580 FXUS65 KGJT 130632 AFDGJTArea Forecast Discussion National Weather Service Grand Junction CO 1232 AM MDT Sat Sep 13 2025
.KEY MESSAGES...
- Scattered showers and storms are expected tomorrow mainly during the afternoon. A few storms may be capable of producing strong winds, hail and heavy rainfall.
- Conditions dry out on Sunday so expect less active weather with below normal temperatures.
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.UPDATE... Issued at 1219 AM MDT Sat Sep 13 2025
Let the Flood Watch expire at midnight. Even though storms are expected again on Saturday with potential for brief heavy rain, coverage looks to be more scattered and deeper moisture starts to decrease as its pushed eastward. Localized flash flooding is still possible especially over recent burn scars and areas of already saturated soils but the flooding threat is not expected to be as widespread as the previous two days.
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.SHORT TERM /THROUGH SUNDAY/... Issued at 334 PM MDT Fri Sep 12 2025
Overall this evening we should see a weakening trend to the convection although there will still be showers and storms. By midnight it becomes more isolated to scattered. Late tonight the shortwave trough swings over Utah. Overall this evening we should see a weakening trend to the convection although there will still be showers and storms. By midnight it becomes more isolated to scattered. Late tonight the shortwave trough swings over Utah and looks to push another round of moisture advection into southwest Colorado. So we could see an increase in shower there as evident on the latest hi-res models. During the morning hours the wave lifts over northeast Utah and northwest Colorado. Moisture does decrease as the deeper plume pushes east of the Divide. Although the lapse rates do steepen, which should allow for modest instability once again. The wave itself should provide lift as well so expect another round of showers and storms with the better chances across the north. The models also show that the jet aloft may still be overhead, which will contribute to the shear. With all of that being said strong to severe storms look possible across a good portion of the area late tomorrow morning and into the early evening. Gusty winds and large hail will be the main impacts, but heavy rainfall can not be ruled out.
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.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 334 PM MDT Fri Sep 12 2025
On Sunday morning the axis of a trough moving across the region will be east of the Rockies. High pressure will briefly build behind the trough. This pattern shift will lead to a drier airmass moving over the region, ending the ongoing return of the monsoon. By Monday night a trough off the Pacific Northwest will be passing to our north. As it passes, it may provide just enough support to increase PoPs along our northern border Tuesday night, and to allow for afternoon convection on Tuesday and Wednesday over the higher terrain. Although, models seem to disagree on both the timing of this through passage, and how far south the trough will dig. In addition, moisture looks to be pretty limited during this period so not much is expected in terms of QPF. High pressure builds again after this trough passage. With the decrease in moisture, and periods of increasing high pressure, seasonable temperatures return through the workweek.
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.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1219 AM MDT Sat Sep 13 2025
Isolated thunderstorms are expected to continue this morning with some development possible across the area after 12Z. Chances are higher for storm development late this morning into the afternoon with storms lasting through sunset and diminishing after 03Z. Kept some PROB30 groups at most TAF sites through the morning with prevailing showers and VCTS during the afternoon as confidence is higher that most TAF sites would see impacts at some point during the afternoon. VFR conditions will be in place with MVFR/IFR in any shower/storm and CIGS lowered to ILS breakpoints at times during convection.
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.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None. UT...None.
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UPDATE...MDA SHORT TERM...KJS LONG TERM...GF AVIATION...TGJT
NWS GJT Office Area Forecast Discussion