Extended Forecast Discussion NWS Weather Prediction Center College Park MD 254 AM EDT Sun Apr 17 2022 Valid 12Z Wed Apr 20 2022 - 12Z Sun Apr 24 2022 ...Weather Pattern Overview... The departure of the strong low pressure system from New England will leave a surface high in its wake across the eastern U.S. on Wednesday. At the same time, an organizing storm system just north of the Canadian border will bring a cold front eastward across the north-central U.S. with a weakening low farther south across the central Plains. Attention then turns to the western U.S. by Friday as an amplified upper level trough becomes established over the Intermountain West, and this will support the development of a potentially strong surface low over the central/northern Plains in time for the weekend. ...Model Guidance Evaluation... The 00Z model guidance suite appears to have above average agreement on the main synoptic scale features through Thursday night, with just some minor differences in cold front timing across the Great Lakes and Midwest. By Friday, the 18/00Z runs of the GFS become more progressive with the axis of the main trough axis across the western U.S., and this difference is even more apparent going into Saturday across the High Plains. Meanwhile, the 00Z CMC and ECMWF are in close agreement and depict a closed low evolving over the Desert Southwest by Friday night, and this also has support from the 00Z UKMET. The earlier 12Z run of the CMC was much slower and on the edge of the ensemble spread. This trend continues through the weekend, and the model preference for the later half of the forecast period is for a CMC/ECMWF/ECENS blend as a starting point. ...Sensible Weather/Threats... In the precipitation department, the West Coast region is expected to remain active with a strong cold front and onshore flow directed inland across the mountainous terrain of central and northern California. This late season event will deliver highly beneficial precipitation to drought-stricken areas of California, with the potential for up to three inches of rain in some areas next week, and 1-3 feet of snow for the Sierra. Elsewhere across the continental U.S., improving weather can be expected for the Northeast as the strong storm system moves out of the region. Another round of organized showers and storms is expected to develop across the central U.S. and extending northward to the Great Lakes by mid-late week as Gulf moisture is advected northward ahead of the organizing storm system over the central Plains. Additional moderate to heavy snow is also expected for portions of the northern Rockies for Friday and into the weekend, with some snow potentially affecting western portions of the Dakotas by next weekend. Temperatures are expected to remain rather chilly from the northern Plains to the Great Lakes and Appalachians through about Wednesday, and these below average readings may persist even longer across North Dakota and northern Minnesota going through the end of the week. On the contrary, warm conditions are currently expected across much of the interior western U.S. for the majority of the forecast period ahead of the upper trough, with well above normal readings probable across the western High Plains by the end of the week and into Texas. Temperatures should also moderate for the Eastern U.S. by Thursday as the surface high moves off the coast and warmer southerly flow commences. Hamrick 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 WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml