641 FXUS02 KWBC 180746 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 346 AM EDT Sun Oct 18 2026 Valid 12Z Tue Oct 20 2026 - 12Z Sat Oct 24 2026 ...Potent Nor'easter to bring maritime and East Coastal impacts... ...Southern California/Southwest/Rockies Heavy Precipitation... ...Overview... A developing Nor'easter is expected to bring wind and coastal flooding impacts to the East Coast mid-to-late week. A cutoff low will bring excessive rainfall concerns from Southern California to the Four Corners states mid-to-late week as well. ...Guidance/Predictability Assessment... There's good agreement on the amplification of a mid-level cut-off low in the East Pacific mid-week, followed by the weakening of it as it enters the Western U.S. by late week. The exact speed of the disturbance remains in question but has improved over the last few runs. The amplitude and location of a downstream upper ridge over the Central U.S. is captured very well by most of the available guidance. Models continue to trend farther away from the East Coast with the location of the Nor'easter mid-week. The ECAIFS and Euro mean were favored in the blend between days 4 and 7 due to notable run-to-run inconsistencies in the deterministic Euro and GFS. ...Weather/Hazards Highlights... A slow moving Nor'easter offers a protracted threat for strong winds, potentially heavy rain and coastal flooding/stormy maritime conditions from the coastal Mid-Atlantic to along/off the Northeast. The mid-latitude cyclone responsible for these hazards is forecast to intensify off the Carolinas late this weekend before drifting back toward the mainland early in the week. Persistent onshore flow should generate strong winds with gusts exceeding 40 kts possible along the immediate coastline. Beach erosion is also likely from the aforementioned strong onshore flow. This developing storm also offers potential subtropical transition to monitor next week as per NHC. Overall, please refer to WPC's Key Messages on our website for more information: www.wpc.ncep.noaa.gov. A shortwave passing south of the Gulf of Alaska is forecast to dig/amplify into a cut-off low over the Eastern Pacific just off the West Coast midweek. The depth and speed of this system will determine how much moisture it can pull into the region. The latest trends suggest an increasing likelihood for anomalous moisture to be pulled into the West. This moisture will then interact with a frontal system and produce scattered to isolated thunderstorms over portions of the Four Corners. Heavy rainfall may occur as well with some Extreme Forecast Index shift of tail signals showing up across Southern California through the Southwest. Some high elevation snowfall is also likely for the Sierra through parts of the Intermountain West to the Rockies with slow progression. System emergence through the Rockies into the Plains will favor the spread of the rainfall shield and emerging Plains convection late period. Another shortwave diving south through British Columbia will send a cold front into the Northwest mid-to-late week. This system could generate high elevation snow for portions of the Northern Rockies/Intermountain West late week. Temperatures will be around average for the East Coast, above average over the Plains and Mississippi Valley/Midwest, and generally below average in the West beneath persistent upper troughing. Kebede/Schichtel 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 forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$