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Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Saturday July 09, 2022 to Friday July 15, 2022

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT July 01 2022

Synopsis: Heatwaves and an increased risk of the rapid onset of drought continue to be the primary hazards during early to mid-July, due to a strengthening, expansive area of mid-level high pressure over the central and western U.S. Dynamical models have relatively good model agreement and consistency with yesterday's guidance supporting this pattern, with slightly less coverage in excessive heat potential across the Northwest but increasing heat signal across the central CONUS . Periods of enhanced Monsoon rainfall and related flash flooding are forecast to affect Arizona and New Mexico. Mid-level low pressure is expected to result in a wetter pattern for Mainland Alaska by the second week of July.

Hazards

• High risk of excessive heat for portions of the Central and Southern Plains and Ozarks Region, Sat-Mon, Jul 9-11.
• Moderate risk of excessive heat for much of the Great Plains, Mississippi Valley, Central and Southern Rockies, and eastern Central Great Basin, Sat-Tue, Jul 9-12.
• Moderate risk of excessive heat for the Desert Southwest, southern California, and the Central Valley of California, Sat-Sun, Jul 9-10.
• Slight risk of excessive heat for much of the central and western CONUS, eastern Corn Belt, and Tennessee Valley, Sat-Fri, Jul 9-15.
• Rapid onset drought risk for parts of the central U.S.
• Slight risk of heavy rain for parts of the Northern Great Plains and Upper Mississippi Valley, Sat-Wed, Jul 9-13.
• Slight risk of heavy rain for parts of Arizona and New Mexico, Tue-Fri, Jul 12-15.
• Flooding possible for parts of Arizona and New Mexico.
• Flooding possible in the James River Basin of South Dakota.

Detailed Summary

For Monday July 04 - Friday July 08: WPC Days 3-7 U.S. Hazards

For Saturday July 09 - Friday July 15: Ensemble means (0Z GEFS, ECMWF, and Canadian) remain in good agreement indicating anomalous 500-hPa ridging across much of the CONUS, excluding the northwestern and northeastern regions. This pattern supports continued support for prolonged increased chances for excessive heat across many portions of the CONUS. Dynamical model guidance generally shows lower chances for excessive heat across the northwestern CONUS while increasing chances across the central CONUS. Therefore, these changes are reflected in the decreased coverage of the slight risk of excessive heat across the Northwest and increased coverage of the moderate and high risk of excessive heat across the central CONUS.

A broad area of slight risk of excessive heat is maintained for week-2, excluding parts of the Northwest, where the GEFS and ECMWF reforecast tools indicate maximum temperatures having at least a 20% chance of exceeding the 85th percentile, and the skill weighted heat index tool showing heat index values exceeding the 90th percentile. An embedded moderate risk area of excessive heat is posted for much of the Great Plains, Mississippi Valley, Central and Southern Rockies, and eastern Central Great Basin, Jul 9 to 12, which is expanded westward and southward due to increased and expanded enhanced probabilities (>40% chance) in the reforecast tools of maximum temperatures exceeding the 85th percentile. The coverage of the moderate risk is anticipated to shrink to the Southern Plains and Mississippi Valley by July 11. A moderate risk of excessive heat is maintained for the Desert Southwest, southern California, and the Central Valley of California early in week-2 (Jul 9-10) given continued tool support. These modifications were based on the building 500-hPa ridge and guidance from the reforecast GEFS and ECMWF temperature tools.

The high risk of excessive heat is also expanded westward and southward due to today's increased heat signal in the tools where the reforecast tools show at least a 60% chance of exceeding the 85th percentile (some parts having at least a 20% chance of exceeding the 95th percentile). The National Blend of Models forecasts potential near record breaking temperatures across the Central Plains and Texas (exceeding 100 deg F) further supporting expansion of the moderate and high risk excessive heat areas. Based on the uncalibrated heat tool, Heat index values are likely to reach 105 degrees F as far north as South Dakota, with less coverage in today's guidance of exceeding 110 degrees F. The greatest chances of heat index values exceeding 110 Deg F is indicated for the Great Plains. Anticipated hot and dry conditions could enhance wildfire risk across the south-central and southwestern CONUS, especially where the National Interagency Fire center (NIFC) indicates moderate to high risk of wildfires toward the end of week-1.

During late June, drought rapidly developed across parts of the southeastern and central U.S. A continuation of rapid onset of drought is maintained in today's outlook for parts of the Lower Ohio Valley and Lower to Middle Mississippi Valley. An additional area of possible rapid onset drought is posted for parts of northwestern Texas across the Red River region and northwestern Louisiana. These risk areas are based on: 30-day precipitation deficits of 2 to 4 inches, drying topsoil, high evapotranspiration rates and water demand at this time of year, little to no rainfall during the next week, and likelihood of above-normal temperatures during the next two weeks.

Northwest flow aloft to the north of the expansive 500-hPa ridge is expected to promote the development of Mesoscale Convective Systems (MCS) from the Dakotas southeastward across the Upper Mississippi Valley through the early part of week-2. Although the track of a MCS is difficult to predict at this lead time, the longwave pattern, uncalibrated 3-day ECMWF ensemble, and climatology support a slight risk of heavy precipitation from July 9 to 13 for parts of the north-central U.S. Additionally recent deterministic GFS solutions indicate favorable shear and enhanced convective available potential energy (CAPE) that would further support MCS activity.

Model solutions continue to depict a favorable placement of the 500-hPa ridge axis over the Four Corners region for enhanced monsoonal flow into the Southwest during week-2. The greatest chance for localized heavy precipitation would be during the second half of the week, as the mid-level ridge slightly weakens and there would be less suppression of precipitation. Due to continued uncalibrated daily model ensemble guidance and the reforecast tools indicating enhanced potential for 3-day rainfall exceeding the 85th percentile, the slight risk of heavy precipitation and related flash flooding hazard are continued.

In the Northern Plains, the Advanced Hydrologic Prediction Service (AHPS) tool continues to show several locations in the James River basin forecast to remain at or above flooding stage leading up to week-2. Any additional precipitation observed over the region during week-2 will fall on saturated soils and keep the flooding threat in place for week-2 and beyond.

Widespread active wildfires across Alaska may continue into week-2, continuing poor air quality conditions. The potential for a wetter pattern during week-2 across much of Mainland Alaska associated with an amplified 500-hPa trough becoming centered over western Alaska may help remediate wildfire risk in some areas.

Forecaster: Melissa Ou

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

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts