Extended Forecast Discussion NWS Weather Prediction Center College Park MD 154 AM EST Mon Jan 3 2022 Valid 12Z Thu Jan 6 2022 - 12Z Mon Jan 10 2022 ***Additional rounds of heavy coastal rain and mountain snow for the northwestern states*** ***Frigid air mass for the north-central U.S. and potential snow for inland portions of the East Coast region late in the week*** ...General Pattern Overview... The upper level flow pattern over the nation will be rather amplified through the end of the week with a large scale trough over the east-central U.S. and a broad ridge over the West Coast, before transitioning to a more quasi-zonal flow by the weekend. An organized low pressure system is expected near the East Coast to close out the week, and another low affects the Great Lakes by Saturday night into Sunday. An arctic air mass will settle southward across much of the north-central U.S. in the wake of the strong cold front. ...Guidance assessment and uncertainty... The 00Z model guidance suite is in very good synoptic scale agreement through Saturday with some mesoscale timing and amplitude differences with the individual shortwave passages. One of the main differences is with the 00Z GFS by depicting a more offshore track with the East Coast low and thus much less impactful for the Northeast, and this was also the case with yesterday's GFS run. By Sunday, the GFS becomes considerably stronger with a potential closed low over the West Coast region, which does not have much ensemble support. The greatest differences by day 7 are apparent this same general region, whilst the trough over the East has good model agreement. The WPC forecast was based primarily on a multi-deterministic model blend through Friday, and then gradually increasing use of the ECENS and GEFS means through next weekend and into Monday. ...Sensible Weather... There will be multiple Pacific storm systems that will affect the Pacific Northwest and inland across portions of the Great Basin and the Northern Rockies. This will result in heavy rain and heavy mountain snow for Thursday and Friday, with a potential atmospheric river event for northern Oregon and southwest Washington during this time. A drying trend should commence in time for the weekend across much of the West as high pressure builds back into the region. Meanwhile, widespread light to moderate precipitation is likely across the eastern third of the U.S. in association with the East Coast low on Friday, with heavy snow possible for portions of the Appalachians. More showers and storms are likely to make a return to the Gulf Coast region by Sunday ahead of the next front. Temperatures are expected to be frigid across the central/northern Plains to the Upper Midwest through the end of the week with a large surface high of arctic origin governing the weather pattern for this region. Subzero highs are once again likely for portions of eastern Montana, North Dakota, and northern Minnesota, and highs in the teens settling as far south as Kansas on Thursday. Some abatement in the severe cold may come to pass across this region on Saturday ahead of the next arctic surge Sunday, which is not expected to be as intense as the earlier arctic blast. Elsewhere, seasonably cold conditions are expected west of the Continental Divide with readings generally within 10 degrees of climatological averages, and mild across the southern Plains and Deep South with highs running 5 to 15 degrees above average this weekend. Hamrick 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