Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
326 PM EDT Tue Jul 16 2019
Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019
...Widespread Excessive Heat Threat...
...Heat Wave Threat...
...Overview and Weather Highlights/Threats...
There is a significant threat for dangerously hot and humid
conditions later this week/weekend into early next week within an
expansive sector of the nation. Later week hot upper ridging will
encompass much of the Southwest and south-central portions of the
Rockies and central and eastern U.S. By early next week, upper
ridging/heat is expected to build up through the west-central
states and begin to gradually moderate downstream down into the
east-central U.S. with upper trough amplification and southward
sagging of a main northern tier states frontal zone. In the hot
sector, widespread locations may tie or set new daily high minimum
records and some maximum temperature records. Heat indices will
persist in some areas upwards of 105 to 115F+ taking into account
high dewpoints, which may lead to some heat advisories issuances.
Overtop, a quasi-zonal mean flow pattern develops over the
northern-tier of the U.S. late week and for the weekend. A
prolonged series of impulses/trough energies will pass over
southern Canada and through the U.S. northern tier states with
uncertain individual system amplitudes and timings. Showers and
thunderstorms capable of producing locally heavy convection/MCS
activity will sporadically develop and propagate within a wavy
frontal/baroclinic zone across the north-central states,
Midwest/Great Lakes and Northeast/Mid-Atlantic. Multiple rounds of
rain/high rain rates may lead to locally excessive rainfall as the
moisture and instability pools along the slow moving and wavy main
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 that spreads into the east-central states early next week
with flow amplification. Also expect renewed monsoonal convection
over the Southwest and southern Rockies later period with flow
transition.
...Guidance/Predictability Assessment...
Latest guidance still depicts a fair amount of uncertainty through
the extended period with embedded systems and local convective
focus. Accordingly, the WPC medium range product suite was mainly
derived from a blend of the reasonably compatable 06 UTC GEFS
mean, 00 UTC NAEFS/ECMWF ensemble means, and WPC continuity.
Schichtel
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
Hazards:
- Heavy rain across portions of the Central Plains, the Central
Rockies, the Central Great Basin, the Southern Rockies, the
Southern Plains, and the Southwest, Mon-Tue, Jul 22-Jul 23.
- Heavy rain across portions of the Lower Mississippi Valley, the
Central Appalachians, the Tennessee Valley, the Mid-Atlantic, the
Southern Appalachians, the Southeast, and the Ohio Valley,
Sun-Mon, Jul 21-Jul 22.
- Heavy rain across portions of the Great Lakes and the Upper
Mississippi Valley, Sat-Sun, Jul 20-Jul 21.
- Heavy rain across portions of the Southeast and the
Mid-Atlantic, Tue, Jul 23.
- Flooding occurring or imminent across portions of the Central
Plains, the Lower Mississippi Valley, the Upper Mississippi
Valley, and the Northern Plains.
- 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 Middle
Mississippi Valley, the Great Lakes, the Ohio Valley, and the
Upper Mississippi Valley, Fri-Sat, Jul 19-Jul 20.
- Excessive heat across portions of the Southeast, the
Mid-Atlantic, the Northeast, and the Central Appalachians,
Fri-Sun, Jul 19-Jul 21.
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