Small Craft Advisory 560, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
351 AM AKDT THU JUL 14 2016

.ANALYSIS AND UPPER LEVELS...

An upper level ridge is located along the Kamchatka Peninsula
extending eastward into the Bering Strait. While, a close high is
positioned over the Southcentral region this morning. Meanwhile,
a closed low at 500 mb is located over the Shumagin Islands with
shortwaves rotating around this feature. Looking at the surface
there is a ridge of high pressure over the Gulf extending into the
Southwest/Southcentral regions. A 1009 mb North Pacific low is
located near 53n 159w with the Scatterometer Wind Imagery showing
small craft east/northeasterly winds along the Eastern Aleutians
extending into the southern end of Kodiak Island this morning.
This system is streaming a swath of moisture into the aforementioned
regions. The surface observations over the Eastern Aleutians, and
Kodiak Island are reporting light rain/fog this morning. In the
Bering there is light winds with marine layer stratus/fog
associated with the upper lever ridge over the region. For
thunderstorm activity today, the thermal trough looks to have
moved slightly farther north along the Alaska Range, and north of
Bethel this morning. This synoptic feature will again create very
unstable conditions combined with diurnal heating to increase the
chances for isolated thunderstorms this afternoon/evening. The
ridge aloft will help keep thunderstorms out of the Anchorage Bowl
as it aides in capping the instability.

&&

.MODEL DISCUSSION...

The models continue to remain in good synoptic agreement. The
models are showing the most unstable conditions across the
Wrangell Mountains, northern Copper River Basin, Alaska Range,
and west of Bethel today. The preferred models of choice were the
Nam, and the Canadian-Reg due to higher resolution. The forecast
confidence remains high as we head into the weekend.

&&

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

The pattern will remain basically the same through Friday night
with a ridge centered over the Copper River basin and low pressure
to the west. Kodiak will see some rain today as a weak front
associated with the low to the west moves through the island, then
conditions will dry out. For the rest of Southcentral Alaska,
daytime temperatures will remain above normal. The hottest
temperatures will be further inland, away from the sea breezes.
Afternoon and evening showers and thunderstorms will continue for
inland areas as the air mass remains rather unstable. The pattern
will show hints of change late Friday night as a cold front
approaches from the northwest.

&&

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

A Pacific low moves into the southeast Bering today and Friday,
with a weakening of the upper ridge in place, resulting in
decreasing temperatures and atmospheric instability. Showers and
thunderstorms will focus along the trough axis and downwind of
interior mountains, but activity will be less organized given
decreased atmospheric instability.

&&

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

Widespread sea stratus and fog will continue, especially over the
western and central Bering Sea. Some elevated showers are
possible from the Pribilof Islands east toward the Kuskokwim Delta
coast through this morning or early afternoon as a shortwave
trough moves west. Otherwise, the main story will be a North
Pacific low currently moving into the Eastern Aleutians which will
then track westward through Friday. This 30-knot low will weaken
after tonight as it makes westward progression with the bulk of
rain remaining from Dutch Harbor east and along the southern end
of the Alaska Peninsula.

&&

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

Confidence is increasing that a warm pattern will remain in place
over southern Alaska through at least early next week, even as
the high pressure currently overhead begins to break down towards
the weekend. Guidance has come into better agreement today that a
deep upper trough approaching the North Slope this weekend will
remain north of the Alaska Range, with 850 mb temperatures over
the southern mainland remaining in the +10 C range for much of
the next week. Additionally, the low currently south of the Alaska
Peninsula will continue to retrograde westward across the Aleutian
chain, allowing a building North Pacific ridge to extend over the
southwest mainland by late Sunday as offshore flow increases over
Southcentral Alaska through Tuesday. This will continue to yield
temperatures above seasonal normal values, as well as the
potential for diurnally driven convective activity. Showers will
be most prevalent across interior portions of the mainland where
the greatest instability will reside, particularly near the
Alaska Range with the upper trough passing just to the north.
Meanwhile, the Bering region will remain in a cloudy and wet
regime as the low moves along the chain, with low stratus and fog
increasing across the eastern Bering by next week as the ridge
builds overhead.

&&

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

&&

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