Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EST Mon Nov 11 2019 Valid 12Z Thu Nov 14 2019 - 12Z Mon Nov 18 2019 16Z Update: The ECMWF and its ensemble mean continue to be slower and more amplified with the shortwave and eventual closed low that will affect the Southeast U.S. by the end of the week and into the weekend. This results in the ECMWF being farthest west and closest to the coast with the developing surface low, whilst the UKMET and CMC are farther offshore. The 6Z GFS was closer to the model consensus regarding the mass fields, and a blend of the GFS, EC mean, some CMC, and previous WPC continuity served as a good starting point in the forecast process. /Hamrick ...Pattern Overview and Guidance/Predictability Assessment... Amplified pattern with rebuilding western ridging and eastern troughing is forecast to hold into next week. Multi-day consistency and inter-ensemble system clustering has been subpar which again leads to a majority ensemble mean weighting next week. Trend has been for a bit more interaction in the Southeast between a exiting/weakening upper low over Mexico and northern stream troughing through the TN Valley Friday, leading to surface low pressure organizing around Florida. How far this moves offshore vs up the coast remains unclear but have trended a bit closer to the coast yet still offshore Sat-Sun (enough to keep QPF over the I-95 corridor). In the West, differences between the ensembles were reflected in the 12Z GFS vs ECMWF/Canadian-- the latter showed an upper low perhaps splitting off well southwest of California and remaining offshore as upper ridging builds atop the low rather while the former moved it inland into the Baja. Ensembles were split but slightly favored the ECMWF-led solution. Tempered this via the 12Z/10 ECMWF ensemble mean. This also worked well in the East/Southeast as the 12Z ECMWF was quite robust with offshore low pressure vs its ensemble mean. Low confidence in this series of events in the East. ...Weather Highlights/Threats... Well below average temperatures will ease after Thursday. However, highs will remain about 5-15 degrees below average along and east of the Mississippi through next weekend. Along/west of the Rockies (but including parts of the Front Range and central Plains), temperatures will stay above average by about 5-15 degrees. Interaction between the southern upper low and frontal boundary in the Gulf could spread rain (possibly modest amounts) 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 Thu-Fri with much less east of the Divide. Yet another system may approach Washington late next Sunday into Monday. Fracasso - Heavy rain across portions of the Southeast, the Mid-Atlantic, and the Pacific Northwest, Thu-Fri, Nov 14-Nov 15. - Heavy rain across portions of the Mid-Atlantic, the Pacific Northwest, and the Northern Great Basin, Sat-Sun, Nov 16-Nov 17. - Heavy rain across portions of the Southeast, the Lower Mississippi Valley, the Pacific Northwest, and the Northern Great Basin, Mon, Nov 18. - Flooding occurring or imminent across portions of the Middle Mississippi Valley and the Northern Plains. - Much below normal temperatures across portions of the Central Plains, the Lower Mississippi Valley, the Central Appalachians, the Tennessee Valley, the Great Lakes, the Middle Mississippi Valley, the Mid-Atlantic, the Southern Appalachians, the Upper Mississippi Valley, the Southeast, the Southern Plains, and the Ohio Valley, Thu-Fri, Nov 14-Nov 15. - Much below normal temperatures across portions of the Great Lakes, the Mid-Atlantic, the Northeast, the Central Appalachians, and the Ohio Valley, Thu-Sat, Nov 14-Nov 16. - Much above normal temperatures across portions of mainland Alaska, Mon, Nov 18. 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