Extended Forecast Discussion NWS Weather Prediction Center College Park MD 250 PM EDT Wed Mar 31 2021 Valid 12Z Sat Apr 03 2021 - 12Z Wed Apr 07 2021 ...Overview... Upper ridging over the northern Atlantic and northeastern Pacific will favor troughing just off the West Coast, moving inland, and a closed low off meandering off New England. In between, ridging will ease out of the Rockies/Southwest into the Plains this weekend before translating through the Upper Midwest next week into the Great Lakes and Mississippi Valley. Split in the jet will provide a drier than average period for the lower 48. ...Guidance Preferences and Predictability Assessment... Model/ensemble guidance suggested that a deterministic blend to start the forecast was adequate (GFS/ECMWF/Canadian/UKMET) with the developing/deepening systems off both coasts. The UKMET and then the GFS were withdrawn from the preferred blend (near the Canadian and ECMWF) after Sunday due to their quicker handling of the western pattern and perhaps mishandling of the incoming shortwave out of Alaska (GFS). Off the East Coast, the models were relatively better-clustered given the blocked pattern. Maintained a preference for a slower, but not slowest, trough/upper low track toward California which was most like the 00Z Canadian as the ECMWF was again on the slowest side, at times, of the ensemble spread. The 00Z ECMWF ensemble mean was next preferred due to its handling of the pattern over the eastern Pacific as a whole but the GEFS mean was only slightly quicker and was reasonable overall. WPC continuity also provided great input by next Wednesday with the speed/definition of the upper and sfc features. ...Sensible Weather and Potential Hazards... Most of the continental U.S. should be relatively quiet in terms of precipitation through the upcoming weekend, with no episodes of heavy rain expected since a large surface high will be governing the overall weather pattern across the central and eastern states. Precipitation coverage should begin to pick up in coverage and intensity across portions of California, Washington, and Oregon as the Pacific storm system slowly approaches that region by Monday and into Tuesday. This could potentially bring some heavy snow to the Sierra Nevada early in the week and perhaps reach the northern Rockies by the middle of next week. Rainfall should be generally light over some valley locations in northern California and perhaps more modest near the CA/OR border along the coast. In the East, a weak system may bring some light rain to the Great Lakes next week while the Atlantic system stays just offshore with most of its precipitation. Temperatures will still be chilly for much of the eastern half of the nation this weekend, although modifying some compared to Friday. Widespread sub-freezing low temperatures are likely Saturday morning from the greater Atlanta metro area through central South Carolina into North Carolina (and points northward and northeastward). This will include areas that are already beyond their normal last freeze date. Very warm temperatures are forecast for much of the central U.S. in time for the weekend, as an upper level ridge builds in along with southerly flow ahead of the next frontal boundary. This will result in readings 15 to 30 degrees above normal. Highs could reach near 70 along the Canadian border, low to mid 80s across portions of Nebraska and South Dakota, and well into the 90s for the lower elevations of the Desert Southwest. Daily record highs may be exceeded in some locations. Some 100 degree readings likely in the hotter desert locations. A slow cooling trend is expected for the West Coast as the upper trough/low moves through. Fracasso/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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml