Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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871 FXUS65 KGJT 302030 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 230 PM MDT Thu May 30 2024 .KEY MESSAGES... - Chances for isolated to scattered showers and thunderstorms remain along portions of the higher terrain each afternoon through early next week. - Temperatures remain above normal this weekend into early next week...an expanding ridge aloft next week suggests temperatures are likely to climb even higher by midweek. - The warmer temperatures means runoff will be well underway with most major stem rivers showing rises over the next several days. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 230 PM MDT Thu May 30 2024 Temperatures have been noticeably cooler since 24 hours ago by up to 10 degrees in some areas up north in the wake of a cold front. The front has swept moisture into the southern CWA per GOES ALPW images and this is where weak convection has been firing over the past few hours. The threat...along with gusty outflow winds...will persist through sunset then quickly die off. Another batch of moisture is already moving on shore in the PacNW and will arrive for another round of weak convection tomorrow. Though mainly isolated in nature the storms should spread to much of the other higher terrain by early afternoon. CAPE remains minimal which will limit overall updraft strength but a few gusts over 45 mph have a small probability (<20%) of occurrence. Cloud cover will be more robust tomorrow with the arrival of the moisture but temperatures should warm several degrees over today`s cooler readings and end up near normal. Looking at the crystal ball these readings are going to feel cool as we are heading toward the possibility of our first triple digit reading in the CWA by late next week. This heat will continue to work over the last of the snowpack and forecast are for many of the main stem rivers to continue to rise and possibly peak within this same time frame. The threat of flooding remains low but both smaller tributaries and larger river systems will still be running fast and cold. Good for play...bad for fishing...continue to use caution as we get through this runoff period. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Issued at 230 PM MDT Thu May 30 2024 With a large and relatively stationary trough located over the West Coast, flow aloft over eastern Utah and western Colorado will remain zonal to southwesterly through the weekend. This will keep conditions relatively stable, with temperatures running 5-10 degrees above normal, and chances for isolated to scattered afternoon showers over the higher terrain. The trough axis finally pushes through sometime on Sunday afternoon, with a weak front tracking across northeast Utah and northwest Colorado. This also happens to be where the best moisture will be pooled, allowing for some increased storm coverage over the higher terrain. Main threats with these storms, as with any during the long term period, will be gusty outflow winds and lightning. As this trough passes through eastern Utah and western Colorado, a piece of energy peals away from the base of the trough near the California/Baja border. This patch of energy will retrograde off the SoCal coast and eventually, by midweek, become a cutoff low. In the meantime, another Pacific low, with an accompanying slug of Pacific moisture, will move into the Pacific Northwest Monday and will track east, with its base brushing the northern portions of the CWA Tuesday afternoon. This will once again lead to an expansion of shower and storm coverage over the higher terrain, favoring areas north of I-70. Now, at this point that cutoff low becomes important. In response to the deepening of this low, an expansive ridge of high pressure builds into the Southwest. Discrepancies crop up with how this ridge reaches the Desert Southwest, whether it comes from the southwest of builds in from the southeast, which then also influences the placement of the ridge axis. The ensemble and deterministic GFS favors the solution that builds the ridge in from the southeast and places the ridge axis as close to directly over eastern Utah and western Colorado possible. The ensemble and deterministic EC favors the opposite, with the ridge axis oriented more southwest to northeast and focused over California and Nevada. Therefore, the GFS solutions favor higher heights aloft, warmer temperatures, and places a pool of above normal moisture over the Four Corners to be recycled in daily convection, while the EC puts us at the edge of the heat and the moisture plume, leading to a slightly cooler and slightly drier solution. Blended guidance, naturally, favors something in between... warmer, with highs 10-15 degrees above normal, but drier, with low-end PoPs confined strictly to the Divide. But despite all these discrepancies, all ensemble guidance is placing forecast highs for the late week period in the top percentile compared to a thirty-year climatology, leading confidence to a period of unusual heat from midweek on. So strap in, summer is most definitely on its way. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1135 AM MDT Thu May 30 2024 A few afternoon breezes may cross the 25 mph threshold at several TAF sites as mixing will be deep in this warm atmosphere. In addition isolated thunderstorms will be possible over the southern Colorado mountians with an outside chance of of a storm impacting KTEX. Gusty winds over 40 mph will be the main threat. This threat will end near sunset with VFR conditions holding over the next 24 hours. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...BGB AVIATION...GJT