Extended Forecast Discussion NWS Weather Prediction Center College Park MD 149 AM EST Mon Feb 21 2022 Valid 12Z Thu Feb 24 2022 - 12Z Mon Feb 28 2022 ...Heavy to excessive rainfall threat from the Mid-South to the Mid-Atlantic Thursday along with a significant heavy snow/ice threat from the Mid-Mississippi Valley northeastward to the Northeast Thursday-Friday... ...Guidance Evaluation/Predictability Assessment... Models and ensembles offer a similar mid-larger scale flow evolution in a pattern with above normal overall predictability. An 18 UTC GFS and 12 UTC ECMWF/UKMET/Canadian composite along with the 01 UTC National Blend of Models seems to provide a good forecast basis days 3-5 (Thursday-Saturday). Blending of these well clustered models tends to mitigate smaller scale system variances consistent with predictability. Newer 00 UTC guidance is consistent. The WPC product suite into days 6/7 was mainly derived from the ECMWF ensemble mean that maintains a slightly more amplified Southeast upper ridge that often lingers on the stronger side of the full envelope of solutions in this type of pattern. This plan maintains great WPC product continuity. ...Pattern Overview and Weather Highlights/Threats... A cold pattern ensues this week as Canadian high pressure settles across much of the lower 48. Upper level troughs will dig through the West/Southwest, with ejecting energies and induced frontal waves progressing downstream overtop a warming Southeast upper ridge. A main upper trough will eject out through the south-central Plains and Mid-South/OH Valley later this week as amplified ridging builds from the east Pacific to the West Coast. This will favor a heavy to excessive rainfall threat from the Mid-South to the Mid-Atlantic Thursday, along with a significant heavy snow/ice threat from the cooled Mid-Mississippi Valley northeastward through Ohio Valley states to the Northeast Thursday into Friday. Later, northeast Pacific upper trough energies and precipitation will slowly work toward the Pacific Northwest days 6/7 (Sun/next Mon). This occurs as lead upper troughing ejects out from the West/Southwest to across the southern U.S. tier to modestly renew waves and precipitation, albeit with more uncertain phasing with an amplifying/cold reinforcing northern stream upper trough then set to dig into the east-central U.S.. The cold high pressure surge will spread much below temperatures across much of the western and central U.S. by mid-late week to include widespread record cold values, especially frigid from the northern High Plains to the Northern/Central Plains where daytime highs and overnight lows could be 30-40+ degrees below normal. This very cold air will spread, but gradually modify later week across the Midwest/East. Meanwhile, much above normal pre-frontal temperatures are expected across the Southeast/East with some record warmth likely, especially overnight mins with upper level ridging and enhanced pre-frontal moisture into the region. 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, 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