Extended Forecast Discussion NWS Weather Prediction Center College Park MD 143 AM EST Sun Nov 10 2019 Valid 12Z Wed Nov 13 2019 - 12Z Sun Nov 17 2019 ...Record cold to slowly ease later this week... ...Pattern Overview and Guidance/Predictability Assessment... Upper ridging will meander off the coast of California, interrupted by troughing late Wednesday/early Thursday and then again on Friday, with broad troughing east of the Rockies. Over Mexico, a closed low will eventually rejoin the southern edge of the westerlies Thursday and track across the northern Gulf of Mexico. The models/ensembles were in good agreement overall but with varying degrees of speed/track/evolution/interaction differences. The 12Z GFS/ECMWF offered reasonable clustering near their ensemble means to form the base of the initial forecast Wed-Fri. Included much more ensemble weighting by next weekend due to differences in western height falls into WA/OR starting late Friday. The GEFS ensembles were quicker than earlier runs and the ECMWF ensembles, resulting in a much more positively-tilted trough and quicker northern stream. Favored the ECMWF ensembles for its better consistency and closer pairing with the 12Z GFS (in a broad sense). Along the Gulf coast, opening upper low may just miss interacting with northern stream troughing resulting in less surface development along the front offshore FL/SC. ...Weather Highlights/Threats... Well below average temperatures that will likely break daily records across a sizable area of the eastern half of the CONUS on Wednesday will ease by the end of the week. However, highs will remain about 10-15 degrees below average along and east of the Mississippi into Friday and 5-10 degrees below average next weekend. A sneaky reinforcing shot of cold Canadian air may skirt through the Northeast Fri/Sat as another surface high moves in. West of the Rockies (but including parts of the Front Range and central Plains), temperatures will stay above average by about 5-10 degrees. Once the southern upper low reaches the Gulf, its interaction with a frontal boundary could spread rain along the I-10 corridor and across the Florida peninsula as low pressure develops near Florida. Next system into the Pacific Northwest will provide focused rain/snow to coastal/mountain OR/WA Friday-Saturday then east of the Divide Saturday-Sunday. By then, moisture will be much more limited and precipitation amounts much lighter. Yet another system may approach Washington late next Sunday. 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