US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 346 PM EDT Fri Jun 11 2021 Valid Monday June 14 2021 - Friday June 18 2021 Hazards: - Heavy rain across portions of the Southeast, the Lower Mississippi Valley, and the Southern Plains, Fri, Jun 18. - Flooding possible across portions of the Southeast, the Southern Plains, and the Tennessee Valley. - Flooding occurring or imminent across portions of the Southeast, the Lower Mississippi Valley, the Southern Plains, and the Tennessee Valley. - Flooding likely across portions of the Lower Mississippi Valley, the Southern Plains, and the Northern Plains. - Excessive heat across portions of California, the Central Great Basin, the Pacific Northwest, and the Northern Great Basin, Thu-Fri, Jun 17-Jun 18. - Excessive heat across portions of the Central Great Basin, the Northern Rockies, the Central Rockies, California, the Northern Great Basin, and the Southwest, Mon-Fri, Jun 14-Jun 18. - Excessive heat across portions of the Central Great Basin, California, and the Southwest, Wed-Fri, Jun 16-Jun 18. - Excessive heat across portions of the Central Plains, the Central Great Basin, the Northern Plains, the Northern Rockies, the Central Rockies, the Middle Mississippi Valley, the Northern Great Basin, and the Upper Mississippi Valley, Mon-Thu, Jun 14-Jun 17. - Excessive heat across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Mon-Tue, Jun 14-Jun 15. - Excessive heat across portions of the Northern Plains and the Northern Rockies, Mon-Wed, Jun 14-Jun 16. - Excessive heat across portions of the Middle Mississippi Valley, the Upper Mississippi Valley, and the Northern Plains, Wed-Thu, Jun 16-Jun 17. Detailed Summary: The biggest weather story during the medium range forecast period (Monday, June 14 to Friday, June 18) will be associated with dangerous heat across much of the west and north-central United States. An impressive upper-level ridge/high pressure system coinciding with the mid-June sun angle and extremely dry soil will lead to potentially record-breaking heat. For the northern/central Plains and northern Rockies, high temperatures 15 to 30 degrees above average will be located across Montana and Wyoming between Monday and Tuesday, before shifting eastward into the Dakotas on Wednesday and reaching portions of the Upper Midwest on Thursday. This equates to widespread highs in the 90s and low triple digits from the central High Plains to the U.S.-Canada border. This level of heat over multiple days in these locations will make it particularly dangerous for individuals spending an extended amount of time outdoors, or those without access to air conditioning. Fortunately, a cold front is expected to swing through the northern Plains next week and offer much needed relief by Thursday and Friday. Meanwhile, deadly heat is forecast to continue building over the Southwest and portions of the Intermountain West. An anomalously strong upper-level high located near the Four Corners region will eventually settle and slowly meander southwestward by the end of next week. Highs well into the triple digits will be found throughout the Southwest, with maximum temperatures into the 120s for the typical desert valleys. Places such as Las Vegas, NV and Phoenix, AZ will experience temperatures into the 110s nearly every day next week. Areas slightly to the north will also bake under excessive heat, while not as extreme as the Southwest. For example, Salt Lake City could see high temperatures reach 100 degrees every day between Monday and Friday, which would be a record for the month of June. The sizzling heat is expected to expand westward and into California and the rest of the central Great Basin by Wednesday and Thursday. Widespread triple digits and a high heat risk will be likely over this region. All in all much of the Southwest and western United States (outside the Pacific Northwest and immediate coastal regions along the West Coast) will experience dangerous, deadly, and potentially record-breaking heat next week. A few monthly and all-time record high temperatures are not out of the question. Residents are urged to drink plenty of water and spend less time outdoors. Additionally, much of the Southwest and central Great Basin is confronting extreme and exceptional drought. The upcoming heat wave and lack of precipitation will exacerbate water supply concerns. Elsewhere, tropical trouble brewing in the Gulf of Mexico may pose a risk of heavy rain along the western and central Gulf Coast States by Friday, June 18. Current ensemble guidance highlights an area between Houston, TX and Mobile, AL as having the greatest chances of receiving tropical downpours and widespread rainfall amounts over an inch. As the time period draws closer and confidence increases, the heavy rain area depicted on the hazards chart will likely shrink. Many different solutions exist regarding the strength of a potential tropical cyclone by the end of next week, thus it will be important to check the latest medium range forecasts when available, as well as the National Hurricane Center. No widespread hazardous weather is expected for Alaska during this time frame. Snell