US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 442 PM EDT Mon Jul 19 2021 Valid Thursday July 22 2021 - Monday July 26 2021 Hazards: - Heavy rain across portions of the Southwest, Thu-Fri, Jul 22-Jul 23. - Heavy rain across portions of the Great Lakes, Sat, Jul 24. - Flooding occurring or imminent across portions of the Central Plains, the Middle Mississippi Valley, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Central Plains and the Middle Mississippi Valley. - Excessive heat across portions of the Northern High Plains, Thu, Jul 22 and Mon, Jul 26. - Excessive heat across portions of the Northern Plains, Thu-Fri, Jul 22-Jul 23. - Excessive heat across portions of the Lower Mississippi Valley, Sun-Mon, Jul 25-Jul 26. - Much above normal temperatures across portions of the Northern Plains, Central High Plains, and Upper Mississippi Valley, Thu-Mon, Jul 22-Jul 26. - Much above normal temperatures across portions of the northern Great Basin and interior Pacific Northwest, Sat-Mon, Jul 24-Jul 26. Detailed Summary: Heavy rain associated with the Monsoon in the Southwest as well as hot weather across the central/western U.S. highlight the hazards outlook for the medium-range forecast period (Thursday, July 22 - Monday, July 26). Daily showers and thunderstorms over the Southwest associated with the Monsoon are expected throughout the period. More widespread, heavier rain totals are forecast on Thursday (July 22) and Friday (July 23) across portions of central Arizona and west-central New Mexico. Additional areas further into southwest Colorado and southern Utah may see some heavier rain totals, and instances of heavy rain are possible further into the period across the region, but the heaviest totals look to remain too isolated for additional designated hazard areas at this time. During the middle to end of the period, a cold front will move east across the Dakotas as a warm front moves north across the Midwest. A second cold front will develop ahead of the first, and both fronts are forecast to move to the southeast across the Midwest, Ohio Valley, and towards the East Coast. These fronts will be accompanied by broad northwesterly flow on the northern/eastern portions of an upper-level ridge over the central/western U.S. Organized convection is expected to develop at the leading edge of the moist airmass Friday evening over the Upper Midwest and move southeastward across portions of eastern Wisconsin and Michigan into the day Saturday (July 24). Although the placement and timing may vary some, an outlook area for heavy rain has been introduced given consistently high rain totals over 1 inch across model guidance for the area. Additional showers and storms with heavy rain are possible ahead of these fronts through the end of the period, with the greatest potential currently focused on the Upper Ohio Valley on Sunday (July 25). However, there is too much uncertainty in the timing and placement of the heavier totals to include additional outlook areas at this time. Meanwhile, the upper-level ridge will remain in place over the central/western U.S. through the forecast period, with areas of excessive heat and above normal temperatures forecast. The excessive heat currently affecting eastern portions of Montana looks to continue into Thursday, with high temperatures in the low 100s forecast. The excessive heat will also expand to the southeast into South Dakota and southwestern Minnesota. Forecast highs around and above 100 are expected on both Thursday and Friday. There looks to be some relief from the excessive heat on Saturday and Sunday as the cold front passes through the area before hotter temperatures in the low 100s return to eastern Montana on Monday. Additionally, forecast high temperatures are expected to remain above average more broadly across the region through the forecast period. Daily highs generally in the mid-90s to 100 are forecast for the Northern Plains and Central High Plains, and in the upper 80s to 90 for the Upper Mississippi Valley. Above average temperatures in the mid-90s to 100 degrees are also forecast over portions of Idaho, including the Snake River Valley, west into the interior Pacific Northwest and northern Great Basin Saturday through Monday (July 26). Further south, a lingering upper-level trough over the South will begin to dissipate and the upper-level ridge will build further east. High temperatures are forecast to increase into the low to mid-90s across portions of the Lower Mississippi Valley and vicinity, which, when combined with high humidity in place, will lead to excessive heat with heat indices at or above 105 on Sunday and Monday. For Alaska, rain showers are expected for the eastern Kenai Peninsula on Saturday and east into the Panhandle on Saturday and Sunday ahead of a storm system over the Gulf of Alaska. However, any heavier totals look to remain isolated at this time. Additionally, generally below normal temperatures are expected across the mainland through the period, particularly in the Far North. However, these temperatures are not expected to be hazardous at this time. Putnam