Small Craft Advisory 619, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
412 AM AKDT SAT AUG 6 2016

.ANALYSIS AND UPPER LEVELS...

The main feature continues to be the vertically stacked low that
sits north of the Pribilof Islands this morning. An associated
front is currently supporting widespread showers across much of
southcentral. A potent shortwave rotating through the flow is
bringing a round of showers to the Alaska Peninsula and Bristol
Bay Regions. Meanwhile broad moist southwesterly flow is aiding in
low clouds and scattered showers further northwest across the
Kuskokwim Valley. A second disorganized low sits in the far
western Bering Sea with an associated front moving across the
western and central Aleutians with additional showers in this
region. Back to the east, the ridge remains centered over the
eastern gulf of Alaska.

&&

.MODEL DISCUSSION...

Models are in great agreement synoptically in the short term as
the low centered over the Pribilofs drifts to the northeast
towards Nunivak Island and lingers through the short term. As a
result broad moist southwesterly flow will be established through
the short term. Downslope winds in the Anchorage area may bring
down some of the rain totals but overall it appears that the
downslope component is not hindering the precipitation from
reaching the surface as much as previously thought.

&&

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

The upper level low will remain near the Nunivak Island/Kuskokwim
Delta region through Sunday night. This will keep moist southerly
flow aloft over south central Alaska. The low will send a couple
of systems through the area this weekend. The first is over south
central Alaska this morning and will move inland and dissipate
this afternoon. The next system will reach Kodiak Island this
afternoon and then the mainland tonight bringing another batch of
rain to the area. This system will then move east later Sunday,
with trailing showers Sunday night.

&&

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

Low pressure continues to spin between the Pribilofs and Nunivak
Island and will continue to pivot disturbances around it and
across Southwest Alaska for the next couple of days. The low will
remain in place and drift north and east off the Y-K Delta
through Sunday, keeping clouds and rain/showers over the entire
region.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

The low over the northern and eastern Bering will reach near gale
force today, with rain continuing across the Aleutians and Alaska
Peninsula in association with a quasi-stationary front with
multiple waves moving east bringing periods of rain and showers.
Northerly flow will help push the front south of the Western
Aleutians by Sunday night bringing relief from the wet conditions.

&&

.LONG TERM FORECAST (Days 3 through 7)...

Models remain in agreement that the upper low over the eastern
Bering will remain through midweek. It will continue to send rain
and shower producing impulses over mainland Ak through that
period. Another upper low moving east from Kamchatka will then
absorb the original Bering low and send more rain and showers to
the mainland through the rest of next week. Although there will be
brief periods of small scale ridging between major portions of
these features, exact timing of breaks in the precipitation is
poorly represented.

At about the same time that the Kamchatka upper low crosses the
Bering late Wed, the weakening remnants of a tropical system will
approach the western Aleutians. Models are in relative disarray in
the handling of this system. What is clear is that it will move
across the Bering, reaching at least the central Bering by the
weekend. At this time it will bring some gale force winds to the
western islands after Wed, with seas enhanced by a long fetch
across the north Pacific. Although confidence is increasing, exact
timing of wind speeds and sea heights remains uncertain.

The forecast utilized gfs and nam for day 3 (Sun night and Mon).
After that time WPC guidance, which utilized ensemble components
as well as the operational EC and GFS, was used. This emphasized
the slower GFS solution with respect to the tropical remnant low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...LIW
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...DS