Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
246 AM EST Wed Dec 20 2023

Valid 12Z Wed Dec 20 2023 - 12Z Fri Dec 22 2023

...There is a Moderate Risk of excessive rainfall over parts of Southern
California on Wednesday and Thursday...

...Rain for most of California...

...Temperatures will be 15 to 25 degrees above average over parts of the
Northern/Central High Plains...

An upper-level off the California Coast will slowly move southward over
the Pacific before moving inland over Northwestern Mexico by Saturday. The
low will stream moisture into California, creating rain and isolated
highest-elevation snow over the Sierra Nevada Mountains. The storm will
produce heavy rain over much of coastal California and inland. Therefore,
the WPC has issued a Moderate Risk of excessive rainfall over parts of
Southern California through Thursday morning. The associated heavy rain
will create numerous areas of flash flooding with narrow canyons/gullies
and burn scars the most vulnerable. Furthermore, many streams may flood,
potentially affecting larger rivers.

On Thursday, the threat of excessive rainfall continues as a plume of
moisture streams into Southern California. Therefore, the WPC has issued a
Moderate Risk of excessive rainfall over parts of Southern California from
Thursday into Friday morning. The associated heavy rain will create
numerous areas of flash flooding with narrow canyons/gullies and burn
scars the most vulnerable. Furthermore, many streams may flood,
potentially affecting larger rivers.

However, the rain over Northern California will end on Thursday. Moreover,
lighter rainfall will fall over parts of the Southwest and Southern
Rockies through Wednesday night.

Meanwhile, weak upper-level ridging and downslope wind will produce
temperatures 15 to 25 degrees above average over parts of the
Northern/Central High Plains. Elsewhere, the circulation around the area
of high pressure over the Southeast/Mid-Atlantic will produce return flow
off the Gulf of Mexico that will slowly moisten the air over the
Central/Southern Plains northward to the Great Lakes. Light rain will
develop over parts of the Western Gulf Coast on Wednesday afternoon,
slowly expanding northward over the Central/Southern Plains by Thursday
evening. Overnight Thursday into Friday, the rain will move/expand into
parts of the Middle/Lower Mississippi Valley and parts of the Great Lakes.


Ziegenfelder


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