Extended Forecast Discussion NWS Weather Prediction Center College Park MD 424 PM EDT Tue Mar 15 2022 Valid 12Z Fri Mar 18 2022 - 12Z Tue Mar 22 2022 ...Overview... A relatively progressive flow pattern with increasing amplitude is expected to be in place across the continental U.S. through the upcoming weekend. The initial system over the Central Plains Friday will be tracking northeastward to the Great Lakes and then the Northeast through Sunday. By late in the weekend to next Monday, a much stronger and amplified trough will progress across the western U.S., and then reaching the Plains by late Monday and into Tuesday, with the overall pattern becoming a bit less progressive by then. This will likely bring widespread, beneficial rains to the western U.S., and evolve into a potentially strong storm system over the Lower/Middle Mississsippi Valley by the end of the forecast period. No significant arctic air intrusions are currently expected, and temperatures will generally oscillate between near normal and well above normal ahead of the various waves of low pressure. ...Guidance Evaluation/Predictability Assessment... The 00z guidance suite was in good agreement regarding the evolution of the synoptic scale pattern across the lower 48 during the medium range period. Therefore, a general model blend of the 00z EC/CMC/UKMET and the 06z GFS were applied through day 5. The 06z GFS was phased out by days 6 & 7 due to a markedly deeper upper-trough over the West compared to model consensus. An ensemble blend consisting of the ECE/GEFS/CMCE with some 00z deterministic EC were utilized for days 6 & 7. ...Weather Highlights/Threats... The next system moving across the Plains could bring some moderate to locally heavy rainfall and scattered thunderstorms to parts of the Ohio/Tennessee Valleys and Southeast on Friday. A new system will emerge over the Pacific Northwest on Friday, spreading much needed rain showers across the lower elevations of the Pacific Northwest/northern California as well as mountain snow over the Cascades and Rockies through Saturday. The surface wave will then strengthen beneath an amplifying upper-level trough on Sunday, allowing for snow and rain to blanket the Rockies through Monday. Moderate to heavy rainfall will spread into the Southern Plains on Monday before expanding into the Lower/Middle Mississippi Valleys on Tuesday. The amplified synoptic pattern supports severe weather activity over parts of eastern Texas into the ArkLaTex on Monday before shifting into the central Gulf coast on Tuesday. Kebede/Hamrick Hazards: - Heavy precipitation across portions of the western Washington, Fri-Sat, Mar 18-Mar 19 and Mon-Tue, Mar 21-Mar 22. - Heavy precipitation across portions of the Sierra Nevada, Sat, Mar 19. - Heavy precipitation across northern Maine, Sat-Sun, Mar 19-Mar 20. - Heavy rain across the eastern portion of the southern Plains, Mon-Tue, Mar 21-Mar 22. - Heavy rain across much of the lower and mid-Mississippi Valley, portions of the Tennessee and Ohio Valleys, and into the Midwest, Tue, Mar 22. - Severe weather across eastern/southern Texas through much of the Deep South and the Gulf Coast, Mon-Tue, Mar 21-Mar 22. - Severe weather across portions of the Southeast and into the central/eastern Gulf Coast, Fri, Mar 18. 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 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