Extended Forecast Discussion NWS Weather Prediction Center College Park MD 236 PM EDT Fri Oct 10 2025 Valid 12Z Mon Oct 13 2025 - 12Z Fri Oct 17 2025 ...Strong coastal low with significant coastal flooding, beach impacts, high winds and heavy rain lingers for the East Coast... ...Heavy rain and flash flooding remain a threat for the Southwest early next week given anomalous tropical East Pacific moisture... ...California Heavy Rain Threat with early next week closed low... ...Overview... A potent coastal storm is forecast to continue to lift slowly northward up the East Coast into early next week. This coastal low may bring strong onshore winds causing coastal flooding, rip currents, beach erosion, and heavy rain to the Mid-Atlantic and Northeast. Meanwhile, upper troughing in the West will draw tropical moisture and remnant tropical energy northward and bring potentially widespread heavy rain and some flash flooding into the Southwest early next week. This trough and another round with a closed low/trough into the West will maintain cooler than average temperatures as well as heavy precipitation chances with focus over California to include higher elevation Sierra snows. Upper ridging should prevail farther east in the central U.S., allowing for unseasonably warm temperatures, and rounds of rain in the north- central U.S. directed around the ridge may increase later next week. ...Guidance/Predictability Assessment... Latest guidance today remains in overall good agreement on the larger scale pattern evolution during the medium range period but still with considerable uncertainty in the details. There is better consensus for the track and timing of the coastal low up the Mid- Atlantic/Northeast coast by Monday, but differences in how close that low tracks to the coast have important implications for inland extend of heavier rainfall. Out West, a deep upper low will drop down the CA coast and eventually shift inland with some uncertainty in the timing of that. The 06z GFS was an outlier late period seemingly stemming from the evolution of a shortwave into the Great Lakes region and its downstream impacts on the rest of the pattern across the CONUS. The WPC forecast used a deterministic model blend for Days 3 and 4, leaning heavier on the ECMWF and CMC with the ensemble means thereafter. This also maintained good agreement with the previous WPC forecast. ...Weather/Hazards Highlights... A dangerous coastal storm will offer a wide array of threats up the East Coast into early next week. By Tuesday, the main heavy rain threat should focus more from coastal Mid- Atlantic to Long Island and coastal New England. There remains ample uncertainty with the inland extent of rain amounts given an uncertain coastal storm evolution and ejection. There could be potential heavy bands of rain, which combined with any urban area could enhance flooding issues. Given the uncertainty opted to maintain a WPC Day 4/Tuesday Marginal Risk for the coastal Mid-Atlantic to Northeast. In addition to heavy rain threats, the combination of persistent and strong onshore winds, high surf, and above normal tides may lead to significant coastal flooding impacts along with strong rip currents and potential beach erosion. See Key Messages being issued by WPC for the latest on this system. The system should pull away from the coast by Tuesday or Wednesday. Early next week, another round of tropical moisture and energy is forecast to enter the Southwest as newly formed Raymond in the Pacific follows in the wake of Priscilla. Precipitable water values are likely to be near max values for this time of year, with the Southwest also in the right entrance region of the upper jet for good dynamical support for heavy rain. However, a limiting factor in terms of flash flooding could be somewhat limited instability under widespread clouds and rain, which could limit rain rates. Also, the current forecast shows the greatest rainfall totals to the southeast of where the heaviest rain could fall in the short range. Thus continue to hold off on any Moderate Risks at this time, but a Slight Risk is in place across portions of Arizona and New Mexico for the Day 4/Monday Excessive Rainfall Outlook. Elsewhere, a moisture plume/atmospheric river is forecast to shift southward across California early next week ahead of a cold front to produce heavy rainfall and mountain snows for California. While it could be relatively fast- moving, some instability could be present and rainfall rates could reach an inch per hour, so have a Marginal Risk of excessive rainfall for parts of California for the WPC Day 4/5 EROs centered on Monday/Tuesday. Lighter mountain snow will also spread across the Intermountain West and Rockies associated with the amplified upper troughing. Farther east, rounds of precipitation are possible in the Plains to Upper Midwest and Great Lakes region with downstream system/energy translations next week out from the West/Rockies as lead moisture and instability pool with genesis of several wavy frontal systems on the northern periphery of a warming south- central U.S. upper ridge. It still remains generally the case that cooler than average temperatures are forecast particularly for highs in the West through next week underneath renewing troughing. Meanwhile, upper ridging in the central U.S. will lead to warmer than average temperatures. Highs in the 70s reaching as far north as the Dakotas Sunday will be 15-20 degrees above average. Temperatures there should cool behind a cold front into the workweek, but temperatures of 10 to 15 degrees above normal will last several days farther south, as unseasonably warm highs in the 90s continue for Texas and Louisiana. Warmer than average temperatures are forecast to stretch into the Midwest. Some cool highs along the East Coast early week should moderate close to normal as the week progresses. Santorelli/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 (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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