Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/15/19

Area Forecast Discussion
National Weather Service Denver/Boulder CO
853 PM MST Thu Feb 14 2019 .UPDATE... Issued at 850 PM MST Thu Feb 14 2019 Confidence is lower in seeing freezing drizzle or rain this evening over the urban corridor and eastern plains after reviewing the newer guidance, as well as the current conditions. Lower clouds are forming near the foothills in the upslope flow, and beginning to spread east, while 0.5 degree radar echoes are increasing from the south. This would point to more possible ice crystals for a seeder-feeder process being able to form snow, rather than freezing drizzle. Viewing recent ACARS soundings from aircraft, there is a little warm layer around 700-750 mb which is above 0 degrees C, with below freezing on top and below. All of this together makes me think if precipitation does form, it should arrive at the surface as snow or sleet. I can`t totally rule out some localized spots of drizzle, but confidence is less in seeing it this evening. The better chance to see this is farther east, over the northeast plains. Another confusing point, is the 00z NAM shows precipitation around the Urban Corridor and nearby plains between 09-12Z, however the westerly downslope winds will be increasing at this point as well as QG ascent weakening and become downward motion. So confidence in this model is low. Snow continues to increase over the mountains with visibilities lowering and roads becoming more snowcovered via webcams. Winter weather advisory is now in effect until tomorrow morning. Snow should be heaviest for about the next 6 to 8 hours before trending down. && .SHORT TERM...(This evening through Friday) Issued at 242 PM MST Thu Feb 14 2019 Snow will increase again late this afternoon and early evening over the north central mountains as the next Pacific wave hits the state. Radar showing a large area of precipitation over the Four Corners area. Moisture will continue to stream east-northeast into the state through the night. Even with the unfavorable southwest upper level winds, expect enough moisture and forcing to produce 4 to 8 inches of snow across the north central mountains. Will continue the Winter Weather Advisory for this. Challenging forecast for the Front Range Urban Corridor and eastern plains for tonight. The models are doing a very poor job resolving the cold front and the amount of cold air behind it. Even the HRRR has been quite bad. The 18Z HRRR temperature 2HR forecast (for 20Z) was 16 degrees off. Feel confident temperatures will be below freezing across northeast by the time precipitation forms. This will lead to snow or freezing drizzle/freezing rain. There may be two mechanisms for precipitation. First, scattered precipitation is expected to move off the mountains and across eastern Colorado. This will fall as snow, unless there is a layer of above freezing temperatures above the cold surface. A few models show this, most don`t. A deeper layer of saturated air near the surface may form due to the cold and moist air and produce freezing drizzle. Models don`t show this happening, but with this airmass being colder and deeper than the models forecast, can`t rule out freezing drizzle. Will add this to the forecast. Precipitation amounts over eastern Colorado will be light with snowfall around an inch or lees. It will quickly dry out behind this system Friday morning with sunny skies for most of the area by late morning. Some moisture will get trapped against the mountains and produce cloud and light snow Friday. Windy conditions are expect late tonight and Friday in the foothills where gusts to 50 mph will be possible. Models indicate the cold air will scour and shift off to the east. Somewhat skeptical about the amount of warming over the plains and especially for the low lying area across the plains. Lower temperatures some, but still expect a mild day. .LONG TERM...(Friday night through Thursday) Issued at 242 PM MST Thu Feb 14 2019 For Friday night into Saturday, a low center off the Pacific NW coast will bring a 180+ kt jet around the base of the trough into the Great Basin late Friday. With the region being under the better lift of the LER of the jet, QG values are higher with good instability into Saturday morning. This will bring another decent shot of snow to the mountains early Saturday with gusty winds through the day. Over the plains, a deep lee side sfc low will keep precipitation at bay through the majority of the morning Saturday with a slight chance of snow with the help of a cold front dropping South by the afternoon. Surface winds will generally be from the NW to W that will increase downsloping effects along the front range and could keep most of the precip more over the eastern plains. Highs for Saturday will be in the 40s with lower temperatures over the eastern plains. For Saturday into Sunday, the upper disturbance will continue to push through the state with the GFS slightly slower than the EC. Snow will continue in the mountains but will come to an end gradually over the far eastern plains as the surface low slips SE across the OK panhandle. A deep low will transition across the northern portions of the CONUS pushing the jet across the South. this will keep the state under NW flow with weak moisture. This will allow for a slight chance of snow in the mountains through Sunday with highs in the lower 30s and overnight lows in the teens on the plains. For next week conditions will become colder with an arctic push from the NW. Sunday into Monday an upper level low over southern CA will begin to move eastward as a secondary system over the northern rockies moves SE. Models show the best QG ascent and lift across the southern rockies with decent moisture in the lower and mid levels from SW flow aloft. This will bring snow to the central and Southern mountains of the State starting overnight into Monday. For the plains, cold, surface high pressure will be south with winds transitioning to a NE direction and increase upslope flow along the foothills Monday morning. This will increase chances of light snow for the plains. With little jet support and the main QG south, expect light snowfall amounts on the plains. Temperatures Monday and through Thursday will start to reflect this cold push with highs in the 20s and low 30s with overnight lows in the single digits. By Monday night into Tuesday, the secondary trough will push SE from CA and move across the state Tuesday morning. Models are showing decent moisture from the SW but with surface winds from the SE, upslope flow will be limited so only expect light accumulations. By Wednesday, the trough will have pushed through drying out conditions and leaving the colder air in place. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 850 PM MST Thu Feb 14 2019 Low clouds are expected to form after 04Z, with ceilings falling below 1000 feet. There will be a chance for snow, with a tiny chance of seeing freezing drizzle as well. Precipitation is expected to be light. Low clouds and possible fog will move in as a Denver Cyclone wraps in the moisture and last through most of the night into the early morning hours. Dry air quickly moves in Friday morning helping to clear skies out. The low clouds should scatter out by 15Z. Gusty east winds will continue at the Denver airports through 04Z before winds turn northerly direction behind a Denver Cyclone that will develop somewhere around southern suburbs, then shifts east of the area. For Friday, light winds are expected during the morning with gusty west winds possible after 16Z. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 9 AM MST Friday for COZ031-033-034. && $$ UPDATE...Kriederman SHORT TERM...Meier LONG TERM...Bowen AVIATION...Meier/Kriederman