Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Tue Mar 4 2025 Valid 12Z Fri Mar 7 2025 - 12Z Tue Mar 11 2025 ...General Overview... After the departure of the major East Coast low storm system, another low pressure system is forecast to develop over the western U.S., which will eject across the central Plains by Friday. It will likely evolve into two separate shortwaves, with one quickly tracking toward the Ohio Valley followed by a southern stream wave in its wake to track generally near or just north of the Gulf Coast with uncertain downstream development along the East Coast early next week. Meanwhile, a Pacific cold front will likely approach the West Coast Sunday night into Monday with rain and mountain snow returning to the region, with a potential closed upper low developing across California during this time. ...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. 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. There are still some model differences there, so a multi-model mean is a reasonable starting point in the forecast process. By next Tuesday with the next trough reaching the West Coast, the GFS is stronger with a closed upper low, whereas the CMC and ECMWF favor more of an open wave aloft. The ensemble means were gradually increased to about 40-60% by early next week. ...Weather/Hazards Highlights... 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. Looking ahead to next weekend, showers and some thunderstorms are expected to develop near the Gulf Coast as the surface low evolves with uncertain downstream cyclogenesis near the Mid-Atlantic. At this time, it does not appear that heavy rainfall with this event will be widespread, and given lingering model differences in QPF placement, the Day 4 and 5 excessive rainfall outlooks don't depict any risk areas. It is possible a Marginal Risk may eventually be needed for portions of the Gulf Coast in future forecast updates. The next round of rain and mountain snow is forecast to reach the West Coast by Sunday as a strong upper trough and cold front approaches the coast and moves inland. There may be an atmospheric river event across portions of central and southern California going into Monday, along with heavy snow for the Sierra and eventually moving inland across the higher terrain of the Intermountain West. 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 Sunday and early next week, there will likely be a warming trend 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 Iowa. 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