Small Craft Advisory 265, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
351 AM AKDT Thu Mar 29 2018

.ANALYSIS AND UPPER LEVELS...
The main upper level feature over the region continues to be a
long wave trough over the Eastern Bering and western mainland
Alaska. A weak surface low over the Kuskokwim Delta and
predominate west/southwest flow around the base of the trough is
leading to areas of light snow over the eastern Kuskokwim Delta,
with clearing skies leading to fog forming near Bethel and along
the coast. A few persistent light snow showers are still showing
up over Anchorage/Matanuska Valley tonight as a series of weak
vorticity maxima continue to track through the area around the
base of the upper trough. Out west, an upper level ridge is
beginning to build in over the western half of the Bering and
Aleutians, bringing rather tranquil weather to that region.

&&

.MODEL DISCUSSION...
The models seem to have a good grasp on the building of the high
pressure into western Alaska and the development of an outflow
pattern along the Chugach Mountains heading into the weekend. The
high resolution models (WRF) have been depicting the showery
activity over Southcentral much better than other models over the
past day or so.

&&

.AVIATION...
PANC...VFR conditions and light winds will be predominate over
the terminal today. An upper trough moves though this afternoon leading
to showers developing over the mountains while dropping ceilings
to around 5000 ft over the terminal.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The upper level trough is west of southcentral Alaska today and
is slowly moving eastward. It will move over the area this
evening and overnight before developing into a cut-off low in the
Gulf Friday. This will keep an isolated snow shower or two around
until the trough moves through tonight. By Friday the low in the
Gulf will allow more northerly flow which will clear skies over
the region and increase winds through channeled terrain.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
One more shortwave trough will move across the region from the
west today and support scattered snow showers area wide through
this evening. A prolonged stretch of dry conditions will then
settle in tonight into Friday as the ridge builds over the Bering
Sea and begins to influence the southwest mainland. Steep
temperature inversions and light low level flow will bring the
potential for widespread fog development Thursday night across
Bristol Bay and the Kuskokwim Delta. Fog potential is a little
more uncertain in subsequent nights as increasing offshore flow
may serve as an inhibiting factor heading into the weekend.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
High pressure will dominate the Bering through the end of the week
as strong subsidence promotes extensive stratus and fog
development in the presence of relatively light winds. The only
surface feature of note will be a weak front extending from a
Kamchatka low, however the ridge will inhibit any eastward
movement and help to keep the front west of the Aleutian chain
through Friday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
High confidence remains with high pressure building in over the
eastern Bering that will last through the weekend before
diminishing and tracking west. This will leave southern Alaska in
an outflow pattern through the weekend and into early next week.
However, the guidance is still struggling with an upper level low
tracking south through the state. Models vary on how the low will
track and how much cold air it will bring, including the timing
of the cold air. This will impact how strong winds are over the
north Gulf coast next week and exactly when the strongest winds
will occur. Operational runs were used through much of the weekend
with the better agreement and ensembles were used moving into
next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

SYNOPSIS AND MODEL DISCUSSION...KVP
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...DK