932 FXUS65 KGJT 152333 AFDGJTArea Forecast Discussion National Weather Service Grand Junction CO 533 PM MDT Mon Sep 15 2025
.KEY MESSAGES...
- Isolated showers with a thunderstorm or two are possible across the north today with dry conditions elsewhere.
- Scattered storms are possible on Tuesday as a cold front tracks across the north. Northern and central higher terrain will be favored for best coverage with isolated storms possible in some valley locations.
- Temperatures through the week will oscillate between 5 degrees below and 5 degrees above normal.
- Moisture potentially returns this weekend but confidence in extent and timing is low at this time.
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.SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 242 PM MDT Mon Sep 15 2025
Coverage of showers increases tonight into tomorrow as a closed low pressure system tracks over Wyoming and associated cool front through the area Tuesday afternoon and evening. Large scale ascent from the jet streak across the southwestern portions of our CWA will keep northeast Utah and northwest Colorado in the area of better dynamic lift as lapse rates steepen tomorrow afternoon. Coverage of showers and storms looks more scattered with the higher terrain being favored but some lower valleys across the north and west-central Colorado could see isolated coverage. The chance of measurable rain is highest in the eastern Uintas and northern/central mountains of western Colorado.
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.LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 242 PM MDT Mon Sep 15 2025
Tuesday`s trough of low pressure sags further south overnight and into Wednesday, dragging a cooler airmass over most of the CWA. High`s vary across the board on Wednesday, with the colder temps noted up north, running about ten degrees below normal to just a few degrees below normal across the Four Corners region. Moisture associated with this wave is more abundant on the lee of the Rockies, though isolated showers and thunderstorms are still possible north of the I-70 corridor and along the spine of the Colorado Rockies. Elsewhere, expect a little taste of Fall as low pressure drags the trough`s axis into eastern Colorado. Mild temps stick around Thursday, while we are settled under northwesterly flow. Temperatures will rebound, though, by the end of the week as a transient ridge of high pressure slides overhead. A SoCal low and active plume of monsoon moisture draped across Arizona may loft enough moisture for showers over eastern Utah and western Colorado this weekend, however, precip probabilities remain low with only a slight chance over the San Juan`s and west-central CO mountains. How the Cali low is ingested into the planetary wave to its north leaves uncertainty in our precipitation forecasts for Saturday but consensus realigns with generally quiet/dry weather at the start of next week.
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.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 506 PM MDT Mon Sep 15 2025
Expect mostly VFR conditions and generally light winds through the TAF period. The exceptions will be isolated showers over the northern mountains through 18Z changing over to thunderstorms and spreading southeast into the central and southern Colorado mountains after 18Z. These thunderstorms may produce brief periods of MVFR conditions below ILS breakpoints at the mountain TAF sites.
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.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None. UT...None.
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SHORT TERM...KJS LONG TERM...ERW AVIATION...DB
NWS GJT Office Area Forecast Discussion