Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 350 AM EDT Wed Jul 03 2024 Valid 12Z Wed Jul 03 2024 - 12Z Fri Jul 05 2024 ...Dangerous heatwave to impact much of the West, while oppressive heat and humidity also swelter areas from the Southern Plains to the Mid-Atlantic... ...Flash flooding and severe thunderstorms possible over the next few days across portions of the Plains, Midwest, and Ohio Valley... Record-breaking and dangerous heat is forecast to make this Fourth of July week a scorcher across much of the West and from the southern Plains to the Mid-Atlantic. Over 110 million residents are currently under heat-related watches, warnings, and advisories throughout 21 states as of early this morning. An upper-level high situated just off the West Coast today is forecast to strengthen and reorient directly over the western U.S. by the end of the week. This pattern will support well above average temperatures over California today before heat spreads further along the West Coast by the end of the week. High temperatures are forecast to reach into the 105-115F range throughout interior California away from the immediate coastline, as well as into much of the Desert Southwest. Afternoon temperatures will also begin to increase across much of Oregon and Washington by Thursday and Friday, with widespread highs soaring into the 90s. Dozens of record highs are possible, expressing the rarity of this early-July heatwave. The duration of this heat is also concerning as scorching above average temperatures are forecast to linger into next week. Heat impacts can compound over time, therefore it is important to remain weather aware and follow the advice of local officials. This level of heat throughout the Sacramento and San Joaquin valleys of California could pose a risk to anyone if proper heat safety is not followed. This includes staying hydrated, out of direct sunlight, and in buildings with sufficient air-conditioning. It is also very important to check on the safety of vulnerable friends, family, and neighbors. Oppressive heat and humidity will also be found throughout the southern Plains and lower Mississippi Valley into the Independence Day holiday while also expanding eastward to the Mid-Atlantic for the end of the week. High temperatures rising into the upper 90s and low 100s are expected, with heat indices soaring into the 110s across the lower Mississippi Valley. Warm overnight conditions in the upper 70s and low 80s will offer little relief, leading to a dangerous situation for those without access to adequate cooling. A cold front entering the southern Plains is anticipated to offer cooler and below average temperatures to Oklahoma and much of northern/western Texas by Friday. An active and stormy weather pattern over the central U.S. is expected to create chances for severe thunderstorms and heavy rainfall, which could impact holiday gatherings this week. A developing area of low pressure over the central High Plains today forecast to progress into the upper Midwest by Thursday along with a lingering frontal boundary stretching from the lower Great Lakes to the central Plains are anticipated to be the triggers for some meteorological fireworks. For today, the best chances for scattered flash flooding due to thunderstorms capable of producing intense rainfall rates is forecast between eastern Kansas and the Ohio Valley along the aforementioned frontal boundary. Instances of severe weather (mainly associated with damaging wind gusts) are also possible, with chances for severe storms also located in parts of the northern/central High Plains closer to the developing low pressure system. By Independence Day, thunderstorm chances span from the southern Plains/Rockies to the middle/upper Mississippi Valley and also eastward to the Ohio Valley and Mid-Atlantic. However, the greatest threat for strong thunderstorms turning severe resides over parts of eastern Kansas, northeast Oklahoma, and southern/central Missouri. Damaging wind gusts and frequent lightning are the most likely weather hazard associated with these Fourth of July storms, with isolated strong storms also possible into the Midwest, Ohio Valley, and Mid-Atlantic. Flash flooding will remain a concern throughout the upper Midwest as well due to yet another round of thunderstorms overlapping areas dealing with ongoing river flooding and saturated soils. Portions of southern Minnesota, eastern South Dakota, western Wisconsin, and northern Iowa currently have the highest probabilities (70-90%) for at least 1 inch of rain on Thursday. Residents and visitors located within areas expecting severe weather and/or heavy rainfall this week are advised to remain weather aware, have multiple ways to receive warnings, and never drive across flooded roadways. Snell Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php