Flood Threat and Excessive Rain For Northern California
A persistent feed of Pacific moisture will bring multiple weather systems into Northern California and the Pacific Northwest (PNW) through next week. Meteorologist use the term “atmospheric river” (AR) to describe this narrow plume of moisture that originates over the Pacific Ocean, tapping high levels of moisture from the Hawaiian Islands to the West Coast of the U.S.
This type of pattern often results in extremely heavy rainfall over a sustained period of time as well as the threat for significant flooding. A NOAA study found that 30-50% of the average annual precipitation over the West Coast can occur from just a few AR events.
Precipitation will be enhanced along the immediate coast and over higher elevation. Rainfall could ultimately exceed 10 inches over the northern third of California. Heavy snow is also likely over the Sierra.
Modest Drought Relief Over the Southeast U.S.
A weak weather system moved over the Southeast U.S. yesterday producing generally light amounts of rainfall. Just enough moisture will draw in from the Gulf of Mexico to produce heavier rainfall from the northwest Florida Panhandle, into southeast Alabama, into South Georgia. The area of most severe drought is indicated by the red-dashed line. Note that rainfall from 0.50 to 1.5 inches fell over southwest sections of Georgia. While this only put a dent in the drought, it was certainly welcome.
Rainfall tapered off over the Savannah River Basin, with no rain over the northern third, and generally 0.50″ or less over central and southern reaches.
Northeast U.S. Snow
With cold air entrenched over the Northeast U.S.—snow is anticipated from West Virginia northeastward. Generally, this system will bring 1 to 3 inches to this region.
As has been the case for weeks now, most of the nation, especially the drought-stricken Midwest and Great Plains, will see no significant precipitation through the entire week.