Extended Forecast Discussion NWS Weather Prediction Center College Park MD 157 AM EST Mon Mar 3 2025 Valid 12Z Thu Mar 6 2025 - 12Z Mon Mar 10 2025 ...General Overview... The strong low pressure system crossing the Central U.S. early this week is expected to be over southern Quebec by Thursday morning, with the cold front exiting the East Coast, followed by cooler conditions to close out the work week. Out West, a broad upper trough over the Intermountain West will likely evolve into two separate shortwaves, with one more progressive and merging with the northern stream flow, and the other lingering longer over the southern Rockies, progressing eastward as a positively tilted trough that will likely support a surface low near the Gulf Coast through Sunday. Meanwhile, a Pacific cold front will likely approach the West Coast Sunday night into Monday with rain and mountain snow returning to the region. ...Guidance/Predictability Assessment... The 00Z model guidance suite has come into better agreement regarding the expected overall evolution of the Western U.S. upper trough compared to the past few model cycles. It appears likely that two separate surface lows will develop, with the first one over the central Plains on Friday, and a second one near the Gulf Coast on Saturday. The UKMET is a little slower with the first low across the Ohio Valley on Saturday and farther to the north with the Gulf Coast low over the weekend. The CMC holds the upper trough back to the west more so than the better clustered GFS/ECMWF and their respective means going into Sunday, so the blend favored more of those solutions instead of the CMC by that time. The ensemble means were gradually increased to about 40-60% by Sunday-Monday. ...Weather/Hazards Highlights... An amplified upper level trough reaches the Northeast U.S. by Thursday afternoon, along with a strong surface low that will track across Quebec, with secondary surface cyclogenesis near Nova Scotia Thursday night. Most of the significant rainfall should already be off the coast by this time, with some lingering showers over Maine and snow across the higher terrain of New England and Upstate New York. The large upper trough over the Western U.S. late in the week, in combination with embedded shortwave energy, will result in numerous snow showers across the Intermountain West and central/northern Rockies, with heavy snow likely for the southern Sierra, the Wasatch Range, and the higher terrain of Wyoming and western Colorado. Mainly moderate heavy rain is expected for southern California and the Peninsular and Transverse mountain ranges, and given recent burn scar sensitivities for portions of this region, a Marginal Risk remains valid for the new Day 4 period Thursday. The overall QPF signal is not as impressive going into Friday (Day 5) across the Rockies and the central Plains, and therefore no risk areas are necessary for the Day 5 period. Looking ahead to next weekend, showers and some thunderstorms are expected to develop near the Gulf Coast as the surface low evolves, and the next round of rain and mountain snow reaches the West Coast by Sunday. Cooler than average readings are likely from the Intermountain West to the western High Plains in conjunction with the upper trough situated across the southern Rockies for the end of the week. Looking ahead to next Sunday/Monday, there will likely be a warm- up across the north-central U.S., with daytime highs potentially 10-20+ degrees above early March averages, with highs potentially reaching well into the 60s from the Dakotas into portions of the Upper Midwest. 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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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