Post-Tropical Cyclone Ian has fully dissipated overnight but the extratropical remnants of the storm will continue to bring widespread showers and storms to the Mid-Atlantic and central Appalachians due to onshore flow on the northern side of the system.
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Forecast rainfall totals through Monday are between 1-2 inches with locally higher amounts possible, particularly around the Chesapeake Bay east into the Delmarva peninsula and southern New Jersey.
Areas closer to the coast will see higher winds between 20-30 miles per hour, with gusts up to 40-50 mph, as well as the risk of coastal flooding.
Forecast high temperatures across much of the East will be up to 10-20 degrees below average due to the rain and widespread clouds as well as a strong Canadian high in place to the north of the system.
Highs Sunday and Monday will be in the 50s to low 60s from New England south into the Mid-Atlantic, Appalachians, and Upper Ohio Valley, with 60s and low 70s for most of the Carolinas.
Highs will be warmer and closer to average across the rest of the Southeast, with mostly upper 70s and low 80s expected.
Meanwhile, an upper-level low over the northern Intermountain West will slowly drift to the east over the Northern High Plains by Tuesday morning as a frontal system remains relatively stationary through the Central Rockies and into the Great Basin.
Anomalously high moisture will continue to circulate throughout the region leading to more showers and thunderstorms Sunday and Monday, with the high moisture and terrain enhancements aiding some storms to produce bouts of heavier rainfall.
Rainfall totals of around and inch are possible in the Four Corners region, and there is a Slight Risk of Excessive Rainfall Sunday for portions of southern Utah and far southwestern Colorado where scattered instances of flash flooding will be possible in areas of more vulnerable terrain, such as slot canyons and dry washes.
Temperatures across the region will be relatively cool, with mostly 60s anticipated.
High elevation snow is also forecast for the Rockies Sunday, with upwards of 4 inches possible for elevations above 9000 feet in northwest Wyoming into east-central Montana and 4-6 inches above 11000 feet in the San Juan Mountains in Colorado.
On either side of the upper-level low, ridging aloft will lead to warmer, above average temperatures Sunday and Monday for the Plains and Midwest as well as the Great Basin and West Coast.
Forecast highs range from the upper 60s to mid-70s for the Northern Plains and Upper Midwest and the low to mid-80s for the Central and Southern Plains.
The Storm Prediction Center has outlined an Elevated Risk of fire weather from western Kansas northeast into eastern Nebraska Sunday and Monday for a combination of warm temperatures with low humidity, breezy winds, and dry antecedent conditions.
High temperatures will also be above average further west with 70s for the Great Basin, 80s for California outside of the immediate coast, and 90s in the Southwest.
The Pacific Northwest will see the most anomalous temperatures, with highs in the low to mid-80s up to 10 to 15 degrees above average for early October. ■