Small Craft Advisory 544, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
422 PM AKDT THU JUL 7 2016

.ANALYSIS AND UPPER LEVELS...
An upper level low over the southern gulf is rapidly moving
southeast. A lingering trough from this low extends northwest
across south central Alaska and the Kuskokwim valley to a trough
near the Bering Strait that is associated with the polar jet.
There is a low over the western Aleutians that is moving to the
east-northeast. A leading front stretches from about the tip of
the Alaska Peninsula through the Pribilof Islands. Upper level
high pressure is over the Bristol Bay area and Kodiak Island.

&&

.MODEL DISCUSSION...
The numerical models are in very good agreement for the short term
portion of the forecast. The forecast challenges include the
possibility of convection (thunderstorms), which each of the
models handles differently. Another issue is morning fog, which
is a boundary level issue that can be a struggle. These are minor
issues, however, and the forecast confidence is above normal
today.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The overall drying/clearing trend will continue tonight with
strengthening low level offshore flow. This will produce gusty
gap winds in the usual locations along Prince William Sound and
the northern Gulf Coast including Seward, Whittier, and Valdez.
This will set the entire region up for extensive sunshine and
warmer temperatures on Friday, especially over the valleys. The
offshore flow will hold on through the morning hours along the
coast leading to warm temperatures there as well, though weak
sea breezes will develop during the afternoon as offshore flow
weakens. A weak upper level short-wave will track from southwest
to northeast across Southcentral on Friday. This will combine
with a strengthening thermal trough over interior Southcentral to
destabilize the atmosphere and lead to development of showers and
a thunderstorms along the mountains. Storm motion will be weak in
most places...so do not expect the showers and thunderstorms to
make it very far off the mountains.

Saturday looks like a fairly similar day to Friday with afternoon
showers and thunderstorms focused near the mountains. A weak low
currently along the Aleutians will reach Kodiak Island Saturday
bringing rain and cooler temperatures. This storm system will
remain down over the Gulf with little or no impact on mainland
Southcentral.

Sunday will start out similarly to Friday and Saturday with quite
a bit of sun. However, a trough dropping into Southwest Alaska
Sunday afternoon will likely lead to increasing clouds Saturday afternoon
and perhaps greater coverage of showers.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
The upper level ridge over the Eastern Bering and Bristol Bay will
gradually flatten as it shifts inland over Southwest Alaska
tonight and Friday. While conditions will be notably drier with
more and larger breaks in the clouds than days past, isolated
showers will still be around especially along the mountains. The
frontal system associated with then next incoming low will reach
the Southwest Alaska coast on Friday where it will stall and
weaken through Friday night. The supporting upper level low will
reach the greater Bristol Bay area Saturday pushing showers
further inland then cross the Alaska Peninsula and move into the
Gulf Saturday afternoon. A shortwave from the north will reach the
west coast Saturday evening then swing into Southwest Alaska
Saturday Night and Sunday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
The upper low currently centered over the western and central
Aleutians will track east through the southern Bering tonight and
Friday to be located just south of the Pribilof Islands Friday
evening. The upper low will swing through Bristol Bay Friday
night and then cross the Alaska Peninsula and move into the Gulf
on Saturday. The flat ridging will build in behind the low,
spreading across the Aleutians Friday night and Saturday and then
expanding north across the Bering through Sunday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The long term forecast will be characterized by high pressure over
the Western Bering that will last through next week and an upper
level low that will sit over the Gulf or just to its south. Sunday
will also see a trough tracking through mainland Alaska from the
north that will bring a potential for showers around Southcentral
Alaska. After that flow over the southern mainland will be light
providing a more typical summer time pattern with fair conditions
in the morning and afternoon convection, mainly along the
mountains. In this pattern temperatures around much of the
southern mainland look to be in the mid 70s with some more
interior locations reaching even higher.

&&

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

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...DK