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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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256 FXUS65 KGJT 151745 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 1145 AM MDT Thu Aug 15 2024 .KEY MESSAGES... - Isolated to widely scattered showers and storms will be possible today and tomorrow, mainly along the Northern Divide mountains. Gusty outflow winds, frequent lightning, and small hail will be the main threats. - Temperatures will run near normal this afternoon, and climb around 5 degrees above normal to round out the work week. - Returning moisture late in the weekend will bring increased coverage of clouds, showers, and storms, as well as a return to near or slightly below normal temperatures. && .SHORT TERM /THROUGH FRIDAY/... Issued at 251 AM MDT Thu Aug 15 2024 With one exception, shower and storm activity has come to an end across eastern Utah and western Colorado, with mostly clear skies in control. Westerly flow aloft has continued to advect drier air into the region, with last night`s 00z GJT sounding having a PWAT of 0.68 inches. This is the lowest value recorded on a GJT sounding in over a week. This shift to a drier pattern for the next several days will bring a warming trend across the region, with highs this afternoon climbing to near normal values, and highs tomorrow topping out around 5 degrees above normal. This will also bring decreasing coverage of afternoon showers and thunderstorms as the deep dry air scours out remnant moisture. Isolated to widely scattered showers and storms will be possible this afternoon, with areas along the northern Divide most favored. With PWAT values dropping to 50-75% of normal tomorrow afternoon, coverage will be isolated at best. So while a stray shower or storm can`t be ruled out, Friday is shaping up to be generally dry and sunny. While eastern Utah and western Colorado remains under the influence of ridging through the end of the week, a deepening trough off the West Coast will bring strengthening southwest flow aloft. This will translate to breezier conditions for Friday afternoon and evening. Typically, this would bring an increased concern for critical fire weather conditions, but after a week of wetting rains across the majority of eastern Utah and western Colorado, fuels are currently too wet to be receptive to fire in many spots. So for now, holding off on any fire weather highlights. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Issued at 251 AM MDT Thu Aug 15 2024 The weekend should start off dry and hot as a high pressure ridge remains in place. PWATs will average between 0.4 and 0.6 inches Friday night into Saturday morning to start off the long term period. Meanwhile, a low pressure trough will approach the Northern California and Pacific Northwest coastline and be enough to push the high pressure ridge eastward over eastern New Mexico into the Texas Panhandle. This will open the door to a southwest monsoonal moisture tap, thereby increasing storm coverage across much of Utah by Saturday afternoon. This moisture and resultant storm coverage looks to spread into western Colorado by Saturday evening, as PWATs increase to the 0.7 to 0.9 inch range by late Saturday afternoon/evening. Given the previous few days will have been drier, this initial surge of moisture looks to result in more of a gusty outflow wind and lightning threat than heavy or wetting rain. It will take some time for the atmosphere to moisten in the lower levels. By Sunday, PWATs are already climbing over an inch which will equate to around 150 to 170 percent of normal. It seems like Sunday into Monday will provide better chances of wetting rain and locally heavy rain with storms which could result in some localized flooding especially among steep terrain, areas of training and burn scars. The southwest flow remains in place at least through Monday with several embedded shortwaves moving through the flow around the periphery of the high and ejected out of the low pressure trough off the PacNW coast. Beyond Monday, there is some uncertainty and discrepancy on the placement of the high pressure system and amount of moisture, which would impact the precipitation forecast. The high looks to meander back to the west Tuesday and Wednesday and possibly beyond into late next week, which would steer the moisture plume to our west and/or take the long way around the high to get to us from the west instead of the south. Much of the forecast also depends on what happens with this PacNW low as this can affect the placement of the high and where this moisture plume sets up. Time will tell as these details are important as we could remain active into next week or dry out towards the latter half of the week if this high retrogrades back to the west and cuts off our moisture tap. Blended guidance still keeps scattered to widespread PoPs in the forecast as at the very least this moisture gets recycled as it doesn`t appear to be any system to help drive the moisture out of here once it arrives this weekend into early next week. Temperatures will start off several degrees above normal Saturday but get knocked back down to near or slightly below normal by Sunday into early next week as moisture increases, resulting in more clouds and showers/storms each afternoon/evening. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1112 AM MDT Thu Aug 15 2024 Expect VFR conditions with generally light, terrain driven winds across the region through the TAF period. Isolated to scattered showers and thunderstorms will develop over the higher terrain through 00Z and there after diminish through the evening hours. Lightning, small hail and gusty outflow winds are the primary threats from these storms. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...BGB LONG TERM...MDA AVIATION...DB