Extended Forecast Discussion NWS Weather Prediction Center College Park MD 210 PM EST Sat Jan 30 2021 Valid 12Z Tue Feb 02 2021 - 12Z Sat Feb 06 2021 ...Winter Storm for the Mid-Atlantic/Northeast early next week and from the West to the Midwest/Northeast mid-later next week... ...Guidance/Predictability Assessment... Global models this morning have generally agreed that a deep cyclone will gradually weaken but will be slow to exit New England early in the medium-range period. Models have a tendency to keep a swath of wintry precipitation across interior New England Tuesday into early Wednesday. Meanwhile, a surge of colder air from Canada is forecast to interact with an upper trough to be ejected into the central/southern Plains by late next week. Deterministic solutions from the global models show considerable difficulties in timing this interaction as large amount of spread is shown regarding the timing and intensity of the incipient cyclogenesis across the central U.S. In addition, these deterministic solutions diverge noticeable away from their corresponding ensemble mean solutions by Day 6 and 7. In spite of the model spread, there is actually decent agreement among the ensemble means from the ECMWF, GEFS, and the CMC that a low pressure system will develop over the central Plains on Thursday and the track across the Great Lakes on Friday. A consensus of the 00Z EC mean, the 06Z GEFS, and the 00Z CMC mean yielded very good agreement with WPC continuity. Therefore, a blend of these three ensemble means were used to construct this morning's WPC forecast charts for Days 6 and 7, with no deterministic solutions included. Some deterministic solutions were included for Days 3 to 5. By next weekend, there appears to be reasonable agreement for a reinforcing shot of cold air to push into the northern and central Plains. ...Weather/Threats Highlights... For the deep cyclone near New England, wintry precipitation inland should culminate on Tuesday before gradual tapering off by Wednesday morning. Some areas along or offshore the coast should continue to experience brisk to strong winds into Thursday as the cyclone will be slow to depart. A strong upper trough digging into California Tue-Wed will support a period of enhanced moisture/rains and heavy Sierra snows, with more modest enhanced amounts focusing on favored terrain and over the south-central Great Basin/Rockies. Variance with the extent of digging leads to subsequent ejection differences. Model differences grow downstream along with uncertain stream phasing/central U.S. storm genesis mid-later next week. It is expected that as the energy comes out of the West and Rockies, a deepening low to the lee of the Rockies will lift toward the Great Lakes during the latter part of next week. Strong warm air advection and moisture return on the backside of the departing high will allow for copious amounts of moisture to work with the better dynamics and forcing. Over the north-central to northeastern U.S., a swath of mixed precipitation and wrap-back snows can be expected near and to the north of the main cyclone track. Another batch of wintry precipitation is forecast to track down the northern and central Rockies late next week associated with a polar front. Kong/Schichtel 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