Extended Forecast Discussion NWS Weather Prediction Center College Park MD 344 PM EST Thu Feb 20 2020 Valid 12Z Sun Feb 23 2020 - 12Z Thu Feb 27 2020 ...Central Rockies to Ohio Valley storm Sunday to Tuesday to be closely followed by a wintry Northwest to Midwest/Northeast storm Sunday through Thursday... ...Guidance/Predictability Assessment and Weather/Hazard Highlights... System #1: A southern stream system will push east from the south-central Rockies Wednesday before weakening as it is drawn into a northern stream trough and shifts northeast across the Midwest Monday and the Northeast through Tuesday. This is a fairly warm storm with the snow/ice risk limited to the northern/western periphery of precipitation, with heavy mountain snows Sunday over the Central Rockies spreading onto the central High Plains (eastern CO). Generally moderate rain will spread east to the Mid MS/TN/OH Valleys, central/southern Appalachians and Eastern Seaboard through Tuesday. The best forcing with this system will generally be north/west of the area that has recently receive excessive rainfall with ongoing flooding. As it typical the GFS is more progressive than the ECMWF, so the WPC front/low/precipitation forecast is a blend of these (06Z GFS and 00Z ECMWF) models primarily with some inclusion of the 00Z CMC/UKMET which are reasonable for this system. System #2: A northern stream upper trough/surface system moving onshore over BC/WA Sunday will dig through the northern Rockies Monday and bring enhanced low elevation rain and heavy mountain snow with fairly slowly progressing system. Models diverge with the motion of this trough around Monday night (Day 4/5) with the amplitude and position of the trough with the 00Z ECMWF even sharper and over the central Rockies than prior runs and particularly the rest of the global guidance suite. So positioning of the low track over the Plains to the east-central US is uncertain, but there is plenty of energy available and by Day 6/7 rapid low pressure development is likely over the northeastern CONUS. Plenty of cold air with this system brings a signal for heavy wrap around snow over the north-central Plains/Great Lakes Day 6 and the interior Northeast for Day 7 with considerable uncertainty at this time. Generally above normal temperatures ahead of the increasing west-central CONUS trough spread east from the southern Rockies/High Plains to the eastern Seaboard Sunday through Tuesday with widespread coverage of minimum temperatures 10 to 15 degrees above normal. Expect much below normal temperatures to spread east from the central/northern Rockies under the trough Tuesday to roughly the Appalachians by Thursday with maximum temperatures 15 to 20 degrees above normal from the central Rockies to the Ohio Valley. Jackson Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy precipitation across portions of the Pacific Northwest, Sun-Mon, Feb 23-Feb 24. - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, and the Ohio Valley, Sun-Mon, Feb 23-Feb 24. - Heavy rain across portions of the Southeast, the Mid-Atlantic, the Southern Appalachians, and the Tennessee Valley, Mon-Tue, Feb 24-Feb 25. - Heavy snow across portions of the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Sun-Mon, Feb 23-Feb 24. - Heavy snow across portions of the Southern/Central Rockies, the Central Great Basin, the Central Plains, and the Southwest, Sun, Feb 23. - Heavy snow across portions of the Central/Northern Plains, the Middle/Upper Mississippi Valley, and the Great Lakes, Tue-Thu, Feb 25-Feb 27. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Mid-Atlantic, the Southeast, and the Ohio Valley. - Flooding likely across portions of the Southeast. - Much below normal temperatures across portions of the Plains, the Rockies, the Mississippi Valley, the Central Great Basin, and the Southwest, Tue-Thu, Feb 25-Feb 27. 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