Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
121 PM EST Sun Dec 12 2021

Valid 00Z Mon Dec 13 2021 - 00Z Wed Dec 15 2021

...There are Slight Risks of Excessive Rainfall over parts of central then
southern California through Tuesday...

...Heavy snow over the Cascades, Sierra Nevada Mountains, and Northern
Rockies...

...Critical Fire Weather risk for parts of the Southern High Plains;
cooldown in the West while central U.S. warms up...

Upper level energy will generate significant rainfall leading to flash
flooding and heavy mountain snow for portions of the West coast over the
next couple of days. A slow moving low pressure system will continue to
spread moisture in the form of low elevation rain and high elevation snow
along a cold front moving from the Northwest down and into the Southwest
over the next couple of days. Heavy rainfall over the central California
coast may lead to flash flooding over susceptible surfaces tonight. A
Slight Risk of Excessive Rainfall is in effect. Heavy snow is likely over
portions of the Northern Rockies and Sierra, while the Cascades and
Olympics will receive light to moderate amounts through Monday morning.
Rain and snow amounts will ramp up as the upper low amplifies and the
associated surface cold front pushes south through California and the
Great Basin into Tuesday. With this, the excessive rainfall threat will
expand into southern California where a few inches may cause significant
flash flooding. Between 2-4 feet of additional snow is forecast to fall
over parts of the Sierra with isolated areas possibly receiving more. Two
day snow totals over portions of the Sierra could easily eclipse 6 feet.
Light to moderate snow will also continue over parts of Oregon and the
Northern Rockies while spreading over northwestern Nevada. The West will
cool down significantly on the backside of this system, with temperatures
dropping 15-20 degrees below average for much of the Central Great Basin
and California.

Elsewhere, ridging over the east and the impending West coast system will
contribute to soaring temperatures over the Great Plains and Middle/Upper
Mississippi Valley through midweek. High temperatures over the Central
Plains will soar into the upper 60s and 70s on Tuesday which will be 20-25
degrees above average. Lows over the Central/Southern Plains and
Mississippi Valley on Tuesday night will drop slightly into the 50s and
60s which will represent a 30+ degree departure from climatology. This
will lead to the potential for records to be broken over those areas. The
Storm Prediction Center's Fire weather risk continues for parts of the
Texas/Oklahoma Panhandle tonight due to 20-25 mph surface winds and low
humidity.

Kebede


Graphics are available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php