Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Thu Mar 24 2022 Valid 12Z Sun Mar 27 2022 - 12Z Thu Mar 31 2022 ...Overview... Next week an upper trough with a likely embedded low is forecast to move from the eastern Pacific into the West and then into the central U.S. by around midweek. This pattern will lead to increasing precipitation chances in the West early in the week before a deepening low in the Plains spreads rain and thunderstorms to the south-central U.S. and possible springtime snow to the northern tier. An upper ridge initially over the West causing warm weather for the West Coast to Plains will be shunted east by the trough, with moderating temperatures. Meanwhile mean troughing and coastal low pressure systems in the East should bring cool temperatures and light precipitation early in the week. ...Guidance Evaluation/Predictability Assessment... Fortunately, model guidance from the 12/18Z yesterday cycle shows better agreement overall compared to the past couple of days, particularly with the upper trough moving through the western/central U.S. Models continue to show good consensus with the ridge axis over the Rockies and troughing across the East at the start of the period Sunday, with the deeper trough/low across the eastern Pacific. After several days of waffling with timing of the trough partially related to phasing or stream separation between an upper low within the trough and a northern stream shortwave, guidance is now better aligned with showing more phasing or at least connection between the two features Monday/Tuesday. This favors a moderately progressive trough without leaving a southern stream low behind like earlier ECMWF runs did. The ridge axis should be flattened and pushed eastward somewhat by the trough while the eastern trough should lift, and models are fairly persistent with those features. By around Wednesday, more differences in the trough axis do arise as 12/18Z and the newer 00Z GFS runs maintain a closed low in the central U.S. within a neutral trough axis. ECMWF and CMC runs show more phasing by Wednesday (though perhaps with some separation again on Thursday) within a slightly positively tilted trough. These issues stem at least partly from strength and timing of the northern stream shortwaves, and these differences may take some time to be ironed out. But at least the overall pattern is coming into shape, and agreement for a surface low strengthening in the central Plains Tuesday is good, but with some differences in track after that. Thus the WPC forecast began with a multi-model deterministic blend of the 18Z GFS and 12Z ECMWF, CMC, and UKMET. Phased in the GEFS and EC ensemble means to about half by the end of the period to address the uncertainty in the details of the pattern. ...Weather Highlights/Threats... Light precipitation could linger across the Great Lakes region and Northeast early next week given strong cyclonic flow and coastal low pressure systems. As the next system moves into the western U.S. early next week, unsettled and active weather is expected for the West Coast states Sunday, which could bring mostly beneficial and welcome rains to the valleys, with the higher elevation areas of the Sierra could see see several inches or more of snow. Current model guidance shows the heaviest rain totals for southern California Sunday and Monday especially enhanced by higher terrain, which could cause flooding issues if heavy rain falls over burn scar areas. Rain and higher elevation snow will spread across the Intermountain West and Rockies Monday and Tuesday. As surface low pressure strengthens in the Plains and tracks east, more widespread rain and thunderstorms are likely for the south-central U.S. Tuesday and Wednesday. Meanwhile on the northern side of the precipitation shield, wintry mix and snow are possible for the north-central U.S. and potentially into the Northeast, but details are lacking that far out in time. Unseasonably warm temperatures are likely underneath upper ridging from the western U.S. into the Plains early next week, and temperatures of 10-25F above normal will be common. Though much of the record-breaking warmth may have phased into the short range period, some record highs and high minimum temperatures could be set or tied Sunday and Monday. Temperatures in the West will moderate closer to normal as the trough approaches, while warmer than average temperatures should push into the southeastern U.S. and moderate as the week progresses. Meanwhile the East should see below average temperatures given mean upper troughing, with highs of 10-25F and lows of 10-15F below normal over the Great Lakes and central Appalachians for the weekend and spreading into the Northeast early next week. These areas are forecast to warm nearer to normal around midweek. Tate 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