Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 AM EDT Mon Mar 29 2021 Valid 12Z Thu Apr 1 2021 - 12Z Mon Apr 5 2021 ...Overall Weather Pattern... An amplified upper level flow pattern is expected to be in place for the end of the week across the eastern half of the U.S. with a deep upper level trough across the Great Lakes and the Northeast. A more zonal pattern ensues by the weekend as the eastern trough lifts out. At the surface, a strong cold front will be exiting the East Coast Thursday morning, with a much colder airmass arriving as a large Canadian surface high builds in east of the Rockies. The next frontal boundary reaches the Pacific Northwest and northern Rockies by next weekend, although not as strong as the past storm system. ...Model Guidance and Predictability... The 00Z model guidance suite is in very good overall agreement through Friday owing to the amplified pattern in place across the eastern half of the nation. The main difference during this time was with the 00Z CMC being much weaker with a southern stream shortwave crossing the southwestern U.S. For next weekend, forecast confidence decreases across the eastern Pacific with both the timing and amplitude of the next trough. The 00Z ECMWF remains considerably slower with the upper low off the California coast by Sunday/Monday, whereas the CMC is much more progressive with the trough well inland across the western U.S. The 00Z GFS appears closest to the ensemble means for the West Coast region during this time period. The WPC fronts/pressures were primarily derived from a GFS/ECMWF/UKMET blend for Thursday and Friday, and then more of the ensemble means for Saturday through Monday whilst still maintaining some of the operational GFS/ECMWF. ...Sensible Weather and Potential Hazards... After widespread rain across the East Coast region on Wednesday, most of the medium range period should be quiet in terms of precipitation with no episodes of heavy rain expected since a large surface high will be governing the overall weather pattern. Strong cold air advection in the wake of the departing storm system will likely lead to a changeover to snow for interior portions of New England and upstate New York during the day Thursday, with perhaps several inches of accumulation for portions of northern New England. Windy conditions are also likely for the East Coast on Thursday with a strong pressure gradient in place. Another 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 next Sunday. 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 Georgia and South Carolina by Friday morning. 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 80s across portions of Nebraska and South Dakota, and the low-mid 90s for the lower elevations of the Desert Southwest. 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