Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 412 AM EDT Wed Jun 26 2024 Valid 12Z Wed Jun 26 2024 - 12Z Fri Jun 28 2024 ...Heat wave continues for the southern Plains, Lower Mississippi Valley, and Southeast... ...Monsoon-like conditions persist for the Four Corners Region... ...Severe storms and flash flooding expected over the northern/central Plains Thursday... A heatwave persists over much of the southern tier of the country as a stubborn upper-level high lingers over the southwestern/south-central U.S. Highs are forecast in the mid- to upper 90s Wednesday across the region, with low 100s expected over portions of South Carolina and Georgia as well as the southern High Plains. Humid conditions will lead to heat index values in the mid- to upper 100s outside of drier areas in the southern High Plains, with widespread Heat Advisories in place. The most intense heat will be over portions of central/southern Oklahoma and northwest Texas, where an Excessive Heat Warning is in place for heat indices as high as 112. In addition, overnight lows in the mid- to upper 70s will provide little relief from the heat overnight. The early arrival and persistence of the intense heat will lead to more heat stress than normal given similar conditions later in the Summer, especially for those without reliable air conditioning. Portions of the Lower Mississippi Valley and Southeast will see some relief on Thursday following a cold front passage, with highs a few degrees lower and slightly less humid conditions. Unfortunately, conditions will remain dangerously hot over portions of Georgia/South Carolina and the southern Plains. Some heat will also spread back into the Mid-Atlantic Wednesday with highs in the mid- to upper 90s. A cold front passage will bring temperatures back down a bit into the 80s to low 90s Thursday. Further to the west, monsoon-like conditions will persist under the upper-level high over the Four Corners region given a continued influx of anomalously high moisture. Daily scattered thunderstorms may produce some locally heavy downpours, with some scattered instances of flash flooding possible, especially for terrain sensitive areas such as burn scars and slot canyons. The greatest storm coverage on Wednesday is expected over portions of northern New Mexico, where a Slight Risk of Excessive Rainfall (level 2/4) is in place. An approaching upper-level system to the north will help to break down the upper-level high and bring more zonal upper-level flow across the region, expanding higher storm chances northward on Thursday with a Slight Risk stretching from northern New Mexico north through western Colorado. Storm chances will increase over portions of the Plains and Midwest ahead of an approaching upper-level system on Thursday. First, on Wednesday, some severe thunderstorms will be possible over the central High Plains as upslope flow brings some increasing moisture and leads to a bit of instability. The Storm Prediction Center has outlined a Slight Risk (level 2/5) of severe weather for the threat of some damaging winds and large hail. Then, as the upper-level system approaches, lee cyclogenesis in the northern High Plains will lead to a strengthening low pressure/frontal system, eventually moving eastward into the Plains through the day Thursday. Enhanced southerly flow ahead of the system will bring moisture northward and lead to a broad area of scattered thunderstorm development over the northern High Plains southward through the central Plains. The Storm Prediction Center has issued a Slight Risk for this region for the threat of large hail and damaging winds, perhaps significant over the northern High Plains, as well as a couple isolated tornadoes. Additionally, two areas of concern for heavy rainfall will develop into Thursday evening. An upper level shortwave passing over the central Plains will help to trigger thunderstorms along and ahead of a lifting warm front, likely organizing into a convective system bringing more widespread heavy rain totals. To the north, strong dynamic forcing ahead of the upper-level system over the northern Plains is also expected to lead to more widespread, organized storm development. Slight Risks of Excessive Rainfall cover both scenarios, with wet antecedent conditions in both locations also contributing to the risk for some scattered instances of flash flooding. Elsewhere, a broad area of showers and thunderstorms will continue eastward ahead of a cold front stretching from New England southwestward through the Mid-Atlantic, Ohio/Tennessee Valleys, and into the Lower Mississippi Valley and eastern portions of the southern Plains Wednesday. Moderate to locally heavy rainfall can expected, with a few isolated instances of flash flooding possible. A few more potent and widespread storms over portions of the Mid-Atlantic/Upper Ohio Valley and the Ozarks/Lower Mississippi Valley could bring the threat for some damaging winds, with Slight Risks of severe weather covering both locations. The front will clear the East Coast over New England and the Mid-Atlantic Thursday while pushing further into the Southeast, with storm chances moving into the Carolinas southwestward through the central Gulf Coast. Another day of diurnal sea breeze driven storms is forecast for Florida Wednesday before conditions begin to dry out on Thursday. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php