Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Wed Mar 1 2023 Valid 12Z Sat Mar 4 2023 - 12Z Wed Mar 8 2023 ...Synoptic Overview... The strong low pressure system over the eastern U.S. should depart from the Northeast by late Saturday with surface high pressure building across the eastern third of the nation through Monday. Behind this system, the overall synoptic scale pattern should then evolve with a slow moving upper trough across much of the western U.S. through the weekend and into early next week, with continuation of unsettled conditions and below normal temperatures over much of the West. The primary Pacific system of note will drop southward from the Gulf of Alaska and reach the offshore waters of the Pacific Northwest during the weekend and then weaken as it idles off the coast. Downstream of this ridge will be a broad ridge axis across the central U.S. with the main upper high over the central Gulf of Mexico. Some weak shortwave energy is expected to track across the northern periphery of this ridge, but nothing particularly strong is currently expected. ...Guidance/Predictability Assessment... Models and ensembles generally offer well clustered solutions going into early next week, and a multi-deterministic model blend serves well as a starting point in the forecast process. By the end of the forecast period Wednesday, the 00Z CMC becomes more zonal aloft compared to the more amplified GFS/ECMWF solutions, whereas the models still agree well with the shallow ridge over the central U.S. during this time. The use of the ensemble means was increased to about 50% by Day 7 to account for increasing mesoscale differences with shortwave passages. ...Weather/Hazard Highlights... A deep upper trough will remain anchored in place over the West Coast this weekend and persist into the first half of next week. This feature and embedded surface low pressures will increase the potential for coastal rain and heavy inland snow from the Pacific Northwest into northern California. Highest precipitation totals during the period should be along the central West Coast into the Sierra Nevada, adding to the already very impressive snow pack over the region. Expect lighter snow to spread across the central and northern Rockies. With low confidence in specifics, shortwave energy streaming eastward from the main West Coast trough could produce one or more areas of light snow from the northern Plains into the Great Lakes, with scattered light rain possible farther south. For the Northeast U.S., some lingering snow and coastal rain/wind is likely through early Saturday afternoon, with improving conditions going into Sunday as the surface low departs the region. The southeast U.S. upper ridge will once again exert its influence across much of the south-central U.S. going into early next week with temperatures expected to be 10-15 degrees above early March levels along with increasing humidity levels from Texas to the Southeast states. The West will continue to feel like the middle of January through the weekend with the Intermountain West and Rocky Mountains consistently having highs on the order of 10-20F below normal, which will equate to highs in the 20s and 30s for most areas north of the Utah/Arizona border. 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