Heat Wave Shifts from Mid-Atlantic to Southeast/Southern Plains by Monday
Storms to Bring Flash Flooding, Damaging Winds, and Tornadoes to New England on Sunday
Severe Storms Expected in the Upper Midwest on Monday
Monsoon-like Conditions Persist in the Southwest
A broad long-wave upper-level ridge over the East Coast and western U.S. on Sunday will keep hot summer temperatures in the forecast for much of the country. Highs are predicted to reach the upper 90s from the Mid-Atlantic to the Southeast/Lower Mississippi Valley/Southern Plains, extending west through the High Plains into the Great Basin and California. Humidity will push heat index values into the low 100s, with warm overnight lows in the mid-70s providing little relief. This heat will be particularly dangerous for parts of the Mid-Atlantic, Southeast, Lower Mississippi Valley, and Southern Plains, prompting heat-related advisories and warnings. Numerous record-tying/breaking highs are possible for the Mid-Atlantic. In the West, heat-related advisories/warnings are also in effect, with temperatures exceeding 100 degrees in northern Utah and parts of central/southern interior California. A cooling trend is expected for the Mid-Atlantic by Monday as an upper-level trough and surface cold front approach, while the Southeast/Lower Mississippi Valley/Southern Plains will continue to experience intense heat. The upper-level ridge over the West will begin to shift eastward, bringing highs in the upper 90s and low 100s to the Central/Southern Plains.
An upper-level trough and surface low pressure/frontal system pushing eastward will bring storm chances from New England to the Mid-Atlantic and Upper Ohio/Tennessee Valleys on Sunday, with moderate to locally heavy rainfall possible. Northern New England is at greatest risk for significant rainfall, with potential downpours of up to 2 inches per hour. A Slight Risk of Excessive Rainfall (level 2/4) is in effect, indicating scattered flash flooding. Strengthening upper and lower-level winds, combined with high moisture and warming temperatures, will promote intense thunderstorms. The Storm Prediction Center has issued an Enhanced Risk of severe weather (level 3/5) for central New England, where damaging winds and a few tornadoes are most likely. A broader Slight Risk (level 2/5) extends from this region southwest through the northern Mid-Atlantic into the Upper Ohio Valley, with an isolated threat of damaging winds. The system is expected to reach the coast by Monday morning, bringing drier conditions, though some storms may linger over northern New England.
In the West, an upper-level shortwave and surface frontal system moving eastward along the northern tier of the West and southern Canada on Sunday will approach the Upper Midwest by Monday afternoon. Warm, moist air flowing northward ahead of the system will lead to storm chances along and ahead of an eastward-moving cold front. A Slight Risk of severe weather remains in place for parts of northern Minnesota and Wisconsin, with potential for damaging winds and large hail. More widespread and organized convection and locally heavy downpours could result in isolated flash flooding. Monsoon-like conditions will persist in the Southwest through at least Monday, with daily showers and thunderstorms. Anomalously high moisture in the region will result in locally heavy downpours and isolated flash flooding. Daily storm chances will also continue over Florida and south Texas.