Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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352 FXUS65 KGJT 292001 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 201 PM MDT Wed May 29 2024 .KEY MESSAGES... - An approaching front will bring slightly cooler, more seasonal temperatures tomorrow and Friday, but a warm-up is in store for the weekend. - Chances for isolated to scattered showers and thunderstorms remain along the higher terrain of the Divide through early next week. - A large ridge is expected to build in mid next week, bringing the potential for a prolonged period of well above normal temperatures and below normal precipitation. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 200 PM MDT Wed May 29 2024 As expected, showers and thunderstorms have already kicked off over the higher terrain this afternoon. While southwesterly flow aloft is advecting some slightly drier midlevel air in, a pocket of 700-500 mb moisture is firmly in place over the terrain north of I-70 and along the Divide mountains. Instability is also maximized over this region, and the fairly robust convection already occurring just confirms that this is the hot spot for the day. Although, some light returns are appearing as far south as the southern San Juans this afternoon, so a light shower at the least will be possible anywhere along the Colorado Divide. Where convection is not occurring, skies remain clear with temperatures soaring, with afternoon highs expected to be close to 10 degrees above normal across the area. It is also rather breezy out there, with areas along and north of the I-70 corridor seeing wind gusts of 30-40 mph. This is thanks to the tightening pressure gradient aloft ahead of an approaching cold front. This front, associated with a Pacific trough working across the Northern Rockies, will move across eastern Utah and western Colorado this evening and into the overnight, and should be near or just east of the Divide by daybreak tomorrow. Aside from the gusty winds mentioned above, this front isn`t expected to have a significant impact on the sensible weather for the Western Slope. It`s fairly weak, and the term "cool front" may be more appropriate as temperatures will only drop about 10 degrees in its wake, and that is really only across northeast Utah and northwest Colorado. Highs there will be near normal tomorrow, but areas along and south of I- 70 will see a drop of maybe 5 degrees tomorrow compared to today. In addition, this front will have a very modest impact on shower or storm activity, due to several factors. First, the midlevel dry air working in will begin to descend, limiting the amount of moisture available to work will. Second, the front`s passage will be after peak heating, and the modest dynamic lift will have no diurnal boost to help it along. Therefore, if anything, the front`s approach may lead to the convection across the north lingering a bit longer into the night, or perhaps spawning one or two stronger storms, but we aren`t expecting to see any robust nocturnal convection with this system. Conditions tomorrow and tomorrow night, in the wake of this front, will be dry, with sunny skies, calmer winds, and, as mentioned above, more seasonal temperatures. A stray shower or thunderstorm remains possible along the Divide, but increasing dry air will really limit coverage. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Issued at 200 PM MDT Wed May 29 2024 Zonal flow will be over the area with the polar jet displaced well to our north across the U.S./Canadian border and the subtropical jet to our south across the U.S./Mexico border. Temperatures will be near normal as a result on Friday with not much change from Thursday after this evening`s frontal passage. Moisture will edge up along the eastern slopes of the Front Range due to a trailing boundary from the previous storm system, allowing for daily isolated thunderstorms each afternoon Friday through the weekend over the high terrain along the western Colorado Divide. Not much impact is expected aside from breezy afternoon winds with mostly to partly sunny skies. The flow aloft turns southwesterly on Saturday into Sunday as a shortwave trough approaches from the Pacific Northwest and tracks across the Northern Rockies and into the Northern High Plains and Upper Midwest on Sunday. The end result is high temperatures warming once again this weekend to about 5 or so degrees above normal with breezy afternoon winds and isolated storms favoring the high terrain. Conditions should remain dry though for most areas according to latest model guidance. Heading into the coming first week of June, a large ridge of high pressure tries to build over the region as additional shortwaves move well north of the area along the polar jet, which will lay along the Canadian border. As this ridge builds, it will eventually try to push the polar jet further north into Canada. This should result in a mostly dry forecast to start off the month of June with temperatures warming into the 5 to 10 degrees above normal range by early next week. This means lower valleys of west-central Colorado, east-central and southeast Utah will be creeping into the low 90s with potential for mid and upper 90s in the southeast Utah desert valleys. The higher valleys seeing 80s and some mountain towns rising into the 70s with 60s at the higher elevations. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1150 AM MDT Wed May 29 2024 VFR conditions should prevail over the next 24 hours. Isolated to scattered showers and thunderstorms have developed late this morning over the northern and central mountains and are expected to favor the high terrain, although some drift into adjacent valleys to the east-northeast cannot be ruled out. Gusty outflow winds to 40 mph or greater are possible near any storms. Confidence was high enough to include VCTS at KHDN, KASE, KEGE and KGUC where convection is expected to continue. Otherwise, breezy afternoon winds of 20 to 35 mph are possible at times with partly to mostly sunny skies elsewhere. Gusty winds and VCSH expected to accompany the frontal passage, especially across the north this evening. Skies should clear and showers dissipating overnight. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BGB LONG TERM...MDA AVIATION...MDA