Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Saturday June 21, 2025 to Friday June 27, 2025

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 13 2025

Synopsis: An area of mid-level high pressure is forecast to remain in place across the eastern contiguous U.S. (CONUS) during the week-2 period. This supports a risk of extreme heat for portions of the central and eastern CONUS. Along the northern periphery of the mid-level high, heavy precipitation is possible in the Northern Plains, Upper Mississippi Valley and Great Lakes. In southern Texas and the southern Four Corners heavy precipitation is also possible associated with easterly waves. Meanwhile, windy conditions are somewhat favorable in portions of the Southern Plains and along parts of the coast of California and Oregon. Flooding is possible in northern Alaska as ice-bound rivers break up.

Hazards

• Moderate risk of extreme heat for portions of the Mid-Atlantic, Tue-Wed, Jun 24-25.
• Slight risk of extreme heat for portions of the Central Plains, Lower and Middle Mississippi Valley and surrounding areas, Sat-Tue, Jun 21-24.
• Slight risk of extreme heat for portions of the Great Lakes, Ohio Valley, and Tennessee Valley, Sun-Wed, Jun 22-25.
• Slight risk of extreme heat for portions of the Northeast, Mid-Atlantic, and Southeast, Mon-Thu, Jun 23-26.
• Slight risk of extreme heat for portions of the Southeast and Florida, Sat, Jun 21.
• Slight risk of extreme heat for portions of the Desert Southwest, Sat, Jun 21.
• Slight risk of heavy precipitation for portions of southern Texas, Sat-Tue, Jun 21-24.
• Slight risk of heavy precipitation for portions of the Northern Plains, Upper Mississippi Valley, and Great Lakes, Sun-Wed, Jun 22-25.
• Slight risk of heavy precipitation for portions of the Four Corners region, Mon-Thu, Jun 23-26.
• Slight risk of high winds for portions of the Southern and Central Plains, Sat-Wed, Jun 21-25.
• Slight risk of high winds for coastal regions from central Oregon south through central California, Sat-Mon, Jun 21-23.
• Flooding Possible for portions of the North Slope of Alaska.

Detailed Summary

For Monday June 16 - Friday June 20: WPC Days 3-7 U.S. Hazards

For Saturday June 21 - Friday June 27: Positive 500-hPa height anomalies are forecast across much of the eastern CONUS during the week-2 period. These anomalies have grown in the latest model guidance with normalized 500-hPa height anomalies 1.5 to 2 standard deviations above normal centered over the Ohio Valley by the middle of week-2. At the surface, dynamical model guidance indicates a strong Bermuda high pressure and return flow off the Gulf helping to enhance low level moisture and inducing a warm and sticky airmass across the eastern and central CONUS.

At the start of week-2, the strongest standardized anomalies are over the Middle Mississippi Valley. This is reflected in the Probabilistic Extremes Tools (PETs) with 30-50% chances from the GEFS and ECENS for temperatures exceeding the 85th climatological percentile across the Central Plains, Middle Mississippi and eastern Ohio Valleys. Over time, the strongest chances shift eastward. By the middle of the period, enhanced chances (40-60%) of the maximum temperature exceeding the 85th percentile have overspread much of the Mid-Atlantic and Northeast. The PETs also highlight increased chances of temperatures exceeding 95 deg F across parts of the Mid-Atlantic by the middle of week-2. As such, we have a series of extreme heat hazard risks progressing eastward with time across the eastern CONUS. Across the central Plains and Mississippi Valley, a slight risk of excessive heat is posted for Jun 21-24. The western portions have the strongest chances of extreme heat early in this forecast period. Secondly, a slight risk of extreme heat has been added today across portions of the southern Great Lakes, Ohio Valley, and northern Tennessee Valley for Jun 22-25. Finally, we have a slight risk of extreme heat for portions of the Northeast, Mid-Atlantic, and Southeast, for Jun 23-26. An embedded moderate risk is posted for parts of the Mid-Atlantic for Jun 24-25. Within the embedded moderate risk are increased chances of air temperatures exceeding 95 deg F and apparent temperatures exceeding 105 deg F. During this time, the standardized mid-level height anomalies are forecast to be near 2 standard deviations above normal over the region.

At the onset of the period parts of the Southeast may see temperatures approaching hazardous criteria beneath positive 500-hPa height anomalies and a particularly moist airmass. This heat is forecast to already be underway by the start of week-2 but ongoing heat, with little relief at night, may cause issues at the start of the period. The National Blend of Models (NBM) is forecasting many overnight record high minimum temperatures across much of the Southeast. Therefore, a slight risk of extreme heat is posted for Jun 21 across portions of Georgia, and Florida.

In the Desert Southwest, dynamical guidance remains supportive of temperatures approaching heat criteria. Temperatures of 105 to 110 are supported by many tools after a brief respite at the end of week-1. Therefore, a slight risk of extreme heat is posted for the Desert Southwest for Jun 21.

Following this initial heat, dynamical model guidance from the GEFS and ECENS begins to show increased chances for precipitation to move into the region. There are multiple tropical waves across the eastern Pacific and Bay of Campeche that are forecast to bring increased moisture transport into northern Mexico and then into the Four Corners region. Precipitable Water (PWAT) anomalies approach a 150% of normal across southeast Arizona and New Mexico by the middle of week-2. Therefore, a slight risk of heavy precipitation is posted for Jun 23-26 across eastern Arizona and western New Mexico.

In southern Texas, dynamical model guidance is developing a reinforcing shot of moisture into the region during week-2. The PETs from the GEFS and ECENS indicated 20-40% chances for 3 day precipitation amounts to exceed the 85th climatological percentile and 1 inch. This could lead to chances of flash flooding due to the short time in which precipitation is forecast to fall and the nature of the watersheds in the region. Therefore, a slight risk of heavy precipitation is forecast for Jun 21-24.

In the Upper Mississippi Valley into the Great Lakes, along the northern periphery of the mid-level ridge, dynamical guidance is indicating increased chances of one or more mesoscale convective systems (MCS) to develop and bring chances for heavy precipitation to the region. The ECENS reforecast and PET show increased chances for above-normal precipitation during week-2 and precipitation exceeding the 85th percentile in the first 3 days of the period, respectively. Similarly, the statistical analog tool highlights increased chances for above-normal precipitation across this region as well. Therefore, a slight risk of heavy precipitation is posted for Jun 22-25 in this region.

Models generally depict fairly strong winds at the southern end of the Gulf moisture inflow. While the PETs are rather mixed, ensemble mean wind speeds from the ECMWF and GEFS both indicate peak daily wind speeds of at least 20mph over western portions of the Southern and Central Plains through the first half of week-2, therefore a slight risk of episodic high winds is posted for this region for Jun 21-25. Forecast ensemble mean wind speeds are also elevated along the West Coast early in week-2 with wind speeds of 25-30mph along the immediate coast from central Oregon south to central California.

Ice-bound rivers are beginning to break up in the North Slope of Alaska. Flooding is possible by the end of week-1 and into week-2 across much of the region as a result of ice jams, aufeis, snow melt, and associated flooding. Therefore, a flooding possible shape is posted for the North Slope.

Forecaster: Ryan Bolt

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

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts