324 FXUS65 KGJT 081006 AFDGJTArea Forecast Discussion National Weather Service Grand Junction CO 406 AM MDT Wed Oct 8 2025
.KEY MESSAGES...
- High temperatures trend 5-10 degrees above average today and tomorrow.
- Isolated showers and thunderstorms develop over the southern San Juans this afternoon.
- A surge of tropical moisture is expected across the Southwest later this week, peaking Friday and Saturday. Widespread showers and storms will be capable of producing flash flooding.
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.SHORT TERM /THROUGH THURSDAY/... Issued at 400 AM MDT Wed Oct 8 2025
As southwesterly flow continue to funnel warmer air into eastern Utah and southwest Colorado, expect unseasonably warm daytime highs. Much of the region will remain dry today in advance of the arrival of tropical moisture from the remnants of Hurricane Priscilla. A few storms cannot be ruled out over the southern San Juans this afternoon.
The aforementioned moisture arrives tonight into tomorrow leading to an uptick in coverage of showers and storms. With PWATs soaring upwards of four standard deviations above normal, much of the forecast area will see much soggier conditions to close out the week. The CAMs support periodic showers and storms spreading northeastward on Thursday. While there will be a localized flash flooding threat, mainly to the recent burn scars, a lack of instability will likely prohibit the efficiency of Thursday`s rains. Rather, they will set the table for a more active weekend ahead.
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.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Issued at 400 AM MDT Wed Oct 8 2025
The models show remarkable agreement through the extended forecast period starting with high pressure over West Texas Thursday evening having pulled deep moisture north out of Sonora Mexico into the Desert Southwest and into eastern Utah and the central valleys of Western Colorado. This moisture with pwats over an inch (300% of normal) will continue to push into the region through Friday with remnant moisture from Priscilla with pwats over an inch and a quarter (350% of normal) pushing into the region Saturday. Temperatures Friday and Saturday will run ten degrees cooler than Thursday due to the heavy cloud cover limiting diurnal heating and due to widespread shower activity. Friday`s precipitation will be more stratified showers due to a tropical warm rain event with this system having 700 mb temps near 8C, but can`t rule out possible isolated thunderstorms from orographic lift and an uncertain passing weak jetstreak through the afternoon. There is a slight risk for heavy rain Friday in southeastern Utah and southwestern Colorado with this warm rain event, but confidence is too low at this time to issue any watch products, Stay tuned for updated on this.
Widespread showers will continue overnight into Saturday with heavier shower and stronger thunderstorms possible late Saturday into the overnight period with increasing upper-level dynamics and a cold front dropping down out of the Pacific Northwest moving through the region early Sunday associated with the low that is off the Pacific Northwest moving inland becoming an openwave system passing to the north. This deeper surge of moisture and stronger dynamics push the increased risks for heavy rain as far north as the Tavaputs and Flat Tops Saturday afternoon through the overnight. Holding off on a watch through this period due to current uncertainty, so again, stay tuned for updates.
Though this cold front will push most of the moisture out of the region, residual moisture will support scattered afternoon showers and thunderstorms favoring the higher terrain daily Sunday through mid week. Behind the cold front, temperatures will remain about five degrees below normal Sunday, warming to near normal Monday through Wednesday with more scattered cloud cover improving diurnal heating. Models are hinting at another surge of tropical moisture from yet another Eastern Pacific tropical storm by mid week, but uncertainty is high on this one.
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.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 1055 PM MDT Tue Oct 7 2025
Expect mostly VFR and generally light winds through the TAF period. The exceptions will be westerly winds gusting 20 kts after 18Z at the mountain TAF sites and moisture moving up from the south spawning afternoon thunderstorms after 20Z along the southern face of the San Juan Mountains with a chance for impacts at KDRO.
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.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None. UT...None.
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SHORT TERM...KAA LONG TERM...DB AVIATION...DB
NWS GJT Office Area Forecast Discussion