Several daily high temperature records are expected to be either tied or broken on Wednesday throughout central/northern California, Idaho, Oregon, and Washington

 Short Range Forecast Discussion

NWS Weather Prediction Center College Park MD 349 PM EDT Tue Aug 16 2022 Valid 00Z Wed Aug 17 2022 - 00Z Fri Aug 19 2022 ...Heavy rain and flash flooding possible across the Southwest and Southern Rockies through at least the end of the week... ...Showers and thunderstorms near a slow-moving frontal boundary to produce locally heavy rain over the Middle/Lower Mississippi Valley tonight into the Deep South on Wednesday and Thursday... ...Dangerous heat and humidity across eastern Texas and the Gulf Coast to mostly dissipate by Thursday, while record-breaking heat builds into the Pacific Northwest... The threat for flash flooding is expected to continue across the southwestern U.S. and into the southern/central Rockies over the next several days as the summer monsoon persists through mid-August. An approaching cold front stretching towards the central Rockies from the southern Plains will help focus additional rounds of thunderstorms across the high terrain of southern Colorado and northern New Mexico into Wednesday. Flash Flood Watches have been issued in order to further highlight the concern. For the Southwest, widespread anomalous atmospheric moisture content remains entrenched over the region and will allow for developing thunderstorms to contain heavy rainfall rates. Overall, impacts through Thursday are expected to be localized and occur underneath isolated downpours. The greatest risk for more scattered flash flooding extends along the U.S.-Mexico border from southern Arizona to far West Texas. An influx of additional moisture associated with a low pressure system, which originated across the western Gulf of Mexico last weekend, will aid in numerous thunderstorms across this region on Wednesday and Thursday. A Slight Risk (level 2/4) of Excessive Rainfall has been issued. The other area at risk for flash flooding over the next few days is along and near a stationary boundary draped from the Southeast to the southern Plains. Numerous showers and thunderstorms are likely to the north of this boundary from southern Missouri to northern Arkansas tonight, which could add up to a few inches of rain and scattered flash flooding. By Wednesday and Thursday, the threat of locally intense rainfall rates should expand along the aforementioned boundary and stretch from the Lower Mississippi Valley to the coastal Carolinas. Some spots within this area could receive several inches of rainfall, leading to localized flooding concerns. Additionally, a few storms will have the potential to strengthen and produce frequent lightning along with isolated damaging wind gusts. Elsewhere, scattered thunderstorms are possible across the northern Plains and Upper Midwest through Thursday. A few storms could turn severe and produce damaging wind gusts and large hail through tonight. For New England, a developing coastal storm is forecast to swing northward into the Gulf of Maine on Wednesday. Moderate-to-locally heavy rain is possible from eastern Massachusetts to northern Maine beginning late tonight, with most rainfall characterized as beneficial for the drought-stricken regions. Gusty winds along coastal sections of New England are also expected, which has prompted High Surf and Wind Advisories to issued for much of Cape Cod and eastern Massachusetts. A few more days of dangerous heat is in store for parts of Texas and the Gulf Coast before the approaching frontal boundary offers additional cloud cover and cooler temperatures. Highs on Wednesday are still anticipated to reach the triple digits throughout central/eastern Texas and northern Louisiana, with humidity causing heat indices to near 110 degrees. By Thursday, the above average and oppressive temperatures are forecast to shrink and consolidate to south-central Texas and the middle/upper Texas Gulf Coast. The most anomalous and potentially record-breaking heat shifts into the Northwest through the end of this week as upper-level ridging builds over the regions. Highs are forecast to soar into the upper 90s and triple digits from central California to the northern Great Basin. This equates to high temperatures around 10-20 degrees above average compared normal mid-August conditions. Several daily high temperature records are expected to be either tied or broken on Wednesday throughout central/northern California, Idaho, Oregon, and Washington, with additional records possible on Thursday. Excessive Heat Warnings and Heat Advisories have been issued along the western United States. For the rest of the Nation, comfortable below average to near average temperatures are anticipated. Snell Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php