Weak onshore flow and upper-level energy will aid in producing coastal rain and higher-elevation snow over the Pacific Northwest/Northern California into the Northern Intermountain Region, Northern/Central Rockies, and Great Basin.
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The snow has prompted Winter Storm Warnings and Winter Weather advisories for the Cascades, Northern Intermountain Region, and Northern/Central Rockies.
Overnight Monday, the coastal rain and higher-elevation snow weaken.
However, on Tuesday, a plume of moisture starts to move into the Northwest.
By late Tuesday morning, the snow levels will lower to near the coast over the Olympic Peninsula, with heavy snow over the Olympic ranges.
The snow will result in reduced visibility and hazardous driving conditions.
Meanwhile, on Monday, a front over the Northern Plains moves eastward to the Upper Great Lakes by Tuesday evening, while a wave of low pressure over the Central Plains deepens and moves into the Upper Great Lakes by Wednesday morning.
Overnight Monday, snow will develop over parts of the Northern/Central Plains.
On Tuesday, snow will develop over the Middle Missouri Valley into the Upper Mississippi Valley.
Heavy snow will develop over the parts of the Upper Great Lakes, which has prompted Winter Storm Watches over the region.
Furthermore, moisture from the Western Gulf of Mexico will stream northward from the Western Gulf Coast/Lower Mississippi Valley into the Upper Great Lakes on Tuesday.
By Tuesday afternoon, showers and severe thunderstorms will develop over the Lower Mississippi Valley into the Western Ohio Valley.
Therefore, the SPC has issued a Moderate Risk of severe thunderstorms over parts of the Lower Mississippi and Tennessee Valleys from Tuesday into Wednesday morning.
The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes.
There is a greater probability of EF2-EF5 tornadoes and wind gusts of 65 knots or greater over parts of the region.
Moreover, there will be heavy rain associated with these thunderstorms.
Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of the Lower Mississippi and Tennessee Valleys from Tuesday into Wednesday morning.
The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable. ■
Modified arctic air combined with a moisture-laden area of low pressure along the Gulf Coast will continue to allow for a broad area of winter weather impacts from the Lower Mississippi Valley to the Southeast today into early Saturday morning.