Extended Forecast Discussion NWS Weather Prediction Center College Park MD 136 PM EDT Tue May 18 2021 Valid 12Z Fri May 21 2021 - 12Z Tue May 25 2021 ...Southern Plains Heavy Rain/Convection Threat lingers into late week... ...Southeast-Central U.S. Heat... ...Cold and Unsettled West with Northern Rockies Snows... ...Guidance Evaluation and Preferences... The latest model guidance offered above average predictability and agreement for the early part of the medium range period (days 3-5; Fri-Sun) with the more amplified flow pattern featuring a closed low over the western U.S. and ridging anchored off the Southeast U.S. coast. Over the course of the period, the western U.S. system will fill and lift northeast as a shortwave while the Southeast ridge settles over the Gulf Coast region. By early next week, the guidance suggests another closed low dropping down British Columbia coast toward the Pacific Northwest but model timing with that feature is still uncertain. The WPC medium-range product suite was derived days 3-5 (Fri-Sun) from a composite of well clustered guidance of the 06 UTC GFS and 00 UTC ECMWF/UKMET/Canadian along with the 13 UTC National Blend of Models. For days 6-7, the GEFS and ECENS means were including as the forecast spread increases. WPC continuity is well maintained. ...Weather Highlights/Hazards... The CONUS amplified pattern as highlighted by troughing over the West, with lead south-central Plains troughing blocked by an amplified ridge out from the East. Ridge amplification offers potential for much above normal temperatures for the Midwest and the East. Some record high minimum and maximum values will be possible, with temperature anomalies 10-20F above normal. Amplified upper troughing over the West favors some moderate precipitation for the north-central Intermountain West/Rockies, including an enhanced snow focus over the northern Rockies. This occurs as post-frontal conditions cool to 10-20F below normal across the Intermountain West/northern Rockies. The focus for precipitation episodes is expected to shift toward the north-central states along a wavy stationary boundary. Moisture and instability will be focused there and some of this convective activity may spill into the Great Lakes region and drive backdoor cold fronts over the Northeast into portions of the Mid-Atlantic. Taylor 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