Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Fri Apr 15 2022 Valid 12Z Mon Apr 18 2022 - 12Z Fri Apr 22 2022 ...Weather Pattern Overview... A relatively progressive pattern through the medium-range period will periodically send fronts and low pressure systems eastward across the nation with some potential for cyclogenesis to occur over the Northeast where a broad upper trough tends to persist. The first system is forecast to move across the Great Lakes on Monday and will likely interact with another frontal wave moving across the Deep South and then potentially phase over the Northeast on Tuesday. Meanwhile, the next system is forecast to move into the West Coast Monday-Tuesday before heading across the rest of the country late next week with the main low pressure center likely tracking north of the Great Lakes. A third system from the Pacific is then forecast to reach the Pacific Northwest on Wednesday and appear to take its time moving across the western U.S. through late next week. ...Model Guidance Evaluation... Model guidance suite this morning appears to show reasonably good agreement with the aforementioned synoptic pattern evolution through much of the medium-range period. By late next week, model differences are most noticeable across the Plains where the ECMWF/EC mean develops a slightly stronger surface low over the southern Plains while the GFS/GEFS emphasizes the northern stream low/front. Earlier in the week, the EC tends to favor a stronger low to track up the New England coast while keeping the northern stream low weaker. The opposite is true with the GFS solutions. Recent model runs have trended toward an intermediate solution with this northern-southern stream interaction, while the most recent GFS indicates a much more robust coastal cyclogenesis. By late next week, the ECMWF has gradually slowed down the low pressure system moving through the Great Lakes to better agree with the GFS and CMC solutions. Therefore the WPC medium-range forecast package was a multi-model/ensemble consensus consisting of 40% 00Z ECMWF/EC mean, 40% 06Z GFS/GEFS, and 20% from the 00Z CMC/CMC mean, with more weights given to the ensemble means on Day 7. ...Sensible Weather/Threats... In the precipitation department, the West Coast region is expected to remain rather unsettled with two well-defined events. The first round of rain and mountain snow is expected late Monday into Tuesday from northern California to Washington state, and the second arriving Thursday and early Friday, extending farther south into central California and also affecting areas to the north. This will be 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 1-2 feet of snow for the Sierra. Elsewhere across the continental U.S., showers and thunderstorms will be exiting the East Coast region early in the week, followed by dry weather as high pressure settles into the region. Another round of organized showers and storms is likely across the central U.S. by midweek as Gulf moisture is advected northward ahead of the organizing storm system over the central Plains. Potential northern-southern stream interaction could bring some form of wet snow across interior New England on Tuesday. Temperatures are expected to remain rather chilly from the northern Plains to the Great Lakes and Appalachians through much of the upcoming week, and these below average readings should also include much of the East Coast region through about Wednesday as the cold Canadian surface high governs the weather pattern. On the contrary, warm conditions are currently expected across much of the interior western U.S. for the majority of the forecast period, with above normal readings probable across the central and southern Plains on Wednesday ahead of the cold front. Temperatures should also moderate for the Eastern U.S. by Thursday as the surface high moves off the coast and warmer southerly flow commences. Kong/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