Extended Forecast Discussion NWS Weather Prediction Center College Park MD 247 AM EDT Sun Sep 15 2019 Valid 12Z Wed Sep 18 2019 - 12Z Sun Sep 22 2019 ...Overview and Guidance Evaluation/Preferences... Models and ensembles offer a reasonably similar and amplified larger scale pattern over the lower 48 and vicinity for much of the upcoming medium range period. Forecast spread and uncertainty for small-mid scale embedded features has also improved, bolstering forecast confidence. Flow will be highlighted by an amplified and unsettling mean upper trough over the West and sprawling/hot late summer east-central states upper ridging. The WPC medium range product suite was primarily derived from a composite blend of the 18 UTC GFS/GEFS, 12 UTC ECMWF/ECMWF ensemble means and the National Blend of Models. ...Weather Highlights/Threats... Tropical Storm Humberto continues to be forecast by NHC to turn east and away from the southeast coast as a hurricane over the next couple of days. A series of amplified upper troughs and lead surface frontal systems will dig into the West then eject northeastward over the north-central U.S. this week. This will bring widespread rains (some very high elevation snow) to the Northwest. Activity spreads south into northern CA and out through the northern/central Great Basin/Rockies. An organized convective focus with locally heavy downpours shifts to the Upper Midwest with leading shortwave energy/height fall passage into midweek and modest/local potential with southward and eastward progressing surface frontal systems. Increased moisture inflow may lead to some record high minimum temperatures. The upstream pattern meanwhile reloads again over the West to reach the north-central states again next weekend. In this pattern expect subtropical moisture out of Mexico on southwest flow aloft over the Southwest/Four Corners states. This moisture may fuel support for aforementioned potential convection downwind into the north-central U.S. Strong ridging downstream over the east-central U.S. will favor well-above average temperatures next week with some near record Deep South heat. Nearby in the western Gulf of Mexico, a trough/wave associated with an upper low favors a potentially heavy over coastal Texas midweek and weak steering aloft may allow this area of rain to persist through late week. Schichtel 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