Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1106 AM EST Wed Jan 30 2019 Valid 12Z Sat Feb 02 2019 - 12Z Wed Feb 06 2019 ...Overview... After the recent amplified pattern across much of the continental U.S. this week, a return to a more quasi-zonal flow pattern appears likely by the beginning of the medium range period this weekend. The storm system that will be crossing the Desert Southwest late this week should be present as an open wave across the south-central U.S. by Saturday as a southern stream disturbance. The pattern change continues going into the first part of next week as the large scale Pacific trough works its way inland and supports surface low development across the Great Plains and Upper Midwest. The response to this will likely be a broad upper trough becoming established over the western U.S. by Tuesday with a warmer weather pattern for the eastern U.S. by the end of the forecast period Wednesday. ...Guidance Evaluation/Preferences... Model guidance this morning has shown closer agreement regarding the track and intensity of a couple of low pressure systems forecast to develop in the central Plains early next week. The GFS in particular has trended toward the ECMWF since the 00Z run. Given the better agreement shown among major global models through the medium range, a general compromise of the 00Z ECMWF and 06Z GFS was used to generate the WPC 500mb and sea-level pressure fields, trending more toward their ensemble means for Days 6 and 7. The model blend yielded a more northerly track for the first cyclone to move across the upper Midwest into the upper Great Lakes on Monday. Another wave is forecast to form along an arctic front over the central Plains on Tuesday. The 06Z GFS begins to accelerate the track of this low toward the Ohio Valley next Wednesday faster than the 00Z ECMWF, but it is within the normal discrepancy shown between these two models. ...Weather Highlights/Hazards... A much milder weather pattern will be prevalent across the majority of the central and eastern U.S. by this weekend with high temperatures running about 10 to 20 degrees above climatological averages, and mild overnight lows across the Midwest and Ohio Valley as flow from the Gulf of Mexico advects higher humidity over the region. A couple of well defined low pressure systems are expected to track across the Great Plains and Midwest over the course of the medium range period, with the potential for significant snow to the northwest of the surface lows that develop across the northern plains and Upper Midwest, and arctic airmasses will likely settle southward across the Dakotas and Montana. Based on current projections, the severity of the cold will be less than the ongoing arctic intrusion now. Heavy rain and mountain snow is expected across much of California and the terrain of the Intermountain West this weekend as a strong Pacific disturbance moves inland. Showers and storms are likely to develop from the Gulf Coast to the Midwest in the warm sectors of the two surface lows. Some of this rainfall may be locally heavy. Kong/Hamrick WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation and winter weather outlook probabilities are found 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