Small Craft Advisory 332, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 PM AKDT Sat Apr 27 2019

.ANALYSIS AND UPPER LEVELS...

The upper level pattern consists of a ridge of high pressure
building over the mainland with an area of low pressure over
the Chukchi Peninsula. Anchoring the low is an upper level trough
centered over the western Aleutians. At the surface, a
corresponding 986 mb low is centered just northwest of Shemya
with a warm front extending eastward over Amchitka, resulting in
rain and low level stratus over western Bering.

Meanwhile, it's another gorgeous day with bluebird skies over
Mainland Alaska. Satellite imagery shows some high level clouds
over the northeastern Gulf coast in response to a dissipating
upper level shortwave. Farther south in the North Pacific, a weak
frontal boundary associated with a low centered near 50N is
generating rain showers and low level cloud cover to the southern
Alaska Peninsula.

&&

.MODEL DISCUSSION...

Overall, model solutions are in good agreement. Some uncertainty
exists regarding a regenerative upper level low over Southcentral
Sun night into Mon morning. The NAM and GFS solutions both keep
this upper level feature centered over the Kenai Peninsula and
delay the onset of precipitation along the northern Gulf coast
until mid- week. Conversely,the EC solution positions the low
farther west resulting in more precipitation starting earlier.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Monday night)...

High pressure over Southcentral will continue to bring warm and
dry conditions through the weekend. A warm front currently in the
North Pacific will lift over Kodiak Island tonight and into the
Gulf of Alaska, bringing rain and gusty, easterly winds to the
western Gulf Coast by Mon morning. Most of the precipitation will
be concentrated on the eastern side of the Kenai Peninsula and
Kodiak Island as easterly winds will allow for downsloping and
drier conditions on the western side. Light precipitation
associated with this front may fall over the Anchorage Bowl by Mon
night, however downsloping conditions over the Chugach will
likely prevent anything more than a brief, localized, shower or
two.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Tonight
through Monday night)...
Spring-like weather will remain through the weekend for Southwest
Alaska, with the ridge overhead bringing dry conditions and light
offshore flow. On Sunday, high clouds from a low south of the
Alaska Peninsula will begin to affect the Bristol Bay region,
but chances of precip won't increase until Monday afternoon. At
that point, showers will begin to move in from the southeast,
becoming increasingly likely through the upslope regions northwest
of Dillingham.
&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Tonight through Monday)... Current conditions show sunny skies
over the Eastern Bering Sea, with rain and clouds on the southern
(windward) side of the Aleutian Islands. The low and front that
are currently affecting the western Aleutians will gradually move
eastward over the next few days, bringing rain and winds through
the central Bering and eventually over the Pribilof Islands and
the Eastern Aleutians by Monday night. South of the Aleutian
Chain, a low in the Northern Pacific will also gradually shift
eastward, so winds will gradually decrease as ridging moves in.
However, with the southerly onshore flow, it is likely the clouds
and gloomy weather will linger in the Eastern Aleutians and along
the southern Alaska Peninsula.

&&

.MARINE (Days 3 through 5)...
(Tuesday through Thursday)

...Bering Sea and Aleutian Coastal Waters...

A far western Bering low on Tuesday will lift towards the
Kamchatka Peninsula, with its associated surface front crossing
the central and eastern Bering south trough the Alaska Peninsula.
Both features will bring sustained winds of 25 to 30 knots across
most of the region. Then for your Wednesday, high pressure will
quickly build across the eastern half of the region, before
another weak surface low approaches the central Aleutians on
Thursday. Seas of 10 to 20 feet on Wednesday will decrease for
Thursday into Friday. Forecast confidence is high during the
period.

...Gulf of Alaska...

Sustained winds of 20 to 25 knots for coastal waters on Tuesday
will weaken for your Wednesday and Thursday, with the offshore
waters generally seeing winds less than those speeds. A weakening
front looks to move into the Gulf by Thursday. Forecast
confidence is high during the period.

&&

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

A challenging forecast is in store for the region, as the models
are in fair agreement when looking at the ensemble members for
the start of the period, and devolve into a mess by the weekend.
If there's any type of continuity, it's that a series of lows will
continue to lift north across the Western Bering/Aleutians.
Meanwhile, a narrow high amplitude ridge is expected to stretch
from the Arctic through the center of the state, with a low
retrograding from interior Canada and another low well south of
the Alaska Peninsula.

However...timing, location, and amplitude of all these features
are in poor agreement, with some models having a mid-level low
right in the middle of a ridge axis on other prognostic forecasts.
About the only consistent signal is for afternoon highs and lows
to be on the increase through the forecast period.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 411-413, 173, 175-178, 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KO
SOUTHCENTRAL ALASKA...KO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...LF
MARINE/LONG TERM...PD