Extended Forecast Discussion NWS Weather Prediction Center College Park MD 215 PM EDT Sat Sep 19 2020 Valid 12Z Tue Sep 22 2020 - 12Z Sat Sep 26 2020 ...Heavy rainfall threat from Beta continues for the northwest Gulf Coast and lower Mississippi Valley into the later half of next week... ...Hurricane Teddy is forecast to move through eastern Atlantic Canada late Tuesday through Wednesday... ...Overview... A deep lows persisting in the Gulf of Alaska into Friday and another east of New England Tuesday/Wednesday allow ridging to increase over the Rockies and onto the Great Plains Wednesday to Friday. In the Gulf, Beta is forecast to be a tropical storm as it slowly moves northeast along/near the middle/upper Texas coast Tuesday through Wednesday night before it weakens as it moves inland over southwest Louisiana Thursday. This track would bring heavy rain along the upper TX and western LA coasts into Thursday with a noted degree of uncertainty. South of Nova Scotia, hurricane Teddy will merge with a non-tropical low before skirting eastern Nova Scotia keeping most wrap-around rain and wind east of Maine. In addition, Teddy will continue to churn up waves along the East Coast which could cause life-threatening surf and rip current conditions. ...Guidance/Predictability Assessment... 00Z/06Z deterministic guidance was reasonable through Wednesday night across the CONUS including the Gulf of Mexico. Starting Thursday preference goes to the 00Z ECMWF/ECENS due to timing of troughs off the Northwest and crossing the Great Lakes. The the 00Z CMC and UKMET were faster with the Great Lakes trough while the 06Z (and now 12Z) GFS were weaker with the Great Lakes. This general blend generally worked well for the 15Z NHC track of Beta. The 06Z/12Z GFS/GEFS are much slower than the 00Z ECMWF/ECENS, which the preference is again for the ECMWF/ECENS. ...Weather/Hazard Highlights... Tropical storm Beta is forecast to take a slow path northeast along the upper TX coast and into southwest LA to the southern MS Valley and spread heavy rain along its track. Given the official track, leaned toward the higher end which includes the 00Z UKMET/ECMWF. Teddy is now expected to be far enough east of Maine to not bring much rain to that state. A cold front and trough from the Gulf of Alaska will bring several days of rainfall to western WA/OR Wednesday through Friday. Showers will continue behind the front eastward over the northern Rockies. Temperatures will remain above to much above normal throughout the period across the north-central U.S. and back into the interior West (through Thu/Fri). Highest anomalies will lie over the Dakotas/Upper Midwest where 80s will be common. The approaching cold front next weekend will start to cool temperatures over the Rockies, but only back down to near normal. Overall, minimum temperatures through the medium range remain above freezing (after recent days of frost/freeze). 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