543 FXUS65 KGJT 021038 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 438 AM MDT Mon Jun 2 2025 .KEY MESSAGES... - A surge of moisture arrives today bringing widespread rainshowers and thunderstorms. Isolated flash flooding and debris flows are possible, especially in slot canyons and below steep terrain. - Unsettled weather remains in place for the week to come featuring below-normal temperatures and periodic precipitation chances. && .SHORT TERM /THROUGH TUESDAY/... Issued at 437 AM MDT Mon Jun 2 2025 Models are in good agreement with satellite imagery and radar returns showing the low lifting into Arizona to the west of Phoenix tracking to the northeast. Radar indicates showers pushed across northern Arizona through the evening and is now moving into southern Utah, but rain didn`t start reaching the ground in northern Arizona until about midnight indicating it`s taking about four hours to saturate the atmosphere to the surface. Satellite also shows the low descending along the Pacific Coast is tracking well with the models. Look for this moisture to continue to push north into the region with showers beginning to reach the ground across the southern areas of eastern Utah and Western Colorado in the hours just after sunrise this morning. These showers will continue to push north to the I-70 corridor by about noon and fill in across the northern areas going into the afternoon. Latest models runs are keeping the frontal boundary dropping down from the northwest mostly to our north along the Wyoming border, but there is some indication it could slide south to about the I-70 corridor overnight into Tuesday before warm air advection pushes it back to the northeast out of the region. The clouds moving into the region ahead of this system look to be fairly thick and will likely blanket most of the region to limit diurnal heating except for the northern most areas. Based on the showers across northern Arizona, surface temperatures are cooling to near the wet-bulb temperature as the lower atmosphere saturates which is limiting instability and convection. This concurs with the Dynamic ensemble predicting lower CAPE`s across the region of a few hundred J/kg. This combined with the lack of upper level dynamics will limit convection today to showers through the morning and early afternoon before thunderstorms fire off. These storms will have the capability to produce moderate to heavy rain which may lead to localized flash flooding in areas prone to such and in areas where storms may train. Across the areas north of the I-70 corridor where more heating may occur, thunderstorm may be stronger especially if the front does move down into the area, but sever weather is not likely with these storms as models are indicating little shear with more backing conditions. As the low tracks east along the New Mexico border through the late afternoon and into the evening, showers will diminish under the subsidence in its wake with the skies clearing out overnight. With plenty of moisture in place across the southern areas and mostly clear skies Tuesday, look for afternoon thunderstorms again across the south extending north into the central mountains. Models are indicating the zonal flow aloft will sweep the moisture out of the northern areas limiting convection across the northern half of the region, but there is low confidence in this forecast and wouldn`t be surprised to see thunderstorms across most of the higher terrain through the afternoon. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 338 PM MDT Sun Jun 1 2025 An unsettled weather pattern remains in place for much of the week ahead leading to cooler temperatures and periodic rain chances throughout the week. After a lull in forcing on Tuesday, another low pressure system is projected to move northeast across the Desert Southwest Wednesday into Thursday. However, the timing, strength, and track are very different between the global models. We`ll have to track the trends over the next couple of days to get a better picture of what this system is capable of. There is better agreement for anomalously high PWATs (175-225% of normal) remaining in place from tomorrow`s system. This could produce another heavy rain threat with scattered to widespread precipitation chances across parts of eastern Utah and western Colorado. Lots of details to sort through between now and then, but this is definitely a period of the forecast you should remain tuned in to this week, especially if you have outdoor recreation plans. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1149 PM MDT Sun Jun 1 2025 A storm system moving up from the southwest is bringing in mid- level ceilings and rain showers overnight across the southern areas. These will continue to spread northeast across the region through the morning becoming widespread by 18Z with isolated to scattered thunderstorms embedded thereafter. These showers and thunderstorms will diminish northwest to southeast after 00Z. Expect gusty outflows winds, lightning and periods of MVFR conditions with passing storms. Conditions below ILS breakpoints will generally occur after 18Z at KASE, KEGE, KRIL, KHDN and KGUC. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...DB LONG TERM...KAA AVIATION...DB