Valid Friday, December 04, 2015 to Tuesday, December 15, 2015
Summary of Forecasts and Hazards
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EST December 01 2015Synopsis
: A frontal system is predicted to
stretch from the Northern Plains to the Southwest at the beginning of the
period and move eastward, sweeping across the lower 48 states until Sunday. A
series of frontal systems are forecast to enter the Pacific Northwest over the
3 to 7 day period into the beginning of week-2, bringing more unsettled weather
to coastal parts of the Pacific Northwest and Northern Rockies. High pressure
is likely to dominate the Contiguous U.S. for much of the 3 to 7 day period,
excluding passage of these fronts. Surface lows are favored to develop over
the Aleutians and Gulf of Alaska, while a stationary front remains in place
across northern mainland Alaska during the 3 to 7 day period.
Detailed Summary For Friday December
04 - Tuesday December 08:
- High winds for coastal parts of Oregon and
Washington, Sat-Sun, Dec 5-6.
- High significant waves for coastal parts of Oregon and Washington, Sat-Sun,
- Heavy precipitation for western Washington, Sat and Tue, Dec 5 and 8.
- Episodes of heavy precipitation for parts of the Northern Rockies, Fri-Wed,
- Much below normal temperatures across the Brooks Range in Alaska, Fri-Mon,
- Heavy precipitation for parts of the Alaska Panhandle, Tue, Dec 8.
- River flooding occurring, likely, or possible over parts of the Central and
Southern Plains and Mississippi Valley.
- Severe drought in the far western CONUS, northern Rockies, and Puerto Rico.
A frontal system is expected to impact much of
the northern half of the west coast of the CONUS over the weekend. This storm
is expected to bring high winds (40 knots or greater) and high significant
waves (24 feet or greater) to coastal parts of the Pacific Northwest on
Saturday and Sunday.
The aforementioned frontal system is predicted to be followed by a series
of frontal systems entering the Pacific Northwest during the 3 to 7 day period
into the beginning of week-2. This active weather pattern is anticipated to
bring heavy valley rain and heavy mountain snow to parts of western Washington
on Saturday, whereas mainly a rain event is expected for Tuesday. This area may
receive 3 inches or greater of liquid equivalent in a 24-hour period.
Additionally, these frontal systems are likely to transport moist air from the
East Pacific into the Northern Rockies, bringing episodes of localized heavy
valley rain and mountain snow to parts of this area throughout much of this
period into the beginning of week-2. This area may receive an inch or greater
of liquid equivalent in a 24-hour period.
A stationary front is anticipated to develop over northern mainland Alaska
at the beginning of the period and remain in place for the 3 to 7 day period.
Surface high pressure north of this front may bring cold Arctic air to northern
Alaska, favoring much below normal temperatures across the Brooks Range Friday
to Monday. Daily temperatures in this area may reach 20 degrees F below normal.
A storm system is forecast to develop over the South Coast of Alaska by
next Tuesday. Strong onshore flow associated with this storm may bring heavy
rain and snow to parts of the Alaska Panhandle (2 inches or greater of liquid
equivalent in a 24-hour period).
Precipitation prior to and during the period leads to occurring, likely or
possible river flooding over parts of the southern Plains and Mississippi
Valley. For Wednesday December 09 -
Tuesday December 15:
The active weather pattern from the 3 to 7 day period
is forecast to extend into the beginning of week-2 in the Pacific Northwest.
Moist flow from the East Pacific is anticipated to continue the potential for
heavy valley rain and mountain snow into Wednesday, December 9 across parts of
the Northern Rockies. The 6Z operational GFS is showing significantly higher
24-hour accumulated liquid equivalent totals (2.5 inches or greater) compared
to the 0Z operational ECMWF (0.8 inches or greater).
Near to above normal temperatures are favored for the CONUS and Alaska
during week-2. Normal to above median precipitation is forecast for the CONUS
Forecaster: Melissa Ou
Click here to see a display of the GFS Ensemble Forecasts
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.