US Day 3-7 Hazards Outlook NWS Weather Prediction Center College Park MD 516 PM EDT Fri Oct 08 2021 Valid Monday October 11 2021 - Friday October 15 2021 Hazards: - Heavy precipitation across portions of the Central Rockies, the Central Plains, the Northern Plains, and the Northern Rockies, Tue-Wed, Oct 12-Oct 13. - Heavy rain across portions of the Central Plains, the Lower Mississippi Valley, the Northern Plains, the Middle Mississippi Valley, the Upper Mississippi Valley, and the Southern Plains, Tue-Wed, Oct 12-Oct 13. - Heavy rain across portions of the Southern Plains, Wed-Fri, Oct 13-Oct 15. - Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Great Lakes, and the Upper Mississippi Valley, Mon, Oct 11. - Heavy snow across portions of the Central Plains, the Central Great Basin, the Northern Plains, the Northern Rockies, the Central Rockies, and the Northern Great Basin, Tue-Wed, Oct 12-Oct 13. - Heavy snow across portions of the Northern Plains, the Northern Rockies, and the Northern Great Basin, Mon-Tue, Oct 11-Oct 12. - Severe weather across portions of the Central Plains and the Southern Plains, Tue, Oct 12. - Flooding possible across portions of the Great Lakes. - Flooding possible across portions of the Great Lakes. - Flooding possible across portions of the Great Lakes. - Flooding occurring or imminent across portions of the Southeast and the Tennessee Valley. - Flooding occurring or imminent across portions of the Tennessee Valley. - Much below normal temperatures across portions of the Central Plains, the Central Rockies, the Central Great Basin, the Northern Plains, the Northern Rockies, the Southern Rockies, California, the Northern Great Basin, the Pacific Northwest, and the Southwest, Tue-Thu, Oct 12-Oct 14. - Enhanced wildfire risk across portions of California, Mon, Oct 11. - Heavy precipitation across portions of mainland Alaska, Mon-Tue, Oct 11-Oct 12. - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Thu, Oct 11-Oct 14. - Heavy rain across portions of the Alaska Panhandle, Mon-Thu, Oct 11-Oct 14. - High winds across portions of mainland Alaska and the Aleutians, Mon-Tue, Oct 11-Oct 12. Detailed Summary: The medium range forecast period (Monday, October 11th - Friday, October 15th) features a chance of heavy rain across the Midwest to begin the week, although the main weather story resides over the Western and Central U.S. ahead of a strong frontal low ejecting out of the Central Rockies. Significant mountain snows are likely over portions of the Rockies, with snow and mixed precipitation possible over lower elevations in the Rockies and portions of the Northern High Plains. Anomalously cool air sweeping in behind a strong cold front is expected to support first freeze chances across portions of the Intermountain West. Further east, a heavy rain threat will stretch across the Central U.S. through midweek, with a focused severe weather threat over the Southern Plains on Tuesday. Heavy rain could linger until the end of next week over Central Texas as the southern end of the cold front stalls out overhead. Hazardous weather in Alaska remains active with another shot of high winds along the Alaska Peninsula beginning Monday, and heavy precipitation along the Southeast Coast/Panhandle Monday onward. Beginning Monday, heavy rain is possible across parts of the Central/Upper Midwest as a lead shortwave trough and associated frontal system lift northeast, siphoning a plume of Gulf moisture with it to support shower and thunderstorm chances over the region. A developing frontal low could serve as a catalyst for enhanced rainfall production with this activity, although the progressive nature of the system should keep the overall threat short lived. Perhaps the biggest overall story in parts of the Midwest and areas east will be the expected warmth through all of next week, where anomalous daytime highs (10-15 degrees above normal) and record breaking overnight low temperatures possible as a ridge builds overhead. This should make for warm but benign weather through the week for the Ohio Valley eastward into the Mid-Atlantic and Northeast. Our attention then turns to the Western U.S. where a strong upper-trough is forecast to dive south from the Pacific Northwest toward the Great Basin and close off by midweek. Ahead of the upper-trough, a strong and fast cold front will pull cool Canadian air south into the Intermountain West, which will translate to daytime high temperatures in the 40s-50s (25-30 degrees below normal) west of the Rockies by Tuesday. With the anomalously cool airmass overhead, overnight low temperatures may drop below freezing overnight, supporting the addition of a Much Below Normal Temperatures area from the 12th-14th across much of the Intermountain West where vegetation impacts may be highest. Moreover, the strengthening low pressure system will facilitate gusty winds over parts of the West Coast and Great Basin through Wednesday, which will contribute to a heightened risk of fire weather in the Sacramento and San Joaquin Valleys Monday per the SPC Day 3-8 Fire Weather Outlook. The influx of cold air coupled with dynamic cooling should also drop snow levels throughout the region, and heavy mountain snows appear likely beginning Monday over potions of the Northern Rockies/Wasatch Range. As the closed low lifts northeast toward the Plains by midweek, the emergence of a deformation zone on the west side of the low will extend heavy snow chances toward the Central Rockies Tuesday. Mixed precipitation remains possible over lower elevations in the Rockies into parts of High Plains as well, especially at night. Beginning Tuesday, a well defined surface low and associated cold front will race northeast out of the Rockies. As the low lifts out, another strong influx of Gulf Moisture is expected to aid in heavy rain production north and east of the low from the Northern Plains southward through midweek. The southern portion of the front may focus a heavy rain threat over Texas through Friday as the front stalls out over parts of the Southern Plains. Meanwhile, SPC continues to monitor Southern Plains for severe weather as the frontal system emerges from Colorado and a favorable airmass surges north out of the Gulf of Mexico. More gusty winds are possible over the Plains Tuesday and Wednesday as the surface low ejects and deepens, but should stay below hazard levels. Over Alaska, a series of low pressure systems will produce high gusty winds across the Aleutians and Alaska Peninsula through midweek. The next batch of active precipitation should arrive along the southern Alaska coastline beginning Monday with the arrival of a strong system southwest from the Gulf of Alaska. Guidance has come into good agreement regarding higher totals initially along the entire Southeast Alaska coast before shifting south toward the Alaska Panhandle through Thursday. Some gusty winds remain possible along the Panhandle on the 12th-13th as a strong low approaches, but uncertainty lingers as to the track of the system. Asherman