Extended Forecast Discussion NWS Weather Prediction Center College Park MD 156 AM EST Sun Jan 29 2023 Valid 12Z Wed Feb 01 2023 - 12Z Sun Feb 05 2023 ...Notable precipitation likely for the latter half of the week including heavy rain in the south-central to southeastern U.S. with freezing rain/snow on the northern side... ...Dangerously cold temperatures and wind chills are forecast across the Northern Plains/Upper Midwest and into the Northeast at times through the week... ...Overview... It remains the case that periods of troughing are likely through much of the northern U.S. this week extending from a persistent Hudson Bay closed low, leading to colder than average temperatures for much of the northern tier. The cold temperatures and wind chills could be most hazardous for the north-central U.S. through around Friday, with significant cold extending into the Northeast by late week. Meanwhile a ridge/upper high over Cuba during much of the week should keep the Southeast warmer than normal. Between these upper-level features and temperature regimes, expect active weather as a southern stream upper trough/low ejects from the Southwest and tracks across the central/southern tier of the CONUS. This combined with a couple wavy fronts along with periods of Gulf inflow will support a couple of significant precipitation events with heavy rain and possible flooding to the south/southeast and wintry weather in the colder air. Later in the week, the West Coast may see increasing precipitation chances with the approach of an eastern Pacific upper trough. ...Guidance/Predictability Assessment... The latest couple of model cycles have been generally agreeable with the overall pattern, including the southern stream upper low centered around northwestern Mexico as the period begins Wednesday and its track and timing as it ejects eastward, maintaining a bit of separation with the northern stream trough likely through Friday. Behind these features models agree regarding a period of upper ridging shifting across the West Wednesday-Thursday and into the central U.S. late this week. Troughy flow coming from the Pacific into the West shows a bit more model variations though. GFS runs have been on the faster side of the guidance envelope while the ECMWF and CMC were slower, with a fair amount of spread in the ensemble members. A middle ground solution not as fast as the 12/18Z GFS seems best at this time. The general idea shows this trough reaching the east-central U.S. by next Sunday with another ridge axis behind it. For this progressive wavy and fairly agreeable pattern, the WPC forecast utilized a multi-model deterministic blend early on with some incorporation of the ensemble means for the latter half of the period. Good continuity with the previous forecast was maintained. ...Weather/Hazard Highlights... The southern stream upper trough/low tracking across the southern U.S. and the broader northern stream trough will provide support for frontal boundaries with waves of low pressure through the south-central to southeastern U.S., which combined with Gulf moisture streaming in will lead to widespread precipitation. On the southern side locally heavy rain is expected, which could cause localized flooding especially at times when there is sufficient instability for higher rain rates. At this time Slight Risks are in place in WPC's experimental Excessive Rainfall Outlook for both day 4/Wednesday from eastern Texas into the Lower Mississippi Valley and day 5/Thursday stretching into the Southeast given good upper-level support, namely excellent difluence/divergence in the right entrance region of the jet, as it tracks eastward. Then on the northern side of the precipitation chances, there is potential for snow across parts of the southern half of the Plains and Mississippi Valley into the Ohio/Tennessee Valleys and the Mid-Atlantic at times, but low confidence continues in the specifics. This is also a pattern that could support freezing rain with ice accumulations with the cold air in place at the surface and potential for warm moist air to flow overtop it. The placement of heaviest rain, freezing rain, and snow all remain in question as small-scale details like surface frontal positions and late week shortwave specifics remain uncertain. Drier conditions are likely for the East by Saturday. Elsewhere, periods of lake effect snow are possible to the lee of the northern/eastern Great Lakes. The West Coast could see increasing precipitation chances by later in the week but with uncertainty over the southward extent and amounts. Currently the best potential for at least some rain/mountain snow is over the Pacific Northwest with moisture possibly extending as far south as northern California, and as far east as the northern Rockies. Very cold conditions over the north-central U.S. during the short range period could continue into the latter part of the week, underneath instances of cold upper troughing. Highs in the single digits are possible in the Dakotas into Minnesota while bitterly cold lows combined with wind will produce dangerous wind chills. Much below normal temperatures then shift into the Northeast by late week, with the possibility of highs below zero in northern New England by Saturday. Temperatures are expected to be generally below normal across much of the Interior West and central U.S. around midweek with gradual moderation thereafter. Meanwhile the far Southeast and Florida Peninsula should see the most consistent above average temperatures, with highs 10-15F above average and plus 10-20F anomalies for lows before a cooler trend next weekend. 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