Extended Forecast Discussion NWS Weather Prediction Center College Park MD 439 PM EDT Wed Sep 30 2020 Valid 12Z Sat Oct 03 2020 - 12Z Wed Oct 07 2020 ...Hot and dry conditions across The West expand into the central U.S. next week... ...Heavy rainfall threat for the Florida Peninsula Sunday into the middle of next week... ...Heavy rainfall threat for the Northeast Monday into Tuesday... ...Overview and Guidance/Predictability Assessment... The very amplified pattern of a western continental ridge and central/eastern U.S. trough culminates in low development over the Midwest Sunday that shifts over the Northeast Monday, reaching the Canadian Maritimes by Tuesday. A deep low setting up over northern Hudson Bay Sunday sets up an active pattern for western Canada to the Great Lakes next week. This pattern is supported by the 00Z ECMWF/CMC which were preferred for the models while the 06Z GFS (and now 12Z) continues a solution of a much more progressive and open eastern low. The 00Z UKMET was in between with a deeper and slower, but still open trough. The Hudson Bay low is in good agreement among global deterministic and ensemble solutions then through the middle of next week, so the preferred blend expands from the 00Z ECMWF/CMC to include the 00Z ECENS/06Z GEFS for Days 6/7. The inclusion of ECMWF and CMC deterministic solutions made for a notable change in the WPC pressure forecast for the Northeast. ...Weather/Hazard Highlights... The shortwave northern stream trough that re-amplifies the east-central trough shifts across the northern Plains to the Midwest Saturday night with developing low pressure and a cold front providing focus for rainfall over the Midwest Sunday and then phasing from a southern stream wave moving up over the eastern Carolinas and the northern stream wave takes place over the central Appalachians. This allows unsettled weather from the Mid-Atlantic to the Northeast Monday into Tuesday. Given the heavy rain across this area last night, there would be a heavy rain/flood threat in the Mid-Atlantic/Northeast from this next system. An existing stationary front over the FL Peninsula this weekend is met with another stalling front from the Northeast storm Monday night/Tuesday keeping a heavy rain threat for the FL Peninsula continuing through the middle of next week. The 06Z GFS was alone with bringing moisture from a western Caribbean wave/disturbance to the lower Rio Grande and the 12Z GFS has backed off a bit there. The upper ridge persisting across The West continues to offer hot and dry conditions with associated fire risks. Expect temperatures to be 5-15 degrees F above normal for the Desert Southwest up through the and Northwest Sunday to expand east to the central/southern Plains next week. A few record high max and mins are possible. The reinforcing cold air surge this weekend will keep temperatures of 5-15 degrees F below normal for much of the central to eastern U.S. Sunday before moderating as it shifts southeast with the cold front early next week. Jackson Hazards: - Heavy rain across portions of the Florida Peninsula and North Carolina coast, Sat-Sun, Oct 3-Oct 4. - Heavy rain across portions of the northern Mid-Atlantic to central and coastal New England, Mon-Tue, Oct 5-Oct 6. - Flooding occurring or imminent over portions of northeastern Florida. - Flooding likely over portions of northeastern Arizona. - Much above normal temperatures across portions of northern California, northern Nevada, and interior Pacific Northwest, Sat-Wed, Oct 3-Oct 7. 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