The Weather Prediction Center

Short Range Forecast Discussion

[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EST Sat Dec 20 2014

Valid 00Z Sun Dec 21 2014 - 00Z Tue Dec 23 2014

...A very wet period is in store for the northwestern U.S...

...A stalled boundary will keep conditions unsettled over the

A powerful Pacific jet accompanied by anomalous moisture content
will allow for very heavy rainfall across the Pacific Northwest
coast with moderate to heavy snows over the interior terrain. This
vast transport of moisture, also known as an Atmospheric River, is
known for bringing some of the heaviest precipitation events to
the western states. The current forecast suggests anywhere between
4 and 8 inches of precipitation will fall across the
Washington/Oregon Cascades, mostly in the form of rain across the
latter section of the mountain range. The WPC winter weather desk
indicates that the Washington Cascades may see snow ranging from 1
to 2 feet through Monday evening. Farther inland, much of the
Intermountain West and Central/Northern Rockies will get in on the
action with similar accumulations across the Blue Mountains,
Bitterroots, Sawtooth, Tetons, Wasatch, along with the Colorado
Rockies. The mid-level energy tracking from the northwestern U.S.
toward the Great Plains will eventually lead to the development of
a robust system spinning over the Middle Mississippi Valley.
However, this feature is not expected to be a large precipitation
maker as a frontal zone along the Gulf Coast will rob most of the
incoming moisture. Expect light snow/ice accumulations anywhere
from the Northern High Plains eastward to the Upper Midwest.

The other active system on the map is the aforementioned stalled
frontal boundary across the Gulf of Mexico and along the
southeastern U.S. coast. Weak disturbances within the
southwesterly flow aloft will help spark areas of showers and
thunderstorms along this front keeping conditions unsettled
throughout the next couple of days. The heaviest axis of rainfall
is expected along the Florida panhandle and just offshore of the
Carolinas where waves of low pressures will track.

Temperatures as a whole will be above normal throughout the period
given the dominance of Pacific air masses into the country. Even
in the wake of the closed low across the middle of the U.S., high
temperatures over the Northern Plains should still reach the
freezing mark. It is expected to become rather breezy though as
the pressure gradient tightens over the Plains in response to the
deep area of low pressure.


Graphics available at

Last Updated: 400 PM EST Sat Dec 20 2014