Extended Forecast Discussion NWS Weather Prediction Center College Park MD 201 PM EST Wed Jan 11 2023 Valid 12Z Sat Jan 14 2023 - 12Z Wed Jan 18 2023 ...Unsettled and Active Pattern Continues for Western U.S. with focus on California Atmospheric Rivers... ...Overview and Guidance/Predictability Assessment... A general model blend consisting of the deterministic 00z EC/CMC/UKMET and 06z GFS was utilized through day 5. The 00z ECE was introduced on day 5 and continued through day 7 with steady increases through the end of the period. The 06z GEFS and 00z CMCE were introduced on day 6 and continued through day 7 with increased weighting. The 13z NBM trended drier overall along the West Coast throughout the medium range period. There's reasonable agreement with respect to the QPF in northern/Central California on day 5, but the last few runs of the EC have thrown a wrench in any plans for an upgrade to the current marginal risk ERO for that area. This can be reevaluated if subsequent runs of the EC trend closer/faster to the other guidance. Some minor targeted changes were made to the QPF along the West Coast to keep our latest guidance from straying too far from to continuity. ...Weather/Hazard Highlights... Unsettled and active weather is expected to continue across portions of the West as a series of atmospheric rivers move onshore. The first in this series of extended range storms will arrive this weekend, and is expected to bring another round of widespread heavy rain across northern and coastal California with heavy snowfall into the Sierra Mountains as well. Worsening flooding or delayed improvement of ongoing issues is possible across this very over-saturated coastal central to southern California. As the energy moves inland on Sunday, rain and higher elevation snows are possible in the Southwest, and eventually return flow out of the Gulf of Mexico may increase precipitation chances into the Plains/Midwest as well. An almost constant fetch of onshore moisture into the Northwest and parts of the California through the period will keep rainfall, though less intense, in the forecast early next week before another possible heavier storm arrives around next Tuesday. In the East, precipitation ahead of the trough should be well off the coast by this weekend, except for some possibly light wrap back snows across northern New England which is dependent on proximity of secondary low development to the coast. Above normal temperatures will move east with time from the Central U.S. this weekend into the Midwest and eventually the East early next week. The greatest anomalies should focus across the Deep South into the Midwest with daytime highs 10 to 20 degrees F above normal. Even more impressive will be the very warm nighttime lows, with readings 20 to 25 degrees F above normal generally across the same region from Sunday onward. Daytime highs across the West and Southwest should be near or below normal amidst plenty of clouds and rainy conditions. Kebede/Santorelli 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, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml