Small Craft Advisory 797, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...DELAYED
National Weather Service Anchorage AK
1027 AM AKDT MON OCT 10 2016

.ANALYSIS AND UPPER LEVELS...
The omega block pattern over much of the Great Land and Bering
Sea is still in place, keeping the longwave pattern stalled.
However, a very dynamic low pressure system is taking shape south
of the central Aleutians. The system looks to at least shift the
whole pattern to the east in coming days. The major players in
this upcoming shift are an existing upper level low well south of
the Alaska Peninsula, and a strong jet streak/shortwave trough duo
in the east Asian jet. A stalled frontal boundary over the
western Gulf is currently being picked up by the cyclonic flow
encompassing most of the Bering, spreading over the southwest
mainland.

&&

.MODEL DISCUSSION...
After many iterations, guidance has finally converged on a
solution concerning the evolution of the dynamic Aleutian system.
The rapidly developing system nearing Adak will elongate and
quickly move to the east as the jet shears out it's upper support.
At the same time the system south of the AKpen will get caught up
in the flow and get pulled into the Bering Sea. These two
interactions will propagate the whole longwave to the east,
displacing the upper ridging further to the east as well.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The battle between the ridging that stretches from the Eastern
Gulf to the Alcan border and the lows south and southwest of
Kodiak Island will persist through the week. Yesterday the front
between these systems was able to move farther up Cook Inlet than
expected which brought clouds through the Susitna valley and some
light rain as far north as Anchorage. Today the frontal area is
farther south which should allow for some partial clearing for
northern Cook Inlet but this pattern may keep some clouds around
with winds increasing throughout the Gulf region and through
Turnagain Arm. Storm force winds look likely around the Barren
Islands for Tuesday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The remnants of the front that brought rain to much of the
Southwest Mainland overnight will move offshore by this afternoon,
leaving just a few showers in its wake for the reminder of the
evening. This will be a relatively short period of quieter weather
however, as the associated low will become absorbed in the low
currently moving trough the Aleutians by this afternoon. This
complex low will not only bring rain back into the region, but
also very gusty winds from the Alaska Peninsula into the southwest
coast. The strongest winds will occur from the Alaska Peninsula
to the south of King Salmon to the Western Capes. Wind gusts in
this area may briefly approach warning criteria (75 mph) this
evening, however due to strong stability during that time this is
not expected to be widespread or long lived enough to warrant a
warning. The Aleutian Range and the Kuskokwim Delta coast on the
other hand will experience a prolonged period of strong winds from
this system that likely persist into mid week due to a persistent
and strong pressure gradient.

Rainfall from this system will likely be very limited near the
lee side of the Aleutian/Alaska Ranges (such as Iliamna and King
Salmon, as well as the Kilbuck Mountains (such as Bethel) due to
strong and persistent downsloping caused by widespread cross-
barrier flow. Once you move further west from these downslope
prone areas (such as western Bristol Bay including Dillingham),
steady rain will occur along with gusty winds through Tuesday.
This rain will also be heavy at times into mid-week along
southeastern faces to the north and west of Dillingham as strong
upslope flow develops.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The weather over the Bering will continue to be focused on the
storm force low currently passing just south of Adak. This low
will briefly weaken to gale force this afternoon, but will then
strengthen again to storm force from the Alaska Peninsula into the
Eastern Bering as it absorbs an approaching North Pacific low
currently well south of the Alaska Peninsula. These lows will
develop into an elongated low complex that will stretch from the
North Pacific into the Central Bering, producing widespread gale
force winds and rain throughout the region that will persist
through Tuesday.

&&

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

On Wednesday, a strong ridge axis will be closing off into a high
latitude blocking high over northern Alaska. A large trough will
be situated underneath the block, with a low center in the
vicinity of the western tip of the Alaska Peninsula. With a strong
easterly cross-barrier flow across both the Chugach and Alaska
Ranges, along with surface high pressure across the interior,
southern Alaska will remain dry with the exception of the Alaska
Peninsula and coastal locations. Thursday night and Friday, the
blocking high will retrograde west with northerly flow aloft
developing across the state. This will allow for colder arctic
air to move into the region with northerly offshore for the
weekend. After that, there is much uncertainty with potential
development of an arctic trough west of the Alaska Range, with the
Canadian and ECMWF favoring this solution while the GFS shifts the
northerly flow back toward the ALCAN. Either way, the impact is
not large with the main storm track expected to remain over the
Bering with cooler and drier conditions centered over the
mainland.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None
MARINE...Storm Warning 130 131 150 160 173 174 175 180
		 Gale Warning 120 132 136 137 138 139 155 165 172 176 177
					  181 185

&&

SYNOPSIS AND MODEL DISCUSSION...MTL
AVIATION...MTL
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...JA