Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue Jul 16 2019
Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019
...Post-Tropical Cyclone Barry to further weaken, but still fuel
heavy rains Thursday across the Northeast as a Post-Tropical
Remnant Low before exiting to Canadian Maritimes Friday...
...Guidance/Predictability Assessment...
Currently (Tuesday morning) the remnant low of what was Tropical
Cyclone Barry is slowly tracking north-northeast through southern
Missouri spreading enhanced rainfall to parts of the
Lower/Mid-Mississippi Valley and western Tennessee Valley. The
Weather Prediction Center has assumed responsibility from the
National Hurricane Center to issue advisories on inland Barry
until the surface circulation has dissipated and an associated
flash flooding threat diminishes. Deepened moisture is expected to
fuel some lingering heavy rains Thursday across the Northeast
before exiting into the Canadian Maritimes Friday.
The latest runs of the global guidance still depicts a fair amount
of uncertainty through the extended period; therefore, followed
suite to the previous forecast and utilized a compromise of the
NAEFS and ECWMF ensemble means. Again, the ECMWF and GEFS mean
clustered reasonably well with this preferred solution that offers
a fairly well established larger scale pattern with much less
certainty with embedded smaller scale impulses and local
convective focus.
...Overview and Weather Highlights/Threats...
Tropical moisture from the remnants of Barry will spread across
the northern Mid-Atlantic and Northeast through Thursday as the
leading edge of the front tracks offshore. Locally heavy rainfall
across these regions may increase the risk for flash flooding,
especially in areas of higher terrain and reduced FFG.
Temperatures near or above seasonal average are forecast for a
vast portion of the southern and central U.S. as ridging remains
in place this coming week. Some locations may tie or set new daily
high minimum records. Heat indices will be around 105 to 115F,
which may lead to some future issuance of heat advisories.
A quasi-zonal flow pattern will develop across the northern-tier
of the U.S. Throughout this coming week a series of hard to time
disturbances will pass through southern Canada and through the
northern states. Showers and thunderstorms capable of producing
locally heavy convection/MCS activity will sporadically develop
and propagate within a wavy frontal/baroclinic zone across the
Northern Plains, Upper Mississippi Valley and into the Upper Great
Lakes region, then into the Lower Great Lakes and Northeast.
Multiple rounds of rain/high rain rates may lead to locally
excessive rainfall as the moisture and instability pools along the
stalled frontal boundary. Although the model spread for QPF is not
as high as previous cycles, it still lower confidence on where and
when the highest amounts occur. Guidance continues to suggest the
max QPF occurs over the Upper Mississippi Valley and Great Lakes
this weekend.
Campbell
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