Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Wed Mar 5 2025 Valid 12Z Sat Mar 08 2025 - 12Z Wed Mar 12 2025 ...General Overview... Another low pressure system will develop across the West and eject into the Central Plains by Friday as the leading system exits the East Coast. Guidance suggests this system will 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 large scale pattern continues to be in good agreement with the evolution with the normal degree of uncertainty in regards to the placement, intensity and QPF amounts for the latter periods. The guidance is signaling for low surface lows to spin up, the first one over the Central Plains and the second near the Gulf Coast and into the western Atlantic early next week. 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).WPC utilized a multi- model approach with increasing weights and inclusion of ensemble means by the latter part of the forecast. This approach maintained continuity while reducing noise for Days 6 and 7. ...Weather/Hazards Highlights... There will be strong and gusty winds lingering across the Northeast as the leading low pressure system tracks further offshore. 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 conditions conducive for wildfires to develop and spread rapidly. Showers and thunderstorms will increase in coverage and intensity near the Gulf Coast as the surface low evolves with uncertain downstream cyclogenesis near the Mid-Atlantic. A Day 4 Marginal Risk for excessive rainfall was introduced for portions of the Lower Mississippi Valley, Gulf Coast and into the Southeast. Lingering model differences factored into keeping Day 5 without an excessive rainfall outlook. By Sunday another round of rain and mountain snow is anticipated to reach the West Coast as a strong upper trough and cold front approaches the coast and moves inland. There is a growing potential for an atmospheric river event to yield heavier rain to portions of central and southern California this weekend 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. Much of the Intermountain West and adjacent High Plains will have cooler than average temperatures with the upper trough positioned across the Southern Rockies. Temperatures will begin to moderate for 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. Campbell/Santorelli 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