Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
135 AM EDT Wed Jul 08 2020
Valid 12Z Sat Jul 11 2020 - 12Z Wed Jul 15 2020
Model differences remain with an Eastern Seaboard coastal low
whose potential development is being monitored by NHC. The last
few GFS runs, including the 00 UTC run, have been the most
progressive with this low into New England into the weekend.
Recent UKMET runs, including the 00 UTC run, have been the most
developed (likely benefiting from a more offshore track over
warmed waters). The WPC blend leans closer to the 12 UTC ECMWF
that fits better within the overall ensemble spread and WPC
continuity. For the rest of the CONUS, there is above average
consensus for troughing over the Northwest and the East to
sandwich an amplified Southwest/south-central U.S. ridge days 3-7.
An ECMWF and GEFS/ECMWF ensemble means blend seems to provides the
best forecast starting point and continuity.
...Weather Pattern/Hazard Highlights...
Ample upper trough energies will work inland over an unsettled
Northwestern U.S. and western Canada. Height falls/ejecting
impulses progress downstream over southern Canada and the U.S.
northern tier. This forces moderating fronts over the broad region
and some strong to severe thunderstorms. Convective rainfall
potential may focus from the Midwest to the Southeast/East.
Meanwhile, triple digits maximum temperatures to approach or
exceed heat records are likely from portions of CA and the
Southwest/southern Great Basin to the south-central Plains. Heat
indices will make it feel closer to 115 degrees in some places. A
local heavy rain/weather/maritime threat is expected to lift from
the coastal Mid-Atlantic to New England Saturday, as contingent
upon potential coastal low development and track.
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at: