599 FXUS02 KWBC 190805 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 405 AM EDT Mon Oct 19 2026 Valid 12Z Thu Oct 22 2026 - 12Z Mon Oct 26 2026 ...Lingering Nor'easter offers East Coast Maritime Impacts... ...Southern California/Southwest/Rockies Heavy Precipitation... ...Overview... A lingering Nor'easter will bring wind and coastal flooding impacts to the East Coast into mid-late week. A cutoff low will support heavy rainfall from Southern California to the Four Corners states mid-to-late week along with some mountain snows. Associated activity will spread through the West Rockies and then work downstream with PLains system genesis. There is also an emerging onshore wet pattern for Florida to monitor late period. ...Guidance/Predictability Assessment... Models are in good agreement on the overall synoptic evolution of the mid-level pattern beginning mid-week. The amplitude of a Western Atlantic trough is the most uncertain aspect of the late week portion of the medium range. Beyond that, the timing/speed of another West Coast trough carries the most model dispersion this weekend. The AiGFS is favored in the days 3-7 blend with other pieces of guidance used less consistently. The ensemble means make up 60% of the blend by day 5, due to growing variance with respect to an incoming shortwave out of British Columbia. The ensemble mean maintain favorable weighting through the end of the period. ...Weather/Hazards Highlights... A Nor'easter will offer threats for high winds and coastal flooding with stormy maritime conditions from the coastal Mid- Atlantic to off the Northeast. The storm will intensify off the Carolinas over the next few days and bring strong winds back to the coastline into mid-late week to protract a threat for beach erosion. The storm offers potential subtropical transition to monitor later week per NHC. 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 into midweek and work inland into California and the Southwest later week. Anomalous moisture will feed into the West to support increasingly widespread rain/thunderstorms over the region and through the Great Basin/Rockies. There's a slight risk (at least 15% chance) of excessive rainfall leading to flash flooding for portions of the Four Corners region, with a strong signal for heavy rainfall over the San Juan Mountains as well as the general southwestern Colorado area peaking on Thursday. The slow moving system will then eject downstream and lead cycle/fronts genesis and return flow should support emerging showers/thunderstorms over the Plains by next weekend, albeit still with timing uncertainty to navigate. Upstream, a closed low with ample upper troughing will dig from the Gulf of Alaska to approach the Northwest and/or offshore late week. This system could generate moderate precipitation including high elevation snows into the Northwest as dependent on ultimate inland penetration to monitor with upcoming guidance. Meanwhile, mean upper trough development and lingering down though the Southeast U.S. may lead into a wet onshore flow period for especially southern Florida late period into next week. An upper ridge will amplify over the Central U.S. leading to above average temperatures across the region through this weekend. 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 $$