Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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823 FXUS65 KGJT 011150 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 550 AM MDT Sat Jun 1 2024 .KEY MESSAGES... - Isolated to scattered thunderstorm development remains a threat each afternoon through early next week with gusty outflow winds more likely than wetting rainfall. - 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 SUNDAY/... Issued at 400 AM MDT Sat Jun 1 2024 Even though transitory ridging works in from the west today, the flow will stay primarily zonal with several embedded shortwaves moving through the flow this weekend. One such weak shortwave tracks across this afternoon with a more robust shortwave this evening, which should work on available moisture and instability to generate isolated to scattered showers and thunderstorms. Most activity will initially favor the high terrain but with the more robust shortwave this evening, activity could spread into the northwest Colorado valleys. Areas north of I-70 still hold the best instability with CAPE north of 500 J/kg, while areas south of I-70 are less than 200 J/kg. Storm coverage could be a bit better today than previously indicated based on these reasons as well as latest hi-res guidance which shows a bit more coverage, especially up north. Although moisture is elevated with mixing ratios upwards of 4 g/kg today, the low levels still remain dry with inverted V sounding profiles, so expect gusty outflow winds to be more of a threat than wetting rain. Not expecting much in the way of rainfall but winds could gust 40 to 50 mph with any storm outflows, especially across the north. Overall, mostly dry conditions and above normal temperatures are expected today despite any showers/storms which should be more high based and virga producing, again isolated to scattered in coverage. Some storms could linger past sunset given forcing from the shortwaves, with any remnant isolated activity likely clearing out or dissipating by midnight. Following on the heels of today`s activity is another shortwave, again clipping the northern areas Sunday afternoon. Coverage looks to favor the high terrain for areas mainly north of I-70 with this shortwave with limited precipitation and more gusty outflow winds from any convection. Temperatures are expected to be warmer today than yesterday and similar on Sunday with highs 4 to 8 degrees above normal. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 400 AM MDT Sat Jun 1 2024 Flow aloft turns northwesterly Sunday night as the shortwave slides over the Front Range and out onto the Plains. Another low pressure system drops south out of the Gulf of Alaska off the BC Coast Sunday and turns east to track along the Canadian Border Sunday night into Monday. With the approach of this trough, look for gusty west winds Monday generally along and north of I-70. Though this system stays well to the north, the southern edge of the trough will brush the northern areas of eastern Utah and Western Colorado Monday night into Tuesday. Models are indicating that this trough will drag a significant patch of moisture currently south of the Aleutian Islands over the North Pacific into the Pacific Northwest and down into the region with IVT`s of 300 to 400 kg/m/s along and north of the I-70 corridor, and IVT`s approaching 200 kg/m/s pushing south into the Four Corners area. Pwats climb above 200% across the region with this surge. Guidance still isn`t picking up on this limiting PoPs to 20% over the Uinta and Park Mountains and less than 10% elsewhere. With the left exit region of the jet passing over the northern areas Monday night, expect nocturnal thunderstorms possible generally north of the I-70 corridor. The trough also tightens the pressure gradient with linear shear values around 30 kts, and a cool front pushes south into the region to about I-70, so wouldn`t be surprised to see an isolated stronger storm possible. This is definitely something to keep an eye on over the next day or two to see if the models pick up on this. As the trough and associated jet moves east, the right exit region moves in over the northern areas and ridging builds in from the southwest putting eastern Utah and Western Colorado under subsidence, clearing out the skies somewhat Tuesday allowing diurnal heating to spawn isolated orographic showers and isolated thunderstorms over the region through the afternoon. The high pressure continues to build in over Intermountain West Wednesday and even though the subsidence will tend to cap convection, expect diurnal heating to spark isolated light showers over the higher terrain with a possible isolated clap of thunder. Models are in concurrence with a Pacific low moving in off the Baja Coast Wednesday and the high pressure sliding southeast over New Mexico, Texas and northern Mexico Thursday which opens the door to a subtropical flow under the high and up into the region Thursday into next weekend. Look for afternoon and evening showers and thunderstorms becoming widely scattered across the region through the latter half of the week. Temperatures start the week at six to eight degrees above normal Monday with a slight dip Tuesday as the trough passes. Wednesday onward will see temperatures climb to 10 to 15 degrees above normal with high sitting over the region. Look for the lower desert valleys to possibly hit the century mark late in the week. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 550 AM MDT Sat Jun 1 2024 ACCAS will increase across the forecast area this morning with isolated to scattered thunderstorm development this afternoon, favoring the high terrain. Expect mostly to partly sunny skies for most areas with breezy afternoon winds to 25 mph at times. Gusty outflow winds can be expected near any shower or storm activity with gusts up to 45 mph possible. Expect VFR conditions to prevail for the most part. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MDA LONG TERM...DB AVIATION...MDA