477 FXUS65 KGJT 071205 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 505 AM MST Sun Nov 7 2021 .SHORT TERM...(Today through Monday) Issued at 504 AM MST Sun Nov 7 2021 A jet streak shifting from the base of the mid-level longwave trough over the eastern Pacific crosses the Great Basin this morning en route to the northern Plains later today. The gradient aloft tightens as the system brushes the northwest corner of the forecast area this afternoon. Meanwhile, at the surface, frontogenetic forcing associated with the jet will sharpen the stalled front to the northwest of the forecast area. As the mixed layer deepens some of the energy from the stronger winds aloft mixes to the surface yielding moderately breezy west and southwest winds during the afternoon. In addition, enhanced mixing will help drive temperatures back above normal this afternoon with highs near yesterday's levels. Meanwhile, much of the cirrus associated with the jet lifts to the northeast during the day as the jet pulls away from the region. A secondary shortwave trough in the southwest flow will drive the stationary front mentioned previously into northeast Utah and extreme northwest Colorado tonight as a cold front. Latest models indicated a lot less moisture entrained in the southwest flow, so the potential for any shower activity along the frontal boundary appeared too low to mention. However, as the shortwave brushes the northernmost zones of northeast Utah and northwest Colorado on Monday, expect scattered showers to develop over the eastern Uinta mountains with more isolated activity over the Elkhead and Park Mountains. Meanwhile, the cold front is driven farther southward on Monday stalling in the vicinity of the I-70 corridor later in the day. This will bring close to 10 degrees of cooling to the north, around 5 degrees across east central Utah and west- central Colorado with only a degree or two cooling across the south. .LONG TERM...(Monday night through Saturday) Issued at 504 AM MST Sun Nov 7 2021 Ensemble guidance and 12Z deterministic model runs (00Z for ECMWF) have reduced the spread of probable solutions for the system rolling through next week. Even though timing differences persist, there has been some alignment in the general pattern across the board and therefore, has increased confidence in widespread precipitation returning to the West Slope by midweek. Beyond 00Z Tuesday, within the next 24 hours the quasi-stationary Alaskan low will finally weaken as it rolls inland over the Alexander Archipelago. The low's transition will also launch a broad shortwave trough and its elongated swath of enhanced QG lift across the Western CONUS. Tuesday afternoon is where things get a little fuzzy, in terms of timing. 12Z GFS and the tail end of the NAM12 runs initiate showers by Tuesday afternoon (though, there's little agreement as to where between the two...) However, overnight inconsistencies simmer and most solutions drag a cold front along with widespread precipitation across the CWA. Current forecast reflects snow levels hovering around 7500 to 8000 ft at midnight Wed and then continuing to drop throughout the day, despite diurnal heating. Showers will likely continue well into Wednesday evening, and even overnight for higher terrain along the Divide. As with most long term forecasts, favored ranges for snowfall will likely fluctuate between model runs until we can hone in on finer details as the storm approaches. Never-the- less, the Park and Gore Ranges, along with the Flat Tops and Elk Mountains in Western Colorado are currently in favor of ending up with the highest, on average, snow totals - likely hitting advisory level snow amounts. Beyond Wednesday, the evolution of said trough downstream returns to a more chaotic solution...but regardless, northwest flow is draped over the West Slope. Thursday remains the coldest day forecast for next week, with temps dropping 5 to 10 degrees below normal. High pressure building back in over the Desert Southwest would lead to a gradual warm up as we round out the work week, allowing temps to rebound back to normal values by the weekend. Mostly dry conditions follow this system, however, moisture spilling over the ridge from the PacNW may keep a small chance for PoPs across the northern mountain zones into the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 504 AM MST Sun Nov 7 2021 VFR conditions will prevail across eastern Utah and western Colorado. High clouds will decrease across the north this morning then increase from the south again tonight. Breezy southwest winds develop this afternoon, but will diminish rapidly this evening with normal drainage flows developing later tonight. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...NL LONG TERM...ERW AVIATION...NL