Extended Forecast Discussion NWS Weather Prediction Center College Park MD 307 PM EST Fri Feb 21 2020 Valid 12Z Mon Feb 24 2020 - 12Z Fri Feb 28 2020 ...Active pattern for the eastern half of the CONUS next week... ...Overview and Guidance/Predictability Assessment... The medium range period will begin Mon with a shortwave trough in the central U.S. and energy streaming southward into the Northern Rockies. This should create a deeper longwave trough that will slowly move across the central and eastern U.S. Tue to Fri, causing active weather across those areas in conjunction with a couple of surface lows. Meanwhile, upstream ridging will be present across the West. 00Z/06Z models and ensembles generally seem to have a good handle on the overall pattern through the period, with some smaller differences. The 00Z UKMET trough was slower than consensus by day 4/Tue and especially day 5/Wed, so leaned away from that solution. The other main difference between models at upper levels was regarding at what point the trough could close off into an upper low. The 06Z GEFS and GFS were particularly enthused about closing off the low by Tue or Wed while other models wait till Thu or Fri. Regardless, the sensible weather effects will be similar, with an initial surface low tracking across the Mississippi and Ohio Valleys early and phasing energy leading to a rapidly deepening surface low ending up over New York Thu with strong upper-level support. Model guidance has steadily had this feature for a few cycles now, so confidence is average to above. Overall preferred a blend of the 00Z and 06Z GFS, 00Z ECMWF and ECENS, 00Z GEFS mean, and 00Z CMC, which should create a consensus between the smaller model differences of the exact depth/extent of the trough and the position/strength of the low. This worked for the flow entering the West from the Pacific as well. ...Weather/Hazard Highlights... With the initial shortwave and surface low, modest to locally heavy rain is expected across the Southeast, lingering over northern Florida for Mon through Wed. Precipitation stretching north and west could cause a period of light snow across portions of the Plains and Midwest, but the details are uncertain. Then with the second, stronger low, wintry weather is possible to its northwest for the Great Lakes and interior Northeast. Rain is again forecast to the south. After some snow in the Northern Rockies to Northern Plains Mon, ridging building in will lead to generally dry conditions for the West through the rest of the week. Given the upper level pattern and a strong surface high spilling into the western and then central U.S., colder than normal temperatures are expected for the Rockies Tue moving eastward throughout the period. The ridging building in the West should lead to above average temperatures for the West Coast. Tate 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, Mon, Feb 24. - Heavy precipitation across portions of the Mid-Atlantic, the Northeast, and the Great Lakes, Wed-Thu, Feb 26-Feb 27. - Heavy rain across portions of the Southeast, and the Southern Appalachians, Mon-Tue, Feb 24-Feb 25. - Heavy snow across portions of the Pacific Northwest, the Northern Rockies, and the Northern Great Basin, Mon, Feb 24. - Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Tue-Thu, Feb 25-Feb 27. - Flooding possible across portions of the Southeast and the Middle Mississippi Valley. - Flooding occurring or imminent across portions of the Southeast, the Middle Mississippi Valley, the Lower Mississippi Valley, the Ohio Valley, and the Tennessee Valley. - Flooding likely across portions of the Southeast and the Southern Plains. - Much below normal temperatures across portions of the Great Plains, the Rockies, the Ohio/Tennessee/Mississippi Valleys, the Mid-Atlantic, the Southern Appalachians, and the Southeast, Tue-Fri, Feb 25-Feb 28. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, 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