Extended Forecast Discussion NWS Weather Prediction Center College Park MD 307 PM EDT Tue Apr 28 2020 Valid 12Z Fri May 01 2020 - 12Z Tue May 05 2020 ...Much above normal temperatures spread from the West to the Deep South... ...Stormy weather for the Northeast Friday into Saturday... ...Pattern Overview and Guidance/Predictability Assessment... The overall synoptic pattern over the CONUS will be a trough offshore the Pacific Northwest coast, a ridge over the West and a trough over the eastern third. With time, the ridge strengthens as it shifts east over the Rockies which in turn will amplify the trough over the East. The Pacific energy will override the ridge, pushing the ridge axis eastward. Multiple lobes of energy within the eastern trough will send a system through the Plains bringing another rough of scattered to widespread rain to the region. This eastern system will bring a heavy rainfall threat to parts of the Mid-Atlantic/Northeast. Stronger Pacific energy will cross the western U.S. Sun/Mon, supporting precipitation from the Pacific Northwest into the Northern Plains, while convectively active downstream flow to the east continues to lose amplitude. With varying degrees of spread daily in relation to the timing/placement of the evolving features, the weighting and inclusion of guidance were unique each day. However, in general, the WPC blend favored the 00Z ECWMF/means, 06Z GFZ, 00Z CMC, 00Z UKMET and the 00Z NAEFS. ...Weather/Hazard Highlights... Portions of the Northeast may have lingering rain, possibly heavy at times, as a departing system undergoes coastal redevelopment. A tight gradient will develop between coastal low and the nearby high pressure; which will allow stronger winds to draw in moisture inland further enhancing rainfall production/efficiency. This may become problematic for areas recently impacted by saturating rains therefore increasing the risk for rapid runoff/local flooding. Warmer and drier conditions are expected across much of the Southwest and portions of the South over the next few days thanks to the mid/upper-level ridge and surface high pressure anchored over the region. Daily temperatures across the Great Basin/ Southwest will average 10 to 25 degrees warmer than average by Friday while the Rockies and the surrounding Plains will be 5 to 15 degrees warmer over the weekend and into early next week. Daily records for afternoon highs and warm overnight lows should be most numerous through Friday, with a few daily records possible across the South into early next week. Onshore flow will spread coastal rain to parts of Washington and Oregon as a Pacific shortwave and cold front moves inland--the low level upslope flow behind the front possibly helping activity to persist over parts of the north-central Rockies/High Plains into the weekend. Another Pacific system should bring an episode of enhanced precipitation to the Pacific Northwest this weekend with continued eastward progression across northern parts of the West and into the Plains. Higher elevations may see periods of snow. As an associated front settles into the south-central Plains and extends into the Mid-MS/OH Valleys and south-central Appalachians by the weekend/early next week, expect increasing potential for some locally moderate to heavy rainfall in its vicinity. Energy aloft emerging from the West may enhance convective activity. Still uncertain specifics by this time frame portends relatively low confidence in the smaller scale details. Campbell/Schichtel 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