Extended Forecast Discussion NWS Weather Prediction Center College Park MD 134 AM EST Tue Feb 18 2020 Valid 12Z Fri Feb 21 2020 - 12Z Tue Feb 25 2020 ...Guidance/Predictability Assessment... Model and ensemble forecast spread overall remains below normal through the rest of this week, increasing gradually early next week. Lingering system timing and emphasis differences seem well mitigated by the blending of reasonably well clustered guidance through medium range time scales. Accordingly, the WPC medium range product suite was based primarily from a composite blend of the 18 UTC GFS/GEFS mean, 12 UTC ECMWF/ECMWF ensemble mean and the National Blend of Models. This forecast strategy maintains good WPC continuity. The latest 00 UTC GFS/GEFS/ECMWF/UKMET and Canadian generally seem well in line with this WPC forecast. ...Weather Pattern and Hazard Highlights... Strong high pressure will prevail over most of the lower 48 late this week and lead to fairly low precipitation coverage. However, a well organized system evolving off California late this week and then progressing eastward will bring moisture into parts of California and the Four Corners states from about late Fri into the weekend. There may be a brief period of enhanced rain and high elevation snow with this system. As height falls and the surface system continue eastward expect precipitation to develop over the Plains/Mississippi Valley this weekend and spread into the eastern states through early next week. Gulf of Mexico return flow may help to 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 of the growing precipitation shield as the ambient/cold high pressure dome recedes. Upstream, an upper trough/surface system moving into the West by late weekend/early next week will bring an episode of enhanced rain and higher elevation snow to the Pacific Northwest, with snows spreading into north-central portions of the Great Basin/Rockies/Plains with slow system progression and reinforcement. Late this week expect below to much below normal temperatures from the north-central Rockies into the Southern Plains as well as Upper Midwest into New England with some locations as low as 15-25F below normal. Much of the remaining eastern two-thirds of the U.S. will be below normal to a less extreme degree. Temperatures will moderate into the weekend though with some lingering coolness over the South/Southeast. The system moving into the West will bring below normal temperatures to most of the region, then Rockies/Plains into early next week. 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