629
FXUS02 KWBC 170736
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
336 AM EDT Fri Jul 17 2026

Valid 12Z Mon Jul 20 2026 - 12Z Fri Jul 24 2026


...Dangerous heat will gradually subside in the north-central U.S.
early next week, but linger over a humid U.S. southern tier...


...Overview...

An amplified upper ridge over the western and central U.S. will
cause dangerous heat across the northern/central Plains into early
next week. The northeast side of the ridge will get gradually
suppressed by shortwave energy entering the Midwest/Great Lakes
into a northeastern U.S. upper trough, which will bring relief from
the heat to northern areas as the trough pushes cold fronts
through the region. Very hot and humid conditions will linger next
week over much of the U.S. southern tier. The shortwaves and fronts
in the upper trough should also yield rounds of heavy rains and
strong to severe thunderstorms from the Great Lakes to the East
Coast next week. Additionally, ample monsoonal moisture will
continue to stream into the Southwest and Intermountain
West/Rockies to fuel rounds of enhanced showers and thunderstorms.

...Guidance/Predictability Assessment...

Guidance is generally still agreeable on the large scale pattern,
but uncertainties still are evident as normal with the smaller
scale details and local convective focus, especially late period.
Forecast spread has seemed to decrease some versus earlier cycles,
and a broad model/ensemble mean/machine learning blend seems to
provide a seemingly solid forecast basis.

It does remain the case that there is still plenty of uncertainty
in the northeast Gulf with potential development of a tropical low.
Recent guidance continues to be relatively weak with the low, and
if it develops true tropical characteristics, it would be more this
weekend. Regardless, there is some confidence for some reflection
of the low or an elongated trough over the Southeast to enhance
rain across parts of Florida and the Southeast. NHC continues to
track this with low probabilities of formation.

...Weather/Hazards Highlights...

Heatwave focus over the northern/central Plains is expected to
ease some early next week. This occurs as supporting upper ridge
influence shifts farther south leading to generally Major HeatRisk
stretching from the central Plains and Middle/Lower Mississippi
Valley to Southeast for next week. Temperatures a few degrees above
already warm averages combined with high humidity could lead to
increased HeatRisk in the south-central U.S. and Gulf Coast states.

Meanwhile, the southwestern to south-central U.S. could see
slightly below average temperatures as ample moisture leads to
clouds and rain/thunderstorms. Flow under the upper ridge will
draw significant monsoonal moisture into the Southwest and
Intermountain West to the Rockies. This moisture will lead to
scattered to numerous showers and thunderstorms with the potential
to produce heavy rainfall and localized flash flooding. Sensitive
places such as burn scars, steep terrain, etc., would be the most
vulnerable to any flooding concerns that may develop. Broad
Marginal Risks of excessive rainfall are in place from the
Southwest across much of the Intermountain West Monday/Tuesday.
Coverage of showers and thunderstorms should gradually increase
eastward over the Rockies/Plains next week to monitor.

Elsewhere, southern stream energy is forecast to meander in the
northeastern Gulf in a moist and unstable environment early next
week as being monitored by NHC. Troughing and tropical moisture in
place (even if there is no true tropical low) could lead to heavy
rain, and Marginal Risks are in place from north-central Florida
to the coastal Southeast for isolated flash flooding Monday.

The next round of potential heavy rains and strong to severe
thunderstorms are forecast to come through the Midwest and Great
Lakes early next week with digging of an energetic shortwave aloft
and vibrant wavy frontal push. As the upper trough position
amplifies and the fronts work southeast Tuesday/Wednesday, heavy
convective rain chances will overspread much of the East, settling
into the Southeast later next week with moderating wavy frontal
progression. A WPC Excessive Rainfall Marginal Risk area was
introduced for Tuesday for the Mid-Atlantic and the Northeast.


Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw







$$