Extended Forecast Discussion NWS Weather Prediction Center College Park MD 243 AM EDT Wed Apr 01 2020 Valid 12Z Sat Apr 04 2020 - 12Z Wed Apr 08 2020 ...Overview and Guidance/Predictability Assessment... Subtropical ridging will again build through the Gulf next week with renewed troughing in the West, downstream of ridging south of Alaska. This will take a frontal system to the East Coast late Sun/early Mon with additional western systems moving out of the Rockies and through the Plains to the end of the period next Wed. The models/ensembles show good clustering early in the forecast period and a deterministic blend sufficed to start, despite lingering timing issues into NorCal. Eastern frontal system should clear the coast on Monday but stall over the Southeast as upper ridging builds from the south. By next Tue/Wed, questions arise in the Southwest as to the speed of the ejecting trough or perhaps closed low. The 12Z ECMWF/GFS were among the quickest of the multi-center ensembles while the 12Z Canadian was in the slowest 10%. Preferred something slower than the older GFS/ECMWF (like the ensemble means) but no solution could really be deemed implausible given the uncertainty upstream over Alaska/North Pacific. Newest 00Z guidance showed a much slower/deeper system which only further illustrates the uncertainty. ...Weather/Hazard Highlights... Expect a large portion of the West to see at least some rain and high elevation snow during the Sat-Wed period, with the Desert Southwest and southern Rockies having the best possibility of staying mostly dry. The digging upper trough and surface front Sun-Mon will likely bring highest totals to northern California/Sierra Nevada and spread a larger shield of precipitation across the West. Southward extent and amounts will vary on the strength/track of the upper trough. Significant snow is likely for the Sierra Sat through at least late Mon or early Tue. Precipitation may linger longer in the Southwest Tue-Wed if the upper system ejects more slowly than advertised. A front pushing eastward this weekend will bring generally light rain (maybe some light snow well north) to parts of the East. Another area of rainfall may develop across the eastern half of the country late weekend into next week with the best signal for some significant totals extending from the Southern Plains into the Tennessee Valley. Other areas could see enhanced activity as well but with lower confidence. Cold air behind the late week system will moderate quickly as temperatures east of the Rockies trend toward above normal by next week. The overall pattern aloft will tend to favor moderately below normal readings west of the Rockies during the period. Minus 5-15F or so anomalies for highs should be most common over California/Nevada early next week. By contrast, high temperatures may approach/exceed records along the Gulf Coast into Florida where upper 80s or low 90s may be possible. Morning lows may tend to be somewhat more extreme versus normal than the daytime highs, staying in the 60s/70s from Texas to South Carolina. Fracasso Additional 3-7 Day Hazards information can be found on the WPC medium range hazards 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