Extended Forecast Discussion NWS Weather Prediction Center College Park MD 236 PM EST Tue Jan 31 2023 Valid 12Z Fri Feb 03 2023 - 12Z Tue Feb 07 2023 ...Dangerously cold temperatures and wind chills are forecast across the north-central U.S. late week spreading into the Northeast for the weekend... ...Overview... The large scale pattern will remain actively progressive and wavy through the extended period, favoring a stronger northern stream. This setup will feature troughing from the Midwest to the Northeast late this week that will support significantly cold temperatures and wind chills. Rain and thunderstorms may linger into Friday for the far Southeast/Florida Peninsula with a southern stream wave. Portions of the West will trend wetter as a couple of rounds of upper troughing coming into the West. The first trough will pass through a majority of the lower 48 states yielding little precipitation with the exception of lake-enhanced snow across the Great Lakes region; once it reaches the East the precipitation will increase. A second trough is more likely to produce precipitation across the central U.S. by the beginning of the coming week. ...Guidance/Predictability Assessment... In general, the model guidance is in decent agreement for most of the extended period. As previously noted, there have been minor differences in the timing of phasing of features particularly with the approaching low/trough in the mid/latter half of the forecast. The CMC has been on the deeper and relatively slower evolution compared to other deterministic solutions. The most recent version keeps that trend initially, however it has trended closer to the timing/location of the energy coming across the Southwest/Four Corners region with the favored ECWMF as well as the GFS. The CMC is still favoring more stream separation, putting most energy in the southern tier. The WPC forecast was based on a heavier lean toward the 00Z ECWMF, the 00/06Z GFS, 00Z CMC and UKMET early in the period. The inclusion of the EC increasing the proportion of the GEFS and EC ensemble means as the period progressed and limiting the amount of 12Z ECMWF. Good continuity was maintained with the previous forecast, and the incoming 00Z models seem to be consistent as well--the 00Z CMC especially seemed to come into better alignment with the first couple of features, though so far it is the most aggressive with closing off a low within the second trough in the West. ...Weather/Hazard Highlights... Rain and thunderstorms will be ongoing across portions of the Southeast on Friday prior to the front moving offshore. In the wake of the departing front, colder and drier air will filter into the eastern states. On Friday highs in the single digits are forecast for the Upper Midwest into northern New England, and bitterly cold lows combined with wind will produce dangerous wind chills especially Saturday morning. Several low maximum and minimum temperatures could be set especially in the Northeast before a moderating trend by Sunday. Most areas across the East will be dry by Saturday, but some moisture return by Sunday could lead to precipitation across the Eastern Seaboard, but with uncertainty for how much falls onshore. A swath of light snow may expand in coverage across the Midwest/Great Lakes/Northeast by the weekend with a clipper system, adding to some light lake effect amounts. For the West, light to moderate precipitation will increase in coverage especially along the coastline and the adjacent terrain as multiple upper troughs pass through the region. The Pacific Northwest into northern California will be the most likely to see lower elevation rain and higher elevation snow, while the northern Rockies and other areas of the Intermountain West could see some light to moderate snow as well. Temperatures are expected to trend warmer than average across most areas, including the central U.S. and spreading into the East early next week. The West could cool down especially in terms of high temperatures underneath a longwave trough by Monday-Tuesday though. Campbell 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