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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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899 FXUS65 KGJT 162223 CCA AFDGJT Area Forecast Discussion...CORRECTED National Weather Service Grand Junction CO 423 PM MDT Fri Aug 16 2024 .KEY MESSAGES... - Weak monsoon moisture will bring isolated to scattered showers and storms on Saturday, favoring the mountains and eastern Utah. - More robust monsoonal moisture will impact the region Sunday and beyond. Showers and thunderstorms will bring back the threat of localized flooding Sunday and into the new work week. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 423 PM MDT Fri Aug 16 2024 Winds in the mountains were gusting at 20 to 30 mph this afternoon with temperatures running a few degrees above normal. There are some areas of near critical fire weather conditions this afternoon with low relative humidity in the lower valleys and across northwestern Colorado. A deep low dropping into the Pacific Northwest and a second low shifting east across the Great Lakes were driving the high over the Southwest eastward into west Texas. This shift in the pattern opens the door to deep monsoonal moisture which is expected to move north through Arizona into eastern Utah and western Colorado Saturday. The return of subtropical moisture will fuel isolated to scattered afternoon showers and thunderstorms over higher terrain. Storms strengthen going into the evening as a shortwave passes to the northwest. The HRRR continued to be more bullish with this system than the other models indicating a strong line of storms moving over the northern two-thirds of the region between 5 PM and midnight. With the southern edge of the jet overhead and IVT`s in excess of 500 kg/ms over eastern Utah and northwest Colorado driving PWAT`s above 1", there will be an increased risk for flash flooding due to localized heavy rain and/or training storms. Not enough confidence to issue headlines at this time, but this is something to watch with the next couple runs of the models. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 423 PM MDT Fri Aug 16 2024 Models continue to return consistent agreement on a blocking high taking up residence over the Rockies this coming week. Despite several pushes from the northeast Pacific, the ridge remains the dominant feature here on the West Slope. This regime will set the stage for monsoonal moisture to work its way under the ridge each day, producing areas of showers and thunderstorms Sunday afternoon and beyond. Model agreement remains high that this regime will stay in place through the extended period. PWAT values 140 to 150 percent of normal are progged for Sunday across much of the CWA. Ensemble forecasts are in agreement that precipitable water values stay up through the week, with some minor deviations thanks to the center of the high wobbling a bit. Some nocturnal activity is expected to linger beyond the afternoon into the late evening/early overnight hours as well. Light steering flow will extend residence time of storms on their source terrain and thereby increase risks for flash flooding. Morning lows will trend warm through the period thanks to elevated dewpoints, while afternoon highs will stick around normal to 5 degrees warmer than climatology. Some hints are cropping up that this pattern will shift by Saturday, but likely not enough for a meaningful break in unsettled conditions. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1130 AM MDT Fri Aug 16 2024 VFR conditions will prevail at terminals this TAF period. Winds will pick up this afternoon, westerly at around 20 mph around the region, then subside this evening. A few scattered mid level clouds will crop up on some terrain features this afternoon, but skies should remain mostly clear around the region. Terrain influenced, light winds return for the overnight period into Saturday morning. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...DB LONG TERM...LTB AVIATION...TGJT