Extended Forecast Discussion NWS Weather Prediction Center College Park MD 217 PM EST Mon Jan 20 2020 Valid 12Z Thu Jan 23 2020 - 12Z Mon Jan 27 2020 ...Overview... Scattered to widespread precipitation is expected to spread from the Lower Mississippi Valley to areas north and east through the weekend and into early next week. There may be periods of locally heavy rain, particularly near portions of the central and eastern Gulf Coast and possibly into the higher terrain of Southern Appalachian region. A swath of wintry precipitation may fall north of the surface low pressure system- across the Midwest, Ohio Valley, Central/Northern Appalachians and the Northeast. In the Pacific Northwest, several frontal systems will bring periods of wet weather to much of Washington/Oregon to start then into northern California by the weekend. Overall, milder temperatures will prevail over most of the CONUS during the period. ...Guidance/Predictability Assessment... Model guidance remained in fair agreement with the system crossing the central and eastern states, however continued to having spread in how the mid/upper level features evolve. This caused noticeable differences in amplitude, timing and where max QPF will focus. A combination of the 00Z ECWMF, 00/06Z GFS, 00Z CMC and the 00Z EC/GEFS means provided a decent starting point. This combo suggested that an area of concentrated precipitation will likely occur near the Gulf Coast and along parts of the Appalachian spine. Moderate, possible locally heavy rain, may increase the threat for flash flooding across the Gulf states/Southeast this weekend. With the progressive nature of this system, the risk may remain Marginal. Off the West Coast, with continued timing differences in the guidance with successive systems, a consensus approach was prudent there as well. ...Weather/Hazard Highlights... A vast portion of the country will have above average temperatures through early next week; ranging from about 5 degrees above seasonal average near the Gulf of Mexico to 10 to 25 above along the U.S and Canadian International border. Daytime highs may stay below average where the rain associated with the southern system is most prevalent. Intermittent periods of precipitation can be expected across the Northwest and parts of California and the Interior as several systems make through way onshore. Rainfall will expand out of Texas to points eastward/northeastward as the system organizes across the lower Mississippi Valley. Moisture-rich air will transport northward from the Gulf of Mexico and will continue to fuel modest precipitation up the eastern Seaboard. The system will likely have some wintry weather on its northern side from the Central Plains to the Great Lakes and Northeast but with uncertain amounts and a marginal thermal environment. Campbell 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, Thu, Jan 23. - Heavy precipitation across portions of Northern California and portions of the Central Appalachians to the Northeast, Sat-Sun, Jan 25-Jan 26. - Heavy rain across portions of the Central Gulf Coast, Thu, Jan 23. - Heavy rain across portions of the Southern Appalachians to the Mid-Atlantic, Jan 24-Jan 26. - Heavy snow across portions of the Sierra Nevada, Sat-Sun, Jan 25-Jan 26. - Flooding possible across portions of the Pacific Northwest. - Flooding occurring or imminent across portions of the Mississippi Valley and the Northern Plains. 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