Extended Forecast Discussion NWS Weather Prediction Center College Park MD 152 PM EST Tue Mar 4 2025 Valid 12Z Fri Mar 07 2025 - 12Z Tue Mar 11 2025 ...General Overview... After the departure of the major East Coast low storm system late this week, 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 approach the West Coast on Monday with rain and mountain snow returning to the region. ...Guidance/Predictability Assessment... The latest model guidance continues to show good agreement on the overall large scale pattern evolution during the medium range period, but still some uncertainty in the details. 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 this weekend, as a southern stream upper low becomes dominant. Models continue to show placement, timing, and strength differences with any kind of surface low along the Gulf Coast and into the western Atlantic early next week. Still, a multi-model blend seems most reasonable as a starting point for the WPC forecast today through the weekend. By Monday-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 (or brief closing of a low). Generally favored a blend of the models/ensembles for late period, and this fit well with previous WPC continuity as well. ...Weather/Hazards Highlights... The associated rainfall with a strong surface low departing the Northeast will be well gone by the start of the period, but strong to gusty winds in its wake could continue into Friday. Rain and Mountain snow will be ongoing across southern California, and the Southwest/Four Corners region through Friday. Moderate to heavy snows are possible for the highest terrain of Utah, Arizona, and the southern Rockies with some gusty winds as well. Strong winds and low relative humidity behind a dry line, will increase the fire weather threat as well. Into the 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. This looks to set up a particularly windy pattern for parts of the West as well. 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. Santorelli/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