Preliminary Forecasts
Issued by NWS
Issued by NWS
961 FXUS02 KWNH 090706 PREEPD Preliminary Extended Forecast Discussion NWS Weather Prediction Center College Park MD 205 AM EST Tue Dec 9 2025 Valid 12Z Fri Dec 12 2025 - 12Z Tue Dec 16 2025 ...Potentially hazardous cold is possible for portions of the Northern Plains and Upper Midwest this weekend... ...Overview... A broad upper level trough with reinforcing shortwaves will continue to dominate areas east of the Rockies with broad ridging persisting along the West Coast/Rockies through this weekend, though the amplitude of both are forecast to weaken/broaden with time. While the heavy precipitation and high wind threat fades in the Northwest, generally progressive clipper systems will be favored in this pattern east of the Rockies with enhanced northern tier wind/snow chances and lake effect snow in the lee of the Great Lakes. An arctic airmass will move in to portions of the north- central U.S. bringing much below normal temperatures and potentially hazardous cold. ...Guidance/Predictability Assessment... The guidance shows excellent agreement on the overall large scale pattern, even extending into a number of shortwave details. For the first half of the period, a general deterministic model blend worked well as a starting point for the WPC surface fronts/pressures/500 hPa heights. For Sunday into Monday, there are enough differences to incorporate some of the 12z ECMWF/NAEFS means. The QPF started with the 01z NBM but needed significant increases in the Great Lakes through the period, the Northwest mid to late period, and portions of the Plains and Ohio Valley late in the period, where incorporation of the 18z and 00z GFS/00z ECMWF appeared necessary, especially near the Gulf Coast where the NBM was inexplicably dry, particularly when compared to past couple wet Canadian global runs. PoPs adjustments were made to account for the QPF changes. For the remainder of the grids, the 01z NBM seemed like a good starting point. ...Weather/Hazards Highlights... Precipitation across the Northwest/Northern Rockies should continue early on and could pick up early next week as the general flow pattern attempts to become more zonal. Snow is possible in the highest terrain of the Washington Cascades and increasingly possible across the Northern Continental Divide. A clipper system/disturbance into the northern High Plains will interact with a stationary frontal boundary and the northern Rockies to bring heavy snow threats to portions of central to eastern Montana Friday, with several inches of snow possible. Additional energy rounding the base of the trough centered over the eastern third of the country will bring rounds of generally light to moderate precipitation, mainly snow, into the Midwest/Great Lakes and eastward towards the Appalachians and Northeast through the weekend. To the South, reinforcing fronts slowing as they approach Florida/the Gulf Coast will bring the threat of rain. A strong temperature gradient is forecast across the High Plains/Plains with 15-25F above average temperatures across the West which spread into the High Plains with time early next week and 20-30F below average temperatures Friday into Monday from the Northern Plains across the Great Lakes, Midwest, and Ohio Valley while weaken somewhat as the airmass migrates into the East next Tuesday. This may result in hazardous cold as morning temperatures dip below zero with wind chills near -20 degrees. This airmass will moderate somewhat as it moves into the Ohio Valley and East next week. Much of the South, Gulf Coast, and Florida will be near normal through the period. Roth/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 (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 $$