Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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997 FXUS65 KGJT 100334 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 934 PM MDT Thu May 9 2024 .KEY MESSAGES... - Snowfall will favor the eastern Uinta mountains in northeast Utah and the higher elevations of the San Juans and central Colorado mountains through Friday. - Snow amounts in excess of 6 inches have a 50 to 60 percent probability of occurring over the highest peaks of the eastern Uintas...eastern San Juans and Elk mountain over the next 36 hours...with lesser probability of at least 30 percent along the travel corridors. - Unsettled conditions will persist through the weekend along with a slow warming trend...however temperatures will remain below normal. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 301 PM MDT Thu May 9 2024 The Plains Rex block has successfully retrograded back to the Intermountain West this afternoon with the main shear axis laying across our CWA. Water vapor is showing a clearly defined wave moving eastward across northern Utah which has been enhancing the precipitation rates over the past 12 hours. Web cams have shown heavy snow rates falling over the eastern Uintas but as expected this modified airmass and time of year has kept snow off the roadways for minimal travel impacts. Ascent has been increasing across our southern CWA as a jet streak is rounding the main circulation...with this area of ascent continuing to lift northward across the CWA overnight as a well defined zone of deformation. In additions the increasing low to mid E/SE flow pulling in Gulf moisture that is pooling on the eastern side of the divide in a post frontal environment. So basically the heavier precipitation we have seen across the northwest CWA will be moving out while redeveloping over higher spine of our Southwest/Western CWA over the next 12 to 18 hours. In between is looks like a general downturn in precipitation will occur overnight. On Friday a combination of increasing isentropic upglide and heating of the day will get this conditionally unstable atmosphere bubbling and more widespread showers break out through the afternoon. With the loss of heating another downturn looks to arise tomorrow night before the main low to our West begins to eastward for the weekend. The forecast trend remains on track with our eastern high peaks seeing significant snowfall rates/amounts over the next 24 hours where 6 to 12 inches of new snow has at least a 60 percent probability of occurring. There could be some brief impacts to roadways overnight into the mid morning hours in our Southwest and central high passes...with melting likely taking care of any snowfall on roads by mid-day. Snowfall amounts and rates look limited Friday night with large scale ascent again on the increase by sunrise over our southern CWA. Below normal temperatures continue. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 301 PM MDT Thu May 9 2024 The weekend will continue to be active as the pesky area of low pressure slowly exits the region. By Saturday the closed low will be centered over the Four Corners with ample wraparound moisture resulting in scattered to numerous showers throughout the day. Mild antecedent conditions will keep snow levels high, generally above 9kft, but areas at and above this elevation can expect upwards of 2 to 5 inches of snow on Saturday. The high sun angle will mitigate impacts but, due to increased instability and forcing as the low starts to lift northeast, convection could briefly drive snow levels down. Either way, the vort max associated with the low will pass through Saturday evening before subsidence begins to settle overhead by Sunday morning. Even so, lingering moisture paired with a colder airmass and orographics will allow at least scattered showers to persist on Sunday, favoring the higher elevations along the Divide. An additional couple of inches of snow will be possible at the higher peaks but, again, little to no impact is expected. Unsettled northerly flow will keep showers in the forecast for Monday morning but a weak transitory ridge will build in from the west for the afternoon. This advection of drier air will see showers taper off in coverage, though scattered activity will continue over the mountains. For Tuesday and Wednesday moisture will once again be on the rise as a trough of low pressure begins to dig into the Intermountain West. This will kick the ridge east and see flow aloft shift to the west/southwest. Winds don`t look to increase too much ahead of this system but, by the midweek point, scattered to potentially numerous showers and some storms can be expected. Temperatures through the period will generally be below normal given the unsettled pattern. A gradual rebound will occur as we head into the new work week as flow begins to shift to a more mild component. A similar trend is expected for low temperatures through the period. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 926 PM MDT Thu May 9 2024 Isolated showers are possible tonight especially around KGUC and KASE. Another round of showers develops towards sunrise and spreads across the region through the afternoon and early evening. A few storms could occur along with 30 mph wind gusts. VFR conditions are most likely although brief MVFR periods are possible. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...MMS AVIATION...TGJT