Extended Forecast Discussion NWS Weather Prediction Center College Park MD 203 AM EST Wed Feb 01 2023 Valid 12Z Sat Feb 04 2023 - 12Z Wed Feb 08 2023 ...Dangerously cold temperatures and wind chills are forecast across the Northeast on Saturday... ...Overview... The overall upper-level pattern during the medium range period will remain fairly wavy and progressive. As the period begins Saturday, troughing will extend from a deep upper low over the Canadian maritimes into the Northeast, leading to significantly cold temperatures and wind chills there. Another trough is forecast to press across the central to eastern U.S. through early next week, but with precipitation limited to the Great Lakes region and perhaps the Eastern Seaboard. Yet another trough approaching the West should lead to a wetter pattern there for the weekend, with generally light to moderate rain and snow amounts. This latter trough is forecast to track into the central U.S. in some fashion by Tuesday-Wednesday, leading to a wetter pattern there. ...Guidance/Predictability Assessment... Model guidance remains in generally good agreement for the early part of the medium range period this weekend. No real outliers were noted, so WPC was able to use a blend of the deterministic 12/18Z model guidance through days 3-4. Greater model differences start to arise by day 5/Monday with the trough in the West and especially as it shifts eastward. Models have been waffling in terms of how much stream separation to create with this energy. GFS runs have been fairly persistent in showing a southern stream closed low breaking off and lingering in the Southwest Tuesday-Wednesday. In terms of the ensembles, mainly GEFS members are the ones that exhibit this type of pattern as well. Meanwhile ECMWF runs have been indicating a phased steadily progressive trough, as have the CMC runs lately, but older runs of the CMC had shown the southern stream closed low. There are also some differences in the models regarding whether additional energy coming from the northwest interacts with the trough, which complicates matters all the more. Thus the WPC forecast transitioned to a blend favoring the ensemble means by half day 6 and over half on day 7 given the operational model differences. Fortunately the ensemble means were aligned fairly well--though, the GEFS means do indicate maintaining more separation through midweek than the EC mean and especially the CMC mean. ...Weather/Hazard Highlights... Very cold conditions are likely for the northeastern U.S. on Saturday underneath cold upper troughing. Many low temperatures on Saturday morning are forecast to break records, and the bitter cold combined with wind will produce dangerous wind chills. Well below normal high temperatures could also set records, as temperatures could stay below zero all day in parts of Maine and in the single digits in much of northern New England. Chilly temperatures are forecast to expand across the Eastern Seaboard Saturday, with temperatures commonly 10-20F below normal. But a pronounced warming trend is expected to occur across much of the country starting in the central U.S. this weekend and expanding into the East early next week. The West however could stay around 5-10F below average especially in terms of highs underneath upper troughing. A frontal system could spread some light snow to the Midwest/Great Lakes regions and Northeast this weekend, and amounts could be enhanced downwind of the Great Lakes. Light precipitation is possible along the Eastern Seaboard with some moisture return by Sunday, but uncertainty remains as to how much falls onshore. Today's forecast shows less East Coast precipitation compared to the forecast from 24 hours ago. Meanwhile in the West, generally light to moderate precipitation is expected this weekend in the form of lower elevation rain and higher elevation snow, with typical terrain enhancement across the coastal ranges and the Sierra Nevada. Snow is forecast to spread into the Intermountain West and Rockies early next week, and then precipitation could overspread the central U.S. by Monday-Tuesday along and ahead of a low pressure/frontal system. Generally this looks to be in the form of rain other than some possible snow in the northern tier (Midwest-Great Lakes), but will continue to monitor. The Pacific Northwest to northern Rockies are likely to see additional rounds of precipitation into the first half of next week. Tate 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