Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 091354
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
454 AM AKST Fri Dec 9 2016
.ANALYSIS AND UPPER LEVELS...
A broad complex low stretching from just south of the Gulf into
the AK pen continues to bring snow showers and offshore flow to
most of the south Mainland and Gulf Coast. There are numerous waves
rotating around this complex. The strongest stretches from Kodiak
Island into the Southcentral, allowing for light snowfall to
develop from the western Gulf into the Cook Inlet region. A
second, weaker wave located just south of the AK pen is bringing
gusty northerly winds and snow showers to that area. Behind this
wave, cold air advection in the northerly flow over the Bering
continues to bring widespread stratus and snow showers to the
Bering Sea coast. Over the western-half of the Bering little has
changed in the pattern since yesterday. The remnants of the
frontal band that moved into the central Bering yesterday
continues to dissipate in place as a another North Pacific low
begins to move into the western Aleutians. This next system will
once again be confined to the western-half of the Bering as
ridging dominates to the east.
Model agreement has improved substantially in the last 24 hours
in the speed of the surface trough moving from the western Gulf
into the AK pen. Due to this better agreement and with snow that
developed throughout Cook Inlet overnight, widespread light snow
was brought into eastern Bristol Bay this morning as the trough
passes through. This good agreement then continues into this
weekend as the parent low over the northeast Pacific makes
landfall over the NW CONUS, allowing for high pressure to
redevelop throughout the south Mainland, increasing forecast
PANC...Once snow showers and cloud cover move out of the area
early this morning, VFR conditions with N-NE winds around 10 kt
will continue through Saturday morning.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Radar imagery this morning shows that the main band of showers
that pushed across the Anchorage Bowl and western Kenai Peninsula
this morning continues to move west and weaken. The main focus of
isentropic assent has pushed further west, with widespread showers
in Kodiak, but just a few lingering showers in the northern Gulf.
While precipitation tapers today across much of the forecast area,
high pressure will remain in place across the mainland, with low
pressure in the Gulf of Alaska. As a result, offshore gusty winds
will continue through local gaps through much of the short term.
The strongest gusts are generally expected this evening into late
tonight as an upper level trough surges southward and cold air
begins to push southward behind it. Winds will slowly abate by
Saturday afternoon and evening, but gap winds will continue as the
favorable pressure gradient remains in place.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The lower southwestern Gulf has a 1008 mb low developing with an
inverted trough extending northward into the Aleutian Range this
morning. This synoptic feature has kicked off light snowfall early
this morning, and will continue as this trough moves from east to
west through this afternoon. Areas from Dillingham east will see
majority of the snowfall this morning before tapering off to
scattered snow showers in the afternoon. The rest of the Southwest
Alaska region will remain under offshore flow through Saturday.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
High pressure briefly remains over the western/central Bering
through Saturday morning. Meanwhile upstream, an upper level
closed low is located just south of the Western Aleutians. At the
surface this feature is reflected as a 989 mb storm force North
Pacific Low pressure system. By Saturday morning this feature
becomes elongated into two low pressure systems just south of the
Western Aleutians. The associated weather front will be draped
through the aforementioned region extending into the western
Bering. Look for gale force southeasterly winds along the Western
Chain with widespread rain/stratus with warm air advection, and
temperatures well above freezing. This weather front becomes
stretched out from the Kamchatka Peninsula southeastward through
the Central Aleutians by Saturday afternoon.
.LONG TERM FORECAST (Days 3 through 7...Fri through Tue)...
Beginning Saturday evening, the big story will be the continued
development of a high latitude blocking high centered over
mainland Alaska. This will be mean warming temperatures aloft and
strengthening low level inversions which will keep temperatures in
low elevations cold. Fog and low stratus will become more of a
threat with weak pressure gradients inland. Meanwhile, the main
storm track will remain over the Bering as a series of
increasingly strong lows and fronts moves north through the Bering
Strait. This will continue to pump up a strong ridge axis across
Alaska heading into the late week. Temperatures will begin to
moderate closer to climatology as strong cross-polar flow
dumps polar air into North America. This pattern will be dry
across Southcentral with only weakening fronts impacting
Southwest Alaska west of the Alaska Range.
MARINE...Heavy Freezing Spray 127 160 180 181 185.
Gale 127 128 130 175 176 177 178.
SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD