Extended Forecast Discussion NWS Weather Prediction Center College Park MD 302 PM EDT Sun Mar 13 2022 Valid 12Z Wed Mar 16 2022 - 12Z Sun Mar 20 2022 ...Overview... Several systems will quickly pass through the lower 48 during the extended period within the relatively progressive and gradual amplifying flow. The initial system over the Southeast will track up the Carolina Coast before exiting into the Atlantic. Low pressure organizing Thursday over the Southern Plains is expected to lift northward through the Central U.S. Friday into Saturday bringing active weather to central/eastern U.S. while the Pacific Northwest remains unsettled with widespread precipitation likely returning next weekend. No significant cold air outbreaks are anticipated and temperatures will oscillate between normal and much above normal ahead of the various waves of low pressure. ...Guidance Evaluation/Predictability Assessment... The latest guidance is fairly clustered with the gradually amplification of the flow over the lower 48 through the first half of the period. Spread does begin to increase with the timing and amplification by the end of the weekend and into next week. A general blend of the ECWMF/GFS/CMC/UKMET was applied initially and continued to provide predictability with the main synoptic features over the CONUS. As previously note, the GFS is persistent on remaining the faster/progressive solution within the cluster and this is causing the QPF placement to be further north/east especially across the Plains and Southeast U.S. with the first system that passes through and with the one over the Plains. For day 6 and 7, the overall flow pattern will amplify, favoring deep troughing over the West and the East. Given the degree of spread, the ECWMF ensemble mean and the GEFS mean were included beyond day 5 increasing in its weighting to 40 percent by the end of the period. ...Weather Highlights/Threats... Widespread showers and thunderstorm are expected across the Gulf Coast states and Southeast as a slow-moving system tracks through Wednesday and Thursday. There may be elevated risk for excessive rainfall along the coastline where there will be better alignment of large scale lift and moisture advection. The next wave of low pressure lifting through the central U.S. into the Great Lakes late Thursday into Saturday will work with increasing Gulf moisture and large scale lift. This should result in an expanding area of showers and thunderstorms with some potential of winter weather on the cold/northwest side of the system. The exact details on any significant accumulations are too uncertain at this time. Another large scale and potentially strong system is expected to pass through the West bringing beneficial rainfall to the Pacific Northwest and perhaps as far south as central California. No major Arctic air intrusions are expected through the period and temperatures will generally trend normal to above normal with the greatest departures from normal expected along/ahead of the various waves of low pressure moving through the flow. Campbell 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