Extended Forecast Discussion NWS Weather Prediction Center College Park MD 327 PM EST Wed Feb 23 2022 Valid 12Z Sat Feb 26 2022 - 12Z Wed Mar 02 2022 18Z Update: The 12Z model guidance suite is in good agreement on the overall synoptic scale pattern on Saturday. However, noteworthy shortwave and timing differences become apparent as early as Sunday, with the 12Z ECMWF more amplified with the southern stream trough crossing the Southern Plains and Deep South through Monday night, and the CMC stronger with the Pacific trough reaching the West Coast and moving inland across the Intermountain West. Major timing differences are apparent across central Canada with the next northern stream shortwave dropping southward, with the GFS much much progressive than the ECMWF, whilst the CMC is less pronounced with this same shortwave. The models are also struggling with how that shortwave from Canada potentially interacts with the Pacific trough exiting the Rockies, and this leads to a more uncertain forecast from the Upper Midwest to the Northeast through the early to middle of next week. At the time of the fronts/pressures preparation, the blend was weighted more heavily towards the GFS/CMC/UKMET/GEFS mean since there was better ensemble clustering for a stronger trough across the eastern U.S. early next week, whereas the 00Z ECMWF was more zonal and did not have as much ensemble support. Given the increasing uncertainty by Tuesday-Wednesday, the forecast was hedged more on the GEFS/ECENS along with some of the CMC/GFS and previous WPC continuity. /Hamrick ------------------------------- ...Pattern Overview... Overall cold and drier conditions are slated for much of the lower 48 states this weekend into early next week to be followed by broad moderation of temperatures spreading from the West to the East early to mid next week. ...Guidance Evaluation/Predictability Assessment... The WPC medium range product suite was primarily derived from the 18 UTC GEFS mean and the 01 UTC National Blend of Models. Despite reasonably similar larger scale pattern evolution, emphasis on any individual model does not seem prudent given recent run to run continuity issues and variance with embedded weather features. While southern stream differences actually seem a bit less pronounced than yesterday, the last few ECMWF and ECMWF ensemble mean runs trended much flatter over the central to eastern U.S. with northern stream upper troughing this weekend into early next week despite amplified upstream ridging over western North America. While embedded system wavelength spacing could support this trend around a Hudson Bay vortex position, instead have leaned the WPC solution to a more amplified and colder 18 UTC GEFS mean or probably the slightly less amplified 00 UTC GEFS mean. This plan best maintains WPC product continuity. ...Weather Highlights/Threats... Cold high pressure will settle across much of the country by this weekend into next week. The weather pattern will also favor drier conditions. An exception may be across the south-central to southeastern U.S. where precipitation could return this weekend. This will be mainly in the form of light to moderate cold rains, but with some snow/ice threat on the northern periphery of the swath of precipitation. In addition, modest precipitation is expected to develop for the Pacific Northwest/Northern CA this weekend with slow approach of northeast Pacific systems. Precipitation totals are forecast to increase over the Pacific Northwest/northern CA and gradually spread across the northwestern states early-mid next week, including terrain enhanced snows. Schichtel/Hamrick 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 Hazards: - Heavy precipitation across portions of the Pacific Northwest and the Northern Great Basin, Sat-Tue, Feb 26-Mar 1. - Heavy rain across portions of the Pacific Northwest, Sat-Tue, Feb 26-Mar 1. - Flooding possible across portions of the Northeast, the Central Appalachians, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Great Lakes. - Flooding likely across portions of the Middle Mississippi Valley, the Lower Mississippi Valley, the Great Lakes, the Ohio Valley, and the Tennessee Valley. - Much below normal temperatures across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Rockies, the Southern Rockies, the Northern Great Basin, and the Southwest, Sat-Sun, Feb 26-Feb 27. - Much below normal temperatures across portions of the Central Plains, the Middle Mississippi Valley, the Lower Mississippi Valley, and the Southern Plains, Sat, Feb 26. - Much below normal temperatures across portions of the Great Lakes, the Upper Mississippi Valley, and the Northern Plains, Sun-Mon, Feb 27-Feb 28. - Much below normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley, Mon, Feb 28. WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml