Extended Forecast Discussion NWS Weather Prediction Center College Park MD 1204 PM EDT Sat Sep 14 2019 Valid 12Z Tue Sep 17 2019 - 12Z Sat Sep 21 2019 ...Overview and Guidance Evaluation/Preferences... The latest (00Z/06Z) global suite and ensemble members have decent agreement over the CONUS through next week and the persistent ridge over the southeastern states...as well as keeping Humberto well off the southeast coast. Run to run consistency has been lacking among the global suite and the greatest differences in the latest suite are with the flow pattern over the northeast Pacific starting on Wednesday/Day 4. This leads to wildly different deterministic solutions from the 00Z/06Z GFS with a strong ridge persisting the Gulf of Alaska and 00Z ECMWF bringing a potent through through that area by Saturday/Day 7. Multi-day teleconnections for the strong eastern CONUS ridge signal troughing in The West, but any particular day a week out could vary. Furthermore the 00Z UKMET greatly develops the western Gulf tropical wave present in most guidance into a low and maintains its strength through the Day 5 limit available at WPC. Accordingly, the WPC medium range product suite was primarily derived from the deterministic 06Z GFS/00Z ECMWF/00Z CMC for Days 3 and 4, then heavily toward ensemble means for Days 5-7. The varied flow pattern off the West Coast for Days 6 and 7 was handled with a blend of the 00Z ECENS and 00Z NAEFS means. ...Weather Highlights/Threats... Tropical Storm Humberto continues to be forecast by NHC to turn east and away from the southeast coast as a hurricane. The first shortwave will push across the northern Plains Tuesday night with some thunderstorm chances. In the Pacific Northwest, a cooling surface front and subsequent upper trough will bring a widespread chance of rain (some very high elevation snow) to the region into Wednesday. This will spread through the northern/central Great Basin/Rockies and into far northern CA before pushing to the northern Plains/Upper Midwest Friday where an increasingly active convective signature becomes evident as the trough takes on a negative tilt. Increased moisture inflow in advance of the first front may lead to record high minimum temperatures over the northern Plains Tuesday and the Upper Midwest Wednesday. Temperatures drop below normal over the northern Plains behind the first system during the midweek before raising ahead of the next system late in the week. Meanwhile, expect subtropical moisture out of Mexico on southwest flow aloft down over the Southwest/Four Corners states. Strong ridging downstream over the east-central U.S. will favor well-above average temperatures next week with some near record Deep South heat. In the western Gulf of Mexico, a trough/wave associated with an upper low favors a potentially heavy over coastal Texas into Wednesday. Weak steering aloft may allow this area of rain to persist through late week. Jackson 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