Extended Forecast Discussion NWS Weather Prediction Center College Park MD 203 PM EST Wed Feb 01 2023 Valid 12Z Sat Feb 04 2023 - 12Z Wed Feb 08 2023 ...Temperatures Saturday across the Northeast will be dangerously cold temperatures... ...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... The latest suite of model guidance maintains decent agreement on the large scale pattern for the weekend/start of the extended period. Over the weekend an upper trough will be tracking offshore the Northeast region, impulses exiting the Rockies into the Plains while trough approaches the West. The trough entering the West has been and continues to be the main feature where the models are waffling on the degree of separation of the northern and southern streams which has led to timing, strength, location and progression differences particularly for the South for the later portion of the extended period. A majority of the guidance have converged to a solution with a closed low over the Southwest that will linger for awhile. While the CMC leans toward this pattern it quickly moves to the front of the cluster and favors a faster track across the Southern Plains through the middle and latter portion of the extended; thus its inclusion was limited. Both the GEFS means and the EC ensemble means had solutions similar to their respective parent models but slightly more progressive across the Southwest. There continues to be some differences in the models regarding whether additional energy coming from the northwest interacts with the trough, which complicates matters all the more. The preferred WPC blend utilized a blend of the 00Z/06Z GFS/00Z ECWMF with lesser weightings of the CMC and UKMET. The inclusion of the the ensemble means began by Day and increased to nearly 50% weighting by the end of the extended forecast. ...Weather/Hazard Highlights... Very chilly conditions are expected across the Northeast Saturday as cold air and gusty winds settle in under upper-level troughing. Dangerous wind chills and possibly new daily temperature records are in store for much of the Northeast region. Temperatures could stay below zero all day in parts of Maine and in the single digits in much of northern New England. This cold airmass is expected to sink further south along the Eastern Seaboard leading to temperatures 10-20F below normal. Temperatures are expected to rebound across the East was warmer temperatures over the central U.S. migrate eastward after the weekend.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. 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. Campbell/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