Extended Forecast Discussion NWS Weather Prediction Center College Park MD 153 PM EST Sun Jan 19 2025 Valid 12Z Wed Jan 22 2025 - 12Z Sun Jan 26 2025 ...Bitterly cold temperatures to continue through about Thursday for parts of the East and the South... ...Overview... Troughing over the Eastern Seaboard to start the period should shift east helping to gradually moderate bitterly cold temperatures to start the period. Reloading of the trough is expected though as another amplified pattern develops upstream across the Central to Eastern U.S. Thursday-Friday. Ridging over the West should shift quickly inland late week as an amplified shortwave into the Northwest drops down the coast and produces positively tilted troughing with possible southern stream closed low development over southern California/the Southwest into next weekend. Much of the early period precipitation should be light in nature and confined to the northern tier, Florida, and perhaps the coastal parts of the East. The developing trough atop the West is expected to lead to some light to moderate precipitation across the West Coast to the Great Basin and Rockies late week into next weekend, while moist inflow returns to the Mid-South for rain potential next weekend and some possible snow toward the Great Lakes. ...Guidance/Predictability Assessment... Model guidance shows generally good agreement on the large scale pattern through the entire extended range period, but uncertainty on the details remains. A multi-model blend worked well for upper troughing deepening across the Plains/Mississippi Valley around Thursday and moving east late week. With lows offshore in the western Atlantic that may produce precipitation along the East Coast, the 00Z CMC seemed to be a western outlier compared to consensus and spread more precipitation into New England, but the 12Z CMC shifted much farther offshore. Models are in better agreement today compared to a day ago with the track and timing of the next trough digging into the Northwest around Friday and shifting south. Its evolution into the weekend is still in question though, as guidance varies with how much energy may separate into the southern stream. As of the 00Z/06Z model runs, most trended away from producing a closed low atop the southwestern U.S. by Sunday, other than the CMC. The AI/ML models were steady with a closed low though. The incoming 12Z GFS/CMC/ECMWF now all show a closed low so expect the next forecast to trend back that direction, but it may take additional time for models to completely stabilize before settling on a solution. Regardless, with the reasonable agreement in the overall pattern, maintained a majority of deterministic models in the blend through the period but with some inclusion of the ensemble means. ...Weather/Hazards Highlights... Bitterly cold temperatures moving into the central U.S. and the Midwest early this week should moderate by the start of the period Wednesday and become near to slightly above normal. Much colder than normal temperatures by 20-30 degrees will continue for parts of the East and South and could set daily record low max and min temperatures. Though still chilly Thursday and Friday, temperatures will gradually moderate in the South and East, reaching near normal this weekend. Meanwhile, California to the Great Basin can expect warmer than normal temperatures through the rest of the workweek before the West cools underneath the upper trough next weekend. Precipitation across the lower 48 during the medium range period should be relatively quiet. Some modest rains are possible across Florida associated with lingering frontal boundaries Wednesday and Thursday, with rain or light snow up the Southeast to Mid-Atlantic to Northeast coast with weak surface lows lifting northward. A couple rounds of light precipitation are forecast from the Northern Plains to Midwest/Great Lakes and Ohio Valley as cold frontal clipper systems move through. More widespread rain and mountain snows will move into the West by Thursday-Friday and shift south with time, hopefully providing some much needed rain to Southern California next weekend. Farther east, moisture return into the Lower Mississippi Valley to Tennessee/Ohio Valleys is expected into next weekend for some modest rain amounts, with snow possible farther north across the Great Lakes. Tate/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