696
FXUS21 KWNC 281812
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 28 2026

SYNOPSIS: A restrengthening area of mid-level high pressure forecast supports a
renewed and expanded risk of extreme heat conditions for many parts of the
western contiguous U.S. (CONUS) during week-2. The combination of anomalously
warm and drier than normal conditions is expected to enhance the risk for
wildfire activity where numerous wildfire incidents have been reported within
highlighted heat risk areas.  Antecedent dryness along with the likelihood of
above-normal temperatures and below-normal precipitation during the next two
weeks supports an increased risk for the Rapid Onset of Drought to parts of the
Great Plains and Corn Belt. A more favorable monsoonal circulation supports an
increased and potentially prolonged risk of heavy precipitation across the
Desert Southwest and lower Four Corners.

HAZARDS

High risk of extreme heat for portions of California, Southwest, Great Basin,
and adjacent parts of the Rockies, Wed-Thu, Aug 5-6.

Moderate risk of extreme heat for portions of the High Plains, Southwest, Great
Basin, Rockies, Northern Intermountain, Pacific Northwest, and California,
Wed-Sat, Aug 5-8.

Slight risk of extreme heat for most of the western two-thirds of the CONUS and
Southeast U.S., Wed-Tue, Aug 5-11.

Slight risk of extreme heat for the Middle and Upper Mississippi, and Ohio
Valleys, Great Lakes, Mid-Atlantic, and Northeast, Wed-Thu, Aug 5-6.

Slight risk of heavy precipitation for parts of the Desert Southwest and
adjacent regions, Wed-Tue, Aug 5-11.

Rapid Onset Drought (ROD) possible for parts of the Great Plains, Middle
Mississippi Valley and Great Lakes.

DETAILED SUMMARY

FOR FRIDAY JULY 31 - TUESDAY AUGUST 04:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR WEDNESDAY AUGUST 05 - TUESDAY AUGUST 11: Towards the middle of next week,
500-hPa mean height anomaly forecasts from the dynamical models are in decent
agreement featuring amplified ridging centered over the southwestern CONUS,
shortwave troughing over southcentral Canada, and a secondary anomalous ridge
center over the Great Lakes and the Northeast. As the shortwave troughing lifts
out near Hudson Bay, an accompanying frontal system is expected to bring cooler
temperatures across much of the Midwest early in the period, though there
remains questions as to the extent and strength of anomalously cold air
reaching areas east of the Mississippi later next week with the secondary mean
ridge center established downstream. Notwithstanding this uncertainty with the
pattern over the eastern U.S., there continues to be good ensemble support for
the restrengthening of the amplified ridging upstream by days 9 and 10 (Aug
6-7), where a renewed risk of extreme heat conditions continues to be the
primary hazards concern across many areas of the western CONUS following a
minor cooldown late in week-1. In addition, the amplifying ridge axis looks to
be in a more favorable position for the advection of monsoonal moisture,
supportive of a potentially prolonged heavy precipitation risk across the
southwestern CONUS during the outlook period.



Based on a convergence of evidence in both raw and calibrated temperature
tools, a high risk extreme heat of extreme heat remains issued for Aug 5-6, and
is expanded to include portions of the California Valley, Great Basin, and
adjacent parts of the Rockies in the updated outlook. Within the high risk
area, both the GEFS and ECMWF Probabilistic Extreme Tools (PETs) indicate
elevated chances (>50%) of maximum daytime temperatures exceeding the 85th
percentile, and the National Blend of Models (NBM) also shows a number of
locations nearing and/or breaking daily temperature records during the first
few days of the period.  A broader moderate risk area of extreme heat remains
posted and is likewise expanded to include the much of the High Plains, Pacific
Northwest, and Northern Intermountain region, and is now valid through Aug 8
before much of the ridging aloft deamplifies. Both the spatial adjustments of
the moderate and high risk areas are also supported by the ECMWF probabilistic
height tools which feature 40-60% (10-20%) chances of 500-hPa heights exceeding
597 (600) dm along an axis from the California Valley to the Front Range of
Colorado, translating to 2-2.5 standard deviations above normal for this time
of year. The combination of anomalously warm and drier than normal conditions
is expected to be favorable for wildfire activity where numerous wildfire
incidents (both contained and ongoing) have been reported within these elevated
heat risk areas.  Surrounding these areas, a slight risk area of extreme heat
is designated for much of the western two-thirds of the CONUS, with an
extension throughout the lower Gulf States and Southeast where enhanced
subtropical ridging looks to become better established. This extension is
supported by the NBM and calibrated heat tools which depict increased chances
for heat index values above 105 and 110 deg F driven by elevated dewpoints.



Tied to the aforementioned secondary anomalous ridge center, a separate slight
risk area of extreme heat also remains posted mainly ahead of the favored
frontal system from the Middle Mississippi Valley into the Northeast early in
week-2. Although this heat threat appears to be more of short duration compared
to that out West, PETs continue to highlight increased chances (>30%) of
daytime temperatures exceeding the 85th percentile on days 8 and 9 (Aug 5-6)
before mid-level heights begin to lower with the approaching mean shortwave
trough. As noted, there is some uncertainty as to how much cooling will take
place as the depth of the mean trough is not particularly deep in the ensemble
guidance. For this reason, the slight risk of high winds issued over the Great
Plains is discontinued today which is supported by the PETs showing a reduction
of wind signals in percentile space relative to yesterday. However, a Rapid
Onset Drought (ROD) risk remains posted over the Plains and Mississippi Valley
over areas with antecedent dryness and near to below normal precipitation is
favored to prevail over the next few weeks. According to the U.S. Drought
Monitor valid July 21, abnormal dryness (D0) and moderate drought (D1) expanded
this past week across the Dakotas implying that ROD is underway. Despite the
cooler temperatures favored early in week-2, any renewed warmth combined with
dry conditions enhances the risk for wildfire activity.



Across the Southwest, deterministic and ensemble based ECMWF solutions continue
to point to increased dewpoints and total precipitable water content
overspreading the Sonoran Desert, consistent with a Gulf of California moisture
surge event by late next week. Given that tropical cyclone activity in the
eastern Pacific is favored to calm down in the wake of Genevieve, any gulf
surge potential is most likely tied with the pairing of a strong thermal low
established over Arizona and transient easterly wave activity over the Sinaloa
Highlands of western Mexico to initiate a moisture event.  Based on raw and
calibrated precipitation tools, a slight risk of heavy precipitation remains
posted with its coverage expanded to include more of the Four Corners.  A
moderate risk of heavy precipitation was considered for early week-2 based on
an uptick in probabilities for 3-day amounts exceeding an inch in the GEFS,
however this risk designation is less supported by the GEFS PET and raw ECMWF
tools.  The slight risk area remains valid for all of week-2 due to the
persistence of wet signals in the ECMWF PET associated with a favorable
monsoonal circulation where additional gulf surge events are possible later in
the period.

FORECASTER: Nick Novella

$$