Extended Forecast Discussion NWS Weather Prediction Center College Park MD 127 AM EST Thu Feb 07 2019 Valid 12Z Sun Feb 10 2019 - 12Z Thu Feb 14 2019 ...Overview and Guidance/Predictability Assessment and Preferences... Pacific flow remains fraught with uncertainty surrounding a stubborn upper high near the Gulf of Alaska. Troughing will generally stay focused near/along the west coast of the lower 48, reinforced either from the north (on the east side of the upper ridge) or from the west (underneath the upper ridge). An upper high over the Florida Straits will weaken and split E-W from Mexico to the Great Antilles, opening up broad troughing into the east. However, how this unfolds is quite uncertain as evidenced by the notable timing/track differences among the guidance from as early as 48 hrs near Alaska. Multi-day trend supports something along the line of the 12Z ECMWF ensemble mean and 12Z ECMWF rather than the 12Z/18Z GFS/GEFS though the 12Z/18Z FV3-GFS runs were at least halfway toward the ECMWF from the operational GFS runs. In order to maintain continuity in the face of recalcitrant ensemble members, opted to rely mostly on the 12Z ECMWF ensemble mean for the basis of the forecast. This will take a system northeastward toward the Great Lakes/Northeast late Monday into Wednesday as a couple more systems sink through the West. ...Weather Highlights/Hazards... Much below average temperatures will remain anchored over the High Plains throughout the medium range period (MT/ND/SD). The rest of the West is forecast to see below average temperatures due to the persistent troughing and episodic cooler surges of Canadian air. This may result in some record cold temperatures for coastal WA/OR and northern California Sun/Mon. Slightly below average temperatures will bleed into the Upper Midwest and then Great Lakes behind the midweek system. A surge of above average temperatures will precede the cold front especially Tuesday. Late this weekend and into early next week another round of potentially heavy precipitation will spread into the Lower to Mid-Mississippi and Tennessee Valleys as moisture surges northward atop a warm front along the Gulf Coast. As a low pressure system strengthens into the Midwest on Tuesday, precipitation is expected to push through the Ohio Valley and into the Mid-Atlantic/Northeast. With temperatures near/below freezing, wintry precipitation will be possible on the northwest/north side of the low and well ahead of the warm front -- generally north of 40N. 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 and southern Washington. 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