Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1026 AM EST Mon Jan 21 2019 Valid 12Z Thu Jan 24 2019 - 12Z Mon Jan 28 2019 ...Overview... Guidance shows an amplified upper pattern featuring an eastern Pacific/West Coast ridge and an expansive east-central North American trough. The overall mean pattern appears to have fairly high predictability, but embedded shortwaves remain more difficult to resolve. The ridge may retrograde a bit next week and teleconnections favors an increased potential for positively tilted troughing to then develop over the West. ...Guidance Evaluation/Preferences... The WPC medium range product suite was derived from a blend of reasonably well clustered guidance from the 00 UTC GEFS/ECMWF ensemble means. The 06 UTC GEFS is not as well clustered. Deterministic models offer even more run to run variance days 4-7 and their less certain detail was downplayed. ...Weather Highlights/Hazards... Frontal waves will focus areas of significant precipitation in the East Thu with the best snow potential over interior New England. The Great Lakes will see episodes of snow all week from a combination of passing systems and lake enhancement, with other areas east of the Rockies seeing some precipitation with low pressure/frontal passages. Another organized precipitation threat over the East exists this weekend into next Mon. While forecast confidence in coverage/intensity has been less than average, the 00 UTC GEFS/ECMWF ensemble means are now in better agreement with the development of a mid-Atlantic coastal low. The rain-snow line should extend fairly far southward given the cold pattern becoming established over the eastern half of the country. Meanwhile at least a couple shortwaves/fronts and trailing high pressure should bring periods of snow to parts of the northern and central Rockies with most activity likely to be in the light-moderate range. Schichtel 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