191 FXUS65 KGJT 151118 AFDGJTArea Forecast Discussion National Weather Service Grand Junction CO 518 AM 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 and shortwave disturbance 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/... Issued at 335 AM MDT Mon Sep 15 2025
All is quiet on the western slope this morning with mostly clear skies and some mid and high level clouds beginning to move into the eastern Uintas ahead of a Pacific Northwest low that will be tracking eastward across the Intermountain West this afternoon. A 60 kt upper level jet will round the base of this trough and we will begin feeling the influence of said jet across the north where breezy conditions look to occur at times. Some moisture also advects across the north, which could result in some isolated showers across the northern mountains and higher valleys along the Colorado-Wyoming border. Most areas aside from the north look to remain dry today with temperatures warming to near normal levels.
Coverage of showers increases tonight into Tuesday as this closed low pressure system tracks across the north through Wyoming and swings a shortwave trough 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 Tuesday 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 wetting rain in the valleys remains low at this time with better chances of wetting precipitation across the eastern Uintas and northern/central mountains of western Colorado. Cooling will be most evident across the north where highs drop from near normal today to 5 to 10 degrees below normal, while areas along and south of I-70 remain near to about 5 degrees above normal for Tuesday.
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.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 136 PM MDT Sun Sep 14 2025
On Wednesday, the low pressure continues southeastward passing over NE CO. Not sure how much moisture will be in place when it arrives, but it looks like the system will bring some with it. The northeast portion of the area appears to be favored Tuesday night, which is where the forcing is the highest. On Wednesday, the models do not produce much QPF on the Western Slope. Although things have been trending wetter so perhaps QPF may increase during that time frame. Ridging will build aloft on Thursday behind the trough passage, but as the ridge axis moves to our east, southwesterly flow may bring our next potential moisture push late in the week. Temperatures return to near normal on Monday, and will continue to oscillate above and below normal through the week.
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.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 518 AM MDT Mon Sep 15 2025
VFR conditions expected to prevail over the next 24 hours with mostly sunny skies with generally light winds although some gusts to 20 kts are possible at times after 18Z. Some cumulus will develop over the high terrain this afternoon with isolated showers or thunderstorms possible over the northern mountains and along the Colorado-Wyoming border. No impacts anticipated to TAF sites.
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.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None. UT...None.
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SHORT TERM...MDA LONG TERM...KJS AVIATION...TGJT
NWS GJT Office Area Forecast Discussion