Extended Forecast Discussion NWS Weather Prediction Center College Park MD 140 AM EST Sun Mar 13 2022 Valid 12Z Wed Mar 16 2022 - 12Z Sun Mar 20 2022 ...Overview... A relatively progressive and gradually more amplified flow pattern across the Lower 48 during the period will allow several storm systems to move quickly through the CONUS. To start, a Southeast coastal system will track up the Carolina coast mid-week before tracking offshore. Low pressure organizing in the southern Plains Thursday is likely to lift 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... Through day 5, the deterministic guidance offered very good agreement and predictability with the main synoptic features over the CONUS. For the Southeast system early on, the GFS is a slightly faster/progressive solution with a more northerly low track, which seems to be where guidance has trended over the last several cycles. The shortwave trough coming out into the Plains Day 4/5 looks to have the typical timing biases, where the GFS is on the faster side but otherwise the deterministic models show fairly agreeable amplitude. By day 6/7, the flow pattern is trending more amplified over the CONUS, with deep troughing becoming more favored over the western U.S. and also over the eastern U.S.. By this point, the deterministic guidance varies a lot, with the CMC vs. GFS/ECMWF nearly out of phase. For now, the deterministic GFS/ECMWF and its ensemble means have good support so the WPC blend days 5-7 was comprised of the deterministic GFS/ECMWF and GEFS/ECENS, removing the CMC/CMCE with the majority of the blended weights toward the ensemble means. ...Weather Highlights/Threats... The slow moving southern stream system tracking along the Gulf Coast and Southeast will draw up plenty of moisture and combined with sufficient instability and forcing should bring widespread thunderstorms Wednesday-Thursday. Some threat of locally heavy rainfall exists along the coast where better ingredients look to exist. 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, though details on any significant accumulations are too uncertain at this time. Finally, by next weekend, another large scale and potentially strong system will move into the western U.S. 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. 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 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