Extended Forecast Discussion NWS Weather Prediction Center College Park MD 129 AM EST Fri Jan 24 2020 Valid 12Z Mon Jan 27 2020 - 12Z Fri Jan 31 2020 ...Overview and Guidance/Predictability Assessment... An anomalous upper-level ridge is forecast to persist across northeastern Asia through the medium range. Teleconnections associated with the ridge will favor continued troughing and cold temperatures for Alaska, and a broad (albeit relatively weak) region of positive height anomalies across Canada, centered around Hudson Bay through much of the period. This setup will prevent any cold air outbreaks from affecting the contiguous U.S. through the medium range, with a broad region of near or above average temperatures expected across most of the CONUS. Across the CONUS, a fairly progressive flow regime will remain in place, with occasional periods of split flow. This makes for a fairly chaotic forecast with relatively low predictability due to numerous small scale features and their potential interactions. A blend of the 18Z GFS and 12Z ECMWF/UKMET was used as a basis for the forecast during days 3-5 (Mon-Wed), with more weight place on the GFS relative to the others. The GFS has shown perhaps a bit more consistency from run-to-run, particularly with a shortwave crossing the southern U.S. Mon-Wed, with a more suppressed solution than the ECMWF over a few recent runs, an idea that the 12Z ECMWF begin to come around to. By later in the forecast period, model differences increase, with some significant differences even among the ensemble guidance. One key differences appears to be the degree to which upper ridging across the east Pacific extends in the the western U.S. The ECMWF and its ensemble allow for shortwave energy across the North Pacific to break down the northern extent of the ridge, with more aggressive height falls across the Northwest by late next week relative to the GFS/GEFS, which keeps somewhat stronger ridging in place. The GFS/GEFS were more amplified in general, with splitting flow across the central U.S. by that time, and the potential for energy to separate into a southern stream component. At this time, believed a compromise was the best approach later in the period, so leaned heavily on a blend of the ECENS/GEFS ensemble means, along with some continued use of deterministic solutions. ...Weather/Hazard Highlights... Several Pacific shortwaves/frontal systems are forecast to impact the Northwest during the extended period, keeping precipitation widespread with lower elevation rain and mountain snows through most of next week. Due to the multi-day nature of the precipitation event, some rain/snow totals could be heavy. Areas of showers and thunderstorms are possible from the Southern Plains to the Lower Mississippi Valley and into Florida with a relatively weak low pressure system expected to cross the southern tier next Tue-Wed. By late next week, overrunning along a lingering front in the Gulf of Mexico ahead of a developing central U.S. trough could once again spread rain across portions of the Gulf Coast. Confidence is low in the specifics of the forecast by late next week, however. Temperatures are forecast to be near or above average across most of the CONUS during the medium range. The most anomalous temperatures should remain focused across the Northern Plains and Upper Midwest, where high temperatures at least 10-15 deg F above average, and low temperatures 15-25 deg above average, will be possible through most of next week. Ryan 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