Extended Forecast Discussion NWS Weather Prediction Center College Park MD 159 AM EST Sat Jan 28 2023 Valid 12Z Tue Jan 31 2023 - 12Z Sat Feb 04 2023 ...Notable precipitation likely next 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 and Upper Midwest at times through next week... ...Overview... Periods of troughing are likely through much of the northern U.S. next 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. during the first half of the week, with significant cold extending into the Northeast for the latter half of next week. Meanwhile a ridge/upper high over Cuba during much of next 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 Tuesday (with some rain and higher elevation snow there) 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 possibly heavy rain 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 main feature of note at the beginning of the medium range period Tuesday will be the upper trough with likely an embedded closed low tracking across the Southwest and eastward through the period, showing some differences in timing and phasing with the northern stream trough. Though model guidance is in better alignment with timing than a day or so ago with this feature, 12/18Z model runs still showed a faster track and opening up of the trough/low to phase in the GFS compared to the ECMWF and CMC runs, which is consistent with historical tendencies of the models. The newer 00Z GFS did slow a bit with the track and phasing and looks quite a bit like the 00Z ECMWF now with the centroid of the upper low through day 5/Thursday, so hopefully models will stay consistent with this agreeable position. Differences with this feature and other shortwaves including those in the northern stream cause differences in the frontal positions across the eastern two-thirds of the U.S., which would be impactful weather-wise especially in the southern-central tier where precipitation types could depend on frontal placement. Upstream, while overall models agree on an upper ridge over the western U.S. around Thursday, they continue to differ with the axis of energy moving east through the Pacific and approaching the West for the latter part of the week to push that ridge eastward. The past few ECMWF runs have appeared to be outliers with being slower to bring in the Pacific trough, the newer 00Z run looks more in line with the consensus of other models. Given these considerations, the WPC forecast favored a multi-model deterministic blend of the 12/18Z guidance early in the period but gradually transitioned to about half models/half GEFS and EC ensemble means by the latter part of the week. This maintained reasonably good continuity with the previous forecast other than typical adjustments for newer guidance. The main changes to the NBM for QPF were to broaden coverage of light amounts, particularly for lake effect impacted areas. ...Weather/Hazard Highlights... The upper trough/low atop the Southwest on Tuesday could produce some rain and higher elevation snow there lingering from the short range period. Then this feature and the overall trough and other shortwaves 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 could lead to multiple rounds of 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 a Slight Risk is in place in WPC's experimental Excessive Rainfall Outlook for day 5/Wednesday given good upper-level support, namely excellent difluence/divergence in the right entrance region of the jet, and somewhat wet antecedent conditions. 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. Elsewhere, periods of lake effect snow are possible to the lee of the northern/eastern Great Lakes. Some light precipitation is possible in the Northwest on Tuesday, but more limited to western Washington by Wednesday. The West Coast could see increasing precipitation chances by the latter half of 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. Very cold conditions over the north-central U.S. during the short range period will continue into next week, in the wake of a strong cold front producing a surge of arctic air. Highs in the single digits and even at or below zero are possible in the Dakotas into Minnesota while bitterly cold lows combined with wind will produce dangerous wind chills. Much below normal temperatures should extend across much of the central U.S. through midweek especially, as well as across much of the Interior West with temperatures 15-25F below normal through Tuesday 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. A few record highs are possible Tuesday-Wednesday. While the western/central U.S. moderates later in the week, the East will trend somewhat colder with New England possibly seeing highs 10-20F below normal by next Friday. 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