Extended Forecast Discussion NWS Weather Prediction Center College Park MD 252 AM EDT Sat Apr 5 2025 Valid 12Z Tue Apr 8 2025 - 12Z Sat Apr 12 2025 ...General Overview... A pattern change is coming for the eastern half of the country for much of the upcoming week after the passage of a strong cold front. Upper level troughing situated over the Great Lakes and Northeast will lead to much cooler conditions compared to what is currently in place now. By midweek, a surface low develops across the Central Plains and reaches the Mid-Atlantic region around Friday night, bringing light to moderate rain from the Midwest to the East Coast, and perhaps some snow across portions of the Great Lakes. By the end of the week, an upper ridge is likely to build across the Intermountain West and Rockies, and an upper level trough off the Pacific Northwest Coast, with multiple rounds of rain and mountain snow expected for western Washington and Oregon. ...Guidance/Predictability Assessment... The 00Z model guidance suite indicates good synoptic scale agreement across the Continental U.S. on Tuesday, although there are still some mesoscale differences with the surface low exiting New England through early Wednesday. The GFS becomes stronger and a little faster with the surface low developing over the Midwest by mid-week, but not to the same extent as yesterday. Going into the end of the week, the guidance is mainly in agreement with the EC- AIFS, with the exception that the AIFS is a little less amplified with the trough across the Ohio Valley. By Saturday, there are more timing differences with the arrival of Pacific shortwaves across the northwestern U.S., and the GFS is slower with the trough across the Southeast states when compared to the CMC/ECMWF/AIFS. The WPC fronts/pressures forecast was mainly based on a multi- deterministic blend on Tuesday, and then mainly 12Z ECMWF/18Z GFS for Wednesday and Thursday with gradually increasing proportions of the GEFS and ECENS through the end of the week, reaching about 50% ensemble means by next Saturday. ...Weather/Hazards Highlights... The heavy rainfall potential decreases quite a bit going into the Tuesday and Wednesday time period, with no risk areas necessary for both the Day 4 and Day 5 excessive rainfall outlooks. With the exception of some locally heavy showers across portions of the central and southern Florida Peninsula, the threat of heavy rainfall should be over by Tuesday across the remainder of the country. If future models trend higher with QPF over South Florida during this time, it is possible a Marginal Risk area may eventually be needed there as we enter the short range forecast period. Elsewhere across the country, rain and mountain snow makes a return to western Washington and Oregon courtesy of onshore flow and a couple of shortwave trough passages next week, but these don't look like major events at this time. Light precipitation crosses the Northern Plains and Midwest into mid-late next week, and the next good chance of rainfall reaches the Eastern U.S. by next Friday into Saturday as a surface low likely develops. Lingering snow is also likely across portions of northern New England through Tuesday evening before the surface low departs the region Tuesday night. In terms of temperatures, much cooler conditions are coming for the Eastern U.S. after the strong cold front exits the East Coast by Monday morning. Afternoon highs are likely to be on the order of 10 to 20 degrees below early April averages on Tuesday and Wednesday from the Ohio Valley/Great Lakes to the Northeast U.S., compliments of the upper low overhead. Readings return closer to average by late in the week for the East Coast states with the upper trough lifting out of the region. Meanwhile, a warm pattern is expected for the Western U.S. through the week with both daytime highs and overnight lows about 10-20 degrees above average, with the greatest anomalies over the Great Basin. 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