Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
430 PM EDT Mon Jul 15 2019
Valid 12Z Thu Jul 18 2019 - 12Z Mon Jul 22 2019
...Tropical Depression Barry to further weaken but still fuel
Northeast heavy rains Thursday as a Post-Tropical Remnant Low
before exiting to Canadian Maritimes Friday...
The Weather Prediction Center assumed responsibility from the
National Hurricane Center to issue advisories on inland Barry
until the surface circlulation has dissipated and an associated
flash flooding threat diminishes. Tropical Depression Barry is
expected to become a Post-Tropical Remnant Low later today and
deepened moisture is expected to fuel some lingering heavy rains
Thursday across the Northeast before exiting into the Canadian
The WPC medium range product suite was prmarily derived from a
composite blend of well clustered guidance from the 00 UTC
NAEFS/ECMWF ensemble means. The 00 UTC ECMWF and GEFS mean also
cluster 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. This maintains good WPC continuity.
This blend did not include the 00 and 06 UTC GFS that produce an
outlier solution with more mid-upper level trough amplification
and significantly more lower atmosheric cooling from the Rockies
to the Midwest Saturday-next Monday. Downplayed this scenario
given continuity and strength of the hot precursor ridge building
up into this region.
...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. Areas of localized
heavy rain may increase the threat for flash flooding, especially
in areas of higher terrain and reduced FFG.
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. There
will likely be multiple periods where rainfall amounts/or rates
become locally excessive as the moisture and instability pooling
frontal boundary stalls over the region. There is quite a range
for QPF within the global models. With a less than average
confidence on the exact timing and placement of any individual
feature, opted to remain on the near the middle/lower end of the
output with this issuance. The regions with the best chances for
higher precipitation is the Upper Mississippi Valley and Great
Lakes Saturday through Sunday.
Summertime ridging over southern and central portions of the U.S.
will spread over much of the Southwest and Southern and Central
Rockies; keeping temperatures near or above seasonal average. Many
locations are expected to be warmer and drier through this the
extended period. 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.
- Heavy rain across portions of the Upper Mississippi Valley and
the Northern Plains, Sun, Jul 21.
- Flooding possible across portions of the Upper Mississippi
- Flooding occurring or imminent across portions of the Central
Plains, the Lower Mississippi
Valley, the Northern Plains, the Middle Mississippi Valley, the
Upper Mississippi Valley, and the
- Flooding likely across portions of the Central Plains, the
Middle Mississippi Valley, the Lower
Mississippi Valley, and the Northern Plains.
- Excessive heat across portions of the Central Plains, the Lower
Mississippi Valley, the Tennessee
Valley, the Middle Mississippi Valley, the Upper Mississippi
Valley, the Great Lakes, and the Ohio
Valley, Thu-Sat, Jul 18-Jul 20.
- Excessive heat across portions of the Southeast, the
Mid-Atlantic, the Northeast, and the Central
Appalachians, Fri-Sun, Jul 19-Jul 21.
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: