Extended Forecast Discussion NWS Weather Prediction Center College Park MD 311 PM EDT Wed Aug 18 2021 Valid 12Z Sat Aug 21 2021 - 12Z Wed Aug 25 2021 ...Henri to strengthen to a Hurricane and threaten New England this weekend... ...Model Analysis and preferences... There is quite a bit of guidance variance with the ultimate track of strengthening Henri over the western Atlantic, but overall there has been a westward more progressive guidance trend over the past few runs that offers an increasing threat for maritime interests and New England this weekend. Please refer to the latest NHC advisories for updated forecasts on Henri. Elsewhere, models and ensembles are in much better general agreement with the 12 UTC GFS now in even better in line with other models, ensembles and the National Blend of Models over much of the nation days 3-7, bolstering forecast confidence. A composite blend is preferred to smooth out the less predictable smaller scale differences consistent with uncertainties. ...Sensible weather and potential hazards... Strengthening Henri looms over a highly settled Western Atlantic and the latest NHC track increasingly threatens New England this weekend with potential for enhanced winds/waves and rainfall. Again, please refer to the latest NHC advisories for updated forecasts. Upstream, amplified upper trough energies will steadily progress from the Northwest to the north-central U.S. then Great Lakes/Midwest this weekend into next week and spread potential for moderate amounts of lead convection/rainfall that may produce more local heavier amounts. Some high elevation snows are possible in this pattern for a cooled Northern Rockies with the approach and passage of the aforementioned upper troughs and associated frontal system and low developments and progression across this broad region. Meanwhile underneath, an upper ridge/high that is forecast to extend across the south-central U.S/South will support a protracted period of hot and humid temperatures over this broad region. Schichtel Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook 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