Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Sun Mar 26 2023 Valid 12Z Wed Mar 29 2023 - 12Z Sun Apr 2 2023 ...Synoptic Overview... The weather pattern mid next week will be featured with strong low pressure system over California that moves inland across the Intermountain West Thursday, and then emerges over the Plains and Midwest by Friday and into next weekend. This will likely result in an increase of showers and thunderstorms across much of the Plains and Midwest states. This trough over the western U.S. will serve to amplify the downstream upper ridge over the south-central U.S. and the Gulf Coast region for the end of the week. By Saturday, a second trough will become established over the Pacific Northwest as a shortwave drops south from the Gulf of Alaska. The closed upper low over the Hudson Bay region will remained nearly anchored in place, and there will be some shortwaves pivoting around the southern periphery of this low across the north-central U.S. through the end of the week. ...Model Guidance/Predictability Assessment... The 00Z model guidance suite is in decent synoptic scale agreement through Thursday night, and a general model blend suffices for this time period. There has been a trend for a more offshore and weaker solution with the developing low off the East Coast Wednesday compared to the 12Z guidance, and this would keep nearly all of its precipitation away from New England. Looking ahead to the end of the week, the 00Z GFS develops a closed low by Friday night across the central Plains and a little faster than the ECMWF/CMC, but not quite as fast as the GEFS mean, which has consistently been more progressive over the past few days with this trough. By next Sunday, the GFS is stronger with the next trough developing over the Pacific Northwest. Taking these factors into account, the forecast for Friday-Sunday was primarily derived from a CMC/ECMWF/GFS blend while gradually increasing use of the ECENS and some of the GEFS mean. ...Weather/Hazards Highlights... The storm system affecting California early next week will likely be abating in intensity by Wednesday with lingering moderate to locally heavy rainfall, with perhaps half an inch to one inch of additional rainfall through Wednesday evening before things begin to dry out. Moderate to heavy snow is also likely for the higher terrain of the Sierra and southern California mountains, where 6 to 12 inches of accumulation is likely on Wednesday. Since most of the significant rainfall should occur prior to 12Z Wednesday, there are no areas on the Day 4 excessive rainfall outlook, although this could change going into the short range period if this storm system slows down in future model runs. On Wednesday, a surface low is likely to develop over the offshore waters of the western Atlantic, and with this forecast cycle, it appears most of the precipitation should remain offshore and not affect the Northeast states, so a more optimistic forecast for this region. By the end of the week, showers and storms are expected to increase ahead of a developing storm system across the Plains and Midwest. Some of these storms could be severe on Thursday across portions of the southern Plains, and windy conditions are likely to develop across much of the Plains in general. Temperatures are expected to be well below late March averages across much of the northern Intermountain West, the Rockies, and the Dakotas for the Wednesday to Friday time period, with highs running 10 to 20+ degrees below average in many cases. The coldest conditions will reside across North Dakota where some morning lows near or even slightly below zero will be possible early on Wednesday. Meanwhile, the presence of the Gulf Coast upper ridge will tend to favor temperatures running up to 15 degrees above average from Texas to the Southeast U.S. and Florida for the end of the week, with the greatest anomalies for overnight lows with increased clouds and winds. 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, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: 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