NOAA July 2024 Outlook: Heatwave Alert for Western US

On Sunday, the NOAA released its outlook for July 2024. Much of the Western U.S. is expected to experience above-normal temperatures, with the Southwest facing potentially excessive heat. Precipitation patterns vary across the country. Alaska is likely cooler and wetter than usual, except for its eastern North Slope and Panhandle regions.

• Related: NOAA ENSO June 2024 Update: La Niña Likely by Late Summer

Here’s an AI-generated summary of the July 2024 outlook for temperature and precipitation, broken down by region. The full discussion is at the bottom.

Temperature:

Western U.S.:

• Great Basin, Southwest, and Intermountain West: Very high chance (70-80%) of above-normal temperatures
• California and Pacific Northwest: Above-normal temperatures, including potentially excessive heat in California during the first week
• Northern Rockies: Initially near or slightly below normal, then shifting to above normal

Northern Plains and Upper Great Lakes:

• Equal chances of above-, near-, or below-normal temperatures
• Some cooler temperatures are possible early in the month

Southern Plains, Texas, Southeast, Ohio Valley, Mid-Atlantic, and New England:

• Elevated odds of above-normal temperatures

Alaska:

• Most of the state: Below-normal temperatures likely
• Eastern portion of the North Slope: Possibly above-normal temperatures due to long-term trends

Precipitation:

Western U.S.:

• Desert Southwest: Equal chances of above-, near-, or below-normal precipitation, with potential for above-normal near the southern borders of New Mexico and Arizona
• Pacific Northwest and Northern Rockies: Below-normal precipitation likely, but with reduced probability compared to earlier forecasts

Upper Mississippi Valley:

• Above-normal precipitation is favored, especially early in the month

Red River Valley (Oklahoma and Texas):

• Below-normal precipitation favored

Gulf Coast, Florida, and East Coast:

• Slightly above-normal precipitation is expected, with some uncertainty due to potential tropical activity

Alaska:

• Most of the state: Above-normal precipitation expected
• Panhandle: Equal chances of above-, near-, or below-normal precipitation

The outlook notes uncertainty due to potential tropical activity, including Hurricane Beryl and disturbances in the Gulf of Mexico and the Atlantic. It also mentions that neither El Niño Southern Oscillation (ENSO) nor the Madden-Julian Oscillation (MJO) are expected to impact the weather patterns in July 2024 significantly.

30-DAY OUTLOOK DISCUSSION FOR JULY 2024 
 
The updated July 2024 temperature and precipitation outlooks for the contiguous 
U.S. (CONUS) and Alaska (AK) take into account the most recently observed 
physical drivers and the latest initializations from the ensemble suites of the 
dynamical models (ECMWF, GEFSv12, GEM, CFSv2, and JMA). 
 
Neither El Niño Southern Oscillation (ENSO) nor the Madden-Julian Oscillation 
(MJO) are expected to have a meaningful impact on the eventual temperature and 
precipitation outcome over CONUS and AK. Niño3.4 anomalies indicate ENSO 
neutral conditions, although 200-hPa velocity potential anomalies are beginning 
to resemble a La Niña background state with enhanced divergence over the 
Maritime Continent and convergence farther east. The MJO is currently weak, 
with any remaining signal indicating the convectively active phase over the 
Indian Ocean. Some ensemble suites of the dynamical models  forecast a 
strengthening MJO propagating to the Maritime Continent. However, convection in 
this region would also be consistent with an emerging La Niña. Regardless, the 
Northern Hemisphere extratropical teleconnections to anomalous tropical 
convection are weak during July. 
 
In the extratropics, sea surface temperature (SST) and soil moisture anomalies 
remain largely unchanged from the original outlook. Namely, below normal 
coastal SSTs are still observed along the western coast of Alaska and the West 
Coast, particularly near California. Above normal coastal SSTs are found along 
the Gulf Coast and East Coast. Soil moisture anomalies are strongly positive in 
the Upper Mississippi Valley. They are negative from the Central Plains to the 
Mid-Atlantic. Soils are becoming increasingly dry across southern OK and 
northern Texas. Despite heavy rains earlier in June, the recent ~3 weeks have 
been very dry along the Red River Valley. 
 
Significant updates to the temperature and precipitation outlooks for July are 
largely related to short term model output for Week 1, which typically has high 
forecast skill. The overall 500-hPa height pattern during Week 1 features very 
strong ridging developing along the West Coast, transient troughing in the 
Northern Plains, and downstream ridging over the East Coast. This pattern 
differs from model initializations last week, which failed to predict the ridge 
along the West Coast and the depth of the trough in the Northern Plains. Over 
AK, ridging is expected over the southern half of the state and troughing is 
anticipated along the North Slope. This pattern leads to a moist onshore flow 
from the Bering Strait. As the month of July progresses into Weeks 2, 3, and 4, 
the troughing in the Northern Plains is forecast to diminish; the ridge along 
the West Coast is expected to move more inland, becoming more centered over the 
Northern Rockies; and the pattern over Alaska looks to persist. 
 
The updated temperature outlook reflects the ridge axis predominantly residing 
over western CONUS with the highest probabilities for above normal temperatures 
reaching 70 to 80% over the Great Basin, Southwest, and Intermountain West. In 
fact, temperatures over California during Week 1 are forecast to be excessively 
hot, which has necessitated the removal of any equal chances (EC) of above-, 
near-, or below-normal temperatures along the California coast. The much above 
normal temperatures are forecast to build northward into the Pacific Northwest 
as Week 1 progresses, which has also led to the removal of EC in that region. 
Some relief may occur along the immediate West Coast via sea breeze mechanisms. 
Entering Week 2, the ridge axis is forecast to move more inland which would 
push temperatures to above normal values in the Northern Rockies, after a 
near-normal or slightly-below normal start to the month due to transient 
troughing in the neighboring Northern Plains. It should also be noted that 
long-term temperature trends  are positive in western CONUS during July, and the 
temperature outlook reflects that reality. In the Northern Plains and upper 
Great Lakes, EC is forecast in this updated outlook due to some near- to 
below-normal temperatures advecting in from the north during Week 1 along with 
above normal soil moisture anomalies. Most models, including the ECMWF, expect 
the transient troughing to abate during Week 2, although the GEFS shows some 
lingering colder than normal temperatures. Farther south and east into the 
Southern Plains, Texas, Southeast, Ohio Valley, Mid-Atlantic, and New England 
elevated odds of above normal temperatures are supported by warm air advection 
downstream of the anticipated troughing in the Northern Plains, long-term 
trends during July, and strong model agreement. 
 
The updated precipitation outlook features a few notable changes. A decent 
moisture plume during the first week of July is anticipated to produce 
relatively widespread thunderstorm activity in the Desert Southwest. While this 
activity lessens during Week 2, there is some indication of it re-emerging as 
the month unfolds. This tilts the odds from below normal in the original 
outlook toward a broad region of EC with a small embedded region of 
above-normal near the southern borders of New Mexico and Arizona. Farther north 
in the Pacific Northwest and Northern Rockies, below normal precipitation is 
still expected with strong ridging over the region. However, some monsoon 
moisture cannot be ruled out, so probabilities for below-normal precipitation 
were broadly lowered. Above normal precipitation is now favored over the Upper 
Mississippi Valley due to heavy rain anticipated during Week 1 as a result of 
the transient troughing. Below normal precipitation is favored along the Red 
River Valley of Oklahoma and Texas, as most models agree the region will remain 
dry with below normal soil moisture anomalies and no apparent moisture 
advection into the region. A thin sliver of above normal precipitation is 
forecast along the Gulf Coast, Florida, and East Coast. Models are mixed in 
this region, but ultimately the long term trend and potential tropical activity 
tilt the odds to above normal. With respect to tropical activity, it should be 
noted that the eventual track of Hurricane Beryl in addition to disturbances in 
the Gulf of Mexico and Main Development Region of the Atlantic all lead to 
uncertainty in the current precipitation outlook. 
 
Finally, for Alaska, onshore flow from the Bering Strait is typically a wet and 
cool pattern during July. Thus, nearly all of the state is favored to have 
below normal temperatures with the exception of the eastern portion of the 
North Slope due to long-term trends . Above normal precipitation is also 
expected over the entire state with the exception of the Panhandle where the 
influence of the ridge along the West Coast results in EC being forecast.