Extended Forecast Discussion NWS Weather Prediction Center College Park MD 119 PM EST Thu Feb 29 2024 Valid 12Z Sun Mar 03 2024 - 12Z Thu Mar 07 2024 ...Heavy Snow and High Wind Threat for the Western and North-Central U.S... ...Wet Pattern for the West Coast and The South... ...Guidance/Predictability Assessment... Agreement between the deterministic solutions is reasonable enough for a general model blend Sunday-Monday with a leading shortwave through the northern Plains, and additional energy into the West. After this, there are growing uncertainties with combination of flow energies across central Canada, with some shortwave energy clipping the Upper Great Lakes. There are amplitude questions out West mid next week and especially with another possibly stronger system into the Pacific Northwest. Run to run varibility has improved to some degree, but still plenty of uncertainty across the board with respect to timing of systems with local weather/hazard impacts. The WPC blend for today incorporated more of the ensemble means with the deterministic GFS/ECMWF days 5-7 to account for uncertainties. This maintained good agreement with the previous WPC forecast as well. ...Overview and Weather/Hazards Highlights... A main weather story concerns the evolution of amplified upper troughing digging into the eastern Pacific that will shift earnestly over the West this weekend. This and subsequent/uncertain and varied additional Pacific systems will support multiple chances for periods of locally moderate precipitation through the West Coast next week. There are also threats for high winds and heavy snow to spread from the West Coast states inland across the Intermountain West to the Rockies, especially for favored terrain/mountains as highlighted in the WPC Winter Weather Outlook (WWO). Valley snowfalls may develop more over time as snow levels decrease with upper system and wavy frontal cooling. This translation should also favor windy wrap-back snow development from the Northern Plains Sunday to over the Upper Midwest Monday within cold Canadian air dug on the backside of the system. Run to run guidance continuity has been less than stellar with the evolution of the weather pattern downstream over time, but protracted moisture return with wavy and now slower to propagate main fronts and a lingering/wavy coastal fronts up the East Coast all point to development of widespread showers/thunderstorms from the Mississippi Valley Monday through the Eastern Seaboard Wednesday into Thursday, but with possible main focus over the Lower Mississippi Valley/Central Gulf Coast States Monday/Tuesday. The WPC Day 5/Monday ERO includes a Marginal Risk area across this region. Pacific upper trough amplification and inland progression this weekend will cool temperatures over much of the West, leading to the spreading of values as cold as 15 degrees below normal, will cooled conditions lingering next week. Expect much above normal warmth will spread across much of the central and eastern U.S. this weekend into early next week before moderating. This should be highlighted by temperatures ranging upwards to 20-30+ degrees above normal to spread from the Mississippi Valley/Midwest/Great Lakes into the Northeast to again challenge daily record values for daytime highs and warm overnight lows. Santorelli/Schichtel 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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 https://www.wpc.ncep.noaa.gov/#page=ovw