Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1039 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 meandering over California, becomes 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 and into the Southeast/Florida. Overall, the models/ensembles showed fairly good agreement, with varying degrees of speed/track/evolution/interaction differences. The 00Z ECMWF/CMC/06Z GFS offered reasonable clustering near their ensemble means and previous shift continuity to form the base of the initial forecast for Wed-Thur. After this time, included increasing amounts of ensemble means (mainly ECENS/NAEFS) due to differences in western U.S. height falls starting Friday. The GFS/CMC remain faster both with shortwave energy entering WA/OR on Friday and with larger scale troughing/possible closed upper low around Baja California later in the period. Completely ignored the CMC after day 5 as it forms a rather amplified/deep upper low over the Southwest U.S., well north and east of even the GFS (which is faster than the ECMWF) and the ensemble means, which all keep energy over Baja or farther west. Along the Gulf coast, the models continue to struggle somewhat with the evolution of an opening upper low and possible surface wave development off the Southeast coast. The GFS is considerably faster/weaker than the ECMWF/means with this feature, though the slower ECMWF may be too amplified. At this point, prefer a blend of the ECENS mean with the NAEFS mean, which brings a solution somewhere in between the operational GFS/ECMWF. ...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 early in the period. The surface low off the Southeast coast should keep the heaviest rains offshore, though depending on coastal proximity, heavy rains may clip the coastline. 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. Santorelli/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