Extended Forecast Discussion NWS Weather Prediction Center College Park MD 804 AM EDT Fri Mar 28 2025 Valid 12Z Mon Mar 31 2025 - 12Z Fri Apr 04 2025 ...Overview... A parade of systems should bring periods of active weather to much of the U.S. next week. A cold front into the East next Monday should bring widespread rain and thunderstorm chances, with some locally heavy rain across the South. Another system into the West should ultimately lead to a surface low emerging into the Plains around midweek and tracking towards the Great Lakes. Widespread moderate to heavy rain may accompany this second cold front. The West should stay relatively cool underneath of almost persistent troughing, while the central to eastern U.S. experiences periods of normal to above normal temperatures. ...Guidance/Predictability Assessment... A shortwave into the East/Northeast Monday-Tuesday show relatively good agreement both on amplitude and timing. The guidance agrees an upper low off the Northwest coast will send energy into the West around Tuesday, but there remains some significant differences in the evolution of this energy downstream. The GFS continues to be an outlier in showing a faster and more compact energy into the Plains on Wednesday with a more eastward track into the Northeast on Thursday. The ECMWF and CMC (with agreement from the ensemble means and AI models) suggests a more northerly track of the shortwave into the Great Lakes, a result of much stronger upper ridging over the western Atlantic and East Coast as compared to the GFS. Another system enters the West late week but the GFS exhibits issues offshore with an upper low/overall less blocky Pacific pattern compared to consensus. By Friday, there is some agreement the flow pattern could turn more amplified and active with a deep Western Ridge and Eastern U.S. ridging. Good enough agreement the first few days of the period allowed for a general model compromise. Added in ensemble mean guidance in place of the GFS midweek and beyond given the general out of sync pattern shown in the GFS. By day 7, used a 60/40 blend of the ensemble means with the deterministic ECMWF and CMC. This helped maintain good agreement with yesterday's WPC forecast as well. ...Weather/Hazards Highlights... A cold front into the East should allow for increased rain and convection across much of the Eastern Seaboard. The best chance for locally heavy to excessive rainfall should be mostly confined to parts of the Southeast where a marginal risk is in place for the Day 4/Monday Excessive Rainfall Outlook. The Storm Prediction Center also suggests strong to severe weather is possible from the Southeast into the Mid-Atlantic as well on Monday. Expect multiple systems to bring rain and higher elevation snow to the West during the period, with rapidly increasing uncertainty in the details after early next week. The best precipitation focus looks to be across Northern California on Monday, so a marginal risk was continued for tonights new Day 4 ERO. Trends in the guidance show another possibly significant system into the West mid-week accompanied by at least moderate precipitation. Leading dynamics from the West should eventually support a central-eastern U.S. system by Wednesday-Thursday, generating another episode of meaningful precipitation over the eastern half of the country. Some snow will be possible from the northern Plains into New England. The warm sector ahead of the front crossing the eastern half of the country into Monday will feature well above normal temperatures. Expect plus 10-20F anomalies for highs and up to plus 20-25F anomalies for morning lows. Near to below normal readings will progress eastward behind the eastern U.S. front, with precipitation keeping some northern Plains to Great Lakes locations 5-10F or so below normal for highs into Tuesday. Temperatures may rebound back above normal over the southern half of the Plains on Wednesday with the warming trend spreading back into the East thereafter. Periods of unsettled weather will keep the diurnal spread over the West Coast states more narrow than usual, with cool highs and near or slightly above normal lows. 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