US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 459 PM EDT Tue Jul 06 2021 Valid Friday July 09 2021 - Tuesday July 13 2021 Hazards: - Heavy rain across portions of the Central and Southern Plains, Sat, Jul 10. - Heavy rain across portions of the Central and Northern Plains, the Middle and Upper Mississippi Valley, the Great Lakes, and the Ohio Valley, Fri-Sun, Jul 9-Jul 11. - Heavy rain across portions of the Northeast, Fri, Jul 9. - Severe weather across portions of the Upper Missouri Valley and the Middle Mississippi Valley Fri, Jul 9. - Flooding possible across portions of the Southeast and the Southern Plains. - Flooding occurring or imminent across portions of the Middle Mississippi Valley. - Excessive heat across portions of California, the Great Basin, and the Interior Northwest, Fri-Mon, Jul 9-Jul 12. - Excessive heat across portions of California and the Southwest, Fri-Tue, Jul 9-Jul 13. - Much above normal temperatures across portions of the Interior Northwest Fri-Sat, Jul 9-Jul 10. - Much above normal temperatures across portions of the Northern High Plains and the Northern Rockies, Sat-Sun, Jul 10-Jul 11. - Heavy rain across portions of southern mainland Alaska, Fri, Jul 9. - Heavy rain across portions of southern mainland Alaska and the Alaska Panhandle, Sat-Mon, Jul 10-Jul 12. Detailed Summary: There are several hazards outlook areas for heavy rain, severe weather, and high temperatures during the medium-range forecast period (Friday, July 9 - Tuesday, July 13). At the start of the period, a cold front will move to the southeast across the Northeast on Friday (July 9th). High low-level moisture in place ahead of the front in addition to influences from the remnants of Elsa will lead to the chance for heavy rain, with forecast totals of 1-2". Further west, an upper-level trough will begin to develop in the lee of the Rockies on Friday (July 9th) and progress to the southeast before beginning to break down by Monday (July 12th). At the surface, a low pressure system will move to the northeast over the Upper Mississippi Valley, with a warm front extending east into the Ohio Valley and a cold front to the southwest over the Central and Southern Plains. All associated features will progress slowly, if not remain stationary for a period, and encourage daily rounds of convection across the Plains and Midwest. Heavy rain is likely in the vicinity of the surface low and along the warm/stationary front from the Dakotas east across the Middle Mississippi Valley and into the Ohio Valley, as well as north into the Upper Mississippi Valley and southern Great Lakes region from Friday (July 9th) through Sunday (July 11th). This may include one or more organized mesoscale convective systems. Widespread rain over 1" is expected, with locally higher amounts over 2-3" possible. Severe weather is also possible on Friday along the warm front near the surface low from the Upper Missouri Valley to the Middle Mississippi Valley as thunderstorms develop amidst a particularly humid airmass and high CAPE. Additionally, heavy rain is expected with convection developing to the southwest along the cold front, particularly on Saturday (July 10th) when 1-2" of rain is forecast. There is a chance for rain extending further east along the front into the Mid-Atlantic, but there was not enough model consensus for higher amounts to include an outlook area for heavy rain at this time. In the west, an upper-level ridge will remain in place over the western U.S. throughout the period. Both excessive heat and much above normal temperatures are forecast across the region. Excessive heat is expected across the Desert Southwest and the San Joaquin Valley in California throughout the period, with daily high temperatures of around 110 and above and little relief at night as lows will only drop into the upper 70s to upper 80s. Excessive heat is also forecast through Monday (July 12th) for the Sacramento Valley in California, portions of the central/northern Great Basin, the Wasatch Front of Utah, the Snake River Valley of Idaho, and portions of southern/eastern Oregon north into eastern Washington and northern Idaho. Forecast high temperatures in the upper 90s to low 100s are expected, and may continue into Tuesday (July 13th), but a weak mid-level trough moving east across the northern edge of the ridge may provide a little relief in these areas. Above normal temperatures in the 90s are also forecast for interior portions of eastern Oregon Friday (July 9th) into Saturday (July 10th) and the Northern Rockies and High Plains of Montana Saturday into Sunday (July 11th) as the upper-level ridge expands northward between passing troughs. In Alaska, an occluding low pressure system will move east across the Gulf of Alaska and into the Panhandle by Monday (July 12th). Moist onshore flow ahead of the system will lead to heavy rain totals of 2" and higher for portions of the southwestern and south-central mainland, including the Kanai Peninsula, on Friday (July 9th). The heavy rain will continue and progress eastward from the south-central mainland into northern portions of the Panhandle on Saturday (July 10th) through Monday July (12th) as the system moves onshore, with daily rainfall totals of 2" and higher possible. Putnam