920
FXUS02 KWBC 231919
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
319 PM EDT Sun Aug 23 2026

Valid 12Z Wed Aug 26 2026 - 12Z Sun Aug 30 2026


...Hazardous Heat to continue for the Desert Southwest and
Southern Plains...

...Overview...

The upper level pattern will feature troughing in the Northwest and
East with a strong ridge anchored over the Southwest. The ridge
will flatten late this week as upper level troughing strengthens
over the Northwest, resulting in some areas seeing relief from the
ongoing heat wave, but hazardous heat will persist for the Desert
Southwest and southern Plains. Moisture on the western periphery
of the ridge will continue to support daily monsoonal convection
across the Intermountain West. Meanwhile, several frontal systems
will push through the upper troughs, bringing showers and storms
from the northern/central Plains to the East Coast.


...Guidance/Predictability Assessment...

Model guidance remains in good agreement on the synoptic pattern
through the week, with some uncertainty creeping in next weekend as
upper level energy moves into the Northwest and across the northern
tier. The GFS is on the southern/western side of the guidance
spread while the ECMWF is on the northern/eastern side. The
placement of this energy will affect precipitation chances from the
Pacific Northwest to the northern Plains, a northern solution
would result in little to no precipitation while a southern
solution could bring significant precipitation. AI guidance
suggests a middle of the road solution, which was favored for
today`s forecast.

Given good agreement, the WPC forecast was initiated with a near
even blend of the deterministic guidance, and contributions from
the GEFS, ECENS, AI GFS, and EC-AIFS were added late week into the
weekend to help smooth out model differences. This blend was
consistent with the previous forecast and the National Blend of
Models.


...Weather/Hazards Highlights...

Under the influence of the main upper high/ridge, daily maximum
temperatures across the southern Plains will continue to rise into
the 90s and 100s with oppressive heat indices. Record-breaking
warm overnight temperatures across the southern tier will further
limit recovery from the heat, especially given heatwave longevity
which may result in heat related illnesses. Conditions will improve
this week for the Lower Mississippi Valley, but widespread Major
to Extreme HeatRisk will persist in the southern Plains. For the
Desert Southwest, daytime max temperatures are forecast to soar
into the 110s, which will create heat concerns this week. Pre-
frontal areas of the Southeast may be a few degrees above normal,
but forecast precipitation and cloud cover will help keep the heat
in check. Please see WPC`s Key Messages for more extreme heat
details.

Meanwhile, lingering monsoonal moisture will stream northward on
the periphery of the upper ridge to help trigger scattered,
diurnally driven convection across the eastern Intermountain West
and Rockies. Individual cells may lead to isolated instances of
flash flooding for sensitive locations such as burn scars, favored
terrain like slot canyons, and urban areas. There is a Marginal
Risk of excessive rainfall for these areas in the Day 4 (Wednesday)
and Day 5 (Thursday) outlooks. Marginal Risk areas are also
highlighted for portions of the Southeast and Mid-Atlantic that
may see repeated rounds of locally heavy precipitation as frontal
boundaries approach and ultimately stall over these regions.

Shortwaves rounding the top of the ridge will trigger showers and
thunderstorms from the northern and central Plains into portions of
the Midwest through mid-week. Later this week, a stronger frontal
system will push across the Northwest and north-Central U.S.,
bringing increasing precipitation chances and potentially heavy
rainfall to the Plains and Midwest. Warm, southerly flow on the
southern side of the system may bring increasing heat to the
southern and central Plains next weekend.


Dolan/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





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