Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 AM EST Sun Feb 21 2021 Valid 12Z Wed Feb 24 2021 - 12Z Sun Feb 28 2021 ...Overview and Guidance Evaluation... The medium range period is forecast to begin on Wednesday with generally zonal upper-level flow, with a noticeable separation of northern and southern stream flow for the middle of the week. The flow pattern should be relatively progressive through the week, as the Northwest trough deepens and tracks eastward, and then additional troughing and energy come into the West for the latter part of the week and becomes a broader synoptic scale trough over the western U.S. by next weekend. Model guidance is in generally good agreement with the synoptic scale pattern through the first half of the medium range period. The 12Z CMC was nearly completely out of phase with the model consensus across the western Pacific for next weekend, but the new 00Z run appears more reasonable. Similar to yesterday, the GFS parallel is slightly slower with most shortwave features compared to the more progressive operational GFS, and the parallel version was favored more for the WPC fronts and pressures. The 12Z ECMWF was also incorporated along with gradually increasing contributions from the EC and GEFS mean. ...Weather/Threats Highlights... The West could be moderately active in terms of precipitation through early Saturday, with heavy snow possible for higher elevations of the Cascades and the northern Rockies. There will likely be a round of moderate snow for the Colorado Rockies and Front Range on Wednesday along and west of the Interstate 25 corridor. By next weekend, a southern stream disturbance may tap enough Gulf of Mexico moisture to produce a swath of moderate rainfall across portions of the Mid-South and potentially some light wintry precipitation across portions of the Midwest. In the temperature department, the building trough and the passage of the cold front across the Intermountain West will herald a change to readings falling to 10-20 degrees below average for the western High Plains to the Rockies. Ahead of the front, temperatures will likely be about 5 to 10 degrees above average across the East Coast region for midweek. By the end of the forecast period next weekend, expect temperatures to be near to slightly below normal for most of the nation. Hamrick Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml