191 FXUS65 KBOU 111548 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 948 AM MDT Thu Oct 11 2018 .UPDATE... Issued at 946 AM MDT Thu Oct 11 2018 Early this morning temperatures across the eastern plain were in the mid to upper 20s. Cloud cover is expected to remain over northeast and north central Colorado through the morning keeping temperatures cool. This afternoon clouds will clear out allowing for warming into the upper 40s on the eastern plains and 30s to 40s over the mountains. The Grand Junction radar shows increasing echos that will move east over the Central Mountains as a trough enters the state. More rain for the mountain valleys and snow showers over the mountains will accompny this moisture. We have expired the Freeze Warning and will continue the Winter Weather Advisory over the Central Mountains. && .SHORT TERM...(Today and tonight) Issued at 225 AM MDT Thu Oct 11 2018 Main concern today revolves around snowfall forecast for the mountains through tonight. Northern Colorado is currently under a moderate west to southwest flow aloft with several waves developing over the Great Basin. Mountains currently have a mid level deck of clouds but further upstream, observations and radar showing an increase in rain and snow shower activity across west central Colorado. This deeper moisture will spread into the north central mountains this morning with increasing snow showers. During the day, the broad upper trof to our west splits, with the northern branch expected to shift over northern Colorado later tonight, while southern branch develops a cutoff circulation off the California coast. With the trof, jet streak and weak QG ascent expected through the day, this will result in widespread snow developing over the northern and north central mountains by later this morning. Orographic flow increases by this evening as mountain top flow shifting to the northwest and increases, with still favorable lapse rates of 6-7c/km. After midnight tonight, as the trof sweeps through, moisture depth becomes more shallow and large scale subsident flow develops. Cross sections show increasing downslope winds developing later tonight with cross barrier flow of 30-40kt. Overall will continue the winter weather advisory for zone 34 through this evening as high resolution models showing the heaviest snow through Summit county. The heavier snow may shift further north later in the day with improved orographic flow. Won't issue an additional advisory for zone 33 but certainly should be watched as snowfall potentail shifts further north. Across lower elevations, observations and satellite imagery still showing fairly widespread stratus remains on the plains with the exception of the far northeast corner with clear to partly skies with temperatures down into the mid/upper 20s. A bit warmer near the Front range under cloud cover and temperatures in the lower to mid 30s. Will still keep the freeze warning going with morning lows flirting with 32 but still not getting that hard freeze with the persistent cloud cover. Should see some warming over the plains today as we loose our upslope flow and may see temperatures break out into the 40s this afternoon. Scattered showers expected to spill out over the plains ahead of the trof with shower type mainly of the liquid variety with the warming temperatures. Showers will continue this evening before diminishing around midnight as trof kicks through and downslope flow develops over the Front Range. .LONG TERM...(Friday through Wednesday) Issued at 225 AM MDT Thu Oct 11 2018 Drier air in NW flow aloft will move across the region on Fri. Enough moisture may linger in the mtns through mid morning with a chance of light snow, otherwise it should be dry through the rest of the day. Temps will be warmer with aftn highs in the 55 to 60 degree range over nern CO. On Sat the flow aloft will become more westerly as an upper level trough moves southeast from the nrn Rockies. Meanwhile a cold front will move into nern CO by early aftn with highs likely occurring by midday in most areas. Temps across the plains will range from the upper 40s nr the WY border with generally 50s elsewhere. By late aftn a few showers may develop near the WY-CO border area. For Sat night into Sun the main upper level trough will move across the area as cold surface high pres builds into nern CO. QG fields show favorable mid lvl ascent Sat night into Sun morning along with deepening moisture and upslope flow. In addition position of upper level jet will likely lead to heavier banded pcpn across portions of the area Sat night. Snow levels will drop quickly Sat evening as colder air moves across the area with the NAM probably having the best handle of changeover to snow at lower elevations. For now advisory type snow amounts appear likely across the higher terrain, urban corridor and possibly across portions of the plains. By midday Sun the snow should gradually end from north to south as the main upper level trough moves southeast, QG fields weaken and upslope component diminishes. Highs will only be in the mid 20s to lower 30s across nern CO. For Sun night the chc of snow will end in the evening hours with clearing skies overnight. With expected snow cover, light winds and clearing skies overnight temps will drop into the teens over nern CO with record lows possible. For Mon dry NNW flow aloft will be over the area as sfc high pres moves southeast of the area. As a result will see dry conditions with some moderation in temps as readings rise back into the 45 to 50 degree range over the plains. Looking ahead to Tue and Wed an upper level ridge will begin to develop with dry conditions expected. Temps will across nern CO will be in the 50s on Tue and then in the upper 50s to mid 60s by Wed. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 946 AM MDT Thu Oct 11 2018 Expect some improvement of ceilings later this morning and then scattered showers this afternoon and evening as the next disturbance passes through. Gradual clearing shoukd occur later tonight with increase downslope flow and may even see surface winds return to a drainage wind from the south and southwest. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight MDT tonight for COZ034. && $$ UPDATE...Sullivan SHORT TERM...Entrekin LONG TERM...RPK AVIATION...Sullivan