Expires:No;;375016 FXUS65 KGJT 260002 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 602 PM MDT Thu Apr 25 2024 .KEY MESSAGES... - Scattered showers and thunderstorms continue this afternoon and evening, with gusty winds and small hail the main threats. - Cool and unsettled weather continues Friday through the weekend as another system moves through. Accumulating mountain snowfall is likely, mainly above 9000 feet. - Warmer weather returns again next week. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 352 PM MDT Thu Apr 25 2024 Scattered showers and thunderstorms have developed as expected this afternoon, in response to a strong mid-level disturbance rotating through overhead. The environment in place has been quite favorable for convection, characterized by strong diabatic heating, around 500 j/kg of SBCAPE... and steep mid-level lapse rates between 8.5 and 9.5C/km. Combined with forcing for ascent along a weak cold front, terrain enhancement, and modest height falls aloft, it's no surprise why current radar and satellite imagery appear the way they do. Overall, the main threat from showers and storms this afternoon and evening is gusty outflow winds with gusts upwards of 45 to 55 mph. Forecast soundings, along with this morning's 12Z GJT observed sounding, show a lot of dry air in the boundary layer... and while some of the stronger storms will be capable of producing small hail and brief heavier rain, the stout inverted V signatures suggest a lot of precip evaporating before reaching the ground. The added momentum of cooling/evaporating air aloft rushing to the surface will thus lead to an isolated wind threat through the evening hours. In fact, we've already observed this earlier today when strong outflow produced a 54 mph wind gust at Cortez-Montezuma County Airport. Otherwise, this afternoon's weather is a far cry from what we've had here as of late, with plenty of clouds and much cooler temperatures taking the edge off our early summer preview. Most storms should diminish within a couple hours after sunset with the loss of daytime heating and a stabilizing boundary layer. That being said, do expect some shower activity to linger into the overnight hours. By Friday morning, the disturbance that is currently passing overhead will be well to our east with a shortwave ridge building in from the west. This should result in a very brief period of mainly dry weather before the next storm system arrives later Friday afternoon. This next system is looking stronger than the first and will be accompanied by a much more potent cold front. Similar to today, we'll have another round of scattered to widespread showers and thunderstorms develop mainly after 21Z with gusty winds and small hail again the primary risks. In the wake of the passing cold front Friday night, attention then turns to winter as accumulating mountain snow is looking likely to round out the work week and start the weekend. While snow showers are probable in the mountains prior, the real action gets going Friday night into Saturday as strong forcing for ascent increases and becomes maximized within difluent flow and the left exit region of a strong upper level jet. The air aloft really isn't all that cold with 700mb temps generally 0C to -5C... but it will still be cold enough to support snow in the eastern Uintas and the Continental Divide mountains near and above 9000 feet. Given the late season nature of this storm and possible impacts at pass levels, decided to go ahead and issue a Winter Weather Advisory with this package for amounts of 6 to 12 inches from Friday night through early Sunday morning. For more details on how the storm plays out through then, see the long term discussion below. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 352 PM MDT Thu Apr 25 2024 On Saturday the low pressure tracks right over the forecast area, so plenty of lift and moisture in place for precipitation. Widespread showers are expected through out the day. This is supported by the high res models, which are now starting to cover that timeframe. Despite being a cold core system temperatures will be rather seasonal therefore snow levels are expected to be in that 7-9 kft range. Impacts from snow above these elevations will be limited by strong solar insolation. A few thunderstorms are possible, but the amount of instability will rely heavily on clouds clearing out. With the low center overhead wind direction will be very location and time dependent. Generally flow will go from southwesterly to westerly, but there may be a period of north/northeast winds so shower movement may be a bit chaotic compared to normal. On Saturday night the low exits out over the Plains. We should see a down tick with precipitation across our area. Although snow showers may linger in the mountains and produce messy travel around the passes. The QPF forecast has come down quite a bit in the last few model runs so confidence in the amounts is low. Just know that slick spots are possible Sunday morning generally at pass level. Moisture is slow to work out of here so with the steep lapse rates in place additional shower development is possible. Monday is looking mostly dry, but a system moving over the Northern Rockies could bring chances back to the northern CWA. Regardless zonal flow becomes established and temperatures begin to warm and by mid week southwest flow returns. This means daytime highs will be 10-15 degrees above normal. For the most part the entire week looks dry, but things could change. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 544 PM MDT Thu Apr 25 2024 The scattered showers and isolated thunderstorms across the region are decreasing and will continue to diminish through the overnight hours lingering mostly in the mountains along the Divide. The gusty winds will also drop off over the next few hours becoming light terrain driven overnight. Expect broken ceilings overnight mostly in the mountains with periods below ILS breakpoints at KASE and KTEX. Look for another round of convection beginning after 10Z becoming widespread showers and scattered thunderstorms by about 21Z across the region. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory from 6 PM Friday to 6 AM MDT Sunday for COZ004-009-010-012-013-018-019. UT...Winter Weather Advisory from 6 AM Friday to 6 AM MDT Sunday for UTZ023. && $$ SHORT TERM...MDM LONG TERM...KJS AVIATION...DB