Small Craft Advisory 432, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 AM AKDT Tue May 29 2018

.ANALYSIS AND UPPER LEVELS...

There is a ridge over the Gulf of Alaska that extends into the
Copper River Basin. There is a low over the Bering with an
occlusion moving into southwest Alaska and a warm front moving
towards Kodiak. The latest satellite image has a fair amount of
mid level clouds which is the remnants of yesterday's thunderstorm
activity. The cirrus shield from the storm to the west is also
moving up Cook Inlet.

&&

.MODEL DISCUSSION...
The GFS and the NAM both ping into convection across the interior
again today associated with diurnal heating but do not place any
of the convective ingredients over Palmer, Wasilla or the
Anchorage Metro Area. The models are in good consensus with the
longwave pattern through the remainder of the week. On the
synoptic scale, the only problem area will be for the Western
Aleutians commencing Friday as the next low moves into the region
from the North Pacific.

&&

.AVIATION...
PANC...VFR conditions are expected to persist through Tue
afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Much of the area will move into a slightly cloudier and cooler
weather pattern through mid week as ridging over the interior
weakens and is replaced by weak but broad southwesterly flow. This
will limit the possibility of thunderstorms to just the Northern
Copper River Basin this afternoon/evening as a pool of cold air
aloft associated with a nearly stationary upper low moves
westward into the area. Otherwise rain showers should be most
widespread along the Gulf Coast as the remnants of a frontal
system pushes through, as well as over the Susitna Valley which
should see the strongest daytime heating today. Gusty gap winds
from Turnagain Arm to the Copper River Basin will increase again
this afternoon, but likely will not be quite as strong as
yesterday with increased cloud cover and stronger down-inlet flow
from the diminishing front in the Gulf. Winds will then remain
light over most of the area on Wednesday under generally cloudy
and showery weather as a weak upper level trough moves overhead.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

Another front is approaching the southwest coast early this
morning, with widespread precipitation developing along and ahead
of it. This front will continue its north and east progression
through today before weakening tomorrow. As it continues its
eastward journey, precipitation will become more showery and
scattered in coverage. The parent low will weaken between Saint
Mathews and Nunivak Islands, maintaining a south to southwest
flow aloft the next few days. This will maintain seasonal
temperatures and a general showery pattern.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A surface low currently in the western Bering Sea will move
towards Saint Matthews Island tomorrow while weakening over the
next few days as it wobbles towards Nunivak Island. Cyclonic flow
around it will maintain some showery type weather, with winds
mainly of the storm force variety, while being somewhat stronger
near the surface low this evening. Otherwise, small craft
conditions will prevail over the next few days, as a ridge builds
across the region from the west, bringing with it decreasing
clouds while maintaining relatively light winds.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The extended portion of the forecast begins Thursday evening with
the next Gulf low beginning to pull away to the southeast towards
Haida Gwaii. The departing system will leave much of mainland
Alaska in weak cyclonic flow beneath a poorly defined longwave
trough heading into the weekend. This upper level pattern should
yield generally pleasant early summer like conditions across a
wide swath of the region, with highs approaching 60 for coastal
locations and climbing well into the 60s inland each afternoon.
Mainly dry conditions should also prevail into Sunday, with
diurnally driven convective activity remaining the primary mode of
precipitation. Showers look to be a little more widespread across
Southcentral than Southwest Alaska at this time as a narrow upper
level ridge builds over the Bering coast by Saturday.

The forecast begins to look more muddled by early next week as
guidance remains farther apart than usual regarding the
progression of a large upper low and attendant surface feature
moving into the Bering region Sunday into Monday. A front looks
to approach the Gulf and southern mainland within this timeframe,
but individual models are all over the map on strength and timing
of this feature. Generally speaking, it appears that this system
will bring a return of cooler and cloudier conditions back to the
southern mainland and particularly Southwest AK by sometime early
next week. This should also produce a slightly more active weather
pattern over the Bering from the weekend onward.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...411 413.

&&

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