268 FXUS65 KGJT 290943 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 343 AM MDT Fri Mar 29 2024 .KEY MESSAGES... - Moderate to heavy narrow bands of snow will continue to impact northern portions of Utah and Colorado through at least mid morning today. Travel will be impacted in these snow bands. - The precipitation will begin to taper off and lift north through the afternoon and evening hours...but continue over the northern mountains of Colorado and Utah. - Gusty winds will develop over southern and central portions of Colorado and Utah on Saturday with a few gusts exceeding 45 mph in the southern desert valleys in the afternoon. - Unsettled conditions continue through the weekend into Monday as another Pacific storm moves through the Intermountain West and Rockies. Significant mountain snow is likely brining travel issues...especially during the overnight hours. && .SHORT TERM /THROUGH SATURDAY/... Issued at 342 AM MDT Fri Mar 29 2024 The banded precipitation has set up as across the CWA as expected and as much snow had likely fallen in some of the lower elevations as is being reported at SNOTELs. Through 3AM the northern mountains have generally received 2-4 inches with a few webcams over the Park showing a bit higher. This is likely what has fallen over portions of NW Colorado in the post frontal environment with the current band moving through Rangely attm. The front looks to have pushed up against the Tavaputs and stalled with the snow band being generated by the mid-level thermal circulation situated between an exiting jet core and one arriving from upstream. It is this upstream jet and an embedded wave that will continue to feed ascent and help release instability through the early afternoon hours. The mid level circulation weakens through the afternoon as the jet begins to lift northward in an increasing southerly flow pattern due to the digging trough off the Cali coast. So it looks like a fairly wet forecast to start the day over at least the northern half of the CWA though the southern mountains will likely get some light snow through the morning as the wave works through. The radar at least suggests we are saturating the mid levels with virga and we should eventually get some of that to the ground over the next few hours along and South of I70. The precipitation shield will continue to lift across the northern CWA this evening and clear the northern border by sunrise on Saturday. The exception will be lingering orographics across the northern mountains of Utah and Colorado. IVT suggest we will continue to see SubTrop moisture pumped into the area in the SW flow downstream of the system that will begin to edge onshore. The bulk of the dynamics are upstream however and we should see a rather quiet start to Saturday. This only lasts through the morning as eventually instability showers develop in the highly mixed atmosphere in the afternoon as we tap into the moisture aloft. This deep mixing also means winds pick up and there is at least a moderate probability (40%) of gusts exceeding 45 mph near the 4 Corners. Temperatures remain cooler across the north under the threat of more cloudiness and precipitation. In the south however it looks like we should warm near to slightly above normal the next few afternoons and may even see some 70s in the lower desert valleys of SE Utah. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 342 AM MDT Fri Mar 29 2024 The mid-level closed low pressure center just off the central California coast splits on Saturday night forming a dipole of low pressure centers. The low forming the northern pole shifts east- northeast to the Great Basin by 12Z/Sun while the southern system moves over the Catalina Islands. As the pattern evolves the northern portion of the forecast area will fall under an area of overrunning enhanced by divergence in the left exit region of the 140+ kt jet moving through the base of the positive tilt trough linking the two low centers. Precipitation will favor the northern zones with the mountains favored. The trough shifts east on Sunday and as the northern low moves over central Wyoming, the cold front associated with this system slides eastward across the forecast area during the day. Mid-level forcing is maximized over the region during this period according to Q derived omega fields and consequently, precipitation will become widespread. The upper level trough moves overhead Sunday night and Monday placing the forecast area under the col between the low over the northern Plains and the southern system over the Southwest. As a result, showers will continue across the area, though moisture levels are indicated to decline and shower activity will become less organized with convective cells become more prevalent. Snow amounts during this period suggest the potential for another round of advisories. Subsidence and drying sets in Monday night bringing an end to the active weather. From Tuesday to Wednesday a ridge of high pressure trailing this weekend's storm will move from the Inter-Mountain West to the northern Rockies. This will place the forecast under a dry, northerly flow aloft through midweek and the weather will remain uneventful. The next storm moves along the Canadian coast on Thursday driving the ridge east and results in strengthening southwest flow ahead of the front associated with the system. As a result, breezy conditions will be developing with a chance of pre- frontal showers over the north Thursday afternoon. The long range period begins with below normal temperatures in response to the cold front which moves through on Sunday with cold air likely to remain entrenched over the area on Monday. The remainder of the week will bring a steady rise in temperatures with highs near normal Tuesday then climbing to near 10 degrees above normal by Thursday. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1120 PM MDT Thu Mar 28 2024 Widespread showers across northern Utah and Colorado transition to more scattered in nature across the central CWA late this evening. MVFR to LIFR conditions will occur as a result of snow and low clouds across the northern TAF sites well past sunrise with a mixture of ILS to MVFR occur in the central and VFR stays in place to the South. Improvement will be slow to arrive on Friday but after 18Z ILS/VFR should become more common across the central and North. Passing convective showers however could quickly change conditions to LIFR through the afternoon. Moderate winds aloft will keep a threat of LLWS and mountain wave turbulence in place over the next 24 hours with some gusts over 30 mph reaching the surface at times. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory until 6 AM MDT Saturday for COZ004-009- 010-012-013. UT...None. && $$ SHORT TERM...15 LONG TERM...NL AVIATION...TGJT |