Winter Storm Warning 19, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
216 PM AKDT Thu Oct 25 2018

.SYNOPSIS...
Aloft...
Long wave pattern consisting of a trough over the Eastern Bering
Sea, Western AK and the Gulf of AK with a ridge over NW Canada and
eastern AK will persist into the weekend as a series of strong
short wave troughs and associated surface lows make their way
from the Gulf of Alaska north into the Interior. By Sun the long
wave trough will progress east over mainland AK. This means that
the the stormy pattern of the past week consisting of periods of rain,
snow, freezing rain, winds, and well above normal temperatures
will continue into Sat.

On Sunday, expect a sharp drop to near normal temperatures along
with more widespread snow. These conditions will continue into
the first several days of next week.

Surface...
A 994 mb low 100 NM north of Prudhoe Bay will move to 300 nm north
of Prudhoe Bay as a a 997 mb low by 4am Fri, to 400 NM north of
Prudhoe Bay as a 1000 mb low by 4pm Fri. An arctic cold front from
the low to Cape Lisburne to the Bering Strait to Nunivak Island
will move to Barter Island to Point Hope to Nunivak Island by 4am
Fri and then persist into Sat. Scattered snow showers and areas
of fog along the front over the North Slope will spread east to
Barter Island tonight.

Widespread rain and snow showers are occuring where the front
lies over open water from Cape Lisburne to the Bering Strait to
St Lawrence Island. This will change over to all snow late
tonight and continue in that area through Sat as the cold air
continues to flow south over the warm water and produce the snow
showers. Expect 1-3 inches of snow over these areas through Sat.
Also expect north winds 30kt along the front, with 40 kt south of
the Bering Strait.

A 960 mb low in the northwest Gulf of AK will move to to the Kenai
Pen as a 976 mb low by 4am Fri, then weaken to 985 mb low by 4pm
Fri, then weaken over the AK Pen Sat. An occluded front stretching
from the low to Skwentna to Fairbanks to Eagle will move to
McGrath to Livengood to a 994 mb low near Eagle by 4am Fri, and
Shageluk to Tanana to Circle to a 996 mb Low near Eagle by 4pm
Fri, along a Shageluk to Bettles to Circle lone by 4am Sat, then
persisting into Sat pm, and then moving east across the Eastern
Interior Sun.

There are now isolated rain and snow showers along this
front with a few freezing rain showers where rain is falling on
frozen ground. Showers will become scattered tonight and Fri north
and west of Fairbanks, and there will still be a chance of
freezing rain along and north of the front. Weak downslope winds
will develop tonight over the Tanana Valley south of the front and
persist into Fri night. This will keep the Tanana Valley from
Fairbanks East mainly dry from late tonight into Fri night.
Will see snow become more widespread along the front in the
Western and northern Interior Fri night and Sat, them spreading to
Across the Eastern INterior Sun. Expect several inches of snow in
the western and northern Interior Fri night Sat with this
feature, with several inches possible in the Eastern Interior
Sun.

&&

.DISCUSSION...
Models initialize well aloft at 12Z and show similar solutions
into Sat, then see bigger differences into Sun. Some differences
in precipitation fields, so will use a combination of the
NAM/GFS/ECMF areal coverage to broaden out the area that precip
occurs which seems to be the case at this time. Favor the ECMF
solution for Sun, which is faster with the next incoming Gulf of
AK low than the other models, and brings the long wave trough east
over mainland AK on Sun more than the GFS/NAM. This will result
in cooler and wetter conditions for the Eastern Interior Sun.

At the Surface at 15Z all models initialize about 6 mb too weak
on surface low in the northern Gulf of AK. Will accommodate this
by increasing winds over Interior 3-5 kt today and tonight.

Coastal Hazard Potential Days 3 and 4...
North winds 30g40kt from the Bering Strait to St Lawrence Island
are causing elevated seas, but rightward displacement of water
caused by the Eckman Spiral is causing lower than normal sea
levels, so waves should be breaking offshore.

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ200-PKZ215-PKZ220-PKZ225-PKZ230.

Gale Warning for PKZ210.
&&

JB OCT 18