Small Craft Advisory 311, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
508 AM AKDT Fri Apr 14 2017

.ANALYSIS AND UPPER LEVELS...
The entire area could be divided into three distinct regimes this
morning. From west to east...1) A mid-upper 970 mb low moving into
the Western Aleutians 2) Decaying warm occlusion over the Eastern
Bering 3) High pressure over South Central. The primary storm
track remains well south of the state as the polar front jet moves
at 150 kts from west to east. A few fingers of the jet are within
our borders with 80 kts supporting the front over the Eastern
Bering and 75 kts over the northern Gulf of AK. Even though
temperatures are warming quite a bit at the surface, it remains
cold aloft. It is nearly -40 degrees C around 20,000' over the
Western Aleutian low and -32 C over the Gulf of AK. This will help
to increase instability and aid shower development in both areas.
Fog has formed over much of the Alaska Peninsula and the
Kuskokwim Delta this morning. Most of it is just east of the warm
occlusion. It will dissipate later today as offshore flow
increases with the front approaching. Conditions remain much the
same over South Central. The lone exception is a bit less wind in
the gaps overnight. This had led to a much colder night in Valdez
and Gulkana versus what we saw 24hrs ago.

&&

.MODEL DISCUSSION...
Biggest discrepancy in the models tonight was regarding the low
position near Dutch Harbor-Cold Bay into the weekend. The NAM and
Canadian Global were significantly further south with this
feature, so we relied on the EC and GFS. This will keep gusty
southerly winds and precipitation going through this area a bit
longer, especially on the favored southern side of the AK
Peninsula. With some of that aforementioned instability in the
Gulf of AK and the development of lasting onshore flow, we did
introduce a slight chance of showers later today over Kodiak.
Otherwise, models remain in great agreement and forecast
confidence is high.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

The relatively warm and sunny days with cool and clear nights are
expected to continue across much of the mainland through this
weekend. Kodiak Island will be the exception though as
increasingly easterly flow and upper level disturbances will bring
increased changes of showers beginning this evening. These
conditions should continue into the weekend. Elsewhere, brisk
outflow conditions across the mainland will diminish through this
morning as pressure gradients relax. As the offshore gradient
relaxes afternoon and early evening sea-breezes will develop in
its place. This will tend to knock down afternoon high
temperatures along the coasts.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
More of the same is in store for the southwest mainland heading
into the weekend as high pressure supports generally warm and dry
conditions across the area. Clouds and patchy fog will continue
over portions of the Kuskokwim Delta as another Bering front
stalls just offshore, with any associated precipitation also
expected to remain offshore. A few clouds may begin to spread back
into the region late Saturday into Sunday morning as the ridge is
undercut by a disturbance lifting northwestward along the coast.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The front in the central Bering will continue to track eastward
today, bringing rain and gusty southerly winds to Saint Paul and
Dutch Harbor by the afternoon. The front's eastward progress will
slow significantly tonight as it encounters the ridge to the east,
with the front then stalling and weakening over the eastern Bering
through this weekend much like the previous feature to impact the
area. A North Pacific wave developing along the front on Saturday
will help to enhance precipitation along the Alaska Peninsula
through Sunday morning. Meanwhile, the western Bering will remain
in a more showery regime as a Kamchatka low tracks into the area
and slowly weakens.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Confidence remains very good that the upper trough descending into
the Yukon Territory this weekend will remain largely east of the
Mainland, allowing for ridging to rebuild by early next week.
This will keep generally sunny but cooler weather to spread into
the Southcentral through early next week with rounds of weak
outflow winds along the Gulf Coast, especially in the Valdez
area.

Over the Bering Sea confidence is much less in the exact low
track of the North Pacific low early next week. There is
increasing confidence however that this low will stay largely
south of the Aleutian chain, providing only a brief period of
gusty winds to the Western-Central Aleutians. Elsewhere weak high
pressure will allow for widespread stratus and showers to spread
throughout the remainder of the Bering.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning...173...174...413.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...DEK