Small Craft Advisory 215, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
350 PM AKST Sat Mar 11 2017

.ANALYSIS AND UPPER LEVELS...
The upper level ridge remains entrenched over the Bering Sea
today with ridging extending over the interior of the state. This
is keeping good subsidence over southwest mainland Alaska with
Southcentral Alaska in northeast flow aloft. The mid level clouds
over Southcentral Alaska this morning that were from the
shortwave moving in from the northeast have mainly moved out of
the area which is opening the door for continued mostly clear
skies. A second shortwave moving southward will move over
southwest Alaska tonight which may bring in some clouds to that
region.

&&

.MODEL DISCUSSION...
Models remain in good agreement with very little differences to
discuss into the middle of next week.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A slow shift in the upper weather pattern begins tonight as low
pressure over the Southeast moves westward into the Gulf. Not
much change at the surface is anticipated until Sunday night when
a trough develops at the surface in the northeast Gulf. With
ridging situated across the interior, wind flow increases for
channeled terrain along the coast. Additionally, winds increase
for Seward, Whittier and the Cook inlet as the pressure gradient
tightens along an inverted trough axis extending from the
developing Gulf low. Low pressure over the gulf organizes into
Tuesday with a center closing off over the central Gulf. For the
beginning of the week this system moderates toward cooler
temperatures and increasing clouds.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Sunny skies, near normal temperatures and northerly winds will
continue through the weekend as broad high pressure remains over
the Bering. These winds will increase and become gusty overnight
tonight into Sunday as a shortwave moves overhead, then persist
into Monday as a wave develops in the Gulf. By late Monday,
another upper level low descending through the Mainland may bring
a brief round of light snow showers to the Kuskokwim Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A persistent Rex Block over the Northern-Western Bering will
continue to bring quiet weather throughout the region into early
next week. The main concern will be with extensive stratus that
has developed to the west of the Pribilof Islands, but with a very
dry low level airmass coming off the sea ice no fog development is
expected.

&&

.LONG TERM FORECAST (Days 3 through 7...Tue through Sat)...
Models continue to advertise a slow and steady pattern change. The
ridge over the western Bering will go from being more of a
negative tilt (oriented northwest to southeast) to a more neutral
orientation (north to south) as we go through the week. This will
allow cold air to move from the Interior into the southern half of
AK helping to carve out a trough in the Gulf of AK. Then by next
weekend, the Bering ridge is almost completely eroded as a broad,
warm low approaches the western Aleutians.

The net effect from this will be calm conditions over much of the
Bering, while cold returns to southern AK with some snow threats.
Seas will remain relatively low and winds light really until a
warm front moves towards the central Bering by Fri. A few
shortwaves driving over the ridge and into Southwest AK will usher
in much colder air starting Tue. This cold air could also bring
the chance for some very light snow, but not impressed with any
feature at this time as the column will be very dry. It will also
lead to some gusty winds mixing down to the surface. For South
Central, models remain in good agreement that low pressure will
make its way into the Northern Gulf of AK. However, there are
subtle differences in exactly how far north and west the moisture
makes it. For now, still looks like best snow chances stay along
the Gulf Coast. But we will monitor closely for any trends if the
low were to track further west towards the colder air. The GFS did
come in with a much stronger low near Southeast AK on Wed, but
since it was a big outlier, we did not incorporate this solution.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales 180.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MO