Extended Forecast Discussion NWS Weather Prediction Center College Park MD 221 PM EDT Wed Mar 23 2022 Valid 12Z Sat Mar 26 2022 - 12Z Wed Mar 30 2022 ...Overview... Deep troughing over the eastern U.S. this weekend will favor seasonably cool temperatures from the Great Lakes to the Northeast. A few embedded shortwaves will reinforce the cool regime and bring blustery conditions and mostly light precipitation. Meanwhile, a ridge anchored over the West will break down as a large scale trough approaches and brings unsettled and active weather to the Northwest and eventually much of the West. As that aforementioned ridge moves into the Plains, temperatures soar to much above normal values which could bring record highs to the Intermountain West to the High Plains. ...Guidance Evaluation/Predictability Assessment... The synoptic setup at the start of the period /Saturday/ shows good model agreement and predictability with a western U.S. ridge and eastern trough. A few embedded shortwaves will move through the cyclonic flow this weekend over the Great Lakes with one particular Clipper helping to induce cyclogenesis off the New England coast Sunday into Monday. Here, model differences are fairly minimal now and a near equal blend of the latest available deterministic guidance was used. The larger model differences are to the west tied to the progression and amplitude of an eastern Pacific trough, particularly the southern piece of that energy. As the positively tilted trough axis reaches the western U.S., some guidance favors closing off a upper low well offshore southern California (i.e. 00Z ECMWF) while others are closer to the coast/inland or more progressive (GFS/CMC). The trend has been for a slower solution that may close off, but perhaps not to the degree the 00Z ECMWF (and its previous runs) suggest. It largely depends on how much phasing or lack of with the northern stream - the ECMWF favors more separation and allows the northern stream energy to race out faster compared to the more phased GFS solution, especially by day 6/7. Either way, the models do show that the troughing reaches the Rockies into the Plains by the end of the period where a strong surface low may materialize. It's a lower confidence forecast, especially from day 5 onward as the energy reaches the Intermountain West. For now, the WPC blend for day 5-7 favored a compromise of the ECMWF/GFS while including higher weights of the ECENS/GEFS means to maintain continuity some while addressing the uncertainty. ...Weather Highlights/Threats... The shortwave energy progression and strong cyclonic flow over the Great Lakes will produce mainly light precipitation across the Great Lakes into portions of the central to northern Appalachians and Northeast this weekend. The exception looks to be for the favored high terrain and upslope flow areas of West Virginia where late season snowfall accumulations could total several inches per the latest Winter Weather Outlook probabilities. As the next system moves into the western U.S. this weekend into early next week, unsettled and active weather is expected on Day 4 /Sunday/ for the Northwest then Day 5-6 /Monday-Tuesday/ for much of California, bringing beneficial and welcome rains to the valleys with the higher elevation areas of the Sierra likely to see several inches or more of snow. As that system moves into the Plains and Midwest, enough cold air on the northern fringe of the precipitation shield could allow for a wintry mix but details are lacking that far out in time. Unseasonably warm temperatures will build and expand underneath upper ridging from the western U.S. into the Plains. Highs that are 10-25F above normal will be common over the weekend from the West Coast across the Great Basin and Southwest to the Plains, and several daily record high temperatures could be set or tied. As the ridge axis shifts eastward, warm anomalies of 15-25F are likely for the High Plains Monday while the West Coast moderates closer to normal. Warmer than normal temperatures remain forecast in the south-central U.S. on Tuesday but may moderate Wednesday while pushing into the Southeast. Meanwhile the East should see near to below average temperatures given mean upper troughing, with coolest temperatures of 10-20F below normal in the Great Lakes and central Appalachians for the weekend and spreading into the Northeast early next week. Tate/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