Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Thu Aug 01 2024 Valid 00Z Fri Aug 02 2024 - 00Z Sun Aug 04 2024 ...Dangerous heat engulfs much of the country as one heatwave continues in the Southeast and another heatwave intensifies and affects interior areas of the Pacific Northwest to the Northern Rockies... ...Stormy conditions for much of the Eastern U.S. into the weekend with marginal severe weather and flash flooding possible in thunderstorms... ...Locally heavy monsoonal shower and thunderstorm chances continue for the Southwest... Widespread, dangerous heat will unfortunately be the main weather story for much of the country. The heat risk metric shows that most of the I-95 corridor will be under the major category for the threat of heat related impacts Friday. High temperatures in the middle to lower 90s will be commonplace. Fortunately, the approach of a frontal boundary and increased precipitation chances will lower the extreme temperatures and most of the Mid-Atlantic to Northeast will see seasonable high temperatures in the mid- upper 80s for the weekend. A strong upper-level ridge will remain in place over the southern-tier of the U.S. the next couple days, allowing for high temperatures to reach into the low 100s over portions of the Southern Plains/High Plains, and the upper 90s for the Lower Mississippi Valley and the Southeast into Sunday. High humidity values for areas east of the High Plains will bring heat indices into the 105 to 110 degree range, potentially as high as 115 for parts of the Lower Mississippi Valley, with many areas under heat-related advisories or warnings. The combination of hot temperatures/high heat indices, as well as very warm morning lows only dropping into the mid- to upper 70s, will be dangerous to anyone without access to adequate air conditioning. An approaching cold front will bring relief to northern portions of the Southern Plains and Middle Mississippi Valley on Friday, with the expectation the heat wave will begin to wane for most locations through the weekend. In the West, an upper-level ridge will also begin to build northward, sending high temperatures across much of the northern tier of the West 10-20 degrees above mid-Summer averages. Temperatures will be on the rise Friday, with highs into the 100-110 degree range for most locations across inland Pacific Northwest, Northern Great basin, and the High Plains. Many near record-tying/breaking highs are possible. Similar to areas further east, many heat-related advisories and warnings have been issued as this heat will also reach dangerous levels for the general public. In fact, the heat risk index is showing some possible locations of the interior Pacific Northwest may approach the extreme category on Friday, where heat related impacts are likely. Smoke from area wildfires will also continue to plague parts of the region, resulting in hazy conditions and poor air quality, and the risk for more wildfires will increase as the hot, dry conditions settle in. An upper-level low/accompanying surface frontal system traversing the northern side of the ridge over the southern tier of the U.S. will bring another round of showers and thunderstorms to the Midwest through the remainder of Thursday. Clusters of thunderstorms will bring the risk of strong winds and perhaps a tornado or two. Going into Friday and Saturday, the severe weather threat should diminish but remain possible as the system moves east into the eastward Ohio Valley, Mississippi Valley, Mid-Atlantic, and portions of the Southeast. Thunderstorms will bring the risk of gusty winds. Along with the severe threat, flash flooding potential will also accompany these storms. A Slight Risk of Excessive Rainfall (level 2/4) covers much of eastern Kentucky. High rainfall rates and the potential for organized convective complexes brings the possibility of seeing a couple of inches of rainfall in a short time. The remainder of the Mid-Atlantic to Northeast will have a risk for some isolated to scattered flash flooding through the weekend as any thunderstorm has the potential to produce a couple of inches of rainfall in a short amount of time as there is plenty of moisture and instability to work with. Persistent Monsoonal conditions over the Southwest will continue to bring daily shower and thunderstorm chances. Sufficient moisture across the region will lead to the threat for some locally heavy downpours and an isolated flash flooding, particularly over terrain sensitive areas such as burn scars. Similar to areas further north, forecast high temperatures more broadly in the region will be trending warm and above average, with 90s and low 100s for most locations outside of the California Coast, and mid-100s to low 110s for the Desert Southwest. Wilder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php