Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Fri Feb 05 2021 Valid 12Z Mon Feb 08 2021 - 12Z Fri Feb 12 2021 ...Northern Plains to Midwest Arctic outbreak gradually expanding to the south and east... ...Pattern Overview and Guidance/Predictability Assessment... Model guidance continues to indicate a negative NAO/AO synoptic pattern that supports a significant outbreak of arctic air from central Canada into the Great Plains during the medium range period. A blocky and retrograding pattern over eastern and northern Canada will keep the northern U.S. open for additional cold air intrusion. Meanwhile, a wavy slow-moving front near the Gulf Coast will keep the arctic air from spreading too far into the Deep South. There is a general model signal for a swath of wintry precipitation to spread across the Midwest to the Northeast from Monday to Tuesday as a wave of low pressure develops along the arctic front. Differences in the timing and intensity of this wave remain significant among global models, with the ECMWF offering the slowest and strongest solution across the Northeast. By the middle of next week, there is general model consensus for the returning moisture from the Gulf to expand north and east across the Deep South and eventually into the East Coast later in the week. The northern portion of the precipitation shield should be in the form of rain and/or ice from the interior Deep South to eventually parts of the Northeast. Elsewhere, the highlight within this pattern will be the much below normal temperatures expected to remain across the northern and central U.S., which will gradually expand further to the south and east during the latter part of next week. The WPC medium-range forecast package was derived from a composite of the 12Z ECMWF/EC mean, the 18Z GFS/GEFS, together with a smaller contribution from the 12Z CMC/CMC mean. More of the ensemble means were used for Days 5 to 7 given the increasing model uncertainties. ...Weather/Threats Highlights... Terrain/upslope snow over the northern Rockies and vicinity should begin to slowly taper off on Monday as the main shortwave energy slides eastward to support frontal wave development over the Northeast mostly on Tuesday. This should lead to a band of potentially meaningful snow from the Midwest into the Northeast from Monday into Tuesday. Meanwhile, a stationary front across southern Florida will lift northward and likely provide a period of enhanced rainfall for the eastern Gulf Coast region into the southeastern U.S. coast. By later next week, there is an increasing chance for Gulf moisture to return and expand in coverage across the southern tier states in an overrunning pattern north of a stationary front across the northern Gulf. With the cold air in place farther inland, a swath of wintry weather is possible from the interior Deep South to the Northeast later next week. Expect the most persistent core of coldest air over the central U.S. to extend from the northern half of the Plains into the Midwest and western Great Lakes. Within this area temperatures that are 15-30F below normal will be common through the period and parts of Montana even be as cold as -40F below normal early next week. A few isolated record cold highs may be possible. Cold temperatures will also spread farther south and eventually to the east with time. This expansion of the cold air should bring temperatures down to 10-25F below normal from the southern Plains into parts of the Ohio Valley by mid-late week. Most areas over the South and East should be near to somewhat above normal into early next week prior to the arrival of the cold air. To the west of the Rockies, initially expect moderately above normal readings over the Great Basin/Southwest and near normal temperatures farther north. The West should see a gradual cooling trend over the course of next week, leading to below normal temperatures over the Northwest and moderation closer to normal farther south. Kong/Rausch 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, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml