Extended Forecast Discussion NWS Weather Prediction Center College Park MD 155 AM EST Mon Jan 20 2020 Valid 12Z Thu Jan 23 2020 - 12Z Mon Jan 27 2020 ...Overview... A system in the Southern Plains Thursday will spread modest to perhaps locally heavy rainfall from the Lower Mississippi Valley northeastward next through Sunday. 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... Consensus of the 12Z (18Z) GFS/ECMWF/Canadian forged a good starting point for most of the forecast period as the 12Z UKMET was again quite different aloft with the evolution of the forming upper low over the central Plains/mid-Mississippi Valley. Models have gravitated toward a similar idea of the lead sfc low lifting out of the ArkLaTex to the Ohio Valley Thu-Fri as its triple point low takes over by Sat in the Carolinas. That entity will lift northeastward toward the NY Bight or 40/70 Benchmark by early Sunday, when spread in the guidance increases forthwith. Generally the GFS/Canadian and most GEFS members were quicker than the ECMWF ensemble members with the 12Z ECMWF on the slower side. Favored a solution between the ensemble camps for now given the conflicting signals of a slower trend overall but still a progressive enough upper pattern. 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... Above average temperatures are favored nearly CONUS-wide through the period. Highest anomalies (10-25F above average) will lie astride the Canadian border with near to slightly above average temperatures (around 5F anomalies) near the Gulf Coast. Daytime highs may stay below average where the rain associated with the southern system is most prevalent. Precipitation will be non-continuous but quite repetitive in the Northwest as several systems push through. The generally mild flow will keep snow levels a bit higher, too. Farther east, rainfall will expand out of Texas to points eastward/northeastward as the system organizes across the lower Mississippi Valley. Gulf inflow will help realize modest rainfall totals along the NW and central Gulf coast that could be locally heavy. Atlantic inflow could maintain at least some modest rainfall amounts across the southern Appalachians into the Mid-Atlantic and southern New England. 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. Fracasso 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 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