Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EST Tue Dec 19 2023

Valid 00Z Wed Dec 20 2023 - 00Z Fri Dec 22 2023

...A slow-moving low pressure system is forecast to bring heavy rain near
the California coast with flash flood potentials...

With the departure of the low pressure system further away into
southeastern Canada, a relatively quiet weather pattern is expected to
prevail across the eastern two-thirds of the country under the influence
of a cool and stable high pressure system.  The most active weather will
be found along the West Coast where a low pressure system is forecast to
stay not too far offshore while moving very slowly to the south through
the next few days.  Rain will be the primary precipitation type associated
with this system except wet snow expected over the higher elevations along
the Sierra Nevada.  The heaviest rainfall is expected to impact areas near
the coast of California from north to south as the system dips generally
southward.  Rainfall amounts are forecast to be 1 to 2 inches with locally
higher amounts near the coast of northern to central California tonight
into Wednesday before shifting southward into the coastal sections of
southern California, where a higher chance of heavy rain with locally a
few inches of rainfall totals possible on Thursday.  Flash flooding may
become an issue given these forecast rainfall amounts.

Meanwhile, the rain/high-elevation snow initially associated with a
weakening system across the Pacific Northwest is expected to taper off
tonight as the system dissipates.  By Thursday, moisture returning from
the Gulf of Mexico behind the eastward-sliding high pressure system in
conjunction with an upper-level shortwave exiting the southern Rockies
will increase the chance of showers and embedded thunderstorms to develop
and expand from the southern Plains toward the mid-Mississippi Valley
south of a stationary front and east of a lee-side trough.  Lake-effect
snow showers near the lower Great Lakes are expected to gradually taper
off tonight.

The eastern and southeastern quadrant of the country will be cooler than
normal through Thursday under the cool high pressure system.  However,
milder than normal temperatures over the remainder of the country will
begin to expand eastward with time and gradually shrink the cool air and
confine it to the vicinity of Florida by Thursday.

Kong


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