Extended Forecast Discussion NWS Weather Prediction Center College Park MD 200 AM EST Thu Feb 11 2021 Valid 12Z Sun Feb 14 2021 - 12Z Thu Feb 18 2021 ...Widespread record cold temperatures on Sunday across the Plains and MS Valley will gradually moderate during next week... ...Stormy pattern will bring multiple wintry precipitation events from coast to coast... Models and ensembles continue to advertise a very active synoptic pattern through the medium range period. Although the large dome of arctic air over the mid-section of the country will gradually moderate by early next week, a broad longwave trough will remain in place across the Plains with back-to-back energetic systems tracking from coast to coast around this trough. The medium range period will start with a developing low pressure system over the southern Rockies, bringing mixed precipitation to the region while spreading snow into the central to southern Plains on Sunday. All models have sped up the eastward progress of this system with more snow spreading into the central High Plains where many locations are forecast to experience record cold sub-zero temperatures Sunday morning. As this system taps in Gulf moisture, indications are that it will develop into a widespread winter weather event from the southern Plains through the Northeast Monday and Tuesday. The GFS has come into better agreement with the ECMWF in bringing the storm up the East Coast on Tuesday with a split storm center tracking up on either sides of the Appalachians. On the other hand, the CMC continues to favor an offshore track. Meanwhile, widespread moderate rain is expected further south near the southeast U.S. coast into Florida near a stationary front. By the middle of next week, there is decent model agreement for the next shortwave to develop into another low pressure system near the Gulf Coast that will eventually track into the East Coast. Although details are still elusive at this stage, it appears that this system will bring another winter weather event from the interior South moving toward the Northeast during the middle of next week. Meanwhile, the next Pacific system will likely bring the next significant precipitation event into the Pacific Northwest on Sunday. The moisture and upper-level energy will track well inland, reaching into the central Rockies by Tuesday with relatively consistent model timing thus far. Mountain snows are expected from the Pacific Northwest to the central Rockies. Energy ejecting into the southern Plains will be key to the development of the aforementioned system tracking across the South midweek. The WPC medium-range forecast package was derived from a composite blend of the 12Z ECMWF/EC ensemble mean, the 18Z GFS/GEFS, together with a smaller contribution from the 12Z CMC/CMC mean and the 01Z NBM. Mostly ensemble means were used on Days 6 and 7 given the increasing model uncertainties. Kong 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