US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 330 PM EDT Mon Jul 12 2021 Valid Thursday July 15 2021 - Monday July 19 2021 Hazards: - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Tennessee Valley, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley, Sat-Sun, Jul 17-Jul 18. - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Great Lakes, the Ohio Valley, and the Southwest, Thu-Fri, Jul 15-Jul 16. - Heavy rain across portions of the Great Lakes, Thu, Jul 15. - Flooding possible across portions of the Southeast, the Middle Mississippi Valley, the Great Lakes, and the Ohio Valley. - Flooding occurring or imminent across portions of the Southeast, the Middle Mississippi Valley, and the Southern Plains. - Flooding likely across portions of the Middle Mississippi Valley. - Excessive heat across portions of the Northern Plains, Fri-Mon, Jul 16-Jul 19. Detailed Summary: The medium range forecast period (Thursday, July 15th to Monday, July 19th) will feature a building upper-level ridge over the Rockies, while a weak upper-level trough is forecast over the Great Lakes and eventually the Northeast by early next week. This weather pattern is expected to lead to several chances for thunderstorms and heavy rain from the Central Plains to the East Coast. Beginning with the end of this week, an area of low pressure is forecast to traverse the Great Lakes region as a trailing cold front slowly swings through the Central Plains, Middle Mississippi Valley, and Ohio Valley. Downpours will quickly exit Michigan by Friday, with lingering thunderstorms capable of producing intense rainfall rates throughout the Ohio Valley and westward into central Kansas through the beginning of the weekend. As the aforementioned frontal boundary slowly stalls throughout the Middle Mississippi Valley on Saturday and Sunday, continued reforming rounds of convection can be expected to spark and track southeastward into portions of northern Arkansas and western Tennessee. Predictability begins to decrease on Sunday as forecast guidance differs regarding how far south the cold front and associated rainfall reach. The potential exits for heavy rain early next week throughout the Lower Mississippi Valley, Deep South, and Tennessee Valley, but confidence was too low to include a highlighted hazard area on today's graphic. Showers and thunderstorms will also become more widespread across the Northeast and Mid-Atlantic on Friday and Saturday, before rainfall chances move southward into the Carolinas and Southeast by early next week. Isolated downpours may cause localized flooding here, but it remains too difficult to pin-point areas with the greatest heavy rain threat at this time frame. Elsewhere, before the upper-level ridge strengthens over the Rockies late this weekend/early next week, additional monsoonal moisture is expected to reach parts of the Southwest. Over an inch of rain is possible over southeast Arizona and southwest New Mexico between Thursday and Friday. This could lead to additional instances of flash flooding. Rainfall chances and the probability of intense rainfall gradually decreases each day starting this weekend. Heat is also expected to remain a concern throughout parts of the West and north-central United States during the medium range period. The highest temperature anomalies are currently expected over the Northern High Plains, where high temperatures could enter the triple digits for several consecutive days beginning on Friday. Hot weather and above average highs into the mid-90s are forecast across North Dakota and into northern Minnesota as well, but these values currently don't reach hazardous criteria. Nonetheless, much of the Dakotas, northeast Wyoming, and the western half of Minnesota are experiencing severe to exceptional drought that will likely worsen due to the upcoming heat and lack of rain. Most of the Northern Rockies and Great Basin won't get a break from the ongoing oppressively hot summer. Above average temperatures are forecast through early next week, with highs into the upper-90s and low triple digits across lower elevations. If trends inch temperatures slightly higher, an Excessive Heat area may be needed for parts of Idaho, Utah, and western Colorado valid for early next week. For the Southwest, although it will remain hot, current expectations are for temperatures to remain only a few degrees above average. For Alaska, a general increase in precipitation is expected to enter western portions of the state by Saturday, but low confidence deterred a highlighted area on today's outlook. Snell