Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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231 FXUS65 KGJT 080917 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 317 AM MDT Sat Jun 8 2024 .KEY MESSAGES... - Afternoon showers and storms will favor the north today, but will expand to include all terrain features Sunday and Monday. Main threats will be gusty winds and lightning. - Temperatures will cool to near normal values by Monday before warming back to 10-15 degrees above normal mid to late next week. - High pressure from Tuesday onward will keep conditions hot, dry, and quiet. && .SHORT TERM /THROUGH SUNDAY/... Issued at 316 AM MDT Sat Jun 8 2024 It`s hard to believe this is early June and not July or August, with how late-summer, monsoonal conditions appear to be. The PWAT value in the 00z Grand Junction sounding came in at 0.73 inches, which is in the top 10% of PWAT values for that date and time, and is much closer to a normal PWAT in late July. This moisture does seem to be focused mainly north of the I-70 corridor, which is also where some very modest instability has lingered into the night. This, in combination with some weak dynamic lift from a passing shortwave to the north, has allowed for convection to continue well into the night across Northwest Colorado. Very dry surface levels have limited the amount of moisture making it to the ground, but has resulted in some quite gusty winds. As the shortwave providing the necessary lift continues tracking east, so too will these showers, and will be east of the Divide by daybreak. Ridging is expected to push northwestward into the Great Basin today, with the ridge axis directly over the Four Corners. This will push drier air across southeast Utah and southwest Colorado today, limiting chances of clouds and showers, and allowing temperatures to climb 10 or so degrees above normal. Meanwhile, areas north of I- 70, will see plenty of low to mid level moisture still in place. Guidance is also hitting at pockets of 500-1000 J/kg of CAPE, meaning there will be plenty of instability to play with. Another shortwave is expected to move across the north this afternoon and evening, providing some modest dynamic lift to combine with daytime heating and fire off another round of afternoon convection. Dry surface air is forecast to remain stubbornly in place, meaning the main threats will be gusty winds and lightning, although there is still a chance for some moderate to heavy rain across the higher terrain. As this wave moves east of the Divide tonight, expect a downturn in shower activity across the area as high pressure reasserts itself. A tap of subtropical moisture being pulled north by the clockwise flow associated with the ridge will help fuel more widespread activity on Sunday. The remnants of the Baja cutoff low will be an open wave over the Desert Southwest on Sunday afternoon, providing some modest lift across the southern portion of the CWA, while yet another passing wave to the north will help with convection over Northeast Utah and northwest Colorado. Expect to see activity fire along the terrain first before drifting off over adjacent valleys. Multiple days of uninterrupted moisture across the north will see increasing chances of heavy rain with afternoon convection, along with the usual threats. Gusty winds and lightning remain the main threat across the south. High temperatures this afternoon will be similar to what we saw yesterday, with the desert valleys of Southeast Utah standing the best chance to see triple digits thanks to drier air. Portions of northeast Utah and northwest Colorado, along with the Central Divide Mountains, stand the best chance to see cooler temperatures this afternoon thanks to clouds and storms. By tomorrow, with increased moisture across the entire region and greater coverage of clouds and storms, temperatures will run around 5 degrees cooler, though still above normal. Overnight lows will remain mild. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 316 AM MDT Sat Jun 8 2024 The next closed low will be dropping off the Baja Coast Sunday Night into Monday as the prior Baja low works across New Mexico to the Southern High Plains during this time. Shearing energy from this low and the tail end of a northern stream system will continue to interact with above normal moisture over the area to produce afternoon showers and thunderstorms. The cloud cover and precipitation should contribute to the coolest day of the forecast on Monday through temperatures will remain slightly above normal. High pressure builds back into the 4 Corners region on Tuesday and persists through Thursday before the Baja low begins to lift into the Southwest. So another string of hot and mainly dry days will return until the late week period when this low brings the next chance of precipitation and likely cooling temperatures back toward normal. There are some models variances as we get out to the late week time frame and beyond. These include the timing and exact trajectory of the SW low as it moves across the Rockies into the weekend. An anomalously strong system will be arriving into the PacNW by late Friday and should dig deeper across the West into early next week. CPC guidance hints at the changes coming upstream and this system could be strong enough to bring more Spring-like weather back to our region in the form of gusty gradient winds. The scenario would definitely heighten fire weather concerns and will be something to monitor over the next several days of models and associated ensemble runs. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1112 PM MDT Fri Jun 7 2024 Showers and isolated thunderstorms will track across northern Utah and Colorado through sunrise with more redevelopment expected again Saturday afternoon. Gusty outflow winds will be the main concern with VFR holding over the next 24 hours. && .HYDROLOGY... Issued at 332 PM MDT Fri Jun 7 2024 High elevation snow will continue to melt under these anomalously warm spring conditions. Cloud cover from today`s showers and storms could suppress the rate of snowmelt, however, additional precip would have the opposite effect. Thus, some areas under today`s passing clouds may see some temporary relief in runoff, while localized basins will see a ramp up from measurable rain and/or rain on snow. Due to these highly localized influences, confidence in how major streams and rivers respond remains low. Following current guidance and river trends, we`re expecting an increase in flows along the Colorado Headwaters. More specifically, Gore Creek, Eagle River and the Roaring Fork River Basin have all shown an increasing trend over the last 24 hours. Current advisories all remain in place through the weekend, and we`ll continue to monitor for any expansions to highlights or for any chance these could upgrade to a warning. Flow/stage in the Elk River in Routt County have slowed down, coming in just under Action Stage last night/this morning. Forecasts have dropped below minor flood stage, however, I am hesitant to take down the warning due to uncertainty in rain on snow potential and another crest approach minor flood stage tonight/Saturday morning. Improving conditions are anticipated following this weekend, as large diurnal swings taper off next week. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BGB LONG TERM...15 AVIATION...TGJT HYDROLOGY...ERW