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

Valid 12Z Tue Dec 19 2023 - 12Z Thu Dec 21 2023

...There is a Slight Risk of excessive rainfall over parts of
Central/Southern California on Wednesday...

...Lake-effect snow downwind of the Lower Great Lakes and upslope snow
over parts of the Central Appalachians...

...Rain for most of the West Coast...

A front moving onshore over the West Coast on Tuesday will dissipate by
Tuesday evening. A second front will come close to the West Coast by
Wednesday morning and then move southward over the Pacific by Thursday.
Moisture associated with the fronts will stream into the West Coast,
producing rain over most of the area. In Addition, locally heavy snow will
develop over the highest elevations of the Sierra Nevada Mountains and
lighter snow over the highest elevations of the Cascades and parts of
Idaho and Nevada. The rain will be moderate to heavy at times. Therefore,
the WPC has issued a Marginal Risk of excessive rainfall over parts of
Northern/ Central California through Wednesday morning. The associated
heavy rain will create localized areas of flash flooding, affecting areas
that experience rapid runoff with heavy rain.

On Wednesday, the threat of excessive rainfall increases as a plume of
moisture streams into Southern California. Therefore, the WPC has issued a
Slight Risk of excessive rainfall over parts of Central/Southern
California from Wednesday into Thursday morning. The associated heavy rain
will create mainly localized areas of flash flooding, with urban areas,
roads, small streams, narrow crayons/gullies, and burn scars the most
vulnerable. Moreover, locally heavy snow will continue over the highest
elevations of the Sierra Nevada Mountains.

Meanwhile, upper-level energy over the Northeast on Tuesday moves eastward
out over the Western Atlantic by Wednesday. The energy and cold air will
aid in creating lake-effect snow downwind of the Lower Great Lakes and
upslope snow over parts of the Central Appalachians on Tuesday, ending
overnight Tuesday.

Elsewhere, return flow off the Gulf of Mexico will slowly moisten the air
over the Central/Southern Plains, producing scattered rain over the region
overnight Wednesday into Thursday.


Ziegenfelder


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