Small Craft Advisory 471, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 AM AKDT WED JUN 8 2016

.ANALYSIS AND UPPER LEVELS...
Southern Alaska is currently situated under a somewhat progressive
upper-level pattern. Two upper level lows, one exiting the area to
the south/east over the Gulf, and the second, bringing active
weather to the Western Aleutians. They are separated by an upper
level ridging over the Eastern Aleutians, and Southwest Alaska.
The upper low over the Western Aleutians is vertically stacked
with a fairly typical summertime surface low. Several fronts are
pinwheeling around this low, bringing gusty winds across the
western Bering and the Central Aleutians. Surface and upper level
ridging over the eastern Bering is promoting areas of fog along
the coast of Southwest Alaska as subsidence helps to keep the
atmosphere stable and resistant to mixing.

A weak disturbance moving southward into southern mainland Alaska
is locally increasing the cloud cover across the Lower Kuskokwim
Valley, Susitna Valley, and the northern Copper River Basin.
Abundant daytime heating with more than 19 hours of daylight
should help to scour out the clouds in their attempts to lower
towards the valley floors. In a somewhat unusual setup, coastal
locations from the Gulf westward to Bristol Bay are mainly clear
this morning with ridging set up across this region.

&&

.MODEL DISCUSSION...
The models are in very good agreement through late Thursday
night, with the global and regional models all depicting the low
over the Western Aleutians and the subsequent cyclogenesis east of
the low late tonight into the day Thursday. Forecast confidence is
high.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Warm and dry conditions will settle in across most of Southcentral
Alaska today as an upper level ridge moves directly overhead. Low
level offshore flow will keep sea breezes largely at bay for the
northern Gulf coast and Prince William Sound which will allow
Seward, Whittier, Valdez, and Cordova to warm up significantly as
well. Not to be outdone, with westerly flow across Kodiak Island
the eastern coast will also see sunny skies and warm temperatures
today. The one exception to all of this nice weather will be up
along the Alaska Range where an upper level trough dropping down
into the Interior will bring some clouds and a chance of showers.

The upper ridge will shift eastward Thursday and Thursday Night.
Most of Southcentral will remain stable under the influence of
the ridge and remain warm and dry. However, as the ridge moves
eastward the front edge of a large storm system along the
Aleutians will make its way toward the Southcentral. A weakening
surface front will bring rain to Kodiak Island Thursday Afternoon
through Thursday Night. Don't expect there to be much forcing left
by the time it reaches the Kenai Peninsula. Thus, do not expect
steady rain to make it to Southcentral, but will see increasing
clouds and likely see some scattered showers as the upper trough
moves in.

Lastly, as the upper ridge moves eastward offshore flow will weaken
and a surface high will build northward from the Gulf Thursday
Afternoon and Evening. This will produce the usual gusty southerly
winds in the Copper River Basin. With very warm and dry conditions
in place this will raise the fire weather danger.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Another beautiful day is shaping up for the mainland on Wednesday.
High pressure will dominate today keeping clouds at bay and
temperatures well above normal. Some left over cloud cover that
spilled over the ridge yesterday will sit over Bristol Bay and the
Kuskokwim Valley early today, but should be vanquished by the
ridge early this afternoon. Conditions will be mostly dry but
there is a slight chance for showers along the Kuskokwims this
evening. Otherwise expect warm and dry weather with light
southwest winds. The ridge quickly exits on Thursday as a front
from the Bering pushes closer. The front will be weakening but
will still spreads rain over much of the mainland on Thursday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The upper level low pressure over the Western Bering Sea has
entered a weakening phase where scattered showers are mostly what
is left around precipitation-wise. However, a triple point low
will form along the front near the Eastern Aleutians bringing
moderate rainfall to Unalaska, the Pribilofs, and the Alaska
Peninsula beginning late this evening before spreading eastward
overnight. The front weakens and moves ashore the mainland on
Thursday leaving much of the area in showers or spotty rain along
the front in the Central Bering.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Models are in agreement that the energy over the central
Aleutians, spread between the original low and the Bering triple
point, will reconsolidate at the triple point on Friday near the
Pribilofs. The associated front will spread inland during the same
period, while high pressure over the rest of the mainland will
slowly retreat to the east. Significant rain will accompany the
front as it moves inland through Friday over Southwest Alaska,
and the eastern half of the Aleutians as well as Kodiak Island. By
later on Friday rain will reach the Kenai Peninsula, with shower
activity over the Chugach and the Talkeetna Mountains. The
forecast utilized some Nam in the east and Gfs in the west.

The front moves northeast on Saturday and another triple point
low develops over the Gulf by Sunday. This system then drifts in
the Gulf into early next week. Beginning Saturday afternoon a
ridge builds into the western Bering which reaches the eastern
Bering early Monday before reaching the mainland through Tuesday.
The next Bering low follows, reaching the Western Aleutians Monday
and the eastern Bering late Tuesday. The forecast utilized the EC
and the ensemble solution from WPC.

The north Gulf coast will have some rain this weekend and then more
significant rainfall from the meandering Gulf low through early
next week. Moisture inland will again be available for afternoon
and evening showers through early next week. Southwest Alaska will
have showers, with a brief break beneath high pressure beginning
Sunday night before the next front arrives on Tuesday. Rain and
showers can be expected across the Aleutians through the period.

&&

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

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...DS