Extended Forecast Discussion NWS Weather Prediction Center College Park MD 137 AM EST Wed Jan 30 2019 Valid 12Z Sat Feb 2 2019 - 12Z Wed Feb 6 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... Similar to the past couple of days, the forecast period begins with decent overall model agreement regarding the synoptic scale pattern, with the exception of the 12Z UKMET that has been slower than the model consensus with the Pacific closed low reaching California this weekend. This also holds true for the second Pacific low approaching the Pacific Northwest early next week, with the UKMET notably farther to the west. By Monday, the 12Z ECMWF is indicating a faster solution than the consensus with the low crossing the Midwest, and the CMC on the northern edge of the guidance. It is interesting to note that the 18Z GFS is actually among the slowest solutions regarding this feature. The 18Z GEFS mean/12Z EC mean both offer a reasonable starting point for low placement during this time. There was enough model consensus among the deterministic GFS/ECMWF/CMC to use a blend of these along with the NBM for the first half of the forecast, and then mainly EC mean with some GEFS mean for the second half of the forecast period. ...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. 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