Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 AM EDT Tue Mar 30 2021 Valid 12Z Fri Apr 2 2021 - 12Z Tue Apr 6 2021 ...Overall Weather Pattern... A deep upper trough and a cold surface high will be in place across the eastern U.S. for the Friday/Saturday time period behind a strong cold front exiting New England. An upper level ridge building across the Plains will bring unseasonable warmth to the central and northern Plains. The next trough builds across the Pacific Northwest by Sunday, bringing a greater chance of precipitation across the Northwest and the northern half of California for the beginning of next week. ...Model Guidance and Predictability... The 00Z model guidance suite is in good overall agreement through Saturday owing to the amplified pattern in place across the eastern half of the nation. Similar to yesterday, the main difference during this time was with the CMC being much weaker with a southern stream shortwave crossing the southwestern U.S. and the southern Plains. By Sunday and beyond, forecast confidence decreases quite a bit across the eastern Pacific with both the timing and amplitude of the next trough. The models and ensembles are struggling with how to handle an upper trough digging down from the Gulf of Alaska and its interaction with a southern stream wave lifting across the eastern Pacific. The 00Z ECMWF continues to indicate a slow moving closed low off the California coast early in the week, whilst the GFS is more progressive and has a closed low over British Columbia. The WPC fronts/pressures were primarily derived from a GFS/ECMWF/UKMET blend for Friday and Saturday, and then more of the ensemble means for Sunday through Tuesday whilst still maintaining some of the operational GFS/ECMWF and previous WPC continuity. ...Sensible Weather and Potential Hazards... Most of the medium range period should be relatively quiet in terms of precipitation, with no episodes of heavy rain expected since a large surface high will be governing the overall weather pattern through the weekend across the central and eastern states. Windy conditions are possible on Friday across portions of the north-central U.S. with a strong pressure gradient in place. One exception to the dry pattern will be across western Washington and Oregon as the next storm system slowly approaches that region, and potentially bringing some snow to the Sierra Nevada by late Sunday and into Monday. Temperatures will be more reminiscent of late February for much of the eastern half of the nation to close out the work week with blustery conditions behind the cold front, and subfreezing low temperatures likely reaching as far south as northern Alabama and Georgia by Friday morning, and widespread 20s from the Ohio Valley to the Northeast. The cold weather will abate going into the weekend as the airmass modifies and the upper level trough lifts out across eastern Canada. Much warmer weather is forecast to return to much of the central and western U.S. in time for the weekend, as an upper level ridge builds in along with southerly flow ahead of the next frontal boundary, and results in readings of 15 to potentially 25 degrees above normal. Highs could reach the low to mid 80s across portions of Nebraska and South Dakota, and the low-mid 90s for the lower elevations of the Desert Southwest. A slow cooling trend is expected for the West Coast and especially the Pacific Northwest where the next upper trough/low is forecast to approach by the weekend. 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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml