Small Craft Advisory 589, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
537 PM AKDT Thu Aug 15 2019

Corrected Marine and Long term Forecast sections

.ANALYSIS AND UPPER LEVELS...
The upper level ridge over the Gulf of Alaska and Alaska Peninsula is
beginning to rebuild over the eastern Bering Sea today as the
upper level lows in the Arctic set up to begin the pattern shift
over the next few days. This current pattern continues to push the
moisture into the Interior of the state keeping the Southwest
mainland and Southcentral dry. There are some areas of marine
stratus along the southwest mainland coast under the stronger high
pressure and some higher clouds overrunning the ridge in the
Kuskokwim Valley and into Southwest Alaska.

The strong surface low near Attu is occluded and getting close to
becoming vertically stacked. However, the front associated with
it does advect moisture up all the way from around 30N.

&&

.MODEL DISCUSSION...
Models have come into good agreement on the track of the upper
level movement of the short wave moving across Southcentral Alaska
Friday night and Saturday and remain in good agreement through
the weekend. The one item that stands out is that the NAM is
continuing to show the core of the upper level low dropping into
Southeast Alaska after tracking through the Yukon while the GFS
and ECMWF keep the main upper level low to the north. Since the
upper level trough moves though Southcentral at around the same
time with either solution, it should not be a big problem for the
forecasts in Southcentral and Southwest. That said, it is does
add a level of uncertainty overall as to if that indicates winds
could be a little higher than currently expected.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist through Friday
mid-afternoon. However, gusty northerly winds will begin to move
into the terminal area late Friday afternoon or early evening and
persist into Saturday.

&&

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

A cold front is expected to move southward through the area
beginning Friday. Overall this is a dry front, although in the
Copper River Basin, showers are expected ahead of the front on
Friday. In the western portion of the area, winds will be the main
impact as this front progresses southward. Gusty winds should be
expected Friday night and Saturday for the Kenai Peninsula and
Susitna Valley, then on Sunday for the north Gulf Coast. The
marine areas should expect to see gusty outflow winds in the
northerly gap areas, creating choppy seas as well.

Temperatures will remain warm on Friday, but the air behind the
front is cooler, so expect more seasonable temperatures on
Saturday and Sunday.

&&

.FIRE WEATHER...

Dry and windy conditions are expected for the weekend as the front
moves through Southcentral. On Friday, winds will begin to pick up
in the late afternoon in the Susitna Valley and Kenai Peninsula.
RH values should drop rather quickly with the onset of the winds
as they will mix drier air down from aloft. The one uncertainty
remains whether the warm temperatures will coincide with the
driest RH values. A Fire Weather Watch is out for these locations
indicating there is a possibility with the onset of the winds and
the drier air to match the warmest temperatures. By Saturday, the
cooler temperatures will have moved in so Red Flag conditions are
less likely. However, this remains one of Southcentral's key fire
weather patterns so this weekend should be one to watch.

&&

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

High pressure over Southwest Alaska becomes more amplified by
Friday afternoon. This will allow for a general clearing trend
with a shift to northerly, offshore flow by Saturday afternoon. A
pattern change is expected through the weekend as a cold front
moves in from the north for Sunday afternoon.

&&

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

A gale force front associated with a low centered over the western
Bering continues to bring gusty southerly flow and precipitation
to the western and central Aleutians. Meanwhile, a strengthening
ridge of high pressure over the eastern Bering slowly drifts to
the west. Gale force southerly winds are expected to persist over
the western Aleutians through Saturday morning before the ridge
forces the front to retreat westward by Sunday afternoon.

&&

.MARINE (Days 3 through 5: Saturday through Monday)...

A weakening front during the day Saturday will bring localized
gales to the western Aleutians west of Adak, though not as far
west as Shemya. Associated small craft advisory conditions are
expected from Atka westward. The front will drift westward through
Sunday but will continue weakening. Gale force gap winds are also
expected from the Barren Islands south on the Gulf side of Afognak
Island through Saturday afternoon before diminishing.

A strong low will approach the western and central Aleutians late
in the day Monday with a chance of gale force winds and high seas
developing Monday evening across the adjacent waters, especially
on the Pacific side.

&&

.LONG TERM FORECAST (Days 3 through 7: Saturday through Wednesday)...

A cooler, much more seasonable air mass will overspread
Southcentral on Saturday, and eventually move into Southwest
Alaska by Monday. This will allow temperatures to return much
closer to normal for this time of year. What will remain very
contrary to the normal is that the cooler air mass behind the
front will be dry. There will be a threat for some mountain
showers along the eastern Alaska Range and the Wrangells each
afternoon. Some of the mountain shower activity may make it to the
Talkeetnas and Prince William Sound Monday and Tuesday, but the
models begin to disagree some on that by that point. The EC has a
chance of light rain in Southwest Alaska on Tuesday. Elsewhere,
however, in all the long-range models, however, that is it for
even a chance of precipitation in Southern Alaska. For what is the
wettest month of the year for many, the fact that the dry pattern
that has persisted for more than 2 weeks now looks to continue
for yet another week is truly astounding. At least in the
temperature department, a large-scale trough is expected to
persist over at least the eastern half of the state right through
into midweek. Thus, the record highs that have been so common as
of late will become a thing of the past.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales 130 131 175-177 411 413.
FIRE WEATHER...Red Flag Watch 121 125 145.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...LF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...TM