051 FXUS02 KWBC 150709 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 309 AM EDT Thu Oct 15 2026 Valid 12Z Sun Oct 18 2026 - 12Z Thu Oct 22 2026 ...Frost/freeze threats across parts of the Mid-Atlantic and Northeast Sunday and Monday... ...A possible East Coast low early to mid next week could bring coastal impacts... ...Overview... A chilly surface high over the Eastern U.S. will bring frost and freeze concerns to parts of the Mid-Atlantic and Northeast early in the period. A cold front sinking through Florida may bring a threat for locally heavy rainfall on Sunday. There is also increasing potential for a low off the East Coast to form along this front, and may bring showers or a locally heavy rainfall threat to parts of the coastal Mid- Atlantic, depending on how close to the coast the low gets. Out West, an upper low will drop down the West Coast with deep troughing likely over the West by next Thursday. This brings the potential for widespread rain and high elevation snows especially Tuesday and Wednesday next week, with some showers increasing across the Central U.S. as well late period. ...Guidance/Predictability Assessment... Aspects of the medium range forecast have become increasingly uncertain over the last day or so. With yesterdays 12z runs and especially tonights 00z runs, there seems to now be a clear trend towards some sort of low or energy from a trough well off the East Coast to linger somewhere off the Mid- Atlantic coast most of the period. There is considerable uncertainty on the placement of any upper and surface low, and its impacts on coastal locations in the Mid- Atlantic. The ECMWF, ECAIFS, and UKMET are closest to the coast, with the CMC a bit more offshore and the GFS well offshore. There is increasing support for this as well in the latest ensembles as well. The WPC forecast tried to take a middle ground approach, but does present a shift in continuity from the previous shift which did not show the presence of the low at all. Significant uncertainty with the track and impacts of this low, but will need to be watched closely. Out West, the 00z guidance tonight has come into better agreement with the evolution of an upper low that drops southward along the coast and eventually moves into the Southwest. Previous runs of the ECMWF had been farther offshore, and slower to bring the trough inland, but the 00z run trended faster. Conversely, yesterdays 12z GFS came in much faster, but the new 00z run was slower again. This is also generally in line with the CMC and ECAIFS, and it seems a general model compromise (with the ensemble means) should serve as a good starting point for the forecast. ...Weather/Hazards Highlights... A cold front moving slowly through Florida will allow for increased onshore flow and locally heavy rainfall, especially along the East Coast. WPC has this region in a marginal risk for Sunday. Coastal low pressure development off the Mid-Atlantic coast may allow for more showers and locally heavy rainfall for especially the eastern Carolinas and southeast Virginia, with possible gusty winds. All of this is highly dependent on how close to the coast this low is, and a closer location would mean much greater impacts, especially if the low lingers for any period of time. Out West, precipitation chances increase by Monday and especially Tuesday into Wednesday with rain and high elevation snow. Some rainfall may begin to develop across the south-central U.S. by mid next week as well. Canadian high pressure will be in place across much of the East on Sunday, with frost/freeze concerns for parts of the Mid-Atlantic and the Northeast. Elsewhere, above normal temperatures will expand across the Central U.S. as conditions trend cooler across the West underneath deep troughing next week. Santorelli 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 $$