037 FXUS65 KGJT 100146 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 746 PM MDT Tue Oct 9 2018 .UPDATE... Issued at 743 PM MDT Tue Oct 9 2018 Updated to move precipitation through NE UT and into NW CO a few hours earlier this evening than initially thought as a convective line moved quickly over the UT and CO border. && .SHORT TERM...(Tonight through Wednesday night) Issued at 409 PM MDT Tue Oct 9 2018 Out with one storm in with the next...then the next and maybe even the next. The upper low was centered nearly over the 4 Corners this morning and is slowly moving eastward as the upstream kicker storm is dropping through S.Idaho. The mix of sun and clouds has led to warmer temperatures with much of yesterday's snow now a memory. Well except over the Mesa and Uintas where it looks better than it did much of last winter. The next system is much more compact than this trough and will swing eastward as it moves out of Idaho moving across the Wyoming border through tomorrow. The large scale ascent from this storm and with the cyclonic jet undercutting it will provide plenty of lift over our CWA which should provide for another decent QPF event. The cold core of this system does move over Northeast Utah into NW Colorado where snow levels should drop down to valley floors at times. This is a case where one or two degrees...both atmosphere and pavement...could make a big difference in snow amounts and impacts. The trend has been slightly warmer in the lowest layers and expect accums along HWY 40 to stay near an inch or below from Hayden to Vernal. Some high spots to the WY border however could see several inches. Impacts are not obvious and have not put into advisory at this time. The northern mountains of Utah and much of the Colorado mountains will do well with this storm system with convection increasing snow rates tomorrow afternoon. The southern mountains will accumulate snow tonight through morning but the dendritic layer appears to be drying out through the afternoon with more showery pcpn expected. Again confidence not as high down south for widespread impacts but mountain passes should see some accumulation for the morning commute. This system dries out from south to north during the afternoon with the Park Range hanging on the longest. Temperatures suggest much of the pavement should be able to melt snow through the afternoon. Heights again lower in the SW CONUS while increasing into PACNW. This again lays out a broad positively tilted trough over the Intermountain West by early Thursday and this sets the stage for another shot of precipitation. .LONG TERM...(Thursday through Tuesday) Issued at 409 PM MDT Tue Oct 9 2018 A different scenario setting up for the Thursday - Thursday night storm. This will be affected more by the subtrop jet lifting back into the area with the warm air advection raising mid level temperatures in the south and pushing snow levels upward. An area of good f-gen will be generated farther north across central Utah and Colorado where the precipitation should be enhanced. Overall the QG forcing is weaker so the precipitation may not be as widespread but could become quite heavy in a small area near the f-gen band. Again the Grand Mesa and Flat Tops seem to be favored by this precipitation and will be watching trend for additional highlights with the second system. The models continue to trend to the West with the weekend digging trough before ridging moves farther inland to begin the new week. This looks like a quick but very cold passing system with H7 temperatures as cold as -10C moving into our northern CWA. The heaviest precipitation will likely be along and east of the divide but this will be an interesting system to watch. Also freezing temperatures in the lower elevations are likely to occur in many areas behind this system...otherwise below normal temperatures stay in place. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 547 PM MDT Tue Oct 9 2018 The next storm system will drop into northeast Utah this evening, increasing shower coverage and reducing CIGS, especially over the Eastern Uinta Mountains, by 03Z. Showers will spread east from 06Z onwards with the higher terrain of western Colorado becoming favored for Wednesday. As has been the trend this week, TAF sites can experience MVFR to IFR CIGS and lower VIS in showers. Mountains will continue to be obscured at times due to snowfall and low clouds. Snow levels will drop to 6500 feet across the north with KHDN, KASE, and KGUC likely to see showers of snow or at least a rain/snow mix during the period. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory from midnight tonight to 6 PM MDT Wednesday for COZ004-009-010-012-013. UT...Winter Weather Advisory until 3 PM MDT Wednesday for UTZ023. && $$ UPDATE...CC SHORT TERM...15 LONG TERM...15 AVIATION...MMS