Extended Forecast Discussion NWS Weather Prediction Center College Park MD 252 AM EDT Sun May 2 2021 Valid 12Z Wed May 5 2021 - 12Z Sun May 9 2021 ...Weather Pattern and Model Guidance... Broad cyclonic flow across the northern tier of the U.S. on Wednesday is expected to remain in place across the Great Lakes and the Northeast through the end of the week. The western Atlantic ridge near the East Coast will be shunted eastward as the trough amplifies. Out West, an upper level ridge axis builds in ahead of the next Pacific storm system as the overall upper level flow pattern becomes more amplified for the middle to end of the week. The deterministic guidance remains in above average agreement on the synoptic scale features across the nation, especially through Friday. One of the main differences noted was a faster progression of the 00Z CMC across the western U.S. for the second half of the medium range period with the Pacific trough moving inland. Similar to yesterday, the GFS is considerably stronger with the potential nor'easter off the East Coast by Friday, and would be an impactful system if that solution comes to pass. The WPC forecast was primarily derived from a multi-deterministic blend through Thursday night, and then a GFS/ECMWF blend along with some of their respective ensemble means for Friday through Sunday, while depicting a more modest low near the Northeast for now. ...Weather/Hazards Highlights... Lingering heavy showers and storms remain likely across portions of the central Gulf Coast on Wednesday, albeit less intense than what is expected early in the week. Depending on the evolution and track of the developing low pressure off the East Coast late in the week, light to moderate rain can be expected across portions of the Mid-Atlantic region and the Northeast states. The next noteworthy rainfall event on the horizon for next weekend would likely be across the middle Mississippi River valley as a stationary front develops over this region. In terms of temperatures, a cool down is expected across much of the eastern U.S. behind the cold front and the upper level trough builds in across the region, with readings of 5 to 10 degrees below normal going into the weekend. Across the western U.S., heat is expected to build in response to the upper level ridge, with highs 10-20 degrees above normal possible for the second half of the week for portions of the Intermountain West and the Desert Southwest. This will equate to some 100+ degree high temperatures for the lower elevations of eastern California and southern Arizona. With the passage of the cold front on Saturday, more seasonal temperatures are expected in time for 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