Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 AM EDT Tue Apr 8 2025 Valid 12Z Fri Apr 11 2025 - 12Z Tue Apr 15 2025 ...General Overview... An amplifying shortwave trough originating from south-central Canada is expected to amplify as it drops southeast across the Ohio Valley, to support a surface low from the Midwest to the Mid- Atlantic coast to close out the work week and emerging off the coast on Saturday. Meanwhile, an upper level ridge builds across the Intermountain West and Rockies Thursday into Friday, and then shifts eastward to the Plains by next weekend. With the ridge departing the West, an upper trough approaches from the Pacific Northwest and supports a cold front crossing the Intermountain West to the central/northern Plains through next Monday. ...Guidance/Predictability Assessment... The 00Z model guidance suite indicates good synoptic scale agreement across the Continental U.S. on Friday. There are still some differences in the surface low evolution near the East Coast and whether a secondary low will form and become the dominant low by Saturday morning, but that is now looking more likely. The area with the greatest model differences is across the West Coast region going into Sunday and across much of the Western U.S. Monday in regards to the evolution of the trough moving inland from the Pacific. The 12Z CMC was most out of alignment with the overall model consensus at the time of fronts preparation, but the 00Z CMC has trended more in line with the consensus. The WPC fronts/pressures forecast was mainly based on a GFS/ECMWF blend on Friday and Saturday, with some UKMET also. There was gradually increasing proportions of the GEFS and ECENS Sunday through early next week to about half. ...Weather/Hazards Highlights... The low pressure system crossing the Ohio Valley and then reaching the East Coast to close out the week will be the next event to monitor. A deepening coastal low near the Mid-Atlantic Coast on Friday and into early Saturday should bring higher rain chances and breezy conditions from the Carolinas to New England. A Marginal Risk area continues for Day 4/Friday from Maryland northward to southern New England with more of an enhanced QPF signal in the deterministic guidance, with perhaps 1-2 inches of rainfall for some areas. Higher elevation snowfall is also likely across northern New England Friday night into Saturday. The rainfall becomes lighter in general by Saturday across the Northeast, and for now the Day 5 ERO has no risk areas. In terms of temperatures, a warm pattern is expected for the Western U.S. for the end of the week with both daytime highs and overnight lows about 10-20 degrees above average, with some readings potentially 25 degrees above average across portions of Wyoming and Montana. These milder conditions then reach the central and northern Plains by next weekend as the ridge shifts eastward, with widespread 15-25 degree positive anomalies across the Central Plains and Midwest by Sunday. 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