flow. This shortwave lifts across the region Friday afternoon, which looks to spark some isolated to widely scattered showers and thunderstorms favoring the San Juans, eastern Uintas and spine of the Divide. While relative humidities will be up compared to today, SW Colorado looks to remain below 15 percent with gusty winds in that post- frontal/post trough regime, which tends to overperform compared to guidance. Therefore, issued a Red Flag Warning for COZ207 (SW Colorado valleys) for Friday (12-8 pm MDT) where critical fire weather conditions are likely.

Conditions dry out this weekend as a ridge of high pressure slides across the area, although this will be kind of a dirty ridge with some high cloud cover and potential for isolated afternoon convection over the high terrain. Nothing substantial but highs will rise back up towards 5 to 10 degrees above normal. The flow then turns southwest with a deep low moving towards the PacNW coast and a cut off low tracking over the Desert Southwest. This will advect some moisture into Arizona towards the Four Corners region, resulting in scattered showers and thunderstorms Monday afternoon, which looks to continue into Tuesday as that PacNW low dives southward across the Intermountain West and into the Great Basin. There is still some model discrepancy on how this low tracks and affects our weather, but GFS seems to have jumped back on board with the ECMWF and cluster analysis that seems to favor this low closing off and stalling over the Great Basin by mid next week. There will be a lot of wiggle room in the forecast depending on how this plays out, which of course has lots of implications in terms of precipitation chances and coverage as well as temperatures. Confidence is low beyond Tuesday.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 534 AM MDT Fri May 22 2026

Some low stratus has developed in the valleys of northern CO this morning. Have had a few ceilings develop, then dissipate. Left TEMPO ceilings in at KHDN to account for some leftover cloud cover impacting the airfield before sunrise cooks it off. Elsewhere, mid and upper level clouds will continue to work through the region in the base of an upper level trough stretched across the Great Basin. Don't anticipate any breakpoint conditions with these clouds. Winds will pick up again this afternoon, gusting to around 25 mph around the region with a few higher gusts in favorable spots adjacent to terrain. Clouds will thin and skies will clear after sunset this evening and winds will return to light and terrain influenced overnight to close out this TAF period.

FIRE WEATHER

Issued at 1035 PM MDT Thu May 21 2026

The front settles near the southern border overnight and post frontal winds will result in another day of critical fire weather conditions for SW Colorado valleys on Friday. The SW Colorado valleys tend to overperform in this post-frontal/post trough regime so went ahead and issued a Red Flag Warning for COZ207 for Friday from 12-8 pm MDT Friday.

Warmer conditions arrive for the weekend with a downward trend in afternoon gusts limiting the fire weather threat into early next week, although localized critical fire weather conditions are possible on Saturday across portions of SW Colorado. Winds increase early next week ahead of an approaching system but moisture moving in with the winds looks to also boost afternoon humidity. This in turn brings more shower and thunderstorm activity into play next week.

GJT WATCHES/WARNINGS/ADVISORIES

CO...Freeze Warning until 10 AM MDT this morning for COZ002. Red Flag Warning from noon today to 8 PM MDT this evening for COZ207. UT...None.