Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
413 PM EDT Wed Jul 17 2019
Valid 12Z Sat Jul 20 2019 - 12Z Wed Jul 24 2019
...Widespread Excessive Heat Threat Through The Weekend...
...Overview and Weather Highlights/Threats...
A large portion of the country will remain hot and humid through
this weekend under a broad ridge which continues an excessive heat
threat. Numerous locations will likely reach, or set new daily
high minimum records and some maximum temperature records this
weekend into Monday. With high humidity and persistent heat
indices of 105 to 115F+, heat headlines will persist. This heat
wave may become problematic for those working or recreating
outdoors, individuals sensitive to heat, especially the elderly
and animals.
Relief from the heat for much of the country occurs early next
week as upper ridging/heat will build over the west-central states
which will allow a trough to develop over the east-central states.
An associated cold front will push southeast across much of the
central and eastern states; crossing the Midwest Sunday and
nearing the Gulf Coast Tuesday night.
A last of a series of impulses will track east from the Canadian
Prairies and into the northern tier of the U.S. this weekend. This
pattern will be favorable for developing showers and thunderstorms
capable of producing locally heavy convection/MCS activity over
the northern Great Plains/Great Lakes Saturday night before
activity focuses more on the cold front Sunday into next week.
Locally excessive rainfall may result from the multiple rounds of
rain/high rain rates over the northern tier. Guidance continues to
suggest the max QPF occurs over the Upper Mississippi Valley and
Great Lakes this weekend that spreads into the east-central and
southeast states early next week with the trough
amplification/cold front. The tail end of this cold front is
likely to bring enhanced upslope flow to the central/southern
Rockies as it sags south Sunday into next week. Expect renewed
monsoonal convection over the Southwest under the developing ridge
starting Monday.
...Guidance/Predictability Assessment...
Uncertainty is greatest with the strength and positioning of a
western Canadian ridge this weekend and the associated effects on
the strength and timing of the downstream trough over the eastern
U.S. early next week. The WPC medium range product suite was
mainly derived from a typical general model blend of deterministic
global guidance for Days 3 to 5 with inclusion of the 00Z GEFS and
ECENS means for Days 6 and 7. The 06Z GEFS mean lags the 00Z GEFS
mean and all other global ensemble means and was therefore
excluded from the blend for Day 6 and 7.
Jackson/Rausch
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,
Sun-Tue, Jul 21-Jul 23.
- Heavy rain across portions of the Mid-Atlantic, the Lower
Mississippi Valley, the Central
Appalachians, the Tennessee Valley, the Northeast, the Southern
Appalachians, the Southeast, the
Southern Plains, and the Ohio Valley, Mon-Tue, Jul 22-Jul 23.
- Heavy rain across portions of the Middle Mississippi Valley, the
Great Lakes, the Upper
Mississippi Valley, and the Northern Plains, Sat-Sun, Jul 20-Jul
21.
- Heavy rain across portions of the Southeast and the
Mid-Atlantic, Wed, Jul 24.
- 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, and the
Northern Plains.
- Excessive heat across portions of the Lower Mississippi Valley,
the Central Appalachians, the
Tennessee Valley, the Middle Mississippi Valley, the Upper
Mississippi Valley, the Great Lakes, and
the Ohio Valley, Sat, Jul 20.
- Excessive heat across portions of the Southeast, the
Mid-Atlantic, the Northeast, and the Central
Appalachians, Sat-Sun, Jul 20-Jul 21.
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