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