Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Tue Jan 29 2019 Valid 12Z Fri Feb 01 2019 - 12Z Tue Feb 05 2019 ...Overview... The departure of a deep upper level vortex over Quebec at the beginning of the forecast period Thursday and gradual weakening of mean troughing aloft over the eastern U.S. late this week and the weekend will promote a significant warming trend over the eastern U.S. At the same time the short-range West Coast mean ridge aloft will give way to a series of Pacific systems that will bring a return of significant precipitation to parts of the West with moisture that will then spread farther eastward. By the latter half of the period, the synoptic scale pattern should evolve toward a positively tilted mean trough over the West and positive height anomalies with some degree of ridging over the East. ...Guidance Evaluation/Preferences... Models and ensemble means are in relatively good agreement at the beginning of the forecast period on Friday with respect to the synoptic scale pattern. By Day 4 on Saturday, speed and amplitude differences are apparent with the large scale trough near California. The 18Z FV3 GFS is not quite as amplified as the operational GFS, and closer to the ECMWF and EC mean solutions, and this remains the case going into Sunday as the disturbance approaches the Plains. With that consideration in mind, the WPC forecast favored the slower set of solutions for this region, but not to the degree indicated by the UKMET given its lack of ensemble support. In the northern stream, a number of solutions suggest amplification of a shortwave across the Canadian prairies next weekend, with an associated surface low passing along the U.S./Canada border toward the Great Lakes. Model consensus was a bit better here and ensemble members showed reasonable clustering with respect to the surface low track, even with some timing/intensity variability evident in deterministic solutions. Given these considerations, the forecast during the second half of the forecast period continued to emphasize the ECMWF/FV3 GFS with increasing use of the ensemble means by late in the forecast period. ...Weather Highlights/Hazards... A pronounced moderating trend is expected by this weekend after the record setting cold temperatures mid-week across the north-central states. It will still be very cold from the Upper Midwest to New England on Friday, with departures on the order of 10 to 20 degrees below normal for late January. The cold temperatures linger across the Northeast U.S. on Saturday whilst moderating significantly from the Ohio Valley to the Great Plains. The majority of the eastern U.S. should be above normal by Sunday with locations from Texas to the Ohio Valley about 10-15 degrees above normal owing to the borad upper level ridge and warmer southerly flow. By early next week, the next surge of arctic air surges south across the northern plains, with indications that it will not be the same magnitude as the ongoing arctic intrusion. Multiple Pacific systems will widespread valley rain and mountain snow to a large portion of the West by Friday and then to much of the Intermountain West and the Rockies for the weekend. The weekend storm system will first spread rain/snow across the Northwest and gradually move south/southeast. The heaviest QPF is expected over favored terrain in California, Arizona, and southern Utah. During the latter half of the period, a surface low is forecast to develop across the central plains, and this may produce a band of significant snow from Nebraska to the Upper Midwest and rain in the warm sector. Showers and storms are likely across the Gulf Coast region as moisture increases across this region. 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