667
FXUS02 KWBC 060618
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
218 AM EDT Thu Aug 6 2026

Valid 12Z Sun Aug 09 2026 - 12Z Thu Aug 13 2026


...Heat wave wanes after Sunday for the Southwest, with heat
threats continuing into next week for the Central U.S. and
Southeast...

...Overview...

A strong and lingering upper high over the Southwest will bring
hazardous heat concerns to the region through Sunday before it
finally begins to weaken a bit. Ridging will then expand eastward
over the Central U.S. and the Southeast, bringing increasing heat
concerns for parts of those regions next week. Meanwhile, a
progressive northern stream trough, and reinforcing waves, will
carry a surface front into the Northeast, with moderate to locally
heavy rainfall. This boundary looks to get hung up over the Great
Lakes with an increasing heavy rainfall threat emerging by next
week. The Bermuda high will help funnel tropical moisture into the
Southeast and Gulf Coast, continuing a wet and humid pattern
through the period that will surge northward at times into the Mid-
Atlantic/Ohio Valley.


...Guidance/Predictability Assessment...

The latest guidance continues to show good agreement on the
overall large scale pattern and evolution, but with some lingering
uncertainty in the details and timing of individual systems. The
mean upper low/trough over Hudson bay will rotate energy through it
across the Great Lakes into the Northeast with some minor timing.
Things become a bit more unclear late in the period as the low may
jog southward, possibly sending a stronger wave into the Great
Lakes region, which has implications for heavy rainfall threats
across the Great Lakes/Ohio Valley region next week. Troughing into
the Northwest shows some uncertainty on how quickly it erodes the
Southwest upper high. Late period shows additional uncertainty as
energy or a compact upper closed low drops into the region. There
is also question on the extent and strength of a subtropical
Atlantic ridge which may extend into the Southeast at times next
week. Given the uncertainty, differences are well within the normal
range for the time period and most solutions remain plausible.

The WPC forecast used a blend of the deterministic guidance for
the first half of the period with increasing weighting of the
ensemble means to 40 percent by days 6 and 7. This maintains good
agreement with the previous shift as well.


...Weather/Hazards Highlights...

Widespread moderate to locally major and extreme HeatRisk will
continue across the Southwest into Sunday before heat wanes in
response to a weakening upper ridge. Heat threats will continue
into next week though for parts of the Central U.S. into the
Mississippi Valley and Southeast where ridging will hold on longer.
Areas of smoke will also remain likely given active fires across
the Western states. Across the northern tier, temperatures should
be near normal the whole period with parts of the East slightly
above normal. A slight cooling trend is expected for the Pacific
Northwest in the wake of a weak/dry cold front this weekend.

A cold front through the Northeast on Sunday will allow for
ongoing showers and storms across the Midwest to the East. More
widespread, moderate to heavy rainfall is also looking increasingly
likely across portions of the Upper Midwest/Great Lakes/Ohio
Valley next week as a portion of the front slows and with
additional energy moving through. A wet pattern sets up over the
South and Southeast, as tropical moisture rounds the west side of
the subtropical Atlantic ridge into early next week. Elsewhere,
monsoonal moisture is likely to continue through the period for
Arizona and New Mexico, reaching portions of Utah and Colorado as
well. The remainder of the West into the Northern Plains should be
mostly dry.


Santorelli


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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