695 FXUS65 KBOU 110356 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 956 PM MDT Wed Oct 10 2018 .UPDATE... Issued at 859 PM MDT Wed Oct 10 2018 Radar echoes have disappeared this evening over the central and northern mountains as there will be a brief break in the precip before the next system arrives late tonight. There were no major changes to the forecast with regards to the next system except to increase QPF over the central mountains between 6am and noon tomorrow. This is because a plume of moisture that is evident on water vapor over Utah and western Colorado will move eastward and will partner with the ascent from the left exit region of an upper level jet streak. This will create moderate precip amounts during this period. The Winter Weather Advisory for 5 to 10 inches remains on track with higher values reaching close to 14 inches on the western slopes. Finally, there is less moisture across the urban corridor and eastern plains this evening which should allow temperatures to drop below freezing tonight. && .SHORT TERM...(This evening through Thursday) Issued at 212 PM MDT Wed Oct 10 2018 You can see the low pressure vorticity max spinning over NW Colorado on GOES-16 WV. This feature will continue to track east over the northern portion of the state pushing the better QG ascent eastward. The best lift has pushed over the plains with increasing subsidence behind it. Light snow will continue in the mountains with gradual clearing into the evening hours. Some light snow will also persist in the foothills with upslope helping with orographic influence. At the surface, winds will go from easterly to SE by 06z helping to dry out precipitation overnight. Clouds will stick around with some fog possible over the far eastern plains, especially over the areas with some snow accumulation still on the ground. Lows will get into the mid to upper 20s on the plains and teens in the high country. A freeze warning will be in place for the Front Range and adjacent plains from 11 pm this evening until 9 am tomorrow morning. This should be the last freeze warning needed as most areas will see lows below 28 degrees. For Thursday, as the low pushes out zonal flow will return over CO with deep WSW flow through 500 mb. Moisture will be pulled up from the SW helping to bring another round of snow to the mountains for Thursday. Snow will start around 6 am Thursday with snow levels down to 7500 ft. Snow will continue into the evening hours with accumulations from 3 to 6 inches over much of the high country with 5 to 10 possible for Summit County and the higher elevations of Park and Clear Creek county. Have issued a winter weather advisory for these areas through midnight Thursday. On the plains, precipitation will increase by the afternoon but snow levels should be high enough for rain or possibly a rain and snow mixture with little to no accumulation. Highs for Thursday will stay on the cooler side once again with temperatures in the 40s on the plains and 20s and 30s in the mountains. .LONG TERM...(Thursday night through Wednesday) Issued at 212 PM MDT Wed Oct 10 2018 The ongoing snow event in the mountains Thursday evening is expected to wind down overnight as the upper trough axis in northwesterly flow aloft rotates out of the state. Drier air will begin moving into the state as upper level ridging is forecast to build in from the west. Mountain areas could pick up a few more inches of snow in the evening as the event winds down. The Winter Weather Advisory will be in effect until midnight. Some light rain or snow will be possible on the plains due to the cyclonic forcing moving overhead. Model moisture fields show deep moisture over eastern Colorado as this weather system moves overhead. Friday and Saturday are still expected to be dry and warmer across the forecast area as the upper level ridging covers the state and the airmass becomes much drier. Medium range models continue to show another vigorous positively tilted trough moving over the state Saturday night and Sunday. This will bring a strong cold front in from the north with temperatures plummeting behind the front. Strong upslope winds will develop, and a significant amount of precipitation is expected. The forecast will show a transition of rain to snow overnight, but it is possible that precipitation will not begin until after the front moves through, and it will all be in the form of snow. The ECMWF is the slowest of the models with precipitation continuing through Sunday afternoon while the GFS wraps things up Sunday morning. High temperatures across the plains will only be around the freezing mark, after morning lows drop into the lower 20s. Sunday night will be another cold night with lows possibly down into the upper teens across the plains. Mountain areas will pick up new snow as the system is moving over, but the primary generator of precipitation is going to be the upslope flow along the Front Range. The first half of next week shows upper ridging developing with a return of mild temperatures and dry conditions across the forecast area. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 859 PM MDT Wed Oct 10 2018 Ceilings will generally hover between 1000 to 3000 feet for much of the night at DEN with a possible lowering to IFR between 10Z and 14Z tomorrow morning. APA and BJC currently have borderline IFR ceilings and these are expected to increase up to MVFR conditions within the next hour or two. Visibilities shouldn't be a big issue at any airport tonight as temperatures will struggle to decrease with the thick clouds overhead. However, light drizzle or mist could develop closer to 10Z with visibilities possible dropping to around 4 miles at DEN and APA. Models currently vary greatly on the extent of the cloud cover over the airports during the day tomorrow. Since they have performed poorly with this shallow cold airmass over the past few days, there is reason to expect that low clouds will persist throughout the day instead of clearing out. Therefore, MVFR ceiling are forecast tomorrow during the day with possible IFR ceilings during afternoon showers. && .BOU WATCHES/WARNINGS/ADVISORIES... Freeze Warning until 9 AM MDT Thursday for COZ038>051. Winter Weather Advisory from 6 AM Thursday to midnight MDT Thursday night for COZ034. && $$ UPDATE...Danielson SHORT TERM...Bowen LONG TERM...Dankers AVIATION...Danielson