Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EDT Sun Sep 01 2019 Valid 12Z Wed Sep 04 2019 - 12Z Sun Sep 08 2019 ...Hurricane Dorian forecast to affect Florida and parts of the Southeast this week before moving out to sea... ...Overview... Upper ridging over the Four Corners/Southern Plains and western Atlantic will help to funnel Hurricane Dorian northward near/along the Florida/Georgia coasts Wednesday. As troughing in the northern stream swings through the Great Lakes/Northeast Wednesday/Thursday, it will tug Dorian northeastward near/along the Carolina coast as additional height falls push through Ontario Friday. Troughing off the west coast will slowly ease inland Wed/Thu and be replenished upstream this upcoming weekend. ...Guidance Evaluation and Preferences... The path of Dorian near/along the Southeast coast means that small shifts in the track will result in large changes to the sensible weather forecast. Consensus position per NHC comes quite close to the SC/NC coast after lifting north of 30N Tuesday. By late Friday, it is expected to quickly move away from the Outer Banks but may still pass near Cape Cod on its way toward Nova Scotia and the North Atlantic. Please consult the forecasts from the National Hurricane Center for the latest information on Dorian. On Wednesday, a cold front in the Great Lakes will push eastward/southeastward into the southern Appalachians by Thursday. This will hang up atop Dorian and eventually become enveloped with the system as it progresses through extratropical transition. Another cold front will push through the Great Lakes late Friday into Saturday. 12Z GFS/ECMWF were reasonable close to each other and their ensembles so that a blend sufficed (18Z was slower here but much quicker with ex-Dorian). In the west, additional troughing will approach WA/OR Saturday with typical uncertainty in the orientation/depth. ...Sensible Weather... Dorian will bring strong winds, heavy rain/flooding, and storm surge to parts of Florida and into the Southeast. As it departs, a cold front will bring cooler temperatures (10-15F below average) to the Mid-Atlantic and Northeast. In the west, above average temperatures are favored especially in the Northwest Wed/Thu ahead of the first upper trough. By next weekend, another shot of cooler air will filter into the Great Lakes and Midwest. Away from Dorian, rainfall coverage should be fairly limited over the lower 48, with the exception being in the Pacific Northwest as the upper trough moves into WA/OR and then into the central Plains next weekend as a cold front sinks southward. The Southwest/Four Corners states may see isolated to scattered rain but with generally light amounts. Fracasso 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