619
FXUS02 KWBC 101914
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
314 PM EDT Mon Aug 10 2026

Valid 12Z Thu Aug 13 2026 - 12Z Mon Aug 17 2026

...Monsoonal moisture to prolong excessive rainfall threat in the
Southwest late week...

...Multi-day heavy rainfall threat extending from parts of the
North-Central Plains and Midwest into the Ohio Valley this week
into the weekend...

...Hazardous heat forecast across much of the South-Central and
Southeast U.S. through early next week...


...Overview...

A progressive regime over the northern and eastern U.S. along with
ridging over south-central U.S. will maintain an active pattern
through the weekend and into next week. The ridge will continue to
support hot conditions that may reach hazardous levels across the
Southern Plains and Southeast. Multiple shortwaves will eject
within the amplified northern flow, leading to numerous thunderstorms
and showers from the Northern Rockies/Plains to as far east as the
Northeast and Mid-Atlantic. Several days of repeated rainfall will
bring flooding concerns, especially from the Four Corners on east
through the Midwest and Ohio Valley. A drier weekend is in store
along the West Coast, but an approaching upper trough over the
northeast Pacific Ocean will increase the odds for showers in the
Pacific Northwest early next week.


...Guidance/Predictability Assessment...

The latest deterministic and ensemble guidance remain in fairly good
agreement on the overall synoptic pattern through the upcoming
weekend, including the persistence of the southern U.S. ridge and
an active northern stream regime. Confidence is comparatively
higher through Thursday and Friday, while uncertainty increases
beginning on Sunday as individual shortwaves and frontal placements
become increasingly difficult to resolve. This will lead to
challenges with forecasting the amplitude and timing of small-
scale features that may impact frontal boundaries and sensible
weather. The ensemble guidance seems to alleviate some of these
challenges. Therefore, a multi-model approach through the earlier
portion of the period were incorporated in the forecast, while
phasing in a heavier blend of ensemble guidance by the weekend and
through Monday.


...Weather/Hazards Highlights...

A progressive northern-stream flow persists across the northern
tier and eastern U.S.. Multiple shortwave disturbances will
traverse the northern tier through the weekend and will interact
with a slow-moving frontal zone extending from the
northern/central Rockies into the Central Plains, Midwest, Ohio
Valley, and eventually across the Great Lakes and Northeast. The
combination of rich low-level moisture, instability, and synoptic-
scale forcing along the boundary will support periodic clusters of
showers and thunderstorms with locally heavy rainfall and flooding
concerns. With the potential for locally intense rainfall rates
and slow moving storms redeveloping over the same area, a broad
Marginal Risk has been highlighted in Day 4 (Thursday) Excessive
Rainfall Outlook (ERO) across portions of the central Plains into
Mid-Mississippi Valley, and Ohio/Tennessee Valley, while a Slight
Risk highlights portions of the Ohio Valley, Midwest, and North-Central
High Plains. The frontal boundary will remain slow moving into the
weekend reinforcing multiple days of showers and thunderstorms
across the same areas, but by Sunday the frontal boundary will lift
into the Great Lakes and Mid-Atlantic and portions of the
Northeast, pushing the showers and thunderstorms further northeast
into the Upper Midwest, Northeast, and Mid-Atlantic.

Across the Southwest, Great Basin, Rockies, and interior
California, an upper-level trough will move into the West by late
week. In response to the trough`s position off the West Coast and
the ridge position in the Southeast, low-level monsoonal moisture
advection will deliver plenty of rich moisture throughout much of
the forecast period. This will lead to the development of scattered
to numerous thunderstorms, particularly over the Four Corners
states. Some storms will produce excessive rainfall over short
periods while also moving rather slowly. Repeated convection may
lead to flash flooding in vulnerable terrain, including burn scars,
slot canyons, and urbanized areas. Therefore, a broad Marginal
Risk on Day 4 ERO highlights much of the area with Slight Risks
over portions of the Rockies/Plains and along the NM/AZ border.

Elsewhere, a frontal boundary will drop southward into portions of
the Southeast and a surface trough will develop ahead of the front
by Friday. As these features interact with warm moist airmass,
scattered thunderstorms will develop over portions of the Southeast
through the weekend.

The Southern Plains, Gulf Coast, and Southeast will remain under
the influence of the persistent upper ridge. Temperatures will
remain well above normal as portions of the Southern Plains reach
the lower 100s, while widespread 90s extend eastward across the
Southeast. High dew points will keep heat indices elevated,
resulting in potentially dangerous heat conditions where the heat
persist for several consecutive days. Major HeatRisk conditions are
expected across a broad portion of the region, with locally
Extreme HeatRisk possible.


Oudit/Mullinax



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
















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