Extended Forecast Discussion NWS Weather Prediction Center College Park MD 239 AM EDT Mon May 03 2021 Valid 12Z Thu May 06 2021 - 12Z Mon May 10 2021 ...Weather Pattern and Model Guidance... An amplified upper level pattern will be in place across the nation through Saturday with well developed troughs near the West Coast and East Coast, with an upper ridge over the Rockies that weakens with time as it emerges over the Plains. As the trough over the Northeast lifts out, a more quasi-zonal pattern is expected by Sunday and Monday, with a second trough building across the West by next Monday. Models and ensembles remain in above average agreement through the end of the week and offer good run to run continuity. There is some variance with the timing and strength of smaller scale systems, but guidance composites tend to mitigate these differences that is consistent with predictability. The GFS remains stronger and farther west with the coastal low near New England Friday night compared to the other guidance, including the GEFS mean, so a more offshore solution is being favored at this time. The greatest model spread resides across the Great Lakes and Ohio Valley region by early next week, so more of the ensemble means were incorporated for the Sunday through Monday time period. ...Weather/Hazards Highlights... Residual showers and some thunderstorms remain likely from the central Gulf Coast into the southeast Wednesday into Thursday, with additional enhanced activity up across the East near a wavy front. A developing coastal low Friday and Saturday along a trailing front with renewed upper trough support should produce unsettled coastal conditions to include some moderate rains for the Mid-Atlantic and Northeast, but the worst weather conditions are expected to remain offshore. By Sunday, another area of enhanced rainfall is becoming more likely across portions of the middle Mississippi River valley as deep Gulf moisture intersects a stationary front, with locally 1-2 inches of rain possible. Upstream over the western U.S., above normal temperatures are likely from the Desert Southwest to the Intermountain West through Friday, which will equate to some 100+ degree high temperatures for the lower elevations of eastern California and southern Arizona on Thursday. With the passage of the cold front on Saturday with emergence of an upper trough over the West, seasonal to below normal temperatures are expected for the weekend. Trough amplification offers the potential for some moderate precipitation from the Pacific Northwest to the Northern Rockies, where terrain enhanced snows are possible. 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