Expires:No;;692886 FXUS65 KGJT 052340 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 540 PM MDT Sun May 5 2024 .KEY MESSAGES... - Very strong winds continue through this evening for much of eastern Utah and western Colorado today, with gusts up to 65 mph for the valleys and 80 mph for the mountains. - A strong spring storm is still on track to bring widespread precipitation tonight and Monday with significant mountain snow expected across the northern Colorado ranges. Light snow accumulations are possible for the higher valleys as well as most other mountain ranges by sunrise Monday. - Much cooler and unsettled weather will be the rule for the rest of the week ahead as several disturbances keep mountain showers in the forecast most afternoons. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 317 PM MDT Sun May 5 2024 As expected, its been a bit windy across the Western Slope today. Our anticipated upper level trough and associated strong cold front continues to approach from the west this afternoon, leading to an ever-tightening southwest gradient overhead. Surface gusts have consistently been in the 45 to 55 mph range with some of the higher elevations gusting in the 65 to 75 mph range. This has been the standard for more than two-thirds of the forecast area with several locations having already hit their high wind criteria today, most notably in the northern zones. These strong winds in the warm sector of the upcoming trough have allowed temperatures to climb several degrees above the norm for early May, though the rapid uptick in clouds has slowed the warming in the last hour or so. Suffice to say, today has been the quintessential sign that big changes are on the way. The cold front is still on track to be right on our doorstep around sunset before quickly pushing southeast across northeast Utah and northwest Colorado tonight. Showers will continue to spread from west to east in response, remaining high-based at first with some more of those pesky winds before the profile gradually saturates. Plenty of forcing associated with this system as the base of the low swings through by mid to late Monday morning. That means conditions could rapidly deteriorate, especially in the high country. As noted previously, rates around an inch per hour cannot be ruled out with snow levels quickly dropping to the 8-9kft mark with the front. Even though winds will weaken once the front passes, when it comes to travel impacts it will barely be noticeable with continued strong winds of 40 to 50 mph in the mountains. Therefore, went ahead and expanded the Winter Weather Advisories to include zones 10, where a quick 3 to 6 inches of snow will fall at those higher sites tonight under those blustery conditions. Borderline criteria remains in the remaining southern and central Colorado mountains but with this quick system confidence is not high enough on the impacts being in more than half of the zone. Monday's forecast remains on track as wraparound moisture impacts the region. Instability in the wake of the front paired with orographics will keep showers and perhaps some embedded storms along the Divide. Denser cloud cover and showers will begin to dissipate elsewhere. The much colder airmass will drop Monday's highs back down to well below normal. On Monday night another piece of energy wrapped around the larger upper level trough will drag across the northern tier of the forecast area. This will see at least scattered showers occur Monday night and into Tuesday morning. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 317 PM MDT Sun May 5 2024 Large scale troughing will dominate the western half of the country by Tuesday, with westerly to northwesterly flow in control over eastern Utah and western Colorado. Moisture wrapping around the low pressure center in the Northern Plains will combine with some subtle waves in the flow aloft to bring rain and snow showers across the higher elevations of northeast Utah and northwest Colorado. This moisture will be modest, but decent dynamic lift with the passing wave and favorable orographics will bring generally 2-4 inches of snow to elevations above 8500-9000 feet in the Flat Tops, Park, and Elkhead ranges. More substantial accumulations are possible in the Park Range above 9500 feet, and the need for a Winter Weather Advisory cannot be ruled out just yet. Outside of these areas, however, Tuesday will be generally dry and on the breezy side. A reinforcing shot of cold air will accompany a largely dry cold frontal passage early on Wednesday, although a few light showers at the higher elevations cannot be completely ruled out. Winds will relax in the wake of this front as the jet core aloft moves east and the entire jet stream sags south of the Four Corners. This also means some very cold morning lows are possible Wednesday morning. Current guidance now has a low of 32F in Grand Junction which, if it verifies, would break the previous record of 33F for that date, set in 1979. In addition, large portions of the forecast area are looking at lows in the 20s and low 30s for Wednesday and Thursday mornings. This could be a problem for agricultural interests as the growing season is well and truly underway at this point. Be sure to stay tuned to the forecast over the next several days, because the potential need for freeze highlights is increasing. The pattern gets much more complex from Wednesday onward, making the forecast difficult to pin down. Ensemble and deterministic model guidance are starting to come around to a solution where the center of low pressure in the northern plains begins to elongate and retrograde west into the southern Great Basin. At the same time, high pressure begins to build into the Pacific Northwest, setting up a Rex Block over the western half of the country. There's suggestion of this elongated area of low pressure spinning off its own cutoff low over southern Nevada and northern Arizona, with eastern Utah and western Colorado coming under weak southerly flow. This would advect some warmer air into the region which, in addition to the general moderating of the cold airmass aloft, would account for the gradual warming trend during the late week period. It's unclear how much moisture this area of low pressure would be able to tap into, but even some modest moisture would be enough to keep those pesky afternoon mountain showers in the forecast through the end of the week. Blocky patterns like these tend to stick around for a while, and models typically have difficulties in such scenarios. A large amount of uncertainty remains for the end of the long term period, as models are all over the place over when the cutoff low finally gets kicked back into the westerly flow and dragged out of the Desert Southwest, and what exactly that means for us here in eastern Utah and western Colorado. Temperatures will remain near to much below normal through the period, warming up to near normal values by late week. Tuesday and Wednesday will see high temperatures running generally 5-10 degrees below normal, with highs almost 20 degrees below normal across northeast Utah and northwest Colorado. Lows on Wednesday and Thursday mornings are set to run 5-10 degrees below normal before also moderating by the end of the week. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 526 PM MDT Sun May 5 2024 Gusty winds of 35 to over 55 mph have been noted across much of the forecast area today with TAF sites also seeing some of these higher gusts. Sustained wind speeds of 30 to 40 mph have also been noted. Showers have formed ahead of a strong cold front but, as of now, no precip being reported on the ground as most precip is evaporating. This will change as the front moves through this evening and overnight where rain and snow will bring some MVFR to the area. Some of these MVFR conditions may persist through 12Z if not beyond especially for KASE and KEGE. Gusty winds will likely continue overnight though should be somewhat lighter than seen this afternoon. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...High Wind Warning until midnight MDT tonight for COZ001-003- 006-011-017-020. Wind Advisory until midnight MDT tonight for COZ002-007-008- 021-022. Winter Weather Advisory until 6 PM MDT Monday for COZ004-010- 013. UT...High Wind Warning until midnight MDT tonight for UTZ022-024- 025-027>029. Wind Advisory until midnight MDT tonight for UTZ023. && $$ SHORT TERM...MMS LONG TERM...BGB AVIATION...TGJT