Extended Forecast Discussion NWS Weather Prediction Center College Park MD 246 AM EDT Mon Apr 15 2019 Valid 12Z Thu Apr 18 2019 - 12Z Mon Apr 22 2019 ...Heavy rainfall and severe weather threat for the central to eastern U.S. later this week... ...Overview... Progressive but amplified pattern will support a dynamic system moving through the central states Thu/Fri into the east by the weekend but possibly taking until next week to fully move offshore. The west will see a front move into Washington/Oregon early Friday and then progress eastward and southward into the Plains and southern Rockies late this weekend into next Monday. ...Guidance Preferences... Blend of the 18Z GFS/GEFS and 12Z ECMWF/ECMWF ensemble mean offered a reasonable starting point to the medium range period, with a deterministic-centered blend including the UKMET/Canadian to start and a 2/5ths ensemble weighting by next Monday. This maintained good continuity overall as the pattern remains fairly well-handled by the ensembles after earlier uncertainties. Still, questions remain in how the eastern system evolves depending on the strength/track of mid-level shortwaves not easily resolved at this lead time. Ensemble clustering suggested a slowing of the front along or just off the east coast with a new surface low/wave developing near the Mid-Atlantic before turning northeastward. Residence time near New England should be limited due to the approaching system from the west by that time. ...Weather Highlights/Threats... Multi-inch rainfall totals with local flooding are probable (enhanced in embedded convection) along/ahead of the front over the lower Mississippi Valley (possibly into parts of the Southeast and Mid-Atlantic) with lesser amounts in a local max area to the north/northeast of the surface low across Wisconsin. Consult SPC for the latest on the severe weather risk. Mild temperatures will precede the front (10-15F above average) to be replaced by cooler than average temperatures after its passage. The Northwest will see generally light precipitation along a front push through the Great Basin and central Rockies this weekend into next Monday. 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