Extended Forecast Discussion NWS Weather Prediction Center College Park MD 211 PM EDT Tue Mar 16 2021 Valid 12Z Fri Mar 19 2021 - 12Z Tue Mar 23 2021 ...Overview... Upper ridging will continue a stead shift eastward Friday through the weekend starting from over the High Plains and southern Canada on Friday and reaching Labrador and the East Coast by Monday. A trough over the East Coast Friday will lift northeastward but trailing energy will likely linger over the Southeast through Monday before slowing shifting offshore, keeping an active pattern for Florida. A system over the Pacific Northwest Friday will shift east to the northern Great Plains by Monday, but a reinforcing trough will dig over the Southwest this weekend before turning northeast over the central part of the CONUS by Tuesday as another low pressure system tracks from the Gulf of Alaska to the Pacific Northwest. ...Model Guidance/Predictability Assessment... A deterministic blend of the 00Z ECMWF/06Z GFS was preferred through the weekend for the trough exiting the Northeast Friday night and the trough over the Northwest and the amplifying trough over the Southwest this weekend. The 00Z Canadian was much stronger with the east coast trough/low as it moves offshore. Out west the 00Z CMC was faster with the progression in the Northwest and the 00Z UKMET was more amplified with the trough in the Southwest. Early next week there were timing and strength differences with the next wave from the Gulf of Alaska with the 00Z ECMWF stronger and more progressive than the 06Z GFS and 00Z CMC, so the preference favors the 00Z ECENS mean and 06Z GEFS mean for Days 6 and 7. ...Weather/Threats Highlights... A slow exiting cold front over the Southwest looked to maintain precip chances along the coastal portions of the Southeast into Florida over the weekend and maybe Monday (for south Florida) depending on how close any systems that develop along the front may be. High pressure over the northern Mid-Atlantic will maintain cool temperatures this weekend for the Carolinas into Florida while return flow over the central part of the country makes for above normal temperatures (up to 20 degrees above normal) to spread east from the northern Plains Friday across the Great Lakes this weekend and the Northeast next week. Near record high temperatures are possible this weekend over the far northern Plains. The western system will spread low elevation rain and higher elevation snow from the Pacific Northwest to the Northern/Central Rockies and northern Great Basin into Monday as the southern portion of the upper trough slows the system progression. Precipitation will expand eastward as surface low pressure organizes to the lee of the Rockies and lifts northeastward, drawing in Gulf moisture ahead of the front. The next low pressure system brings precipitation mainly to the Pacific Northwest on Monday. Cooler than normal temperatures along the West Coast expand east to the Rockies behind the front. Jackson 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