Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1059 AM EST Tue Feb 05 2019 Valid 12Z Fri Feb 08 2019 - 12Z Tue Feb 12 2019 ...Overview... Upper ridging will dominate the area just west of the Gulf of Alaska as well as across the Florida Straits. This will favor renewed troughing along the West Coast and broad WSW flow aloft through the east. ...Guidance/Predictability Assessment and Preferences... For days 3-4 (Fri-Sat), the low across the northeastern U.S./Canada and the low offshore of the U.S. West Coast both seemed well handled by the operational and ensemble models, so the WPC forecast was based on a blend of the 00Z operational ECMWF and its ensemble as well as the 00Z GFS and GEFS and 06Z GFS. By days 5-6, the operational 00Z ECMWF began to split the upper-level energy near and in the western U.S., sending a shortwave eastward into the Intermountain West and leading to a more progressive pattern at days 6-7 across the central U.S. Other models do not have this tendency, and it is not well supported by the means, nor by teleconnections related to the upper ridging near Alaska. Thus opted not to use the operational 00Z EC for the latter half of the medium range period. The EC/GEFS means were used, with some continuity as well. ...Weather Highlights/Hazards... Much below average temperatures will be focused over the Northern High Plains throughout the medium range period, north of an arctic front that will linger near the Divide. Below average temperatures will approach the Midwest as well, with the encroachment of arctic air. The rest of the West will mostly see below average temperatures due to the persistent troughing. A cold front in the east will push the well above average temperatures along the Eastern Seaboard on Friday out to sea, which will be replaced by near average to colder than average readings for the weekend. Meanwhile, the beginning of next week is forecast to be warm for the Southeast. Lake-effect snows will resume Friday into Saturday as colder air wraps around the departing surface low. Late this weekend and into early next week, another round of potentially heavy precipitation will spread into the Mid-Mississippi and Tennessee Valleys via the combination of another weak impulse out of the Rockies and a slow surge of moisture atop a warm front along the Gulf Coast. Through the West, low pressure systems will bring several rounds of light to moderate valley rain/mountain snow to the region, especially from central CA/Sierra northward to Oregon. Tate/Fracasso WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities are found 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