Extended Forecast Discussion NWS Weather Prediction Center College Park MD 201 AM EST Wed Feb 19 2020 Valid 12Z Sat Feb 22 2020 - 12Z Wed Feb 26 2020 ...Dynamic Southwest to Northeast U.S. then Wintry Northwest to Midwest Lows... ...Guidance/Predictability Assessment... Latest model and ensemble solution spread slowly increases over time, but remains at below normal values overall through medium range time scales. This bolsters forecast confidence. WPC medium range products were based mainly from a composite blend of well clustered guidance from the 12 UTC GFS/ECMWF, 12 UTC GEFS/ECMWF ensemble means, and the National Blend of Models. Blend emphasis was gradually transitioned from the models toward the ensemble means days 3-7 to address lingering system timing and emphasis differences. WPC continuity was well maintained and the newer 00 UTC models and ensembles now overall seem in line. ...Weather Pattern and Hazard Highlights... System #1: Mainly dry high pressure will linger over the East this weekend in anticipation of an approaching southern stream system set to progress from southern California and the Southwest U.S. to the south-central U.S. A moderate precipitation swath from the Southwest/Four Corners/Rockies Saturday will include terrain enhanced snows. Precipitation will develop more in ernest into the Mid-Lower MS and TN Valleys Sun and spread across the eastern states through early next week as height falls and main surface system tracks east-northeastward. Gulf of Mexico return flow will promote locally moderate to heavy rainfall over parts of the mid-lower Mississippi and Tennessee Valleys/southern Appalachians, areas that will be sensitive to additional rainfall given ongoing runoff issues. This will be a fairly warm system, but there is a risk for snow/ice on the northern periphery (particularly for the Northeast) of the growing precipitation shield as the ambient/cold high pressure dome recedes and with coastal low development. System #2: Upstream, a more northern stream upper trough/surface system moving into the Northwest Sunday will dig through the Great Basin and Rockies Sunday will bring enhanced rain and higher elevation snow to the Pacific Northwest, with heavy snow potential spreading into north-central portions of the Great Basin/Rockies/Plains with slow system progression and reinforcement. Downstream system development and track over the n-central U.S. and Midwest offers an emerging pattern favorable for precipitation that would include a threat of widespread heavy snow over the n-central states early-mid next week. Much below normal temperatures spread east with the dome of high pressure Friday into Saturday. Temperatures of 10 to 15 degrees below normal are expected from the southern Plains to the Eastern Seaboard Friday and just the Southeast on Saturday. Temperatures will moderate across these areas through early next week. The system moving into the Northwest will bring below normal temperatures to most of the region Sunday into Monday, expanding to the Rockies/Plains Monday into Tuesday/Wednesday. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards 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