Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Wed Jan 06 2021 Valid 12Z Sat Jan 09 2021 - 12Z Wed Jan 13 2021 ...Overview... Upper ridging over northwestern Canada will slip southwestward and build over the western CONUS by the middle of next week. This will favor troughing in the east by way of several lead systems in the northern and southern stream. Eastern Pacific systems should track into Canada with their fronts producing daily light to moderate precipitation for especially coastal Washington and Oregon this weekend into early next week, perhaps followed by more appreciable precipitation next week. System organizing over the western Gulf of Mexico will bring rain to the northern Gulf coast as it moves eastward/northeastward Monday and then off the Southeast coast. Uncertainty remains in how developed this system may become. Pacific origin of most flow reaching the lower 48 will keep any arctic air in Canada for the next week but the mean trough aloft extending into the southern Plains and succession of southern tier systems will promote cooler than normal temperatures over much of the southern U.S. ...Guidance/Predictability Assessment... With the smaller-scale features dominating the first few days of the forecast, resulting in poorer-than-average run-to-run continuity, preferred a blend of the recent deterministic guidance as each likely exhibited some good and poorer aspects of the forecast overall. Trend around Monday next week may be toward stronger height falls through Ontario concurrent with the eastward motion of the Gulf system. Though the two may not interact over the East Coast, their resultant movement into the Atlantic along with any trailing shortwaves out of the northern Rockies will act to anchor the trough in the East. Ensembles show this well by next Wednesday with the ECMWF ensembles more amplified than the GEFS overall. Gave a majority weight to the ECMWF ensembles as the upstream Pacific pattern suggests more meridional flow and a sharper ridge/trough couplet. ...Weather/Threats Highlights... The Pacific Northwest will continue to see periods of precipitation with only few breaks during the period. Current guidance is not yet unanimous but there is a decent signal that heaviest rain/high elevation snow will fall next week, especially over Washington. System out of the southern Rockies Saturday will tap the Gulf for moisture reaching into the Texas and Louisiana coasts around late Sat through at least Sun night. This could lead to some modest rain along the coast, with the heaviest rainfall just offshore as the trend continues in that direction. To the north, temperatures may be cold enough for some light wintry weather from the Texas Panhandle eastward to the ArkLaTex. Confidence is low for precipitation coverage and type over the East toward the end of the period, but maintained at least light amounts along and east of the southern Appalachians given the uncertainty. Northern tier locations, especially from Montana into Minnesota, will be consistently well above normal for temperatures. Expect some plus 10F or greater anomalies each day. Morning lows should generally be farther above normal than the daytime highs and plus 20F or greater anomalies are possible for Saturday lows and perhaps again around the middle of next week. California will tend to be above normal but with only single-digit anomalies. The southern Plains and South will likely see below normal highs most of the period, with one area of minus 5-15F or so anomalies on Sunday over Texas. Temperatures will moderate only a bit from west to east (toward the Carolinas) into next week. Fracasso/Rausch 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