Heavy Rain Expected across the USA

A relatively warm and wet weather pattern overspreading the Nation through

at least the next few days is anticipated to produce heavy precipitation

across the West Coast and parts of the Deep South. For the western U.S., a

lull in unsettled weather today will be replaced by potentially excessive

rainfall and heavy mountain snow beginning on Thursday as an initial wave

of moisture moves onshore followed by a potent atmospheric river. Most of

the potential impacts are anticipated across central/northern California

and parts of southwest Oregon. Here, rainfall amounts of 3 to 6 inches are

forecast through early this weekend. Heavy rain may lead to scattered

instances of flash flooding, especially near recent burn scars where

terrain is most susceptible to rapid runoff. A Slight Risk (level 2/4) of

Excessive Rainfall has been issued for these regions in order to further

highlight the flash flood threat. Heavy snow is possible across the higher

elevations of the Cascades and Sierra, with storm total snowfall amounts

up to several feet are possible. Most of the snow will be confined to the

highest terrain as warm Pacific air pushes snow levels very high and

generally above pass level. Moisture will also spread into the

Intermountain West along the strong Pacific jet stream, with moderate to

heavy snow possible across northern Nevada by Friday night.

Shifting to the central and eastern U.S., an upper-level trough swinging

into the Great Plains tonight in conjunction with a high pressure system

sliding off the East Coast will allow for an abundance of warm and moist

air to surge northward out of the Gulf of Mexico. A quick-hitting swath of

snowfall is possible to the north of a developing low pressure system

between tonight and Thursday as it progresses from Kansas to the Upper

Midwest. The best chances for over 4 inches of snow is currently expected

to remain confined to central High Plains of Colorado. Farther east,

shower and thunderstorm activity is anticipated to develop across parts of

eastern Texas and the Lower Mississippi Valley on Thursday and Friday as

atmospheric moisture content increases ahead of an approaching cold front.

Some isolated storms could turn severe, with damaging wind gusts the

primary risk. A few instances of flash flooding are also possible. The

active weather is expected to shift east by the end of the week and

produce locally heavy rainfall from the central Gulf Coast to parts of the

Ohio Valley.