Small Craft Advisory 269, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
431 AM AKDT Fri Mar 31 2017

.ANALYSIS AND UPPER LEVELS...
The Southcentral Alaska region remains with onshore flow, with a
972 mb storm force low located over the Shumagin Islands region
this morning. The upper levels depict a shortwave over the
northern Gulf, and this synoptic feature is reflected at the
surface with a occluded front. The radar imagery is showing
widespread showers over the Prince William Sound, Eastern Kenai
Peninsula, and the Alaska Peninsula through the Bristol Bay
interior. The Anchorage Bowl is getting its usual downslope drier
condition associated with the cross-barrier flow. While warm air
advection continues to keep surface temperatures in the mid 30s
along the northern coastal communities, and low 30s for inland
areas.

&&

.MODEL DISCUSSION...
The models remain in good agreement as the next North Pacific low
pressure system tracks towards Kodiak Island before moving inland.
The models have some uncertainty as the low moves inland. The GFS
keeps the low farther west tracking through the upper Shelikof
Strait, and the NAM/ECMWF models depict this system farther east
over the lower Eastern Kenai Peninsula. The NAM has joined the
other models in agreement with the advancement of the warm air
into the Bristol Bay interior. Therefore, this will result in
limited snowfall amounts over the Bristol Bay interior. The
GFS/NAM were the preferred model of choice through the short-
term forecast. The forecast confidence is above average as we
head into the weekend.

&&

.AVIATION...
PANC...The Anchorage Bowl continues in drier downslope conditions,
and results in VFR condition through the weekend.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Southerly flow will continue through tonight as the upper level
low remains over the eastern Bering Sea and southwest Alaska. This
will keep bringing precipitation to coastal locations. Inland
locations will be protected from most of the precip by the coastal
ranges, but some showers will sneak through. The upper level low
will swing into the Gulf on Saturday and reach the northern Gulf
coast Saturday night. Temperatures throughout Southcentral
Alaska will increase today and Saturday as the air mass associated
with the low is fairly warm.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Snow develops along a surface low and associated front along
Bristol Bay today, and spreads north through the Kuskokwim.
Moderate snow is expected along the mountains west of Dillingham
as orographic lift enhances precipitation. Wrap around moisture
also continues snow development along the Alaska peninsula as the
surface low stalls across the Bristol Bay tonight. This pattern
persists throughout the weekend, however intensity lightens by
Saturday as the surface low fills. North to east Winds shift to a
westerly flow pattern along the Alaska Peninsula on Saturday with
the surface low moving inland near Dillingham.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
Gusty northerly flow and snow prevails through the weekend across
the eastern half of the Bering as a surface low takes residence
along Bristol Bay, and high pressure moves into the western
waters. Flurries or isolated snow showers can be expected across
much of the Bering, and Aleutians as shortwaves move along from
west to east through the upper level flow pattern. Surface ridging
sliding from Kamchatka to the Central Aleutians brings lighter
winds across the western waters for the upcoming weekend.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Continued upper level support upstream of an upper level trough
anchored across the Bering Sea and northern Pacific Ocean will
help amplify the through much of next week. As this happens, a
surplus of jet energy will help wrap up a series of upper level
waves into fairly strong closed upper level lows. The most
noticeable of these lows will be one that develops somewhere near
42N to 44N, and 164W to 159W on Tuesday. As this low develops, a
very strong surface low will develop in response, and quickly
push into the Gulf of Alaska. Another low is expected to develop
Thursday or Friday, but will likely be deflected further east
toward the Alaska Panhandle as the upper level trough shifts
eastwards. However, the low on Tuesday which moves into the
central Gulf of Alaska on Wednesday will bring some strong winds
to the offshore, and coastal waters while another round of
moderate rain (and snow at higher elevations) to the Gulf coast.
Inland locations once again look to remain dry as the low position
will likely keep many locations downsloped. Temperatures across
Southcentral Alaska will likely remain a good bit above normal as
warmer air continues to get advected northward due in large part
to the amplified trough across the region. Southwest Alaska will
not be as warm or as wet as Southcentral Alaska as the orientation
of the upper level trough will keep much of the warmer and wetter
air east of the area.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning...119 130 131 132 139 150 155 172 351 352.
Heavy Freezing Spray Warning...179 414.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...MC