Composite Map Day 8-14

Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Tuesday July 21, 2026 to Monday July 27, 2026

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 13 2026

Synopsis: Persistent mid-level high pressure over the Four Corners occurring near the peak of summer brings the risk of extreme heat for much of the central and southeastern Contiguous U.S. (CONUS) as well as portions of California throughout week-2. Mid-level low pressure over the Northeast U.S. may result in heavy precipitation for portions of the southern Mid-Atlantic region early in the forecast period. Increasing inflow of tropical moisture is favored to enhance monsoon rains over the Desert Southwest through the middle of week-2.

Hazards

• Slight risk of extreme heat for the Central Valley of California, Tue-Mon, Jul 21-27.
• Slight risk of extreme heat for much of the Southern Plains, Lower Mississippi Valley, and Southeast U.S., as well as portions of the Central Plains and Mid-Atlantic, Tue-Mon, Jul 21-27.
• Slight risk of heavy precipitation for much of Virginia and the Carolinas, and for adjacent portions of Georgia, Tue-Thu, Jul 21-23.
• Slight risk of heavy precipitation for much of the Desert Southwest and southern Great Basin, Tue-Sat, Jul 21-25.
• Rapid onset drought (ROD) possible for portions of the Dakotas.

Detailed Summary

For Thursday July 16 - Monday July 20: WPC Days 3-7 U.S. Hazards

For Tuesday July 21 - Monday July 27: Multiple model ensembles depict anomalous mid-level ridging persisting over the western CONUS throughout week-2, with a closed 594-dm contour emerging over the Four Corners by the middle of the forecast period. This pattern is highly favorable for above-normal temperatures across much of the Lower 48, and when occurring near the peak of summer brings a widespread risk of extreme heat, particularly for the western CONUS. Generally southerly flow off the Gulf of America is favored to boost dewpoints east of the Rockies, resulting in potentially hazardous heat index values for much of the Great Plains and along the Gulf Coast.

The potential for extreme heat continues to be supported by a variety of forecast tools, although a downward trend in signal strength has been noted over the past few days. The Probabilistic Extremes Tool (PET) from the GEFS indicates widespread 20% chances of maximum temperatures to exceed the 85th climatological percentile for all but the northeastern portion of the CONUS throughout the forecast period. The ECMWF PET is much more circumspect, exceeding the above percentile threshold only over portions of the Pacific Northwest and Southeast U.S. The GEFS-ECWMF combined extreme heat tool shows widespread 20% or greater chances (as high as 50% for portions of the West) of either maximum temperatures or heat index values to exceed the 90th percentile at some point during the week-2 period for most of the CONUS except the Northeast and Desert Southwest. As with the PETs, when considered individually the two models disagree widely with respect to regions affected and signal strength. Given the continuing decrease in signal strength in general and an increased signal for monsoon activity much of the Interior West is no longer highlighted for extreme heat, however a slight risk of extreme heat remains posted for the Central Valley of California, as well as much of the southeastern and south-central CONUS, both valid for all of week-2. The persistent Four Corners ridge is favored to induce anomalously warm temperatures well north into the Great Plains, although these temperatures are less likely to reach hazardous thresholds. However,the combination of anomalous warmth, near to below normal precipitation favored during week-2, and antecedent dryness supports an enhanced risk of ROD across portions of the Northern Plains.

Model ensembles are showing increased signal of enhanced precipitation stemming from the southwestern monsoon. Dynamical models are depicting a potential enhancement of monsoon convection through the middle of week-2, with uncalibrated probabilities from the ECWMF and GEFS indicating widespread 50% chances of 3-day precipitation totals to exceed half an inch, with some locations seeing 20% chances of 1 inch accumulations. Given this, a slight risk of heavy precipitation is posted for much of the Desert Southwest and southern Great Basin, valid Jul 21-25. This region is prone to flash flooding with relatively small precipitation accumulations especially along dry creek beds and in canyons and extreme caution should be exercised in such areas should thunderstorm activity initiate nearby. Monsoonal thunderstorms can also produce dry lightning, resulting in increased wildfire risk.

Tied to the troughing favored over the eastern U.S. early in week-2, ensembles continue to point to surface low development along the Eastern Seaboard. Relative to yesterday, models place the heaviest precipitation further eastward with the bulk of potentially hazardous accumulation totals remaining offshore. However, both the raw GEFS and ECMWF probability of exceedance tools remain supportive of a heavy precipitation risk, depicting 20-40% chances of 3-day amounts exceeding an inch over southern Virginia and the Carolinas. Therefore, a corresponding slight risk for heavy precipitation remains posted in the outlook valid Jul 21-23.

Forecaster: Danny Barandiaran

$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts