172 
FXUS01 KWBC 210728
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
226 AM EST Sun Dec 21 2025

Valid 12Z Sun Dec 21 2025 - 12Z Tue Dec 23 2025

..There is a Moderate Risk of excessive rainfall over parts of
Northern California on Sunday and Monday...

...Heavy snow downwind from Lake Ontario...

...Rain/freezing rain possible over the Northern Plains and
Pennsylvania...

A front extending along the Northeast and Mid-Atlantic States
swings southwestward to the Central Gulf Coast States and the
Southern Plains, and moves eastward off the Northeast and
Mid-Atlantic Coast by Sunday afternoon. Moisture flowing northward
from the Gulf will overrun the boundary over the Central Gulf
Coast Area, producing rain over the region through Monday morning.
Moreover, upper-level energy moving over the Great Lakes to the
Northeast will produce lake-effect snow downwind from the Great
Lakes through early Monday morning. Heavy snow will develop
downwind from Lake Ontario through Monday evening.

Meanwhile, disorganized upper-level energy moving over the Upper
Midwest will trigger light snow over the Upper Mississippi Valley
into the Great Lakes early Monday morning that will expand into
the Northeast by Monday evening into Tuesday. Along the rain/snow
line in Pennsylvania, areas of rain/freezing rain will develop
over the region Monday night into Tuesday morning.

Furthermore, rain will develop over parts of the Tennessee/Ohio
Valleys by Monday evening, expanding into parts of the
Mid-Atlantic by Tuesday. Moreover, there will be a chance of
rain/freezing rain over parts of the Northern Plains on Monday
into Tuesday morning. 

In the meantime, moisture from the Pacific will stream eastward
over the Pacific Northwest/Northern California, producing rain
over the Northwest, Northern/Central California, and the Great
Basin. The flow off the ocean will produce heavy rain over parts
of Northern California. Therefore, the WPC has issued a Moderate
Risk (level 3/4) of excessive rainfall over parts of Northern
California from Sunday into Tuesday morning. Numerous flash
flooding events are possible. In addition, many streams may flood,
potentially affecting larger rivers. The flooding may include
debris flows in or near recently burned areas. Snow will also
develop over the highest elevations of the Sierra-Nevada
Mountains, the Cascades, the Northern Intermountain Region, and
the Northern Rockies on Sunday and Monday.


Ziegenfelder


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

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